llvll4l2c91350

R/T - .786

60' - 2.30

1/8 - 9.948

MPH - 70.75

1/4 - 15.445

MPH - 90.22

um i think this is pretty bad for a 91 350 lol. this was with the shifter in D. manual shifting i did even worse shifting at around 5000. seems to totally die after 4000RPM with WOT. my buddy has an 85 305 TPI with basically the same mods as me, and it seems to pull harder at higher RPMs. on the highway when he punches it you can feel it pull and RPMs rising faster than on mine. im totally lost now as to what to do. dont want to invest any more money in bolt ons since there's gotta be a problem with the engine itself. any comments or suggestion welcome.

Damon

You've got a problem somewhere. I'm thinking one of 3 areas:

1. Ignition. Either it's just worn out (plugs, wires, cap, rotor, coil, etc- the usual stuff) or you're getting some spark retard in the upper RPMs. Is your base timing set correctly with the timing wire disconnected? Over-advancing it can make the bottom end feel strong but kill upper RPM power (either from detonation or just from being advanced beyond the point of maximum power). Have you run a scan tool on it to see if you're getting spark retard in the upper RPMs?

2. Choked exhaust. Clogged cats will cause you to nose-over in the upper RPMs for sure. So will a muffler that is internally damaged.

3. Lack of fuel. You holding fuel pressure at WOT in the upper RPMs? Duck taping a fuel gague to the windshield (temporarily!!) and making a few WOT runs can tell you if your fuel delivery system in up to snuff real quick.

Damon

Oh, and one more..... is your throttle getting fully open when you mash the pedal?? This one has tripped up MANY people (including myself) from time to time. Get in and mash the pedal while someone else checks to see the throttle arm is getting a full 90* open. A simple thing like a floor mat this is too thick or wadded up under the pedal can drive you nuts with stuff like this.

A possibly related thing to check- is the TPS adjusted correctly so you are getting a full 4.5V at WOT? I think 4.5V is the spec, but I haven't worked on a later S/D TPI like yours in a while. I know 4.5V was the spec on earlier TPIs.

llvll4l2c91350

i have my base timing set at 8*. dont know what the spark condition is at high RPMs since i dont have a scanner. the plugs, wires, rotor, cap, etc. are not worn out AFAIK. i try to keep the car always in good tune. the coil is still the stock one i believe.

the exhaust. i have a flowmaster muffler, headers and semi-gutted cats. when i did the headers i got rid of half the material in each cat. didnt wanna trip a code. i remember one time i checked engine vacuum and it was within spec. a restricted exhaust would show up on the gauge wouldn't it?

i'll try the fuel test at WOT. i dont think i've ever checked the fuel pressure on this car. the MAP is in the way so its a PITA to get to the valve. i will check it now though.

i'll check the throttle as well. i recently set my IAC minimum air and the TPS wont adjust below .7V at closed throttle. at WOT the highest it went was .3 something i think. is this a bad sensor not letting me adjust it to spec?

so i'll be checkin all this stuff ASAP. also if all this checks out, would a bad cam not let the car rev any higher? im thinking since the motor isn't original, someone messed with it or put a peanut cam on it.

oh, could also be a tranny.

Metaldrgn

you probably don't have a good cam for your engine (the tech guys you talk to won't tell you what will run ok in your car not really high end. you gotta talk to people and find out what the best one would be because they make all hte difference when and where your power band takes place). Intakes ported? Tubular exhaust? pistons stock cast iron or a forged lighter aluminum alloy or something alike? My 305 could probably beat your quater mile by at least a second

llvll4l2c91350

i dont know any history on the engine. dunno what, if anything, has been changed inside. the only thing ported is the plenum at the front. i have 1 5/8 headers. a buddy of mine also suggested could be a bad cam. i have good torque, but it just doesn't rev as high as his 305 does. and since i know nothing about taking an engine apart, i feel i'm screwed.

Metaldrgn

A 350 can rev just as high as a 305, and put out more power while doing it. It's all cam that determins that. There are different cams for different occassions and you shouldn't go with a fullout race cam unless whatever car you are going to put it into is just for that and everything else compliments the cam. You should get a roller cam and a hydraulic one at that because I am guessing that is not just your track car right? If you haven't really done it before then you should take it to a pro shop where they can recommend a third party cam for your needs.

Dan88IrocZ

I'd really look at your ignition system man...

I believe you had the stock coil??

Change it and feel a big diff on your butt dyno! :lala:

I had a 90,000 mile coil, car had plenty of torque, but my upper rpm's totally blew ***...big diff once I changed it.

I just noticed that your trap speed is decent. You 60 foot sucks ***, seems as if you were spinning, or hopping pretty good. Try a set of sticky tires..

llvll4l2c91350

yep my coil is definitely not aftermarket. also when i raced i didn't brake rev cuz i knew i would spin out bad. i took off normally, easy on the pedal first (still spun somewhat), then gunned it when i got traction. sticky tires will come eventually. first i wanna get this car to breathe a lil better and maybe hit 14s, lol.

im thinking of just taking the motor apart and putting in a ZZ4 cam, although i have no idea what the specs on it are. just now i'm getting into racing and modding, so its hard for me to understand all this talk about engines and cams, etc.

the quarter mile seems loooooong, and doing it in less than 14 seconds seems very very hard at this point.

Dan88IrocZ

Take care of the tires first man, that way you can brake stand her up and be ready to rip through your power band. I bet your motor isn't as slow as you think it is...Do a high-perf tune up and DEFINETLY put some sticky meats on her and you'll be having a blast.

90Formula-X-F

In my opinion, Which is 30 years as a tech... Get rid of the bosch platinums. Put in a set of stock A/C's or Autolites. Without multispark ignition the Bosch are a poor performer and in my opinion they are junk anyway. As long as you have a TPI base and runners cam choice is important more than just about any other set up. Utilize the torque and aquire quickness. Make it play hard in the area where it was designed to run. High torque creates maX possible volumetric efficiency per application. Tpi best finds it's horsepower quickly with high torque. Combine all that while moving massive amounts of air/fuel and exhaust under 5000 RPM and you create a very quick high powered street rod. If my car ran some of the times I see on here after the investments in performance I'd burn it. Cylinder heads by far are the # 1 thing that makes the biggest diffrence. That's one area you want to do right. The rest of the engine could only then be designed after the heads are basicly in hand. That's where you start. You can see by what I've done with mine that the cost was almost just a basic performance rebuild. The rest was a lot of work. 91 speed density systems have a great stock fuel curve with the OE prom for TPI. Change plugs and run it again. I bet it does better..


- 355ci, WS6, 5speed -
* Ported & Polished Big Valve Cylinder Heads (Cast # 993)
* 2.02 & 1.6 Manley Pro-Flo Valves
* Harland Sharp 1.6 Ratio Roller Rockers
* Crane Valve Springs and Retainers
* G.M.P.P. Ram Jet Roller Cam
* Crane Roller Lifters
* Speed Pro/TRW 1.25 Dome Forged Pistons
* Windage Tray
* Lightweight Nodular 16lb Flywheel

* Induction - Ported and Gasket Matched
Plentum
Manifold
Runners
52mm Holley Throttle Body
Custom Built Adjustable Fuel Pressure Regulator
#19 GPH Injectors running at 50lbs

* Exhaust All New
Edlebrock Chrome T.E.S. Headers
High-Flow 3" Carsound Cat
Dynomax 3" Mandrel Bent Exhaust Tubing and Tail Pipes
Flowmaster American Thunder Muffler

My edit..... I had a buzz when I wrote above and I do mean it when doing internal engine mods which you don't have anyway. Junk the plugs man. Run it again and be amazed. I get an engine miss in and I pull a wire off and see Bosch platinums and I can bet ones fouled. To cold, doesn't burn off the oil let alone get a good clean air fuel burn.

MdFormula350

ouch man dont worry my first time racing my ran like 15.3 at 86 mph or something like that. i didnt know what the heck i was doing

u definitely need to get that 60 foot down, i am ordering my msd coil tonight

talk to you later, dont feel bad :lala:

llvll4l2c91350

thanx for the replies. i went ahead and got a new MSD blaster coil and checked the fuel pressure at idle. stays around 39 PSI. however the needle is fluctuating rapidly but doesn't go out of range. is this normal?

also i'ma get rapid fire spark plugs since they seem to be popular on this site. the tires can wait. i know i need traction. but its the hi RPM difference in power between my friend's 85 camaro 305 and my 350 that has me concerned right now. i rode in it several times. you can tell the difference.

Metaldrgn

Also, something noone mentioned is that when you get a better coil you should gap the spark plugs to .005"-.010" past their rating because that extra voltage makes it easier to jump the gap on the plugs and ignites the fuel mixture faster. You should also reduce your timing a degree or so if you hear any pinging or knocking. I had some bosch platinum plugs and they worked great for me, but you need just the single fire ones so you can check the gap(they are supposed to be pregapped, but they usually can be off up to ~.01").

Hey, you'll also find that a cam gives you more than a coil because a coil doesn't have any effect on airflow which is the single most important factor for creating more power.

90Formula-X-F

Your talking about your friend with a 5.0... My 90 Formula is a WS6, 5speed,5.0 that came with the same cam as the 5.7 liter in that year. I never lost to another 3rd gen. Now I'm sure I never ran up against any that were wickedly fast but people constantly would catch back up to me with their mouths wide open asking " What have you got in thing " .. It was bone stock... The mods I have now make my car extremely faster than it's ever been with just plain sheer quickness.

The movement of massive amounts of air quickly. The wrong cam will put you in a higher RPM range trying to reach max potential just to get air starved before it can happen. The torque curve would be more than likely wrong. Start reading this board friday nights and see how many people have worse E.T.'s than you with a ton more money invested. Then look in the sig for a cam... Lots of comp cams in there and it's not because they are popular.

91L98Z28

Wow, and I thought my '91 z28 was slow!

First....what was the weather conditions at the time? you need to correct the numbers for weather. If it was hot and yucky humid or the baro is low, that will hurt your time.

second, i would suggest going back to a 180 stat. my personal opinion is that 160 is just too cold and can play games with the stock computer.

third, verify your homemade cai isn't choking the engine somehow.

Third, work on your 60' time!! you are giving up about half a sec by not being able to cut a 2.0. My car runs 14.9 on a 2.3 60', and 14.5 on a 2.0 60'. My best is a 14.46 with a 1.98 60' (on street radials, so yes it's possible) and my worst is 15.1 on a 2.43.

Fourth, if your cats have been "semi gutted" then just get rid of them or replace them with new ones. no doubt they are hurting you.

Fifth, pull the timing back out to 5-6. the stock L98 heads are rather prone to detonation, and you could be running into constant retard going down the 1/4, especially if you are running crud gas and it's hot outside. yes, you should be running the highest octane pump gas available.

Sixth, if you aren't getting into at least 4.0V or higher TPS at WOT, then you could be running down the 1/4 at 14.7:1 instead of running enriched. Anotherwords, the computer may not know you're at WOT.

And of course, the simple things: fuel filter, no tranny slip, etc...

Metaldrgn

I have a comp cam and I can beat every stock 350 third gen camaros out there plus alot of modded ones (that's with a 305). It isn't the maker, it's the way the duration, seperation, and centerangle are setup. Most people get cams not knowing what the hell they are doing and get the wrong one or some inexperienced guy from a cam factory gives you bad advice.

Metaldrgn

oh, also it is a good idea to get higher lb/hr injectors. They only come with like 20-22 stock. I am not sure exactly which one would be best for you, but the 26 lb/hr should be good and replace that stock fuel pump and regulator if you haven't already.

Dragroc

I second what 90Formula-X-F said about the spark plugs...Those plugs were making my car miss extremely bad when they were only around 3 months old, I changed them out with some AC Delco plugs and haven't had a single problem yet.

I also second alot of what 91L98Z28 said. I thought the same thing about your semi gutted cats, cause my car at one time had a clogged cat, and it went from running pretty good to running like a 4 cylinder, I couldn't believe the difference it made when I had it changed. Definately check your throttle position sensor if not replace it and adjust it. If you say yours doesn't adjust, notch it with a rotary tool and make it adjust. Use 93 octane and nothing less...I have my initial timing at 12* with no problems whatsoever but this might not be the case for you. Next time you are at the track, take a timing light with you and adjust timing at the track and verify the changes with your timeslips(let the car cool inbetween runs of course).

And in my opinion when you get all of the above stuff mentioned checked and out of the way, invest in a new intake like the Miniram or a Holley Stealth Ram, you won't believe the difference they can make, and as long as everything else is in check, these intakes won't let the power die after 4000rpm. And as far as you saying your friends car revs through the powerband faster, get a set of gears for the rearend, they make a TON of difference, especially if you are cursed with the infamous 2.77 or 2.73 gear.

llvll4l2c91350

ok the cats are coming off for sure. i didnt bother to do that at first cuz i didnt wanna trip an EGR code. still gotta change plugs and try to bring the TPS voltage to where its supposed to be.

i bought a new MSD coil and Holley AFPR set at 50 PSI. im also thinkin of ditching the stock TPI and going with hi flow runners and intake and cam. problem with a miniram or stealthram is that they're not emissions legal. who knows if i'll end up moving in the future. when my current tires wear out i'll be replacing 'em with ones with more grip.

the weather wasn't really hot or humid. just a cool dry night. pretty comfortable. but i refuse to believe this car is that slow. my problem is i just started learning to race, manual shift, bring the car up to 5000 RPMs and it was my first time at the track. so im new at this. i didn't punch it all the way cuz i thought i wouldn't need to. it was prolly my own fault for not getting in the 14s. even though i needed to take the car to its limit, i didnt do that (although i thought i did). and i had a passenger with me. maybe that made a difference also. its a lot different when racing at the track than on the streets. takes a lot more concentration i think. i'm going again next friday. i wont even worry about the pathetic 15.4. i should do better the second time around.

Air_Adam

Close the windows and leave the tops on if you have t-tops. Lots of drag there...

You probably already know that, but I suggest it just incase...

Also, just drive it really hard (like you would at the strip) a few times and pay really close attention to when the power seems to level off... then at the track, shift at or just before this rpm.

91L98Z28

yep, you're getting into the swing of things, you have to keep going back!

by the way -- you had a passenger with you?!?! That is just total dead weight. Every 100lbs of dead weight is 0.1. Thus your 15.4 with a 200lb buddy is really a 15.2 with no buddy.

By the way, you may want to invest in some kind of wide band O2 sensor, perhaps the DIY kit that is out there, and do some chip tuning. Between the 160 stat and the 50psi of fuel pressure, you are probably running VERY rich at WOT. These things are calibrated pretty rich stock, and the 160 stat and 50psi fuel pressure will just add even more. TO get a rather rough idea if you are "overall too rich" or "overall too lean", you can go to the track and make 5 runs, at five different pressure settings (50-48-46-44-42) and see which one results in the greatest MPH.

And yes, you need to drive it like you stole it. Within two seconds of being off the line, your foot should be flat on the floor with the gas pedal pinned, and you don't let off till ya pass the line. Ideally you would floor it immediately, but you have to do what you have to do for traction. My personal car (on yokohama s306 touring tires) will take 50% throttle for about 1 second and then i can floor it.

Make sure you aren't letting up before the end of the dragstrip either. It can be a lot of things to be thinking about your first time, and it's easy to get on the brakes a bit too early!!

Why not have an experienced driver put 2-3 passes on your car? Just to see what it will do.

llvll4l2c91350

yea i had the windows up. i'll try that fuel pressure trick. i need to get there earlier next time. but yeah, drive it hard and not let off til the end. 2 things to do that i'm sure i didnt do very well. i realize it's all about practice and tuning. i can't just take 1 or 2 runs and thats it. im slowly learning. this is the first time im actually running a car hard and modding it. i drove my previous 88 Formula 350 like a grandma all the time. but this is fun. and i'm learning at the same time. even with the bad time, it was still a memorable night. next time i'll make sure to run it harder, and have my friend make a run with it as well. i got this fear of something breaking at those high RPMs. but hey, life is pretty boring if you dont take risks.

so every 100lbs = 0.1 seconds. damn no wonder then. i should easily be in the 14s without my friend in the car! (just joking dude if you're reading this )

Tom84L69

As noted earlier, what gear do you have? They make all the difference in the world.

llvll4l2c91350

3.23s

i think i'm good with these. decent acceleration and not very high RPMs on the highway.

Mark A Shields

Why does someone keep mentioning cams, it has nothing to do with his problem. A stock 350 should run mid 14s when in good tune, even yes with the stock cam.

This may sound stupid, but are you sure it's a 350? Many people try selling these cars as if they were, check the 8th digit VIN and make sure it's an 8.

When's the last time you did a tune up on the car?

llvll4l2c91350

yea it's a 350. i checked both the VIN and the casting at the back of the block. says 5.7. however it isn't the original motor that came with the car. who knows what kinda history it has. but compression is good, doesn't smoke, no leaks, and it has plenty of torque. it's hard to pinpoint the problem if the car isn't driven. who knows, nothing could be wrong with it, i may just need to drive it harder.

tune up was done about 6 months ago. dont remember exactly. but it seems a lot of ppl have had problems with the bosch plugs. gonna try rapid fires and see if it makes a difference. i should also go with MSD wires to go with the coil.

i should also add that about a year and a half ago both heads were replaced due to one of 'em being cracked and leaking coolant. AFAIK they're still stock L98 heads.

Damon

I'm totally with what 89Z28 said. Even about the plugs. Had the same expereince with Bosch Platinums.

Your fuel pressure should be ROCK STEADY at all times. 39 PSI seems about right at idle, however. Is that with the vacuum line disconnected? GM set their regulators to about 42 PSI stock and with the vacuum line it drops about 1 PSI for every 2" of manifold vacuum. However, fuel pressure readings at idle are MEANINGLESS. You have to get that thing out on the road and see what it's doing at WOT. Duck tape the gague to the windshiled if you have to- that's what I do. Should be holding right at ~42PSI throughout the whole run with a stock regulator. if it's nosing-over or just not near that much pressure at any point then you have fuel supply issues.

Definitely gut the cats out the rest of the way. I got a sneaking suspicion about them. Older cars like these have no way of knowing if the cats are functional like newer 97-up cars do. onc clogged cat can ruin your whole day!

Also, if you're only getting 3V at the TPS sensor at a verified full WOT, the TPS is toast. Time to replace and dial it in again.

Metaldrgn

check the timing. change it more and more degrees BTDC with a timing light until you start to hear the engine knock. The best performance is when it's right before it. Seeing how all engines are different, there is no ONE correct timing degree for your engine that someone else can recommend. My dad's friend that's been a mechanic for 35 years told me that. He used to own his own business and tought me a few things. What I was saying is that once you get to your max base performance with what you have, a cam and a full or part porting and polish would really help you out alot. more than a coil (one better than a new gm one) or spark plugs can do for you. Take out your plugs and check the gap too because sometimes detonation and regular ignition can increase the gap and usually you don't have to replace them if the ones in there aren't too old, deformed, corroded, fouled or something like that.

I'm curious if any of you actually try gapping your plugs before you put them into your engine and start saying they are crap. Are you sure it wasn't a vacuum leak or a clogged or bent hose? Did you make sure you kept your plug wires away from any metal because if it arcs you WILL LOSE ALOT of performance. Are your wires MSD or some cheap brand?