StealthElephant

I'm hoping somebody can help me.

I'm having major problems with my new 350. I just can't get it to run right. It drives around perfectly, very smooth. If I come to a stop at a redlight it will stall. It drives fine, but if it sits in drive for more then 15 seconds the whole car beings to shake, the engine slows down and stutters and stalls. Reving doesn't help, throwing it in neutral doesn't help. You can prolong it, but in the end it will stall. Restart it, drive away, and it will drive all day long fine.

I also can't get the car to stop pinging. I can retard the timing to the point where it will only ping at 40+MPH but I can't get rid of the timing. Someone told me that maybe I need to jet the carb up and that if I ran a little richer my pinging would stop. That my powervalve is wrong. But if I can't stop the pinging at 40MPH under the lighest load, how can I ever expect it to not ping at WOT. Too much compression is what I'm starting to think. 10.7:1 , everyone told me I could run that. I called summit and asked for 10.7:1 pistons and the guy said that was too much for pump gas. Everyone who helped me build the engine told me 93 octane and I can run 10.7:1 domed pistons all day long. That if the pistons are advertised 10.7:1 that when the engine is built the actually compression would be about half a point less.

I'm being told SOO many different things. That my plugs I'm running are too hot and that the car drives around fine because they stay cooler when the car is under load, but when I'm in idle that they are getting heat soaked and thats why it stalls after a little while.

The car will stall at WOT. Basically, while adjusting the timing affects it, the car is stuttering and stalling from a dead stop at WOT. Someone told me that my floats need to be adjusted and that when the car jerks the fuel moves and cuts out. But I can adjust the timing of the ignition to the point where it just stutters and runs like **** until the engine hits like 2000RPM.
Nobody I know seems to be able to diagnose the problem. Carb, spark plugs, compression....the engine seems mechanically sound, no odd sounds etc. Also, when I shut the car off, it knocks after, I have to turn the engine off in drive.

Just so much wrong with the engine....the thing would idle at 300RPM when we first tuned it though. It drives smooth for the most part. But it wont' stop stalling, pinging, and you can't go WOT.

Any help would be great. Anyone with a similar build who could help me out....this is killing me. I've got a brand new Accel HEI in there, everything with the induction/ignition is brand new.

92 zzz28

Well, I don't know how much help I can be but I can throw out a few suggestions.

First of all, I will say that your compression, in my opinion, is too high for iron heads. I think you are running iron heads anyway, if I am wrong, then your compression is okay. Cast iron heads don't dissapate heat as quickly as aluminum, hence less static compression. So, if I were you I would try and use colder plugs. To give you an example of just a plug swap. My new engine combo, see sig, I first used the same heat range plug as I had in the old combo with about 11.1:1 CR. The engine ran okay, but had a lot of stumbling and hesitating. I changed the plugs to the stock heat range (hotter than what I had used to begin with) because my CR is now low. To my surprise, the engine runs much smoother. I still have tuning issues but it made a huge difference.

Another plug story involves a friend's Mustang. He was running over 11:1 CR and was experiencing lots of detonation. Many people told him to do all sorts fo things. First, I suggested trying a colder plug and that did it. His knock was not as bad sounding as yours, but maybe it is worth trying first.

Hope this helps...

F-BIRD'88

10.7:1 is a little high even with vortec heads.
But it should not be high enough to cause the serious stalling and pinging at part throttle you are experiencing.
But it is marginally too high and is adding to the problem.

Does the motor run hot on the water temp guage?

A bad or marginal cooling system would really add to the problem.
the under hood temps on a third gen are bad enough.

I'm thinking a sticky valve guide, grabbing the valve when the motor is hot. Pinging will definatly over heat the valves.
A marginally tight valve guide would grap the valve stem when this happens.

Need to go through and eliminate all the other more likely suspects first thou. Like a vacuum leak faulty carb (wrong jetting, dirt infected etc) Ignition fault.

On a th700r4 a faulty converter lock up solenoid in the trans will cause this too. This is a common fault and only does it when the trans is hot.
You could have two separate issues.

Will the car restart immediately after stalling or does it require a cool down to start and run smooth?

StealthElephant

It fires right back up, I have noticed that if I stall and restart it right away, I only get about 5 seconds of idle time before it starts to stall again. Whereas if I drive for a sec, and the engine gets load around 15-20PMH I will get the full 15sec. The longer I drive, the longer I get at a stop before it stalls. I've driven around the block, then sat in front of my house to diagnose the problem and see what affects the stalling.

My engine had major vacuum issues when we first tried tuning it. Like 7inches of vacuum at 700RPM. We went through 3 points distributors and it would NOT hold idle under 1000RPM. We had a dead spot between 500RPM and 900RPM. Basically, it would idle at 500RPM BEFORE vacuum advance kicked in, but if you tried to get it to idle at like 750 the vacuum advance would kick in and rev it to like 1100. We had a dead spots between 500-700RPM, where either you had no vacuum advance and the idle was too low to go into gear, or the vacuum advance would kick in and it would rev way too high. We thought we had a vacuum leak but it made no sense, we redid the intake manifold, that sucker is not leaking. I'm very confident when I say I don't have a vacuum leak, that was our first guess, and we checked for that, resealing the intake had no effect.

The engine was not behaving properly from the start, the only time we could get it to be decent was with the new accel HEI distributor we put in. It wouldnt' even drive or hold idle until the accel unit. Now it idles anywhere we want, but everyone whos helped me work on my engine says that something is wrong with it. Mechcanically it's sound, but something is making it not run right. My boss helped me build the engine. he is completely over his head, he told me that my engine should not have such bad vacuum and that it should not be so sensitive. I mean, Comp cam advertises 15inches of vacuum at idle, I could barely pull 10 with the accel unit. And that was with a 750 Idle out of gear. I have since jacked the idle up to around 900 out of gear so i probably have a little better vacuum. When we reved the engine to 2000RPM out of gear while tuning it would pull 17inches of vacuum. We checked for leaks.....and it idles decent, which is what is so weird, because it will idle SOO smooth and then suddenly get rough and stall. Its not like I have a rough idle all the time. My brakes work fine....nothing makes sense.....


I have no lockup, Ive got the TCI lockup kit on order.

It pings when warm or cold, and the pinging hasn't seemed to "get worse". I've heard full on pinging on other cars, and I seem to have a mild case, but then again, thats only at very part throttle. I don't have my water temp hooked up, nor do I have my tach hooked up. We tried hooking the water temp up and it didnt' work. I'm supposed to be heading over on wednesday to do that and change my plugs etc. I have no tools at my house, all the work is at my bosses garage. Basically we spend 2 months working on the engine, he couldn't figure out the problem. He basically told me he had no idea why the engine wouldn't run, and that i was going to have to take the engine to a shop. That day my other buddy came over with his accel HEI distrib and told me to just put his distrib in to see if it helped, he and I threw that in, and that was the first time we ever got the engine to idle and run at 750. So we had 3 prior bad points distributors. At that point I took my car home and I am only driving it to school, its my only car, this was suppsed to take 3 weeks, not 3 months. I have no choice but to drive it...I can't even change my plugs till I get back to my bosses house. I knew I was going to hit snags and such, but this has been ridiculous.

If I could get the car to stop stalling I would be happy, even if we ignore the pinging, it makes no sense why it just stalls after 15 seconds. I have fuel, I have my stock inline pump with a 3 port regulator, the pump runs....Ive checked the floats (I have the clear things so you can see the fuel level) and they are set fine...my only question is the idle fuel mixture. I'm more interested in why my car stalls then why it pings though im sure theres a connection. i can only assume that im not running hot....I mean, the pinging doesn't get worse the hotter the car gets, should i get a 160* tstat?

sorry if ive got alot of "holes" that need to be answered before a good diagnosis can be made, but im just looking for any ideas on what is going on so we can slowly eliminate problems.

thnx

F-BIRD'88

Hummm sounds more complicated than most problems.

First, vacuum advance has nothing to do with the idle.
If you have to use vacuum advance to make it idle there is something wrong.
With the vacuum plugged in to "ported vacuum" there should be no vacuum signal at idle. Idle should not change when you unplug it.
Unless the carb throttle blades are way too far open. that would explain the flat spots in the throttle response.
Are the throttle blades way too far open at idle?
Remove the carb and look at the throttle blades. the idle transition slots should only be showing a little under the throttle blades. "about .030" if its much different than this the carb will not idle or respond to throttle smoothly at and off idle.
Does the car have a healthy spark. Try grounding the motor to the firewall. My car will miss every time you rev it up unless the motor has a ground wire directly attached to the firewall from the block. Don't know why but it does. as long as the ground wire is on its fine.
To eliminate a carb leanout condition (fuel, vacuum leak) related problem (fuel perculation ,vapour lock) shoot some propane (from a propane torch) down the carb when it starts to stall and see if it recovers. If it suddenly recovers with the addition of a little propane its starving for fuel.

At any rate get rid of the hi pressure intank fuel pump and regulator and get a 7psi fuel pump for the carb as soon as you can. You'll be much better off. A Carter #4594 electric pump is not expensive, is reliable and needs no regulator or return line.
Loosen the gas cap, if the tank vent line is collapsing cause of heat, the car will stall cause the tank will come under vacuum.
Once you've elimated all possible fuel and spark faults that leaves a mechanical problem as a possibilty.
Could be a sticky valve or a sticky or collapsing lifter.

Really need to know how hot the motor is running at.
Do any of the sparkplugs appear unusual? lean/clean/ white?
black/carbon fouled?

StealthElephant

The #1 plug came out at one point in the middle....it was pretty clean....the engine def was running a little lean from what the plug looked like, but nothing major.

Ok, I'll explain it again a little clearer.

We would set the base ignition timing at around 10-12* advance with the vacuum advance unhooked and a vacuum gauge hooked up in its place. If we set the base timing to say, 500RPM then hooked the vacuum advance up, it would not advance, just sit at 500, obviously, we couldn't shift into drive w/o stalling with it that low. If we put the idle to say 700, then hooked up the advance, the advance would kick in and sent it to 1000RPM. We couldn't get it to idle with the first 3 distributors. The new Accel HEI unit went in, and it was all fine, we could set the base idle to about 500RPM and when we hooked up vacuum advance it would rev up to about 700 RPM which was perfect. Then we could adjust the idle screw to whereever we wanted.

The spark is bright blue, again, the #1 plug was pulled and we had perfect spark. The engine was willing to idle at 350RPM with the vacuum advance off, so we know combustion is happening fine.

If the car is "leaning" out in idle why does it run smoothly for the first 5-20 seconds?

I'll try and get more info, thnx

five7kid

iTrader: (14)

That is indicative of requiring too much throttle opening for idle. You're uncovering the timed vacuum port, which means you've also got the transition slots exposed too much at idle.

Try this: Take the carb off, turn it upside down (might want to drain the bowls before you do this), adjust the idle speed screw so the transition slots are exposed about the same as their width. Install the carb, and adjust the idle with just the mixture screws as best you can (you may have to blip the throttle by hand to keep it running until you can get the mixture screws close). Then do the final idle speed adjustment with the normal screw. Hopefully, you won't have to open it up too much. Also, try to do your adjustments with the car in gear (safety first here - have the park brake set, the wheels chocked, someone in the driver's seat to hold the brake pedal so the car doesn't take off on you).

F-BIRD'88

Give it some propane to see if it is fuel starved when it starts to act up.
Could be the pump, a collapsed line or the tank vent.

StealthElephant

Well the idle problem was fixed with the new distributor. Right now I'm trying to figure out why it's stalling. It must be a fuel issue since it idles for a short time perfectly and drives fine.

My only thoughts are that for some reason the carb is not getting fuel after a certain amount of time. I also believe maybe the spark plugs are getting hot or something of that nature. I can rev the engine BEFORE it begins to stall, and if I keep reving it I can keep it from stalling, it will be fine. If I wait until it starts to stall I can't recover it, it will rev up once or twice then just completely cut out.

I just don't get it, it drives around all day long. You come to a stop, it idles perfectly for 10-20 seconds, then just gets all rough and ****ty. I've just let it stall out, it will first shake and get rough, the engine will slow down, like slowly drop RPM til it just cuts out. Again, if the fuel is cutting out why? I have an inline pump.

RB83L69

How much fuel is in the carb bowls when it dies? That'll tell you in a hurry if it's really running out of gas. Which is not completely impossible, if you have an electric fuel pump, and it's wired through an oil pressure switch or something like that.

scottland

im not sure what carb your running, but make sure your choke is working right, if that bad boy starts to close at a idle, it will stall the motor in a hurry. also double check your timing, and make sure that TDC on your timing tab is really TDC on the #1 cylinder.

im not all too keen on electric fuel pumps, but i do believe they will pump with the ignition switch in the run position, so try taking the fuel line off of the carb, and putting it in a gallon jug, that fuel pump should fill the gallon jug in a hurry, and the fuel should have a lot of pressure, if its not, check your fuel pump.

StealthElephant

When we set the regulator, it was giving 7-8PSI on our gauge.

I will definately look at the bowls while it's idling and see if they drop.

The electric choke on my carb is not set up, it's locked open all the time.

TDC of #1 was checked 3 times, its within 1-2 degrees.

The electric fuel pump was wired so that it would turn on when the key is put in the "ready" position (it turns when my electric fans do, though they're not hooked up together)

We basically just kept testing power lines til one of them went on when the key was turned, when I turn my key (not starting) but when I put it in the ready postion I hear it turn on, it's pumping fuel, because when we were adjusting the floats my boss couldn't get get the gasket to reseal and fuel was spraying everywhere, I had to put the key in the "off" position.

430T/A

what fuel pump are you running? I'm assuming by your posts that it is a factory pump. if it is a tpi fuel pump, a tbi or a 2.8 pump it will not ever work properly. you need to drop the tank and pull the pump out. a mechanical pump will probably fix alot of your problems.

I cannot emphasize this enough

THE FACTORY V8PUMPS SUPPLY ALOT OF PRESSURE AND ALMOST ENOUGH VOLUME, WHEN YOU USE A REGULATOR TO GET YOUR DESIRED PRESSURE, IF YOUR USING A TPI PUMP WHICH CAN SUPPLY 50 LBSM AND YOU TURN IT DOWN TO 7 OR 8, YOU CUT YOUR VOLUME INTO PRACTICALLY NOTHING!!!!!!!!! IT WONT WORK!!! YOU NEED A CARB SPECIFIC PUMP!!!

StealthElephant

Is that the cause of my idle problems? Why it drives fine but refuses to idle at lights w/o stalling?

Are there any inline pumps that work with a regulator? I want to have the pump there for the time when the car goes back to EFI.

five7kid

iTrader: (14)

That is way over-stated.

You need a 3-port regulator that includes a return line. The pressure to the pump will be controlled by the reg, and the excess flow will be returned to the tank via the return line. When demand increases, the flow to the carb will be increased by reducing the flow in the return - sensed by the reg as a pressure drop to the carb. Use of a 3-port reg when going from EFI to carb is discussed often on these boards (comes up a lot on the carb forum), and many, many people run the 3-port successfully with the factory TPI in-tank pump.

The problem with a dead-heading 2-port reg is for the pump (it will burn it out), not the carb. If you are using a 2-port reg, then for the sake of your pump's health, get a 3-port reg with return in there. There is a possibility that a 2-port reg would not control pressure to the carb properly and cause flooding, but that is also possible with a 3-port reg.

You need to gather information such as fuel pressure, fuel bowl levels, etc., as they exist when these problems occur.

By the way, if your idle speed still picks up when you connect your vacuum advance to the timed (or ported) vacuum source, replacing the distributor did not solve all of your problems.

StealthElephant

I have a 3 port mallory reg, I researched before I did anything, everyone said as long as I had a return line I would be fine. It doesn' t make sense, the pump is running fine, I have fuel. I'm still going to check, I have sight glasses on my carb so I can see my float levels or whatever.

430T/A

Check the volume of fuel your getting. thats the bottom line, I had bad luck with the 3 port mallory regulator so I a weary of using it.

BUT, if he is running the 2.8 pump that will not work. thats where I went wrong, if he is using a TBI or a TPI pump he should be ok. teh 6 cylinder pumps have alot of pressure but no volume.



It seems as though you may have other problems. I'd first to a check of the fireing order. sounds like you might have it off, also check for vaccum leaks. have you tried tuning or re-jetting the carb? I'd also check your valve lash its possible its to tight on a vavle. a qucik way to make sure your vavle are sealing is to hook a vacuum guage to the intake manifold and fire it up. if the needle fluctuates at all at a constant rpm, one of your vavles is not closing or sealing.

RB83L69

I doubt it's a volume problem, as such. Volume problems show up at extended WOT (through the lights), pulling trailers up hills, etc.; not idle.

Still sounds to me like the pump stops pumping at idle for whatever reason; after a while the carb drains down, that's all she wrote.

If you can goose the throttle every few seconds and keep it running, that's a pretty good sign that for whatever reason, it's not pumping fuel at idle. Empty fuel bowls would be the proof.

There should be no vacuum at the ported vacuum port with the throttles at idle. You'll never get it to idle right if the timing changes with the intake vacuum. Your vac advance shouldn't start to come in until the throttles are far enough open to hold it at 1000-1200 RPM.

StealthElephant

I will do that.

Valve lash is as close to perfect as it can get. Firing order is perfect. We attached an air compressor to the spark plug port, and pumped air in, no valve leak. We did another compression test, 210PSI. The engine "seems" to be mechanically solid, no odd sounds.

I will def see if my fuel bowls are drying out and see if the RPM fluctuates. I can't remember if it fluctuated when we tested last time. I think it was "pretty" good. How "consistent" should vacuum be at a constant RPM? Like....how much "jumping" is a positive leaky valve?

?? Ok, so the carb has a vacuum line that runs to the distributor vacuum advance port, that is what controls the vacuum advance. Your saying when we pull the vacuum advance line off the distributor and hook our vacuum gauge up to it and set base ignition timing. That once we are satified with the mechancail ignition timing (say 8-10*) that once we take that gauge out, and replug the vacuum line back intro the distributor that the idle rpm SHOULD NOT change? So if we set idle with the distributor not hooked up, when the distriubor vacuum is plugged back in the RPM shoudl NOT change? I'm very intrested in this because the guy who helped me build my engine is telling me that it SHOULD go up.

F-BIRD'88

Not if you have the vacuum line attached to the right port on the carb.

The right port for vacuum advance is Ported vacuum.
the other one is full manifold vacuum.

When the carb blades are opened the right amount at curb idle
there will be little or no vacuum at the ported vacuum source.
If the throttles are too far open when at idle then there will be vacuum there.

The other vacuum port will have full manifold vacuum available reguardless of the throttle position.

Hook it up wrong or have the throttles positioned wrong at idle and the idle will go up and down, because the ignition timing is varying on the rise and fall of manifold vacuum.
this self propetuates a surging idle speed . Causes more tuning problems than it will cure.

StealthElephant

Holy ****, so I could have my distributors vacuum advance hooked up to full vacuum instead of ported vacuum and that could be why I'm having so many problems. I've noticed that my pinging goes away under WOT, and is actually worse on the lower end under part throttle. Does that mean if I have the wrong vacuum port hooked up I could have FULL advance WAYYYY too early which could also be why I can't retard the timing enough to stop pinging? Anyone know which port on the holley street avenger is the ported vacuum? I know for a FACT when we were plugging in the vacuum advance that nobody looked at the instructions. Thats what the guy whos built 100 engines before was supposed to take care of....

I can't say enough for all the help you've guys have given me. Thanks

jimmy_mac

The first time I put a holley on a car I pluged into the full manifold port because I was used to the Q-jet. The Q-jets ported vacuum is at the base in front but the holleys is passenger side on top. Hope that's all your problem is.

five7kid

iTrader: (14)

It's been a long time since vacuum advance has been intended for full manifold vacuum. But, some old schooler's still do it that way. If you do, you should be using an adjustable vacuum advance so you can tune out the part-throttle pinging.

The ported vacuum source is located on the passenger side, about mid-way up the side of the carb, in front of the choke.

It's still possible to have part-throttle pinging problems using ported vacuum. Again, that's where the adjustable vacuum advance comes in.

StealthElephant

Yep, the ported vacuum had a nice rubber sock over it. I put the vacuum line on that one, and bam, when I started my car, it was reving much lower. I put it in gear, it barely made it out of the driveway. A little tinkering with the timing and a slight change of idle screw and it was running like a champ.

I don't have stumble or bogging at the low end, if I punch it, my tires spin (first time, it was stalling and bogging terribly before, probably from having full advance to early) I get instant response now, and the low end pinging "seems" to have gone away. I think it was still pinging a little, I couldn't tell. before when the car was fully warmed up it was noticable from 20-40MPH under load, I thougth I heard something but I'm not sure, a couple of my rocker arms sound loose as they are making a "clacky clack" sound. Anyone ever hear of rocker arm clearance problems...because my valve covers are shaking alot, my one buddy said they seem like they are actually hitting the top of the valve cover slightly. now i don't know if that "pinging" sound ive been hearing has actually been my rocker arms clacking, but again, the sound goes away when i let off the gas, only under load does it make the sound, if i just maintain speed the sound goes away. It doesn't sound like pinging anymore, i hear a clack and my carb sucking air, it def doesn't sound like the pinging i was having before. i need to get some people to listen.


The one thing still not right is why it stalls. Now, after tuning it and driving it around my neighborhood for a while (im sure my neighbors didn't appreciate that WOT tirefest) I shut it off FULLY warmed up. For the first time it didn't knock and run on after I shut it off. I've been shutting it off in drive to keep it from running on since i got it running. Then I did the ultimate test, will it stall in gear at a dead stop. I noticed two things, first off, it held idle for almost a full minte before stalling compared to the normal 15-30 seconds. Nearly double the time I normally get. Next, the car idled "smooth" for the first 10-15 seconds, then got "rough", the car started shaking, I felt the engine sorta "skip" then resume, "skip" then resume over and over. This is where it normally stalls, it did all the things it would normally do before stalling, it would shake/skip and sound like it's stumbling, but instead of stalling, it would recover itself, just kept repeating the skip/stumble but then recovering itself. it went on like that for almost 25 seconds, I was crossing my fingers hoping it would keep recovering but it did eventually stall. The way it was idling the last 30 seconds was like rough and lopey compared to the normal VERY smooth of the first 15 seconds

Now i'm wondering if ive gotten 1/2 way to fixing my engine. Maybe some colder plugs will help me get better idle. When i got the autolite plugs im running right now, i asked for stock plugs for a chevy truck with L31 (vortec) heads, so he probably gave me standard temp plugs. i can only hope colder plugs will help my idle quality....i need to get some 2nd opinions on if im still pinging, ive been listening to the car so much i can't even tell

I am going to my friends garage and hook my tach/water temp up tomorrow night. So in about 20 hours I should have my car tuned with new spark plugs.

Again, thanks to everyone...it's def running better.

Dave

nape

iTrader: (1)

My '91 TA with a 350 TPI will do the same thing if I gap the plugs to the stock gap of .035".

If I gap them to .040" it runs great. It's the weirdest problem I've ever encountered, I was sure it was a vacuum problem until I did it. The only reason I thought to change it is because it ran great before the plug change.

ACDelco R45TS plugs if you're wondering. Stock heat range.