Fuel System: Heat Riser Mod, To Intake Manifold

[JoeHall]

Several have suggested closing off the exhaust manifold passages in the intake manifold, in order to reduce heat under the carb, and thereby reduce heat related problems with modern gas.

Having tried that, I ran into problems: took too long for the carb to warm up; choke went off long before carb stopped coughing & spitting; later, once heat transferred eventually, the car still boiled the gas after a hot shutdown, and resulted in same hot re-start problems. I never kept them in place till winter, but am thinking carb icing may have became an issue in clod weather.

PROPOSAL: Fabricate and install butterfly valves in each end of the exhaust runner in the intake manifold. Use springs similar to the existing heat riser valve, that would hold the valves open when cold, then close them when warmed up. Alternatively, just use a manual valve to open & close them in hot and cool seasons.

Opinions ? Input ?

[DEEPNHOCK]

Blocking the heat crossover passage is usually only done on fair weather engines or Stude's...
I hear ten pluses to every minus for doing this.
If you have a carb issue, then blocking the passages off won't cure that.
I wouldn't bother with building valve gizmo things....Just more to go wrong down the road..

[Clem64]

Joe, this is how I dealt with similar issues with our stock 61' Hawk (289, 2bbl. Stromberg carb). About 2 years ago the stalling got so bad that sometimes I couldn't even drive but a few miles from home and the car would stall out. First, I unhooked the spring on the heat riser valve and pushed the valve open full time. Next, I added several more carb. gaskets to help insulate the carb. from excess intake manifold heat. Next, I wrapped the fuel lines with fuel hose (split along one side to slide over the line) wherever I could reach, from the gas tank all the way up to the carb. and fixed in place with plastic ties. Next, I installed an electric fuel pump and completely removed the mechanical pump. This final item may be the most important other than adding the electric pump, I only fill the car with NON-alcohol 91 octane premium. Sure, it costs another 60 cents a gallon, however the car no longer stalls and runs as it should, well worth it as far as I am concerned.

[Bud]

I don't recommend blocking off the heat riser passages in the intake manifold as it could cause carburetor icing under certain weather conditions. It may be possible to reduce the amount of heat by placing restrictors like the ones used on small block Chevy manifolds in the crossover ports. Bud

[JoeHall]

These are some of the things I have tried over the years: insulated the gas lines with tin foil, larger hoses and clothes pins; electric fuel pump; wired the riser valve open; cooler thermostat; HD radiator; HD fan; electric fans; wood, phenolic & aluminum carb spacers; aluminum heat shield below the carb; rabbit's foot on the key chain, and probably some others I have forgotten. Lastly, I installed EFI, and this seems to have cured it. Problem is, I have three cars, and EFI is kinda expensive. It also takes awhile to install and dial in, and is a bit unsightly (not that I care).

I have found in the Stude world there are three camps when it comes to heat related gas problems: those who have never had the problem, those who have, and those who run brand X motors and do not have the problem.