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Old 11-27-2020, 01:19 AM
Vetteman61 Vetteman61 is offline
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Default Electric Choke = Heat Crossover Block Off

I want to get verification that I'm correct before I install this.

Pontiac 455 - Street/driver. I'm changing to a carb with electric choke. Is there any reason I would need to keep the heat crossover on the intake. Am I OK to use the block offs provided with the intake gaskets?

Thanks,
Brandon

  #2  
Old 11-27-2020, 01:46 AM
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b-man b-man is offline
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Default

The intake heat is nice to have on a driver, sometimes the engine stumbles and runs poorly for about the first half hour without the heat. Operating the choke is only one of the functions of the exhaust crossover under the carb.

Either way, the blockoffs provided in gasket kits will burn through rather quickly and become ineffective.

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Old 11-27-2020, 01:57 AM
Joe's Garage Joe's Garage is offline
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Default Electric chokes allow the choke to function - sort of - without exhaust heat, but....

That's only one part of the need for some heat in the intake manifold and/or carburetor.

If the temp is almost always warmer - like here in Las Vega$ - you will only need a few minutes more 'warm up' time most of the year. Not even really noticeable when it's 110* outside.

In colder weather - say Wyoming or Nebraska or Illinois or anywhere north of I40 where there is a frigid winter 'season' - the warm-up time during that colder season will be reallllllly long. Think ten or twenty minutes long (or even a half-hour, as B-man noted) before the car idles well without your foot on the gas.

That's because the exhaust heat in the intake manifold also helps the fuel to atomize better and wards off carburetor 'icing' during cold and especially cold and humid weather.

While you can adjust the electric choke to stay on longer, and adjust the idle and low-speed mixtures somewhat richer to compensate, it's honestly better to have some heat in the intake.

We will admit that we've run factory aluminum intakes without the crossover and with block-off plates plenty of times and just put up with the car being finicky when it's cold outside. It definitely felt like there was more power with the cooler intake manifold.

If you are using the stock air cleaner that has the ability to install an exhaust preheater tube down to the exhaust manifold, that will help overcome the lack of heat in the intake without 'overheating' the intake.

Good luck!

  #4  
Old 11-27-2020, 02:05 AM
Vetteman61 Vetteman61 is offline
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OK, thanks for the reply. The car is a station wagon family hauler and does get driven in the cold season/weather (just not during salt), so I'll keep the crossovers.

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