quadrojunk

I have a 84 firebird with a HO 305 I have built it up a little with a comp cam, Edl intake and a 650 cfm Edl carb and headers. After the engine has ran and I shut it off the fuel boils in the carb and leaks into the intake. I have removed the hood, used a spacer plate and installed a 185 thermostat. Nothing has helped my problem. I know it is a common issue, I just want to know if anyone has found a way to fix this problem?

Air_Adam

What are the symptoms of the problem? Slow cranking? Normal cranking but no firing, etc...?

I'd bet its a heat soak problem with the starter, and its cranking slowly. Common problem with these cars.

quadrojunk

I can start it cold no problem drive it to town and if I shut if off then crank it back up within 2 minuets it is fine. Anything longer and it has to turn over for 8 to10 seconds before starting and I can see/smell rich exhaust smoke. It clears up as soon as the engine is rev'ed. I know it is fuel leaking into the intake, it must be caused by heat. The intake and carb get so hot. I cant seem to get the temp of the carb down.

F-BIRD'88

Remove the edelbrock performer intake manifold and block off the exhaust heat raisers that pipe exhaust heat up under the carb plenum. The edelbrock performer intake gets too hot with the passages open. The carb will run cooler and nicer with these passages blocked off. Install a wooden carb spacer under the carb.

Air_Adam

Thats not going to help him... that passage is there to get the intake warm to help atomization of fuel, especially during warm up. Blocking that will just make it take longer to warm up and use more fuel doing it.

What it actually sounds like may be your problem is the ignition module inside the distributor. Have you ever changed yours? If so, when - and what brand was it?

I ask because ignition module problems aren't uncommon in these cars, and when they start to fail, they give you hot start/hot run problems like what you are experiencing. Once they cool off, the problem will go away untill it gets hot again - untill it just quits all together.

If you've never changed yours, it might be a good idea to have yours tested, or just replace it anyway, as it isn't a very expensive part.

Not Danny

I agree that it's probably your distributar, i just fixed the same problem in my 83 z, it wasn't the modual itself but the wires going to it,talk to a friend who owns a junkyard and it turns out that he has seen a lot that the wires pull away from the centershaft or break entirly. All i did was repalce the distributar and my problem went away.

77monte

With fuel leaking into the intake when the engine is off i would first look at adjusting the floats in the carb... i found on all 3 of my edelbrock carbs that the floats aren't even close to where they need to be.. as soon as i adjusted them i had better start ups with less plug fouling and it doesn't leak fuel into the intake with the engine off..

F-BIRD'88

You,re right about the exhaust passages being there to aid quick warm up. But with the stock cast iron manifold.
The thin cast aluminum performer manifold heats up much quicker.
Getting too hot especially in the summer.
The excessive plenum heat causes an abundance of vapourized fuel to collect in the manifold and creates a hot start condition requireing excessive cranking time to restart when hot. It just gets too hot. Unless your in Siberia (or Alberta) in the middle of the winter you can reduce the plenum temp by blocking off the heat passages.
The edelbrock carb with its inboard fuel bowl design just adds to the problem. Excessive fuel perculation.Isulating the carb from the manifold with a divided wooden car spacer helps a lot. Edelbrock carb accessory.
This is the cause of his hot weather hot start problem.
if it was a nidule problem the car would stall when hot. His runs fine once he gets it restarted and clears the manifold of
exessive fuel vapour. Modern GM HEI 990 modules rarely go bad.

I believe Edelbrock addresses this common problem in their
troubleshooting section . You have to fine tune the manifold plenum heat to suit your car. Some block off one side, some just restrict one or both sides. I just block the raisers off completely for the performer intake.

quadrojunk

I have never had a problem out of Edelbrock before this. Other than the normal rod swap. This carb though, I have had to remove the linkage for the seconary and change the rod spring to the yellow. This carb has been a pain from the start. I think its right now other than the fuel boiling. So how durrable is the wood spacer plate?

I know this is a third gen forum but do yall mind pics/questions on a second gen? I ask because I have an 81 with a 455.

sofakingdom

iTrader: (1)

I doubt the problem is the carb.

When my car did that once a long time ago, it was because the fuel pump was getting too hot. The fuel in the pump was boiling and forcing its way into the carb and spilling into the intake. Like the moron I truly am, I had got in a hurry for some forgotten reason, and put the pump and plate on with no gasket; only silicone. Mine did it with a Q-Jet and also a Holley. The pump was getting hot enough to burn my hand.

Put 2 fuel pump blockoff plate gaskets on it, and 2 fuel pump gaskets. That COMPLETELY stifled that behavior in my car.

Somebody also makes a phenolic blockoff plate, that would probably be even more effective. I can't remember who it is though.

Sonix

iTrader: (1)

Wouldn't that space the mech fuel pump too far outboard to get any stroke on the pump?

sofakingdom

iTrader: (1)

Seems like it's worked pretty well for the last 12 or 14 years or so, and a fuel pump or 2... even a couple of different blocks... but who knows, with my luck, that could all change at any minute.... That would be in line with the story of my life.

Seriously though, there's ALOT of tolerance in the fuel pump stroke. I doubt that those few thousandths of extra paper would ever upset it in any motor. For that matter, I've seen some FP gaskets over the years, that were ahelluvalot thicker than the ones that I've been using. Can't be too terribly critical.