fesa

Dear all,

I recently installed a new Edelbrock carburetor in my 80s Corvette. Since then I am having lots of issues with fuel boiling (I think), as the engine does not start properly after I haven driven my Corvette for some time (e.g. 30mins) - cold start is not issue, also a start after e.g. 5mins drive is no issue. However, as soon as I have driven longer, the engine doesn't start. I have to fully press the gas pedal and start at the same time - then the engine starts.

From what I read so far here in the forum, the issue seems to be that the fuel in the carburetor is boiling. I have attached two pictures from my engine, maybe somebody can give me a hint what I (or my mechanic if I am unable to) could change to cure the problem?




Any help is greatly appreciated!

CAMS69

Im gonna subscribe to this thread. I also have the similar problem as you..
edelbrock carb, cold start great, hot start takes longer but does start.
I notice you have a thin gasket between carb and intake, i replaced with a 1/2" phenolic one and it helped a small amount.
Also people will tell you to get that plastic filter out of there...

Jebbysan

What intake gasket did you use? If you did not use a 1204 Fel Pro......the center hole for the heat riser may be open which will heat up the intake a bunch.
Where is your timing set at? Excessive advance or retard can cause high exhaust temps which exasperates the problem I mentioned above.
What is your fuel pressure set at?

Jebby

fesa

Does that help materially? Of course, that should be an easy fix - however I doubt it will solve all my problems, will it?

Jebbysan

It will not solve anything except squelching the possibility of your car catching on fire.....

Jebby

MelWff

Another issue you have is that 2" tall air filter is strangely the engines ability to breath.

mysixtynine

The edlebrock carb is basically an old Carter design. They were very prone to boiling. In your install instructions you should see a section just above the IDLE Mixture section. Maybe page 8 I dont know what install book you have.

That section just above talks about "When restarting the vehicle after it has been sitting for 10-30 mins you may experience some difficulty starting (stopping to get gas is enough to bring it on). The result will be similar to a flooded carburetor"

You basically need a heat insulator gasket similar to part number 9266/9265 depending on what carb/intake you have. Its basically 3/8" insulator to keep the carb away from the hot manifold.

Some guys make them out of wood or other types of material.

It simply works IF YOU HAVE THE HOOD CLEARANCE be-careful of your air cleaner stud and its only like $25 max. It may not work 100% but it definitely helps.

Just saw jebbys post and he makes some really good points as well about the cross over.

Also just me... i am not a fan of plastic or glass fuel filters.. I would use a metal one and i would insulate your fuel line away from the HOT intake heater core hose. If you could even wrap the heater core hose with some insulator right at the area where its close or touching the filter it would be beneficial as well.

fesa

Thanks, Jebby. Not exactly sure with intake gasket was used (the invoice I have doesn't specify exactly), I will make a picture later to verify.

Fuel pressure seems to be low (I think), as the filter is always only 1/3rd full (when engine is switched off). Can I easily change that one? Sorry for the newbie question...!!

MelWff

Are you using a 180 F thermostat?

Jebbysan

Newbie questions are no problem.....
You can remove the choke stand plate and shine a light or stick a poker down the hole to see if the heat riser port is blocked off. If it isn't.....I recommend going through the trouble of blocking it off. Mucho heat comes through there and heat soaks the intake....especially an aluminum one.





Jebby

MelWff

The amount of fuel is no indication of fuel pressure.
I notice you are in Austria, is your mechanic familiar with modified American cars?

Jebbysan

Get this fuel line kit and some fitting and braided hose to run to your fuel pump......this will help keep fuel temps down.

https://www.summitracing.com/parts/EDL-8131

Jebby

cv67

Changing carbs wont help its the ethanol fuel...try a heat shield under it summit sells them. May or may not take care of it not much you can do. Even EFI systems with TBI sometimes have an issue wiht this.
Others use an electric fuel pump I wouldnt waste my $ though

fesa

He should be, as he is a mechanic specialized on US cars. I am having my doubts recently, though...

gkull

Years ago I used an EDL 750 carb. When I stopped you could pop the hood and hear fuel boiling in the bowls. I had a single plane without an exhaust cross over. I installed a 1/2 wood spacer. Wood is a better thermal block than Phenolic. I used an open spacer. Dual plain could use a two hole. Sold at summit racing.

As to a 2 inch filter blocking air flow.... It depends on the diameter of the filter, filters resistance to air flow, and the engines real needs. 14X2 has lots of surface area. 80 even mildly modded isn't very volumetrically efficient requiring lots of air.

MelWff

Is there an Austrian Corvette club that could suggest another mechanic?

Rescue Rogers

I had this same issue

1. put in a phenolic spacer or one made of the material of our choice except aluminum. I used 1/2 inch and then went to 1 inch but i have a lot of room
2. you may need a drop base air cleaner to clear the hood. take out the carb cleaner stud and put a ball of tinfoil on top of the lid and slowly close the hood to get the gap
3. install a fuel pressure regulator and gauge and set it to 4-5 psi.
4. keep your fuel lines away from any heat source or wrap them with a reflective material to help keep the fuel lines cool
5. i have not used one but there is a metal or aluminum shied that is put under the carb to deflect heat as well. I've heard good things here
6. You can also try an air gap intake if you have the hood clearance as well
7. you can try openning the hood enough to let out all the heat when you stop as well
8. you can carry starting fluid and spray it everytime you want to start it as well. Major PITA but it works in a pinch

71chimera

https://www.aedperformance.com/parts...s.html?start=0

Birchwood plywood

Sayfoo

Do they use that in Austria too???
I do believe that is a big part of this problem here in California, USA.
Heat shield and phenolic carb spacer did help a little on my car.

F4Gary

Block off the exhaust crossover ports and either wire your heat riser valve open or take it off and cut out the butterfly valve in it.