I've got a 350 c.i. mostly stock engine with a manual transmission in a '73 Vette that runs fine cold, runs fine up to operating temp and runs fine for about 30 minutes (depending on outside temp), however, refuses to idle once it gets "hot" (although the temp gage never goes above 185 degrees. When it reaches this conditions, it runs fine above 1500 rpm (?) I have an Edelbrock RPM Performer intake manifold, an Edelbrock 650 cfm carb, an Edelbrock manual fuel pump (that does not exceed 6.5 psi fuel pressure to the carb) and the idle ignition timing is set at 12 degrees BTDC. This thing acts like a case of classic vapor lock, however, ? Anybody have any ideas?

 

When you say it refuses to idle, does it die when hot?

How are the hot restarts?

Could be float level set too high.

 

It dies after the engine gets "hot" and will not restart until it sits fo a couple hours. I've capped the power brake and PCV fittiings from the carb and there are no other vacuum leaks from the manifold. (Wen I installed the Felpro intake manifold gasket set, the instructions were a little confusing-either the block off/restrictor metal plates went on the left side or right side depending on how you read it. The carb/manifold now has an electric choke-the "old" carb/mafold used the heat from the manifold to sense when the engine was hot and opened the choke-not sure if this is the cause of my problem.)

 

Does the choke open fully after warm-up?

Have you tried to restart hot while holding the throttle wide open?

Also check down the carb bores after a hot shut down for gas. Symptons sound like too much gas.

Did it run properly after the carb was originally installed?

 

The choke does open fully after the engine is warm and the engine "tries" to restart after it has shutdown (cranks and catches avery once in awhile but, dosn't start).

I'll look down the carb bores next time I get it out and run it (tomorrow?) Although, the float level was checked and adjusted in the carb when I installed it (and I don't remember the setting), should I verify it again?

This thing has never run correctly since the initial install. I've got another carb my buddy had tuned for his hopped up 383 sbc, however, we think it's going to be too big for my application (it's a 750 cfm Edelbrock).

 

Since I'm not familiar w/ the Edelbrock carb (is it a spreadbore?), this is a stab in the dark. Does it have a foam float like the Q-jet? If it does and it wasn't new, I'd replace it.

Do you set the float level w/ the car running like a Holley or disassembled like a Q-jet?

Be sure to try the WOT on a hot restart. The symptoms sound like either float level to high (or a saturated foam float) or carb boil over (bad needle and seat).

The 750 carb would probably be OK temporarily and could be used to see if it's your carb or something else. If it's a vacuum secondary, would probably be OK long term but might require re-jetting.

 

It's a squarebore carb and I think it has a hard plastic/metal float (haven't had it apart lately). Although, it is brand new and never been used before it's about 3 years old (the guy never used it).

Unfortunately, float adj. is not like a Holley-you have to disassemble the unit and then make the adjustment.

I'll give your suggestions a try this week and let you know how it turns out. Thanks for all your help.

 

Since it's new, then the float should be OK, but the setting should be verified. While your in there, check the needle and seat.

All of this is predicated on the problem being too much fuel. If it's not that, then I'd start checking electrical components starting w/ the coil.