Cast iron intake mannyfolds will hold a LOT of heat in them, and transfer it to the carb. One way to help keep the heat down is to block off the heat riser passage in the intake. This might make your cold weather starts a little more aggravating, but it would also help with the fuel boiling issues. Another thing is to check the quality of the fuel...lower grade fuel will tend to percolate more easily than better quality fuels.






|UPDATED|10/24/2012 10:32:05 AM (AZT)|/UPDATED|

I agree with Adam on the gas we get today, with the "blend" not being no where close to what these cars were set up to use but what is one to do when they tweak the fuel as they do. Had one carb company tell me if can get pure gasoline without the ethnol and higher octane will help.......if can find and can pay the price, otherwise life is what it is. I know on my '81 since the engine compartment is packed from the factory, when been on the road and temps are up or outside air is hotter, when I stop I just pop the hood and let the hot air escape and that seems to help....but only if you can leave the hood up where ever you are stopping.

I too always open the hood when I park after a long ride.  A few stations here in SC are goingto 'pure gas' with no ethanol.  My C5 loves that stuff and I actually do get a little bit better mileage.  In my '78, I have no idea what mileage I get, but that too seems (probably just my imagination) run a bit better on the pure gas.  I have also heard (per Dr. Adams comments) that a ceramic, or phenolic spacer, is better than a metal spacer. 

As Joel said in his earlier post, use the heat riser block off gasket set.It will probably not effect your cold starting as much as it may keep the choke from going off quick enough and could cause a rich fuel issue when cold. When I first used this gasket set I wired my choke open which made starting cold much harder but I added an electric choke kit which cured that problem.  Heres a pic of the felpro gasket Number.
Best of luck
Rodney


|UPDATED|10/31/2012 1:41:35 PM (AZT)|/UPDATED|

Does your ride have the original air cleaner with all of the components connected and operating?  The big air cleaner is actually a heat sink and it tends to take up some of the heat in the area of the carburetor.  Also, with the  original air intake, the carb gets cool air forced into its throat, which is always better than hot air.  If a car has an after market cleaner with none of the engineered components, the carb is getting hot air during running and the cleaner does not have the mass to act as a heat sink.  I wonder if owners who have trouble with boiling gas, have modified the car with a different air cleaner?  The original design acts to warm the car up faster, thus the carb, but the intake flap opens and the exhaust heat exchanger closes, so that the temperature is controlled as per design.  Just wonder about the addition of different air cleaners as the cause of boiling in the carb.

FWIW from an internet source: 

Yes, mothballs will slightly assist the octane rating of gasoline. HOWEVER, in that grain of truth there lurks the potential for disaster. One must use very few mothballs (naphthalene only) because the ratio of carbon to hydrogen in the molecules makes for a very dirty burning fuel. Too many mothballs and your engine will load up with carbon deposits -- very bad news in the performance department.

Also DO NOT mistakenly use moth crystals (paradichlorobenzene). The chlorine atoms in this material becomes HCl upon combustion. Hydrochloric acid (HCl) is very destructive to engine internals.

Finally, unless your engine is high compression and in need of high octane fuel, enhancing the octane rating of the fuel over what is required is simply a waste of money. High octane fuel burned in an engine designed for lower octane fuel does not increase engine power.

Here is an update :Installed Mr.gasket heat shield today on my '77 I couldn't be happier I went for long ride (probably last one this year) to get temp up got home pulled in garage opened hood and could actually put my hand on top of air cleaner before you could cook your supper. So thank you everyone once again for your help what a great site.

What combination of plates did you use

I only used 2 of the alum. plates