Blocking heat crossover

[Rooster34]

Hey guys and gals hope all is well! Had a quick question. On blocking the heat crossover on my 1965 318 poly head. Ive have done some refreshing in the engine but keeping it mostly stock along with the 2 barrel intake manifold and 2 bble carb. Ill be running a 264 450 cam with tti headers and the heads are milled to get 10:1 compression. I live in Southern Maine and sometimes can see Temps drop to double digit negatives. Engine isn't bored over and no electronic ignition will be installed. Just wondering what the benefit is of blocking it off. Thanks!

 

[Davea Lux]

Hey guys and gals hope all is well! Had a quick question. On blocking the heat crossover on my 1965 318 poly head. Ive have done some refreshing in the engine but keeping it mostly stock along with the 2 barrel intake manifold and 2 bble carb. Ill be running a 264 450 cam with tti headers and the heads are milled to get 10:1 compression. I live in Southern Maine and sometimes can see Temps drop to double digit negatives. Engine isn't bored over and no electronic ignition will be installed. Just wondering what the benefit is of blocking it off. Thanks!

Blocking the heat riser passage lowers the temp of the carb and and keeps it from potentially boiling in hot summer weather. A cooler carb is usually more efficient and performs better. Overheated carb is Usually not a problem on a 318 poly with a BBD carb unless the heat riser is stuck shut. Downside is that the automatic choke won't work with the heat riser passage is blocked. You will need to go to a manual choke or a different carb a with an electric choke if you plan to drive the car in cold weather. With a cam and headers, you might want to consider a 4BBL carb setup in the 600CFM range to get full benefit out of the performance upgrade.

Dave

 

[413]

If you drive cold or cool weather then don’t do it. The bottom of the intake will be cold and the engine will stumble on most acceleration for 30 minutes until that intake floor gets warm.

It will work when it’s hot outside, like 80+ degrees.
Or a racing engine. Your 318 2 bbl won’t like it.

Go to Ethanol-free gas stations in the U.S. and Canada and Find a station to buy ethanol free fuel and your car will run better, and hot start better.

 

[odcics2]

Great quality gas, like BP, has the correct additives that help drive ability.
BP consistently tops the list of best fuel. This info comes from the FCA fuel lab.

 

[Rooster34]

Great quality gas, like BP, has the correct additives that help drive ability.
BP consistently tops the list of best fuel. This info comes from the FCA fuel lab.

If you drive cold or cool weather then don’t do it. The bottom of the intake will be cold and the engine will stumble on most acceleration for 30 minutes until that intake floor gets warm.

It will work when it’s hot outside, like 80+ degrees.
Or a racing engine. Your 318 2 bbl won’t like it.

Go to Ethanol-free gas stations in the U.S. and Canada and Find a station to buy ethanol free fuel and your car will run better, and hot start better.

Blocking the heat riser passage lowers the temp of the carb and and keeps it from potentially boiling in hot summer weather. A cooler carb is usually more efficient and performs better. Overheated carb is Usually not a problem on a 318 poly with a BBD carb unless the heat riser is stuck shut. Downside is that the automatic choke won't work with the heat riser passage is blocked. You will need to go to a manual choke or a different carb a with an electric choke if you plan to drive the car in cold weather. With a cam and headers, you might want to consider a 4BBL carb setup in the 600CFM range to get full benefit out of the performance upgrade.

Dave

Thanks for the info guys! I think ill refrain from doing that Mod for now as I do plan to drive it a bit in the winter and I will be running the stock 2 bbl for sometime until next year.

 

[BIGBARNEYCARS]

Thanks for the info guys! I think ill refrain from doing that Mod for now as I do plan to drive it a bit in the winter and I will be running the stock 2 bbl for sometime until next year.

Good idea at your latitude az others have already said, Jer