Tired of fighting with this car. Anyone want a crack at it?

32 ratsass is on to something ,I also heard they could also short out but dont quote me on that,Im a gm guy

 

what does the plugs look like?

 

On my engine I have a roller cam, a fairly high lift, some where in the 560 to 570 range. This pulls my vacuum numbers down really low, around an 11, all of this tightens my tuning mark to a very tight tolerance and plays hell on my carb. If I put a vacuum gauge on the engine and allow the carb to load up, I can see the vacuum numbers start to dwindle.
My cam idle spec is around 1100 rpm. If I take and set my cam at 1400 I get an elevated vacuum of about a 15, I still see a dwindling vacuum number even if I accelerate to a higher RPM. If I swap out the springs so that the lower vacuum pull opens the carb up to breath I get a much better result.
It's fairly easy to swap out needles and springs on these carbs so that's how I adjust the mix.
If you had this much of a vacuum leak you should see it on a gauge as it happens and not be able to pull the vac numbers up. Keep in mind, as you load the carb up, you are fouling the plugs, so almost every time this happens you will need to clean them up to get a new test run.
If you have any kind of a cam in the engine this notion of run out of the box is done, anything that lowers the vacuum or draws on the vacuum system is just going to drive you that much more insane.
The other question would be how are you running your block evacuation system? Do you have your valve covers capped? My engine was giving me even more hell until I ran a PCV from one valve cover into the carb front and put a breather on the other, this seems to temper the air a bit and not cause such a radical choke reaction.
I think that it's most likely that sooner or later I will de cam my engine a bit, this would make my life a lot easier.

If it were this situation with the plate moving, would this be something that were attached to the vacuum system. See it just never adds up that the engine will die and then clear and miraculously restart. It seems as if the fuel is just liquifying in the intake or fogging in there, then it dies and you wait a couple of minutes and she teases you and fires up again only to load up and die. I think the fuel turns to liquid in the intake. I have an MSD electronic on mine so it's not the plate.

 

Starving for fuel? Could be a bad fuel pump, bad hose sucking air between the pump and the tank. Put a fuel pressure gauge next to the carb and observe the pressure when it runs bad or dies. After it dies look in the carb and work the butterflies and see it the accel pump is squirting fuel.

 

I would try to rule out a jumped timing chain. Also Have you checked fuel pressure? Too much or too little can cause unusual problems. Just my 2 cents.

 

Wow Lobucrod i guess i type too slow....

 

Do you have a pressure gauge on your fuel line? That will tell you if you have fuel pressure. If you have pressure it won't be the pump.

 

The vacuum leak sounds logical. While the choke is on, there's extra fuel for the additional air of a vacuum leak. As the engine warms up, the choke comes off and it leans out and dies.
Once it dies, have you verified the choke is opening up and isn't sticking shut?
Once it dies, look down into the carb (or use a mirror) while opening the throttle. (don't crank the engine while doing this it could backfire in your face) If you see fuel squirt as you open the throttle, it's getting fuel.
Get one of those in line spark testers that snap between the sparkplug and plug wire. (usually pretty cheap) that light up when voltage passes through the wire. If it doesn't blink when you go to restart it, then it's not getting spark.

 

Looks like I type slow too.

Just a thought, Edelbrock carbs like around 5.5 psi of fuel pressure. Most mechanical pumps put out around 9 psi or so.

 

If it was up here I would sort it out for ya. Pm me if you want maybe we can talk and I can help you sort it out at least i should be able to get you pointed in the right direction.

 

This car would be a good one to hook up to an old Sun scope with exhaust gas analyzer so you could track both the spark and fuel mixture.

I'm trying to think of something that you haven't tried. Are you using a mechanical pump? Ford uses an eccentric bolted to the camshaft which has been known to come loose. When the needle valve closes the pump is harder to move and the tab on the eccentric can come out of the hole and stop turning so the pump stops pumping. When the gas in the carb runs out and the engine stops, it can drop back in as it is cranked to start. A fuel pressure gauge would rule this out.

 

Check your valve guides, it would account for a "vacuum" leak and rough idle. Once it is warm you have excessive vacuum loss and stalling.

 

Take the gas cap off just for the hell of it. JC

 

I second this one. Just had it happen to me on my 64 Galaxie last fall on way back form the exhaust shop. Was a very common problem back in the day. I keep one in my trunk along with new points. I migh have missed it but you do have " unresisted" 12 volts going to your Pertronics right?

 

Keep in mind, if there is a vacuum leak with the intake gaskets, it may not be on the top side. I had one that had me chasing my tail for several days. There was a vacuum leak into one of the intake runners from the lifter valley so the acetylene around the intake ports to check for a vacuum trick did not work.

It was doing the same kind of thing as yours. It ran half decent until it warmed up & the choke came off, then it died & would not restart until it had cooled off completely.

I only found it after I got mad & yanked the intake. the inside of one runner in the head was fouled with oil from it sucking in the engine oil. Are any of your plugs fouled with oil?

 

I ran my Pertronix billet distributor on a resisted wire (pink) wire on a ford for a while, they say to bypass any ressistor wires and get a full 12V feed do to higher RPM ignition flutter, I never noticed any flutter, only issue I had was getting the timing set, are you using a unresisted 12V sorce?

 

If all else fails check the gas. I have bought gas right out of the pump and it wouldnt even burn with a match to it. It like to drove me nuts before i figured it out.

 

Haven't had a problem with my petronix so far!

 

Before you do anything else what was the original problem? Go back to where you started. Either you started fixing something that was not the problem or you are making more problems.Start with the basics,check the compression,spark,timing,and fuel delivery.Just because you changed a part doesn't mean you fixed the problem,defective parts or mistakes made along the way will only make things worse. Always check the basics FIRST!!! The last car I sold I could not get running right,it was an 1974 Alfa Romeo and it was running on 2 cylinders I changed the plugs,checked the spark but it would only fire on 2 cylinders.I gave up after screwing with the fuel injection and everything else I could think of.The second guy to look at it fixed it in 2 minutes.........The two center cylinder wires were crossed !!!!! The last person that worked on it had crossed them an I went right for the hard stuff. Boy did I learn my lesson that day.So go back to the beginning and start over.Good Luck.

 

there is several threads on this board about pertronix. maybe it is a aplaction mix-up or system malfunction. check the numbers and wire locations.

 

wow wow wow. Thanks everyone! Tons of great ideas to check and check again. I'm making a list and just going to knock it out. Some of the stuff I know (or thought) I did in the past, but when you get so frustrated and walk away for a "little" while and that little while turns into days, weeks, months, it gets harder to remember. Its too hard to go back to all the questions to reply right now, but I am listening to every one of them. I'll keep at it.

 

check the bushing in the distributor, if the shaft moves at all this will change your gap on your points.

 

Sounds like a bad condenser to me. Lippy

 

if it' consistently doing it after 10 minutes then examine ten minute items- what happens in ten minutes-

coils can get hot

engine gets hot and boils the carb- you have a phenolic but check it anyway.

engine gets hot and opens a vacuum leak through expansion.

clogged vent can suction a fuel tank. take off the cap, retest. also crud at the pick up can block it.

You said the fuel line is cool- but also a new exhaust- it isn't aimed at the fuel line back under the car, is it?

Start eliminating things- put a SMALL amount of gas in a known clean boat tank on the fender and run a new line to the fuel pump -if it runs all night, then your issue is between the pump and the fuel cap.

rick

 

Interesting advice from all and I am looking forward to hearing the final solution. I am having a very similar ongoing problem with a 351M engine. Have replaced the distributor, intake gasket, ignition box, ground wire, spark plugs and wires, and even swapped on another carb... Driving me NUTS.

 

Back to the original question: Yes there is a way to check for a worn timing chain. Put a timing light on the running motor. If the timing mark at the crankshaft jumps around under the light, the chain is more than likely the culprit. Chain slop causes the valve timing to be all over the map due to the cam being jerked around. This causes the distributor (cam driven) to be firing at the wrong times. Hence the 'jumping' timing mark at the crankshaft.

 

Frank

Recently, I installed a new Accel 8140c 12 Volt "super stock" universal performance coil which was bolted directly to the head of my chevy 250 inline six. When the weather warmed up (80) and after the engine had been ran for at least an hour with temps at 195 - 205 the engine would not restart. only after I let the engine cool to about 120 would it start. I went through an old parts box and found a "Delco - Remy" coil (which was originally on the engine when I bought the car) hooked it up; problem solved. where was your coil manufactured?

You may consider blowing out your fuel line with compressed air.

 

Forgot to mention, this 'jerking' occurs with no-load, as when at idle. Under a load (acceleration), the chain is pulled tight on the working side, smoothing out the ignition and valve timing. However both actions will be retarded by the amount of chain stretch.

 

Temporarily replace the petronix with points.
The way you describe the way the car runs (or doesn't run) sounds just like the problems I had with the petronix $%#@*. I've had two go bad and seen and heard of many more bite the dust.

And some people have never had a problem with petronix ignition and swear by em'.

 

PAY ATTENTION.
A good friend JUST went through this. He has a big block '69 383 swapped in a '83 Dodge Diplomat. Set up simple- points, holley carb etc. Right after he got it running, started to miss, hard start etc, he swapped coils, points, whole dist, then thought maybe it was a vac leak or lean pop - swapped carb, etc...

Turned out to be a bad coil, the brand new Napa he started with went bad, the year old used he swapped on was bad, the BRAND NEW one from Car Quest won't even start the car!, finally he borrowed the 15yr old one on my 455 I knew was good, that fixed it.

Not saying that's your issue, but if you have a friend with some known good parts, that run good on another motor...

I was thinking maybe timing chain, but his was new, no slack, if it was a degree issue it would run constantly bad, not vary like it did....