Need some help guys...
Car: 1987 305 LG4
Just got done putting everything back together, new cam, some head porting/polishing, had valve job, everything put together correctly as far as I'm concerned.
I had some earlier problems with loud knocking, b/c of timing (and fouled plugs), really hard starting, if at all, but all that is set correctly and plugs replaced, new cap and rotor button, wires.

The problem I am having now is this. Car fires right up, first try. It was running incredibly rough (idle), and was seemingly missing/vibrating. When I took it up the road, has a hard time accelerating, even though timing is correct. I could get a little spin of the tires on dry pavement before all this was done (posi), but now I cant, car seems to hesitate pretty bad. Will get up to high RPM's, but takes longer than should. In other words the car is SLOWER than crappola.
Ok, I was suspecting a bad ground (i had painted the heads and manifold), so today I unhooked two of the grounds (rear of the head and front of manifold) and took some sandpaper and sanded them down as best I could, bolted them back on, and ran the car, (I am under the impression that these grounds are for the ECM, right?) seemed to run a LOT better, I could spin the tires a small amount on the pavement. But the car still seems like it should have more potential. Should I check the other ground, or the ones I did already and try and get better grounds from them? I think the knock sensor played with my computer quite a bit from earlier when I had terrible knocking from poorly adjusted timing. I went to adjust the timing today after it was running better from those new grounds, and I coudlnt even find the timing mark when trying to time it, it was about 50 degrees advanced. When I tried to turn the distributor back to get it close to 0 degrees where it should be, it woudlnt go (tried to shut off). I read just tonight that I may need to reset the ECM to clear the tables that it may have built up from running it before with that bad knocking, is this true?

Also, when I installed my headers, there was no O2 hole so I removed the O2 sensor. The car ran fine before doing all this, which leads me to believe that it should run at least comparitively similar now, if not to its full potential, cause of the limp mode it feeds the carb. But I plan on fixing that soon also.

I may be leaving some info out here, Ill add anything if I remember. I've spent about 4 saturdays trying to find out this problem and I'd REALLY......no really, REALLY like to have my car finished soon for spring/summer....I'm sure you all can sympathize here!

Any help very much appreciated!
Thanks,
Ben

 

i'd suspect vacuum leak, timing off, or valves misadjusted

 

LG-4, eh?

We could have a long way to go here.

First off, get the O2 sensor back into the pipe and properly connected to the ECM if you are still running a computer controlled carb and distributor. Without it the ECM goes into "limp home" and runs the engine rich and with very little spark advance. Zippo performance.

Second, you need to check your timing with all the computer advance taken out. Disconnect the 4-wire harness coming out the back of the distributor to the wiring harness that runs over the tranny tunnel. These are the wires that the ECM talks to the distributor. Unplugging this harness will return you to "base timing" that you set manually. LG-4 with a stock chip the spec is 0*, but you can easily bump it up to 4-6* BTDC for better performance with no ill effects.

Third, yes, it will take about 1/2 hour of street driving under various throttle conditions for the ECM to "unlearn" it's spark knock tables. Or you can just take a battery cable off for 30 seconds and go back to the base tables.

Last- how big a cam?

 

Timing was set properly with the ECM unplugged from the dist.
It was set properly before taking off the grounds and 'cleaning' them. After I had done this, I checked the timing again to see if anything had changed, and it I coudlnt find the mark with the timing light. It was about 50* adv. Same effect with the dist hooked back up to the dist. There was no difference in timing, yet it would move while reving the engine. Whereas, before doing the grounds, it was definitely offset correctly by the computer when NOT in bypass mode. So something had changed... Definitely weird.
The cam is the Comp Cams 270H-R10, with .500 and .500 gross valve lift and duration at .050 In215 Ex215, lobe sep. 110.
It was picked out by a guy I know that builds race engines day in day out, I know some people will say that this cam may be too big for the 305, but I'm gonna take his advice here, so with that aside, I think the car should , at the very least, still run decently.
I noticed that it does run filthy rich, the exhaust pipes are coated in soot from running it. Perhaps with the O2 sensor in it would send out the right mixutre to the M/C. How much would you be able to notice a decrease in performance with running rich like that? Well, lets say, would it MAKE that much a difference. Car seemed to run fine before doing all this, like i said, with no O2 sensor, so I dont know why it woudlnt run about the same at the least, with just a new cam basically. Maybe with the more air/fuel going into the cylinders, the situation would worsen because of the mixture???
One of my mechanics told me that with headers, the O2 sensor may not operate correctly or to its full potential, because of the heat differences between the manifolds and headers, is this true? I know they have to be 600 degrees to function properly but I would think that those headers would operate that hot...

 

Oops, forgot to answer Ede. I've checked ALL vacuum lines multiple times, definitely not a problem there. Like I said, timing was set properly, as were the valves. Valve lash were set to 0 lash, then 1/4 turn.

I am wondering also, could the ECM be bad. I would think that if it were to be bad, it would be totally gone, as in fried. But perhaps some circuits still work in it? I had a new one last weekend cause I suspected it, but I took it back thinking i was on the right track elsewhere. I shoulda just plugged it in to make sure it wasnt it.

 

Anyone?...

 

i had simular situation thought i had vacum leak reseal intake 3 times went through all the ignition still nothing well come to find out i didnt put cam in right my timming set had 3 key ways i linded up dot to dot but that was not right in my motor the dot i lined it up to was even the timming dot hard to explain but i was 99.9% sure i did it right but it wasnt i fixed that now she runs like a champ i know you dont wanna hear that but niether did i good luck later

 

383 were you using an aftermarket timing set or was this on the stock set. I didnt check to see if there were more than one timing mark on the gear...

 

im useing an aftermarket timming set there was a dot on it but thats not what i was suppose line it up to but i didnt even see the other markings the dot is most visible like i said i thought 4 sure i put it in right had 3 others look at it to make sure but after i look at everything else thats wjat it ended up being runs like a champ now good luck later

 

the first and probaly easiest thing to do is have a muffler shop weld a O2 bung in the header and hook up that O2 sensor. without it the car will run like a half crippled three legged dog. the ECM uses that signal probably the most of all to make mixture/timming adjustments. it's by far the cheapest and easiest thing to do first, if that isn't it then start checking things like cam gear alignment. either way you will eventually have to get the sensor installed and it may save you alot of work just doing it first.

 

I have the O2 sensor in now, I will have to hook it up the next time I go home for the weekend.
Another thing that is concerning me that I just now thought of (I dont know why I didnt remember way earlier) is that on (if I remember correctly) the #6 (cant remember E or I) valve, I had to tighten the rocker arm nut down considerably farther than the rest to set valve lash on that valve. I'm wondering if it isnt a spring that is broke. They are stock springs, had them off while porting the heads, reinstalled them. I dont know why the spring would have all-of-a-suddenly gone out, but after talking to my mechanic, he said that they can go at any time. I have pins in the studs so I know they dindt pull up and I'm positive that the stud wasnt pulled before hand. Would a broken/worn spring be a likely cause, and would something as minor as 1 broken spring cause such a drastic performance loss?
I've noticed from driving it to the shop and back for the O2 sensor that:
1. While idling, no knock is apparent.
2. Knock comes on around 2000-2500 rpms and more, getting louder
3. Seemingly, the knock gets louder as timing is advanced, but presently timing is at 0* and still knocking at higher RPM's
4. I do know for a fact that the timing set was installed correctly.

Sorry for all the questions, its not that I am trying to get off cheap by 'theoretically' diagnosing the problem here, but I'm trying to get ideas as to what it may be before I go home for a weekend (live 2 1/2 hours away at college) and its kind of hard to find time to work on this thing. It just makes it much easier if I do some research before I even go home, so I dont make a complete waste of a weekend (which I seem to be doing a lot of).

Once again thanks everyone for the help.
-Ben

 

I had a very similar problem after putting the LT1 cam in my Formula. Ran like crap and NO power. Ended up being the same issue 383 had. Lower gear on the timing set had multple key ways and I used the wrong one, had it waaay to far advanced.....

 

A couple things to check:

I've got a 305 TPI and with more than .500 lift, you might have some piston/valve clearance issues.. or over adjusted valves.. Last time I set my valves, I set it to zero lash and that was it.. Others say 1/4 turn.. some say 1/2 turn.. I've even had one guy say up to 2 turns is okay.. I'd recommend 1/2 turn. I plan on resetting my valve adjustment to 1/2 now that my engine is running..

Check to make sure you have the right firing order.. I know I always double check and sometimes you get sloppy and switch neighboring wires..

That's all I can think of at this point..

Good luck,

Bruce89TA

 

Thanks Bruce. I set all valves to 1/4 turn past 0 lash. Base timing is set to 0* and I have quadruple triple checked all plug wires. I think I've read numerous times on here that there should be no piston to valve clearance problems, but I could be wrong (my mechanic seemed to think this also).

I know I should have checked valve guide to retainer clearances, but I didnt want to waste yet ANOTHER weekend getting that done. I honestly dont think that that is the problem tho. I am still leaning towards that one valve spring, I'll have my dad check it out tomorrow. If that's not the case, I may have to pull off the pass. side head and have a look. I'll post back what happens.

Thanks all,
-Ben

 

are you running an aftermarket timming set? before you go pulling off the head check your timming set i was so sure mine was right and i pulled off my head i thought i had a broken ring cause i had one cylinder pumping up to 220 on a compression test it was my timming set all along do a compression test and a leak down they tell you alot dont rule out timming set yet later

 

The timing set is stock (new chain) gears were good. My mechanic said the stock gears only had one timing mark, and it wouldnt even run if they were wrong anyways.

 

ok but id still do a leak down and a compression test helps you pin point the probs later

 

Ok Im gonna do the compression test on the rest of the cylinders. I did 3 of the 8 cylinders (3, 2, and 4) last weekend (didnt have time for all 8) and they were all perfect.

Can someone give me a real quick idea of a leakdown test. I've seen that phrase used many times but not sure exactly what it is...

-Ben

 

its a guage kit you can buy or rent you thread the hose into you spark plug hole the othe side of the guage you plug into you air compressor the guage will show you how fast the air leaks out of your cylinder also if you listen closely you can hear where the air is leaking valve seals ring it is a really good test id do it before you tear anything off later

 

87,

You'll need a consistent source of compressed air. Since you already have a compression tester, you have the most difficult part of the leakage tester. The rest can be purchased for about $85.00 or assembled for about $25.00. You'll need a pressure regulator, two 100 PSI gauges, and some fittings. You'll also need a 1mm or 0.040" drill (#60).

 

Ok thanks a lot guys, that helps a lot. I'll try and get this done and see what I come up with. I dont know why there would be any problem whatsoever with rings/seals/valve seats/etc, everything is freshly put together and there were no problems before (motor was in excellent shape). But I guess you never know, I'll give it a try.

Thanks,
-Ben

 

whoa whoa whoa! your running how much lift with stock springs. not stock replacements but the ones that came on the car in 87? dude, those badboys are only good to like .450 lift. you have probably killed those springs. i am not sure if i would trust your mechanic friend either. what size valves are you running? even with porting and polishing, that cam is way to big for a stock spring/valve combo. man, i wouldn't have rung anything over about .442 (crane blue racer cam) in that combo. a cam that is too big can also slow you down.

 

I realize that too big a cam can slow you down, but Comp claims this cam is excellent in low to mid range power so I dont think its trully a high RPM cam. I am pretty sure that this guy checked the stock spring lengths/max lifts/seat pressures when he picked out the cam, but you may be right. That or he could have gotten some misleading info, because I know that this guy knows what he's doing. He said there may be a possibility that I may need spring spacers to increase the seat pressure, but that it should be OK as is. He wanted to take the heads with him to Columbus OH to have the springs and everything tested with some high tech machine, just to make sure everything lines up ok, but I didnt want to wait yet ANOTHER week. Guess I probably should have now, cause it's taken me WEEKS of weekend work on this thing anyways, it could have saved me quite a bit of trouble. Guess I learned the hard way. Well, I guess the question now is, what can I do to find out whats going on without pulling the heads back off. I don't have the time to be messing with this thing for weekends on end, so I'm just going to send it to a mechanic I know to check this stuff out, and save me some time. By the time I spend $20 every weekend in gas, plus waste my whole saturday, it will probably just be worth it to pay my mechanic to take a look at it. He can probably tell whats wrong with it pretty quickly.

 

Wait a minute, straighten me out here if I'm wrong, but I see people on here successfully running the Comp Cams XR262 to 268 (in the 305 of course) and even the XR262 has a lift of .462/.469 and you are saying the max lift you would go is .442? I'm not trying to be smart, I'm just trying to figure this out. Am I correct here?

Even so, assuming the clearance was CLOSE with stock valve springs, and assuming that I overtightened this one valve, then possibly I could have smoked just that one spring from being so close to it's max lift already (the one the rocker arm nut is significantly tightened more than the others) and that could be causing problems now?

 

ok that is entirely too much lift for a stock spring.

 

How many miles were on the car when you tore it down to do all this stuff to it. After running the stock springs for a long time the get to weak for even a stock cam much less an aftermarket cam with that much lift. I understand not wanting to spit out more money or take the time to do it but you are just asking for problems, and it sounds like they may have already replied. Even if this isnt the current problem you are liable to have your valves float pretty easy at higher rpms.


Ben

 

Car had about 75,000 miles mostly highway miles. It's never been ripped on.
Ya being a college student has quite a few disadvantages, one of them being constantly short of cash. Figured I'd save a few bucks if the stock ones were ok. I was told that they would probably do since the motor doesnt have an extreme amount of miles on it and since they supposedly would handle the amount of lift the cam dished out, and since this is my first time doing a project like this, I figured I would listen to what this guy has to say. Actually, his actual words of advice were that "if it were him, he would just throw a new set of springs on, they are inexpensive and could potentially save hassle down the road...but you can probably get by with the stock ones, but they may need a spacer to get the correct amount of seat pressure from them."
So he didnt just directly tell me to use the stock ones, I guess its my fault for being cheap.
Either way, I need to find out the problem soon, if it happens to be the springs that are the problem, then I will have learned my lesson. In a way I'm hoping they are the problem, so that its not something more serious. I should find out by the end of the week and I'll post what I find out.

Thanks guys,
-Ben

 

My eyes lit up when I read that you had used the stock LG-4 springs with a cam that has .500" lift.

I recently replaced my dying old LG-4 with a mild 350, and the difference between comp cam springs that came with the kit (to support a XE-262, .460"/.470") and the old stock LG-4's was quite noticable.

As far as I know, or have heard, those springs are only good to .450" max, brand new, and even that figure is somewhat dodgy. I would replace those springs with what the cam manufacturer recommends before some serious mayhem occurs under your hood.

Good luck with it man.

 

Thanks for the advice, looks like I'll be ordering a set of new springs!

 

Ok I was just looking at my Cam Spec card here, it calls for Comp 986-16 springs (Jegs 249-986-16 #) 1.440'' diameter double spring w/damper 120# @ 1.800'' closed, 290# @ 1.250'' open, coil bind @ 1.100''. My question is, will these fit the stock heads (diameter), I looked in my Haynes manual (as well as a search on here) and couldnt find the width of spring that the stock heads are machined for. Anyone have a number or can tell me if they will fit. Again, its a 1987 LG4 (cast iron heads).
For what it's worth, I'm going to just install what the cam calls for, that way I know that it's done right. Shoulda done this in the first place, so lesson learned. Even if it isnt the problem, at least I can eliminate weak and/or broken sprins as a problem right? I suppose I better check all pushrods also...
Sorry this post is getting so long, but I appreciate you guys' opinions. Thanks.

 

Nope those springs will not fit in the existing spring pockets, unless you remove the heads and have 'em cut to install the springs.

Go over to www.competitionproducts.com Email or call their tech people, tell 'em what cam you have and that you need stock diameter 1.250" springs....



HTH

 

If I remember correctly, the stock spring diameter is 1.25" so, no.. the 986 springs will not fit without machining..

 

1.25" .... gotcha, that helps a lot. I'll take a look at that site ctandc thanks a lot!

 

I know you said you're on a budget, but since emissions are out the window you should really get rid of the stock CC Q-jet/computer/dist and repalce them with non-cc pieces. Even if everything was in perfect running order, and new, your stock computer isn't going to be able to take advantage of such a large cam. BTW, word of advice...ALWAYS replace valve springs when doing a cam swap. Even if the existing springs were the right type, after 30-40k miles (or less depending on the application) they should be replaced anyway.

 

Thanks for the advice LT1guy. Ya I think I will replace springs from now on.
Actually when I get money I would like to throw in a non cc distributor and carb. It's just that money is really short right now. I didnt even really have money for what I've already done but I had to take advantage of my car being put away for the winter. Probably wont happen for a while as I am getting married this summer and will still be in college for another couple of years, but ya I do plan on it sometime. Just gotta do what little you can when you get it in my case.

 

I dont totaly agree with him this. There are several people on the boards makeing good power with them. They have better manners on the street. They are 650 cfm stock, and you can open them up to 750 just by grinding away a tab on the linkage that stops them from opening all the way. If you do this and get a good set of secondary rods and hanger it will perform pretty good. I actually still have the cc q-jet on my cammed 350 with ported heads. I just got it together and havent been able to drive it far yet or get the timing or carb adjusted just right, but I can spin my tires clear through first and into second. This is with bridgestone potenza RE730's. They are one of the stickier street tires out there. These carbs also will tend to get better fuel mileage because of the smaller primaries and the fact that the computer keeps your air fuel ratio good as long as you are in the primaries.

Ben

 

I was wondering about something today at work. Can anyone give me a really quick lesson on cam degreeing. Now that I think of it, I hope I was right when I installed it, so then I can eliminate the possibility of it being off.
Cam card says the specs are for the cam installed at 106 intake center line. So my question is, would this be just the normal cam swap, aligning the timing marks on the bottom and top gear as, say the stock timing set, would be marked.
If someone could answer me this question, I can hopefully eliminate the possibility that it is installed wrongly. I wasnt aware that I may need to degree the cam (if indeed I did), I thought degreeing was more for the top-horsepower-pushers out there, kind of like a fine-tuning thing.

 

As long as the cam was ground right you should be fine if you just lined up the dots. Some people get adjustable timing sets so that they can change it a couple degrees either way from where the dots line up. This just moves the power band up and down a bit. Some people also degree the cam just to make sure it was ground right.

Ben

 

Excellent, thanks.

Here is what I am down to, and I will be checking these things out this weekend (no particular order of what I think is most probable):

1. collapsed lifter from me overtightening to try and compensate for the ticking caused by pushrod/pin interference (now taken care of), but if the lifter is totally collapsed from that, even though I have backed off and rechecked all valve lashes, it could still be permanently damaged/collapsed correct? I think if one is collapsed I should be able to push down on the pushrod by the rocker arm and it should go down due to the oil bleeding out of the lifter correct?

2. possible springs too weak for cam, causing the retainers to hit the valve guides or other interference in spring travel. I will do a complete visual check of all springs to check for cracks, and maybe pull a few to see if they are weak (probably have to use a spring compression tool correct?) I talked with the guy who selected the cam today, the guy he talked to about my springs was his machinist who he uses a lot, I guess, and he said they are good for .500 lift, so I'm not going to completely rule that as the cause yet. I dont want to have to go through changing all the springs quite yet if I dont absolutley have to. Even if they are weak, I dont see where the knocking is coming from unless there is a valve bouncing off the seat when it closes, but I dont know of the probability of that is, let alone why it would only be on the pass. side of the engine, seemingly.

3. from not running with the O2 sensor, it's been running completely rich for a certain time (the whole while I've had it together and messing with it to be exact). I'm thinking (but not certain of the validity of this idea) that there could be excessive carbon builup in the chambers from this, causing detonation at higher RPM's (hotter combustion chambers). Although it doesnt seem like a ping, I'll keep this as a possible cause for now and mist some water in the carb this weekend to see if this helps any.

4. i have a bolt(s) loose somewhere. I was reading through some old posts today and noticed some people had had bolts loose on the balancer and other places, causing loud knocking sounds. I'll check all bolts, although I dont know if something like this would be enough to make a count on the KS

All of these things could potentially cause knock, which leads me to believe that the computer is retarding the timing to compensate due to the knock sensor picking these up. And that is what (at least partially) is causing it to run with not a whole lot of prep. (My complete theory haha)

My dad has been trying to look at it when he has time at night after work. Says that it will sit there and idle beautifully, no fluctuations or any other problems. Car revs with flawless hesitation also. If it wasnt for the knocking, it would seem almost perfect. Besides the lack of power of course, which I'm guessing is from timing retardation.

Another thing. I am going to listen to the frequency of the knocking and try to confirm that it's the speed of the valvetrain and not the crankshaft. Just to make sure. Even so I'm going to completely eliminate the possibility of a knocking rod right now. It didnt knock at ALL before so there is no reason why it should now.

If anyone else has any good probabilities that they think I should check, please let me know, I'm gonna use this as a start for a checklist for this weekend. At least I can eliminate some things from the mess.

PHEW ok im done now....

 

You could try taking a piece of heater hose and putting one end to your ear and using the other to try and find where it is coming from.

Ben

 

I wasn't knocking quadrajets...only cc-control on carbed cars. You can change whatever you want on the carb, but what about the ridiculous advance curve? Most of the HP in swapping to non-cc comes from gaining control of your ignition timing. Personally, I'd rather change weights and springs than go to all the effort of burning chips for a MickeyMouse system like this. I'm not saying there isn't room for improvement on the stock setup, only that to make real HP its best to get rid of the computer. I think anyone who has driven both will agree.

 

Your stock heads have spring seats that are probably machined to 1.260". You do the math.

1. You may not be able to compress the push rod against the lifter plunger and force the oil out, unless you can generate a couple hundred pounds of pressure on the push rod. The most reliable method is to set the lash with the engine hot and running if you can (unless you're using high-bleed lifters).

2. What is the spring seat pressure and rate?

3. If you're using the ECM, you NEED to have a working O² sensor. Even though you can "cheat" by adjusting the primary side idle fuel mixture correctly, the ECM will never reach closed-loop mode without an O² signal, so you're always in "Limp-Home" mode for fuel and spark trim. Awful.

4. Loose bolts aren't a good thing, no matter what. I hope none of those are on main and rod caps.

If you suspect a main or rod bearing, or wrist pin noise, you can usually identify it by killing the spark on the suspect cylinder and running the engine at about 1,800 RPM.

 

I agree that it would be nice to be able to adjust the timing like on a non computer controlled setup. I also think that it depends on the application that he is going to use this car in. If you want better fuel mileage on the street you could stick with the cc quadrajet, and get a aftermarket chip for the better timing curves. I am running this setup on my 350 with aftermarket rods and hanger in the secondaries. I plan on getting the gmpp 350 HO chip for the computer to give me the better spark tables. I should still be able to retain better fuel mileage and get at least real close to what the non computer controlled guys can hp wise. And for myself, if I cant thats ok too, because I have an LT1 that will be in the car eventually and it will def be comp controlled lol. I know my car will car will spin clear through first and into second with my potenza re730's on the back, and I had the timing set wrong, and havent messed with the carb other than secondary rods and hangers. This is also with the LG4 timing tables which do honestly suck. I figure that once I get the chip and my timing set right and do some tuning to the carb it should be good enough to hold me over till the LT1.

Now back to our regularly scheduled programming.

Ben