hard starting big block tri power

[Ray G.]

Hi folks, My friend has a 69 427-435. It has had a driver body off 7 or 8 years ago. When cold the car starts fine, starter spins quickly and she fires right up and idle's fine. The car goes like hell.
However, drive it a bit, and once she is warm she just does not want to start. The carbs were done last year by a reputable shop in Salem, Mass. We have replaced the ignition with Petronix and the hot coil. New plugs, new factory wires, we are stumped. The problem is the same as before we did anything to it. Any thoughts? Thanks in advance Ray

[Wayne W.]

Re: Clarification

The question is. When you say it wont start, do you mean that it turns over hard or it turns over easy but will not fire? The former is caused by low voltage, high compression, weak starter, high timing etc. The latter is caused by flooding usually.

[Wayne W.]

Re: Clarification

The question is. When you say it wont start, do you mean that it turns over hard or it turns over easy but will not fire? The former is caused by low voltage, high compression, weak starter, high timing etc. The latter is caused by flooding usually.

[Ray G.]

Re: Clarification

Wayne, yes the engine will spin like crazy even when hot, to the point of wearing down the battery, then it will catch and fire. After these events we have checked the plugs and did not see any fouling or gas soaked plugs, so we kind of discounted flooding.
However, the Carb resto shop said, when he first brought the car over there that he saw gas flowing into the manifold after the car was shut down and that after the rebuild that would correct the problem. Well It is still doing it, but we thought that problem was fixed.

Ray

[Ray G.]

Re: Clarification

Wayne, yes the engine will spin like crazy even when hot, to the point of wearing down the battery, then it will catch and fire. After these events we have checked the plugs and did not see any fouling or gas soaked plugs, so we kind of discounted flooding.
However, the Carb resto shop said, when he first brought the car over there that he saw gas flowing into the manifold after the car was shut down and that after the rebuild that would correct the problem. Well It is still doing it, but we thought that problem was fixed.

Ray

[Rob M.]

Re: Clarification

Have you checked the float levels? A high fuel level can cause drooling after the engine has been run, thus creating a very rich fuel mixture when you try to start it. Maybe you can take the sight plug out of the carb while it is running and see if the level rises when you shut it off a let it set.

Does it fire up quicker if you open the throttle all the way before you turn the key? If so this is an indication of a very rich start up condition.

My 71 LT-1 had this problem and I could not get it fixed until I installed a MSD ignition. The MSD put out such a hot spark that the engine would fire instantly even with the "hot and rich mixture" condition. Good luck.
Rob

[Rob M.]

Re: Clarification

Have you checked the float levels? A high fuel level can cause drooling after the engine has been run, thus creating a very rich fuel mixture when you try to start it. Maybe you can take the sight plug out of the carb while it is running and see if the level rises when you shut it off a let it set.

Does it fire up quicker if you open the throttle all the way before you turn the key? If so this is an indication of a very rich start up condition.

My 71 LT-1 had this problem and I could not get it fixed until I installed a MSD ignition. The MSD put out such a hot spark that the engine would fire instantly even with the "hot and rich mixture" condition. Good luck.
Rob

[TLSmith]

Re: hard starting big block tri power

Ray:

two items;

1) If you are running a Quadrajet, not sure what year they started using these, there two lead plugs on the bottom of the carb that are known to leak creating rich conditions, especially after sitting. Check with your rebuilder to see if he sealed these, usually epoxied.

2) Is carb heating up with engine and boiling over when stoped. A common problem on many high performance engines. Easily cured with a phenolic (hope this is spelled right) spacer or heat shield.

[TLSmith]

Re: hard starting big block tri power

Ray:

two items;

1) If you are running a Quadrajet, not sure what year they started using these, there two lead plugs on the bottom of the carb that are known to leak creating rich conditions, especially after sitting. Check with your rebuilder to see if he sealed these, usually epoxied.

2) Is carb heating up with engine and boiling over when stoped. A common problem on many high performance engines. Easily cured with a phenolic (hope this is spelled right) spacer or heat shield.

[Wayne K.]

Re: Clarification

If the float adjustment doesn't fix the problem then I would suspect there is one or more carbs with a warped metering block or plate.

[Wayne K.]

Re: Clarification

If the float adjustment doesn't fix the problem then I would suspect there is one or more carbs with a warped metering block or plate.

[Wayne W.]

Re: Clarification

Yes, this is the most common problem with the Holleys. Remove the air cleaner and run the car for a while. Shut it down and without touching anything look over into the carbs. You will see gas running out onto the plates. A good rebuild by someone familiar with this symptom should solve the problem.

[Wayne W.]

Re: Clarification

Yes, this is the most common problem with the Holleys. Remove the air cleaner and run the car for a while. Shut it down and without touching anything look over into the carbs. You will see gas running out onto the plates. A good rebuild by someone familiar with this symptom should solve the problem.

[Jack H.]

Re: Clarification

It's probably time for overhaul/restoration of your carb setup. The tripower was not known for its thermal durability (center carb more likely to warp due to confined space for heat dissipation). BUT, we saw similar funnies with a factory fresh setup on a '69 400 HP system. We racked out brains trying to find and KILL the problem(s) to no avail until we rented time on a chassis dyno and rigged TV cameras to watch the carbs....

At wide open throttle and max RPM, we saw the fuel bowls 'boiling' generating random geysers of raw gas spewing out of the vent stacks. Similar 'pops' could happen during engine shut down and thermal soak.... Getting rid of alcohol blended fuel, cured the problem. I gotta believe todays ethanol & MTBE blended fuels are NOT so friendly to fuel systems that aren't pressurized all the way down the pike....

[Jack H.]

Re: Clarification

It's probably time for overhaul/restoration of your carb setup. The tripower was not known for its thermal durability (center carb more likely to warp due to confined space for heat dissipation). BUT, we saw similar funnies with a factory fresh setup on a '69 400 HP system. We racked out brains trying to find and KILL the problem(s) to no avail until we rented time on a chassis dyno and rigged TV cameras to watch the carbs....

At wide open throttle and max RPM, we saw the fuel bowls 'boiling' generating random geysers of raw gas spewing out of the vent stacks. Similar 'pops' could happen during engine shut down and thermal soak.... Getting rid of alcohol blended fuel, cured the problem. I gotta believe todays ethanol & MTBE blended fuels are NOT so friendly to fuel systems that aren't pressurized all the way down the pike....