Finally bought a third gen! It's an '86 Trans am 5 speed with a little over 101k miles and seems to be in good shape. I've been going thru the car fixing things. CCC carb is already gone. Had a crappy Chinese knockoff carb and the computer HEI which was not timing correctly. I got a new 600 Holley off marketplace and a Summit HEI. I put in #65 jets, purple vac sec spring, set timing to 12 initial and about 34 total, and it runs pretty good. I got an exhaust system from a fourth gen off marketplace, so exhaust is, for now, stock manifolds and y pipe to 3" I pipe, some unknown brand 3" inlet crossflow muffler with dual 2 1/2" tailpipes. I will upgrade to shorty headers and a better y pipe once a find a good used set. Rear is a 10 bolt 3.23 with posi that still works. I'm looking to make this a good cruiser with hopefully decent mpg and respectable performance.

Being an '86, I believe this LG4 should have flat tops with 9.5:1 static CR. Should I be running highest octane pump gas available? I don't hear any pinging on regular 87, even at part throttle with vac adv hooked up. I already have this flat tappet Comp cam kit: K12-365-4. Got a really good deal on it years ago and knew I would use it eventually. I think it would be pretty perfect in this motor but would appreciate experienced opinions. Specs are 216/223, 260/272, 113 LSA, and will provide .468/.462 lift with 1.5 rockers. Comes with 26981 beehive springs. Will those springs work in the stock heads? Can I use the stock springs for break in for a little less spring pressure?

Super excited to bring this little 305 to life! It's got some decent torque but only pulls to about 4500, not surprisingly given the pathetic specs of the stock cam. Thanks in advance!

 

Probably not. There's more ENERGY (aka power) in lower octane fuel. The advantage of the higher octane stuff is, it resists spark knock, at compression above 10½:1 or so. At the compression in those old LG4s, it's not an issue. Don't waste your money. You'll spend more to go slower. And not ONLY from the weight reduction centered on the driver's wallet.

NO. Just NO. Not for ANYTHING. They are TRASH even if brand-new. Even if the cam is stock. Problem is, they don't have enough tension when new, and then they work-harden as they get old. So what you end up with is springs that hardly hold the valves closed AT ALL, EVER, butt "over the nose", they act like BOLTS until they BREAK or destroy the cam.

Go grab a coat hanger out of your closet. Bend it back and forth at one spot abuncha times. Feel that spot. THAT'S what valve springs endure. Granted, they're made of better steel than coat hangers, butt, they're STILL STEEL. The same properties. The same behaviors apply. Even if, perhaps (or not), over some greater number of bend-back-and-forth cycles.

So, NO. Just NO. Get something decent. Even though that cam is ALTOGETHER TOO MUCH for an otherwise stock LG4, you'll have better results if you get SOME kind of REAL springs. The "entry level" ones from Comp (981), Crane, Summit, ANYBODY.

The 26981 are fine for that cam. Better than the old 981s for that matter. Butt DO NOT try to run ANY aftermarket cam with stock springs. EVER. Butt yes, to answer your question, those springs will drop right onto your existing heads, with no machine work required; as long as you measure and shim them up properly. In fact you could put those springs on your otherwise stock motor RIGHT NOW, and if was the betting kind (I'm not... in one of my past lives I taught statistics at a well-known university) I might be willing to bet you'd IMMEDIATELY recognize an improvement.

All that said, as long as those stock manifolds are on there, ANYTHING ELSE you do to that motor, is POINTLESS. Imagine if your shower had a drinking straw for its drain, and you wanted to take longer hotter more vigorous showers, butt you CAN'T, because the shower pan fills up and floods your floor. Will putting a bigger shower head on it help keep the shower from overflowing? Will turning up the water pressure? Will increasing the size of the supply pipes help keep your floor dry? NO. That's what exhaust is like. If you can't get the spent material OUT, it DOESN'T MATTER how much MORE you can (theoretically) get in. That cam is too much even for a well-optimized LG4 with headers; it's COMPLETELY out of range for one with those manifolds. Put it on your shelf until you get headers and a good Y-pipe. Not sure about "good used" headers; that's a taller order in 2024 than you might think. Not even sure nowadays, besides Dyno Don if he's even still making them, what's out there. I have SLP butt they're LONG SINCE out of the ANTIQUE car business so they're no help as far as new ones. Be assured also, no "universal" "block hugger" shorties will work in this chassis.

3.23 gears is not enough for a cam like that in a crappy motor like that with no CID. You need 3.73 AT LEAST. You'd be AMAZED how much difference that makes, although with a stock LG4 and those TOTAL CRAP manifolds, you'll have the effect of, you can stomp on the gas from a stop and SMOKE the tires, butt you won't be able to pass a semi at 55 mph on a 2-lane road no matter how long you try. You'll be able to pull up next to his trailer wheels MAYBE, with your motor SCREAMING, butt it won't go one inch per second faster than that. GOTTA GET RID OF those manifolds.
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I know the stock springs are old and weak, but I was wondering if they would work to break in the new cam. I haven't killed a flat tappet yet but I have heard the horror stories. I would absolutely switch to the 981 springs from the kit after breaking it in.

I know the duration is a little much for a stock 305, but was thinking the relatively wide 113 LSA would help with the overlap. Maybe I could advance it some and install it at 106 or so instead of 109 to help some too. I could get a cheap Summit cam, like the 1102, and use everything else from the kit I have - lifters, springs, valve seals, double roller timing set. Could switch to the bigger cam later on if i go back in and port the heads or switch to Vortecs or something. I wouldn't be opposed to that if you think the 260XFI is way too much.

I know, I know.. I can't unsee that stock y pipe disaster and it is haunting me. I will definitely switch out the logs for headers and get a decent y pipe. Still shopping around for used or new. Just haven't found what I want yet. Trying to figure out what pieces will work together and not spend a fortune. I like the 3.23 gears for this car. At least it's not the 2.73 gear like I have in another car. Yikes! I know it's not helping things, but I have steeper gears in other vehicles and I want more of a cruise gear for this car. I think the 3.23 is a pretty good compromise for me.

 

Which letter of the word "NO" do I need to explain in greater detail? Is it the "N" or the "O"?

DO NOT UNDER ANY CIRCUMSTANCES WHATSOEVER attempt to run ANY aftermarket cam WHATSOEVER under ANY stock springs WHATSOEVER under any CIRCUMSTANCES WHATSOEVER. I think that's related to the word "NO" butt in case I'm not clear, I'll clarify,

TAKE YOUR STOCK SPRINGS OFF AND THROW THEM IN THE TRASH WHERE THEY'VE BELONGED SINCE THE DAY THEY WERE INSTALLED IN YOUR ENGINE. They are absolute unvarnished unmitigated unadulterated unmodified unalloyed GARBAGE. THROW THEM IN THE TRASH.

Put your new springs on AS SOON AS POSSIBLE if not sooner.

That cam is too much for any otherwise stock LG4. Complete exhaust FROM THE HEADS TO THE STREET, plus better gears (to allow the engine to reach some sort of RPMs that the cam will give it), may make up for that. Don't blame me when you put that cam in your motor, and the car is UTTERLY GUTLESS from a stop. I cannot tell you how many customers I've had over the years that brought me some inappropriate cam for their motor, as yours is, and insisted I put it in; then complained that their car "used to" leave hard, butt now it is a TOTAL SLUG off the line. PLEASE believe me when I tell you, jamming too much cam in a stock motor with stock gears and a stocxk converter, is THE SHORT RECIPE to getting humiliated by MINIVANS driven by soccer moms. You're headed down that road if you don't listen.

 

HAHA I love your enthusiasm. I have read of others using stock springs for breaking in flat tappet cams and it seems like a good idea. I think Comp even recommends using only outer springs for break in and installing inner and outer after the 20 minute break in. I have actually ran stock springs with aftermarket cams, in an SBC, in a 300 Ford, and in a Pontiac. They were pretty mild cams, about like this one. It did work, and is still working, but I do understand it is certainly not ideal. I will definitely use the beehive springs provided in the kit.

After mulling it over some, I am thinking this XFI260, albeit bigger than what would be ideal, has to be better overall than the 174/190 @ .050 or whatever stock cam. Someone can correct me if not, but I bet it would feel about the same in the midrange and would actually pull decent past 4500 rpm, maybe to like 5k or a little more. Glad I'm not plagued with the 8.5:1 SCR version of the LG4.

 

I used a K1102 or K1103 on an LG4 years ago. I did have headers, full 3in exhaust gears, S10 TC... Still i wasnt impresssed, car went 14.88 1/4 mi.

 

Working on a deal on some headers and y pipe right now. I think I'll swap this cam in and see how it does. The numbers are pretty similar to the 1103 but with notably less seat duration, probably a faster, more modern profile. And it's got a number more on LSA. Should perform better than the 1103 in a 305, I think. Sounds like it'll still be pretty lackluster but fun for a while. Next would be getting into the heads, which at that point since it'll have well over 100k miles, I'd probably start putting together a 350.

 

Got it thru state inspection and just started digging into it. I got Edelbrock shorty headers and a y pipe. The y pipe collector is only 2 1/4" for some reason, so I will cut that off and put a 3" pipe onto it and tie that to the 4th gen I pipe. But first, I am putting the cam in. I wanted to do some before testing, so I got a Dragy. Pretty neat little device. I maybe could've done better, not the best conditions, but after a few attempts I managed 0-60 in 9.34 and the 1/4 in 15.83. That's a stock 305 LG4 with a Holley 600 and 4th gen 3" I pipe and 3" in, dual 2 1/2" out muffler.

I am curious what difference the cam itself will make, but ultimately hoping for to mid 14s in the 1/4 and 0-60 in the 7s. I think that is attainable with the cam, valve springs, and headers.

 

Your baseline 15.8 1/4 mile time is about right. Headers, 3" exhaust and the cam you have picked should get you into the mid 14's without much issue. Change the rear end gears and high 13's should be doable.

However, you mentioned that you may consider a 350 swap in the future. If that's your plan, then I would skip the cam swap on this 305. It's just too much work for a motor you are ultimately going to pull (swapping a cam with the motor in the car kinda sucks). I would do the headers/exhaust and dial in the carb jetting and timing, then start building the 350 to swap in later.

 

I hear ya, but too late, lol. I tore it down and got the new cam in last night. Just got the double roller set installed and cleaned up all the gasket surfaces and sludge in the valley. I think I'll adjust the valves and start putting it back together tonight; finish up tomorrow. It hasn't been too bad so far. I've been thru this before on other cars and it's just a matter of taking the time to do it. I enjoy it for the most part and it's always worth it in the end. I am blessed to have a detached garage with a lift and all the tools I need, so that helps.

I am debating lowering the oil pan to install the front cover or trying to sneak it back on. I put a cam in my TBI 350 Cadillac years ago and was able to get the cover back on without even lowering the oil pan. It has leaked ever since, haha, but not enough to make me want to fix it. Just a little drop on the front and a little silver dollar sized puddle after sitting for a few weeks.

Glad that baseline isn't far off. It feels pretty slow, almost like something is wrong slow, haha. The first few times I opened it up it felt stronger, probably just the excitement of a new car and a 5 speed. I quickly got used to the 160 hp or whatever. I think I may keep going with the 305 if it doesn't reject the cam transplant. Seems like close to 1 hp per cube isn't too difficult with porting the stock 416 heads. The cam I stabbed in there and the full exhaust should all be good for about that much. I think close to 300 hp would be really fun in this little car.

 

That’s cool and nothing wrong with the cam swap on the 305. I did a cam swap on my ‘86 IROC LG4 5-speed a long time ago. It did wake it up a bit and moved the hp a little higher in the rpm. The cam I did was a little smaller than the one you’re installing, so you’ll see even more of a difference.

I also did not drop the oil pan and it always leaked after that. Not enough to drip on the ground, but the front of the motor was always wet. I would drop the pan if I did it again. I can’t stand oil leaks.

Yes, the stock 160hp LG4 is pretty slow, especially these days compared to every modern car. You’ll be in the 250-275hp range with the cam/headers/exhaust and no head work. Will make it feel like a different car. Head porting would get you in the neighborhood of 300hp.

Hopefully you’re not using the stock air cleaner. Those things are very restrictive.

 

I ended up lowering the pan. I just removed all the bolts except for the rear two and it lowered about a half inch. Pushed the cover on from underneath and then pushed the pan and seal back up to meet it. Worked pretty well and hopefully won't leak. I just need to adjust the valves and start bolting everything back together. I'm doing the Vice Grip Garage method of adjusting to zero lash on all valves, turning the crank 90*, then zero again on all, then 90, until a full revolution and no rockers are loose. Then I'll give them all a half turn to preload the lifters. Should work just the same and take any thinking out of it. I'll have to go back in and change out the springs and valve seals once the cam is broken in.

Yes, that stock air cleaner was the first thing to go. Not much hood clearance, so I have a 14 x 2 1/2 open element with a drop base. Kind of disappointing they even made these cars with such a massively restrictive air cleaner and exhaust, and a pathetically small cam. I'll have it about to where it should've been when it was delivered. Should be fun with 250-275 horse. And if I feel like it, some head work and gears would bring it to the next level. Thanks for all the feedback! Can't wait to see how she runs, hopefully tomorrow.

 

All sounds good, but on the valve adjustment I have not had good results doing it the way you are describing on anything other than a stock cam. Too much duration and overlap on aftermarket cams to adjust more than one valve at a time. Best bet is to just do one rocker at a time making sure that lifter is on the cam base circle and then rotate the crank to the next one.

Check for coil bind on the stock springs with the higher lift, but I think I would just go ahead and replace the springs before starting it up. Too much risk of damage with the stock springs and a bigger cam, even if only used for break in. When you do the new springs, I would also recommend the screw in rocker stud conversion.

 

I'm going to second the suggestion for new valve springs (including during break-in). That cam is nearly .500" lift and the Xtreme Energy series cams have aggressive lobe profiles that require a spring that is up to the task...

 

I did leave in the stock springs to break in the cam. It is actually .468/.462 lift with 1.5 rockers. It is advertised as more because it is intended for the TPI 350 with stock 1.6 rockers. I left them in to break in the cam. I couldn't resist and did some testing with the new cam in after changing the oil of course. It did 0-60 in 8.7. I felt the slightest surging in power at the top of second gear, around 4500-5000, likely due to weak spring pressure. I have it back in the shop for the valve springs and seals, and the headers. I am in the process of getting rid of the logs and air lines and all that junk. What a PITA. So far the cam swap might be easier than the headers, lol.

New cam sounds awesome, btw. Still makes 16 1/5"Hg at 700 idle rpm. It doesn't really have a chop to it, maybe it will after the headers are on because I know the horrific y pipe and logs change the sound. I don't care so much what the idle sounds like, it's just that so many act like a cam this size is too much for a 305, but I don't see why. It already performs much better in every way and still makes plenty of vacuum. Maybe if it was a lower static CR, but I lucked out with a 9.5 SCR 305. So far, this cam seems like a perfect fit for this motor.

 

It's not gonna have a "chop" with those specs, but that really doesn't matter. It's the performance that matters...

 

I know, that's my point. I agree, it's the performance that matters. My point is that this cam is not at all too big for this engine. If it was too big, it would probably have a really rough idle. I think this cam will be a really good performer in this engine. I'm looking forward to finishing things up and doing some real testing.

 

What is that ticking sound? Sounds like a lifter.

 

The problems with stock springs on a new aftermarket cam are as follows:


Their seat pressure is too low; meaning, with a cam that has aggressive ramps, the valves will bounce off the seats when they're supposed to be closing, aka "float", which HAMMERS all the other valve train parts to death

Their rate is too high; meaning, even though the seat pressure is inadequate to properly control the valves, their pressure "over the nose" is too high

Their coil-bind limit - the point at which they are fully compressed to where their coils touch - is usually somewhere below .500"; if this happens on even ONE valve, it WILL destroy the cam, even if all else is perfect

They are extremely inconsistent, not only in their manufacture, butt also in their installation, meaning, there is WILD variation in a stock motor in all of the above from one valve to another (none of which matters with weeeeeeenie stock cams which is why the factory doesn't bother to get it any more consistent than they do; that would be the seventh form of muda, if you're familiar with process control)

After however many miles, they are both fatigued and work-hardened, meaning the seat pressure is even lower than new ones, and the rate is even higher, up until the point that they break


A "flat-tappet" cam such as yours ISN'T flat, and a "flat tappet" ("tappet" is an obsolete word for "lifter") ISN'T flat either. "Flat" lifters are actually convex, with a radius of something like 5 feet; if you put 2 of them together bottom-to-bottom, their curvature is enough to easily see with the naked eye. The cam lobe is "taller" on the side toward the front of the engine by a few .001"s, so it's "slanted" toward being smaller at the rear of the lobe than the front. The lifter does not sit "centered" on the cam lobe; rather, the lifter bore relationship to the cam is such that the front edge of the lobe, the "taller" side of it, sits near the outer edge of the lifter. There is ideally only one contact point between the lifter and the lobe because of their geometry; this point is near the front edge of the lobe butt not all the way at the edge, and somewhere out near the edge of the lifter butt not right at the edge, maybe 2/3 of the way from the center out toward the edge. The cam is pulled back into the block by the force of the distributor gear driving the oil pump, and also by the interface of the lobes to the lifters as described, which is why there isn't any kind of "retainer" needed for a flat-tappet cam, the way there is for a roller-tappet one. Since the contact point is out near the edge of the lifter, the motion of the cam underneath the lifter tries to make the lifter rotate. This rotation is ABSOLUTELY CRITICALLY NECESSARY; with it, the lifter sort of rolls around over the top of the cam lobe almost like a ball bearing, butt without it, the lobe and lifter simply slide against each other as the cam spins but the lifter sits still. This sliding action is not sustainable: the lobe will first wear a little bar-shaped divot in the lifter which then PREVENTS the lifter from EVER spinning (it is PERMANENTLY ruined), then as the lobe also wears, eventually the lobe rounds off and the lifter base gets EATEN. Promoting this rotation action is what "break in" is all about: it MUST BE established within the first few revolutions of the cam, otherwise the whole thing is DOOMED. Once a lifter lobe acquires the bar-shaped divot, it can no longer rotate, and if it happens to EVEN ONE of the 16, IT'S OVER. The process is irreversible.

When a cam lobe and lifter eat each other, an ENORMOUS amount of very hard steel gets ground into VERY sharp little shavings, which are made MAGNETIC by the action of this failure mode, and shed into the oil. WITHOUT FAIL, these chips will get into the bearings and DESTROY them, as well of course as the crank. Also without fail, they will coat the inside of all the oil passages and stick to them due to their magnetism, making them VERY DIFFICULT to remove. Since the vat or parts washer doesn't dissolve metal, THE ONLY WAY to get rid of them, is to tear the engine COMPLETELY down, remove the cam bearings, remove EVERY plug from EVERY oil passage, and run a wire brush through EVERY passage, with plenty of soap and hot water. When I say EVERY plug, I mean the 3 in the front of the block and the 3 in the rear, around the cam journals, as well as the one in the vertical passage that separates the dirty oil from the pump headed to the filter, from the clean oil returning from the filter. When I say EVERY passage, I mean the ones all around the oil filter region, the one going up the rear of the block below the oil pressure sending unit, the 3 going from front to rear all around the cam, the 5 going from the center one of those through the cam bearings and down to the main bearings, the ones in the crankshaft going from the mains to the rods, and MOST CRITICALLY, the grooves around the cam bores behind the cam bearings. Failure to properly clean these MAGNETIC shavings out of the block is one of the reasons for serial engine failure by amateur builders. (sometimes even by the pros) Rifle brushes are perfect: .410 shotgun size for the biggest passages, .30 for the front-rear ones, and .22 for the small vertical ones although it's such a tight fit that you'll probably have to throw it away after one block, and a toothbrush-looking one for behind the cam bearings. Fortunately rifle brushes are cheeep.

The SINGLE MOST CRITICAL point in the life of a flat-tappet cam and lifters is the first few seconds after the first start-up.

This is why old used stock springs are SO DANGEROUS on top of a new cam, and why it's SO STUUUUUUPID to take that risk. Break-in is the absolute most important moment of the cam's life. Just ONE EFFFFF-UP of just ONE lifter can COMPLETELY destroy an otherwise healthy engine. Virtually always, by the time you realize it's happened, it's already too late. The first symptom will be a lifter that ticks and you can't make it shut up by adjusting; then you'll notice a cylinder (or more) that doesn't run the same as the others because one of its valves isn't opening near as much; then if allowed to continue, it'll spin bearings, usually the first to go will be one of the front few rod bearings butt they'll all be UNBELIEVABLY tore up. The only way to diagnose it before catastrophic failure is to observe the push rods with the engine running: they are supposed to spin along with the lifter, and if they're not ALL spinning, then the ones that don't spin, are in this process of circling the drain. Worst of all, the bottom of the lifter gets all mushroomed out, and it EATS the lifter bore; once this happens, there's NO POSSIBLE WAY for the next new lifter to even work, since it's no longer tight in the bore, and the block is SCRAP. Yes, it's possible to "sleeve" a lifter bore; yes, it's also more expensive most of the time, than to just get another block. When repair cost exceeds replacement cost, the common term for such an object is "scrap".

This why YOU DON'T WANT TO USE STOCK SPRINGS FOR BREAK-IN. They are wrong IN EVERY WAY for promoting long and successful cam and lifter life. And they can cost you THE ENTIRE ENGINE, far beyond just the cam & lifters, surprisingly EASILY. It's far more common than you think. Or at least, was at one time; nowadays, with roller cams, all of this is no longer an issue.

Too bad you didn't listen. I hope for your sake that you haven't ruined your new cam. That would be most unfortunate, and a hard way to learn the lesson you didn't listen to, the way I had to learn it as a n00b, since Algore hadn't invented the Interwebz yet back then. Good luck with that.

 

I've done about eight cam swaps, all flat tappets except for a couple rollers. I haven't lost a cam yet in any of the flat tappets. A few of them actually got the springs they're supposed to have, a few still with stock springs. They are all pretty mild cams. With this engine in particular, I shouldn't be close to coil bind being under .470" lift. They even make break-in springs with less pressure to help promote lifter rotation during the break in process. Once that's established, obviously you switch to the correct springs. It makes sense to me to use stock springs as break in springs, unless you are right up against coil bind amounts of lift, which I am not. The notion of higher spring pressure over the nose with stock springs is interesting. So, at max lift points with stock springs the spring pressure is actually higher than the aftermarket springs? I did not realize that.

Anyway, I don't have any lifter ticking or any signs of any issues at all. I have it torn down and I will be replacing the springs tonight. Should have it all back together with the new headers and y pipe as well by the end of the week. I am a little worried about my Cadillac wait a 395 marine cam, or Ram Jet cam, with stock springs. That's not really a "big" cam but those stock springs are 34 years old and, well they probably suck. I'll probably change those one of these days, too. Thanks for all the help and feedback.

 

As said, good luck. I hope it works out.

Yes. Compare for example, Comp 986 (dual spring w damper), Comp 981, and whatever specs you can find for stock springs. Compare their pressures at the seat when properly set up, at .425" or whatever for stock peak lift, and .500". Could get interesting. Even more so if you compare good aftermarket springs to wore-out stock ones.

Yes I know about break-in springs. They are NOT the same as stock springs, with their high rate.

Used stock springs are THE ABSOLUTE WORST choice for cam break-in. I hope yours work out for you, butt don't try to say you weren't warned.

 

I see! I appreciate the patience and thorough explanation. Welp, I guess I'll find out if the cam survives.

The valve seals that came in the kit are 16 positive type seals that are too small to fit the valves. This kit is for a TPI 350, so I am guessing those heads have smaller valve stems. On my engine, the intakes have positive style seals and the exhausts have rock-hard umbrella seals. Went thru some spare parts and found some seals that seem to work okay. I have a set of KOK 198c positive seals that seem to fit the intake. I think that's who actually makes them, KOK. It says that right on the seal, but they were probably branded Fel Pro or something. I just have the unopened bag with no label. Any idea if these are correct for these heads? I also have a set of 502 umbrella seals that, as far as I can tell, work on the exhaust side just fine. Retainer to seal clearance measures over .600" on both intake and exhaust, so that should be plenty with my lift.

Also, the installed height for these springs is 1.7" and I measured right about that on the intake but more like 1.77" on the exhaust. I read somewhere that omitting the rotator on the exhaust requires a .060 shim under the spring, so that makes sense with what I measured. Will Comp 4751-16 work to shim up the exhaust springs?

One more thing, while looking for valve seals I found a set of new 1.6 Comp roller tip rockers I had bought for another project but never used. Should I maybe use them on this? My thought is that .469/.463 with the stock 1.5 rockers is plenty for now with the stock, unported heads, but I don't know.

 

I've never seen that method before. Interesting.

 

Probably good enough for somebody that thinks used stock springs are good enough for cam break-in.

Best o luck to him.

 

I finally got the whole project properly wrapped up tonight. Springs, shims for 1.7 install height, retainers, keepers, valve seals, headers, 3" pipe welded to the y pipe collector and 3" pipes connecting to intermediate 3" pipe. Car runs great and sounds awesome. It did 0-60 in 7.58. That's with a lot of wheel spin, shifting at about 5500 just because that felt right.

It only did 15.7 in the 1/4 but I lifted and coasted toward the end of the run. It was breaking up noticeably. Driving normally it is completely fine but it has a misfire going on under load at the higher rpms. Not sure if that's ignition or fuel. I'm running a new Summit HEI with new wires and new Holley 600. I wonder if the #65 jets I put in the carb are too small now. I wanted to replace the platinum NGK plugs that were in there because they look like they've been in there a while and I'm not sure this is benefiting from platinum. I got some CR43TS AC plugs but there were too long with the headers. I'll probably start with the plugs.

Overall though, it's such a dramatic improvement. It's actually respectable now. If I can nail down how to launch this thing with minimal tire spin, if that's possible on street tires, and fix this misfire issue, it'll be around 7 seconds 0-60 and 14s in the 1/4 no problem. Thanks for the encouragement and info helping me get there!

 

This thread has been a fun read. I remember those days....I did the old $89 Summit cam/lifters on my LG4 dropped a full second of it's 1/4 mile time even using stock springs, air cleaner, and exhaust. Worth it.

OP, you're misfire/break up could be from a wiped lobe. Sofa could be right.

 

I had timing a little conservative with 12 base and 34 total mechanical. I tried 16/38 and it ran just about exactly the same. I don't hear any engine ticking or pinging or anything. It sounds fine and pulls strong in first gear, but it feels like it's fuel starved at those high rpms after under load for several seconds. I think I'll put the timing back down, change the plugs, and maybe jet up a few sizes. I also have a stupid carb adapter on there. I might try to cut the center out to make it an open spacer, or get rid of it altogether if the Holley will work on the spreadbore manifold with just a square flat plate under it. Just working out some kinks now and hoping the cam is okay.

 

I replaced the plugs, put in #69 jets up from #65, cut out the middle of the carb adapter; also put light springs in the dist, cleaned the cap terminals, and put in a new rotor because I had one. It ran noticeably better and smoother, but still had the break up at the top of third gear, more of a smooth surging now at over 4k. Really felt like a fuel thing at this point. I checked the floats - front was perfect, rear was way low. I raised the rear float and I think that did it. No more power surging. It did 0-60 in 7.36, best yet, but 1/4 mile still only 15.5. Is that about right for this combo? I figure it must be the gearing at this point. You all are right, of course, I think she needs some 3.73s or thereabouts. It basically only uses third gear in the 1/4 with the 3.23s.

 

Are you still running stock exhaust manifolds?
Getting wheel spin on launch? What tires are you running?

Rear gears are holding it back a little, but I would think 14’s are doable even with the 3.23’s. What’s your trap speed at the end of the 1/4?

 

I installed Edelbrock shorty headers and y pipe into 3" fourth gen exhaust. Muffler is unknown 3" in, two 2 1/2" out. Tires are some cheap 255/45/17 street tires. If I dump the clutch at about 2k, it spins, and goes a little sideways. Which is about the fastest launch I have been able to achieve. If I launch it at more like 1200 or so and dump it, it kind of lugs and then takes off, which I think is a little slower. With the surging problem seemingly cured, it did the 1/4 in 15.52 at 92 mph. Shifting at about 5500 rpm.

 

Sounds like better tires would help.

I’d expect about 95mph, so you’re pretty close there. Maybe a bit more tuning will get there.

What is the elevation above sea level where you are testing?

 

I am at about 600' above sea level. I might put some dot slicks on steelies for my test runs. Reading on the "Post your 305 1/4 miles times" thread, I saw where someone shaved over .3 in the 1/4 by uncapping a cutout after the y pipe. I think I may put in a cutout after the y. The used fourth gen intermediate pipe I got is smashed flat over the axle. Not completely flat, but someone was hammering on it to clear the axle or something. It's definitely not 3" diameter for that whole u bend.

I think I can jet back down to #65 or so in the primaries now that I discovered the low secondary float issue. It smells pretty gassy after test runs now. Other than that exhaust restriction and overly rich primary, and maybe some better tires, I am not really sure what else to try. I thought it would be in the 14s as it is now. It kind of seems like I'm missing something.

 

Is it still breaking up on the top end?

 

No, I think the break up was getting into the secondaries with the float so low that it emptied quickly. As far as I can tell, raising the rear float cured it. In mulling this over, I think it's got too much restriction in and maybe out too. While holding the throttle wide open I can look down the front carb barrels and see the four hole adapter spacer right under it redirecting air. to the spread bore holes. I did cut out the top portion to make it act like an open spacer, and blended it down hoping for decent flow, but it still impedes the airflow quite a bit just looking at it.

I am wondering if a lot of people with these 305s in the 14s either have a q-jet on the stock intake or some other spread bore carb, or an aftermarket intake with a square bore carb. I'm thinking my square bore Holley with the adapter under it directing air to the stock spread bore intake is screwing up the flow too much. That and having that smashed flat pipe over the axle isn't helping either. It's got everything else to be running stronger... I think it's time for an intake swap at least.

 

How are you timing this thing? A Cell phone app? Or are you taking it to the track every time?

Your trap (if from a track) is alright, your ET is slow, but your description of your launch may explain that part. What's your 60'? On a 92 trap, you should be ET'ing ~14.8 on typical street tire with a typical 2.0x 60' time. This is using track numbers, not app numbers.

"Dumping" the clutch is not going to get you good 60' times....Or good ET's. It's going go get you wheel spin, or as you discovered w/your 1200 RPM launch, a bog. You need to modulate the clutch, such that the engine is not bogging, nor are the tires breaking loose....but you're exploiting all the tq the engine can produce. It's a balance of RPM and clutch engaging....kind of like starting out up a hill - you don't dump the clutch there....and you don't slip it to hell, you balance your throttle, RPM and clutch slippage to get the car going. Same thing here, except the throttle should be WOT and you're managing engine RPM with the clutch pedal. You should be able to find an "ideal" RPM for your combo where you start your launch, then slip the clutch over a period of about 1.5 - 2 seconds in such a way that the engine RPM doesn't meaningfully vary from your starting RPM, to full clutch hook-up....and your off. That method will get you about the most tq to the tires, w/o overwhelming the tires with tq spikes from dumping and flywheel inertia. It'll also avoid over loading the tq of the engine and causing a bog.

Using ^that^ technique, I can typically 60' 1.8x - 1.9's on regular street tires w/stockish RWD cars. A comparison point for you (and this is a different intake), I had an '83 CFI Trans Am, After putting in a T5, Edelbrock "headers" and Y-pipe, and TPI cat/cat back (still w/the stock 3.23 gear, like yours) I went 14.5@95 with that thing. It could have ET'd better on that trap, with better driving, I was young and didn't know how to come out as well as I do now, but that was probably a 2.0x 60' time, or so.

HTH

 

This is using a dragy device and app. I thought that was pretty accurate but maybe not? On the 15.5 at 92 mph run, the 60' was 2.5, so that's pretty bad I guess. That's a half second right there. Sounds like I need to dial in the launch technique and feather the clutch some. I'd like to take this thing to the track when I get the time. I don't have one close by and the two nearest ones are probably closed now anyway. Glad I am getting this figured out some before actually taking it to a track tho. I do think an intake and exhaust cutout would probably help a lot on the big end and shave off a few tenths. I am not used to launching a manual car. I've got a lot of improvement to make in that regard. I use my heel on the brake and toes on the throttle so I hold the rpms up some and don't roll back. I just need to work the clutch.

 

Yeah, the 2.5s 60’ is hurting your E.T. You should be able to get to about a 2.0s 60’ and that should be high 14’s and your 92mph trap speed shouldn’t change.

Practice practice. Figuring out the right launch rpm takes some trial and error, but it will probably be somewhere around 2500-3000rpm, then a bit of clutch slipping while you quickly but progressively increase throttle to wide open.

Are you doing a brakestand burnout before your run to warm up the tires? Doesn’t need to be a big tire smoking burnout, but a 3-4 second burnout will get the tires warm so they will grip.

Despite all of this, you may not do better than about a 2.2s 60’ on the street. At the drag strip they prep the track surface and it’s a lot stickier, which will give you your best times.

 

They are surprisingly accurate, but measure different metrics than the track does. At the track, you have a two things happening that actually make your times and traps inaccurate...but dead consistent.
1. The start beam is triggered by the front of your wheel, the TIMING starts when the rear of your front wheel clears the beam, so you get about 1', 3 mph, and .3 second "free" as your car accelerates before the front tire clears the beam.
2. TRAP: the trap speed at the drag track is measured by two beams; one at the end of 1320' and the other about 66' prior to the end. Well, your car is still accelerating at the end of the 1/4 mile, so it's going slower 66' before the end, than it is AT the end. Your trap speed is roughly the measured time from 66' before then end, and the time at the end, which obviously calculates to a lower mph number than the car's actual speed at 1320'.

The draggy and most apps, measure the cars acceleration from the dig -no "rollout" of the front tire, and measures "trap" AT 1320' -the very end, so it's you'r car's actual speed at 1320', not it's speed at about 1287'. Therefore, a run down a drag track, timed by the track and by an app will show a slower ET for app....combined with a higher trap speed for the app than the track's numbers.

You ran a 15.2@92, as measured by the app. If you ran that identical pass at a track, the time slip would look more like a 14.9@90. 14.9 @ 90 is a decent, street tire ET to Trap ratio (could be better), but the 90 mph is not great, IMO for a cam/headers/exhaust/carb 305 w/a 5 speed. It's not terrible, but I think it should do better.


Yep, that's pretty bad. Deduct the "roll out" that you'd get at a track (typically) and that number becomes a 2.2 60', which is still pretty bad. Good driving should chop .2 right off that, and you will translate that directly to the ET....and then some. That alone (driving) would turn your 15.2 number into a 14.9 number...even with the same trap speed. If you were on a real track, your 14.9 number that I predict you'd see on a time slip, would become a 14.7. Now you're getting some where and you've modded nothing but your driving and locale.


Driver mod. Best/cheapest mod that you can make to a car. AND, the best way to make any given car "look better than it should be". ...and that is a LOT of fun!
You could disconnect your exhaust at the cat, or before the cat, make a few passes w/the draggy app and see how much trap you gain. Trap is a direct indicator of HP, where ET is more an indicator of how well that HP was put to the ground. If you gain meaningful trap w/the exhaust disconnected, then a cut out will for sure, help. Or a better cat back system.

It's cool that you're chipping away at this. Keep working on it!

 

What an incredible wealth of knowledge on this forum. I can't thank everyone enough for all the help and sharing in this community. I think I really need to get rid of this adapter spacer under the carb. It developed this slight vac leak. Not terrible, but I took the carb off to change the jets to 66, gaskets still look totally fine. I omitted the flat plate I installed between the carb and adapter, with a gasket on either side of course, and it's still got this little leak. This adapter is definitely not ideal anyway. It'll work for now, but I'm looking for an intake. I think I like the E 7104 and found one on FB I might snag up.

Anyway, I did not warm the tires prior to the runs and I still had about 32 psi. I rejetted the carb and aired down to 20 psi but the roads are wet out tonight. I will take it out and experiment with the launch with warmed tires once the pavement is dry. I'm pumped to see what I can get out of it. This is so much fun, btw. I'm used to auto cars and just doing burnouts, haha this is next level for me and I love it. I have some 15x8 Centerlines on my '69 GTO with street tires. I think I will get some 275/50/15 dot slicks for those wheels and see how these cars will do with some actual drag racing oriented rubber.

I don't have a cat. I just made a 3" pipe connect the y to the fourth gen 3" intermediate pipe. I will experiment the exhaust later. Probably not the biggest choke point right now. Really looking forward to getting the launch down and getting a real intake setup. Then maybe some tires and exhaust tweaking.

 

Keep updating this thread. I'm enjoying it, at least! I'm sure others are too.

 

20 psi is probably a bit too low, usually 24-26 psi on street tires is what I have run sucessfully in the past at the track. When you air down the pressure too low you actually lose contact patch through the center of the tire.

 

Thanks! That makes sense, I will put some air back in. Fast, btw, you helped me years ago with advice on a cam and valve seals for my '90 Caddy 350 TBI. I put in the 395 marine cam. It's still running great! The LT headers, dual exhaust, TBI mods, TBI intake, open air cleaner, and cam completely changed that car. Probably added nearly 100 hp.

Still raining or I'd take out the bird today. Maybe tomorrow. It'll be dry, cold, but dry at least.

 

Just got a best 0-60 of 6.98 and the 1/4 in 15.12 at 94. I think my main improvement for the 0-60 and ET was in my shifting, not lifting throttle completely, or much at all between gears. Still experimenting with my launch technique. It's really a fine line between the bog and no traction. That best run still only had a 2.47 60'. Best 60' was only 2.39 in a different run.

Only got in a handful of real attempts. It's very annoying waiting for traffic to clear and finding ideal stretches with consistent elevation and not too many curves. Not to mention, it's pretty cold and my heater core is bypassed because back when I was doing my before testing I found a lake of coolant on the passenger floor. I'm trying to do this in the evening when there's less traffic, but there's still traffic around here and this time of year it's dark, and cold, and certainly not ideal. I'm looking forward to better conditions so I can nail this down. Glad to see some improvement tho. At least the 0-60 and ET came down, and trap speed went up.

 

Much better. Trap speed is good, which means your horsepower is where it's expected (in the neighborhood of 250hp at the flywheel). With good tires, on a prepped drag strip and a good launch, you should be able to do a 1.9-2.0 60' and a mid 14 second 1/4 mile run.

 

Good that you picked up 2 mph. Nice work. You're learning and getting better which is awesome and really rewarding. WRT shifting, in that car, I'd recommend not lifting at all, during max effort runs. I probably wouldn't flat foot shift every run....certainly not on runs that you know (from launch or whatever) that they've already gone south...no need to work the trans/clutch that hard if the run is already bad....but after you've gotten your driving dialed, Flat-foot shifting makes a tangible improvement. Worth it.

You're absolutely right that launch is a total balancing act; it HAS to be, b/c literally the goal is to put the drive tires right on the very cusp of their tractive limit. If you're below that (not coming off the clutch fast enough), then you're leaving ET on the table. If you exceed that, the tires break free.....and you've leaving ET on the table. This is one reason why electric cars can be so fast off the line; they can literally manage tractive force/tq to each wheel in real time, 100's of times per revolution... it's a perfect launch every time, where the tire is right at the cusp of it's limit for the duration of the launch. You are trying to mimic that, w/o the benefit of wheel speed sensor, tq vectoring, and/or instant tq management. So what have you got to cover for that? Your azz. And practice, feeling it, over and over until you're intimately aware of the tractive limit of your tires, the clutch engagement rate/feel etc. and then you can repeated come out of the hole, like a machine, like a robot.

My lengthy diatribe above was to bring awareness to the fact that the App numbers are different, than track numbers....which more of us are familiar with, and thus, are the "standard" measuring stick. I agree that he should see 1.9-2.0 60's and mid 14's. HOWEVER...

The 60' he's going to see on his app is going to look more like a 2.2-2.3 b/c of the lack of rollout.
The ET he's going to drive toward, is going to be 14.7's -ish, which'd get him 14.5's -ish (mid 14's) at a real track
And traps, I think he should be trapping ~95 using drag track timing devices, so he's still off that by a bit. But it's coming along. OP might be able to kiss 95 mph....(97-98 -ish? on his app) w/aggressive flat-foot shifting and hitting the right shift points for that combo.

Now, I'm not trying to be picky or bust anyone's *****...just want to make sure the OP understands the effects of the two measuring systems so he can target the right goals.

 

Awesome insight on track times versus app times. I thought differences were just due to inaccuracy of apps and the info from the satellites they get info from. I had no idea that measurements were actually being taken differently. I am very eager to get the car to an actual track this year. I am not too crazy about trying to run quarter miles on the streets. With traffic and turns and asphalt, etc, there are just too many variables. Of course now the roads are snow covered and/or being salted. I did install an EPS manifold I got off the facespace marketplace. I swear the car feels like it revs better/more easily. Eager to try it out but the conditions are terrible right now in about every way. I did find a 350 in I forgot I had in my shed when cleaning it out. That may be a good build project for next year for this car.

 

The EPS is a great manifold for many setups. Years ago it did not exist yet when I ran a Performer RPM spreadbore on my 305. The RPM provided a very noticeable gain over the stock aluminum Q-Jet manifold. Car Craft tested one on their early dished piston 1982 era LG4 they ultimately made 325 hp with using Vortec heads and Comp 262 flat tappet cam. Even with the stock camshaft the RPM made substantial power improvements across most of the torque curve compared to a standard Performer or the stock GM manifold.

 

A little warmer out today so I took out the bird for a couple quick passes. Previous best was 0-60 in 6.98 and the 1/4 in 15.12 at 94.14 mph. Best 60' was 2.39 in a separate run.

Tonight she did 0-60 in 6.53, the 1/4 in 14.78 at 95.87 and the 60' was 2.42. Woohoo, broke into the 14s! Lol. I pretty much did nothing since the last run except change the intake manifold. So, about a half second improvement 0-60, a few tenths in the 1/4, and a little under 2 mph, all attributed to the Edelbrock EPS and eliminating that dang carb adapter. First run I had a lot of spin and a 2.44 60'. For the second run with the record times, I gave it a less throttle and let it bog a little. No wheel spin at all but still only a 2.42 60'. I am not sure I can get the 60' much better than the 2.39 I got back in December, at least not on these tires on the street.

I am happy with the improvements. I am already, of course, thinking of what I should do next - gears, tires, spray? But first, the driveline vibration is pretty severe. At 80 mph and up it vibrates pretty badly, and when I let off after making a run it feels like the rear end is about to fall out of it on decel. I've had the driveshaft out a few times and the u-joints seem fine. Rear seems fine too. I wonder if the driveshaft got bent somehow slightly or got out of balance. I don't know. Whatever it is, it is not obvious, but it probably should be fixed before I do anything else fun.

 

So, my 87 Formula did that vibration dance and decel funkiness some years ago. I did all the normal checks and couldn't find anything. I then pulled the rear end cover and found the issue. I could see tooth-bite wear marks on the differential carrier going all the way around. My "fix" was to remove the driveshaft, take off the nut that holds the yoke on the pinion, replace the seal, torque down a NEW pinion nut. And the problem was solved. The tell might be if you see a little fresh oil gathering around that front input seal...

It seems that the pinion nut had come a little loose from all the hard driving antics...