exhaust crossover in intake manifold

[r15303]

I have a 440-6 with an alum. intake manifold.  Been reading some literature from Holley and they say to block the passage on an alum. manifold but leave it open on a cast iron.  What do you guys think?

[r15303]

Also - did and 70 440-6 come with alum. manufolds from the factory?  I thought I read somewhere that some early ones did. 

[go-fish]

I'm not sure if the factory ever used aluminum intakes on 440-6. 340-6 were iron I believe.
On the heat cross-over, it helps engine warm up in cold weather but once you are warmed up it does nothing for performance.

[dodge freak 2]

Its were you live or when you drive your car. If its a summer time only car or you live in AZ, FL, etc. you should block it.

I live in Michigan and drive it when ever the streets are clean. I keep my exhaust heat open year round. Keeps the spark plugs clean, motor warms up fast, it idles better--because the plugs stay clean. I Think unless its 80+ you lose very little power with it open. In fact in the winter the motor has more power with the intake heated, helps burn all the fuel.

Factory knew what they were doing using exhaust heat but many people love to block it. With the cheap gas we have now it does help stop pinging, vapor lock but my motor does not seem to have those problems. I tried having it block for a year and a half, never again so long as I live in Michigan, were even the nights are cool.

[Chryco Psycho]

Get a Fel Pro 1215 intake gasket , it has the crossover blocked , I block them on virtually every build ,in 69 the A12 cars were the only ones with 6 packs & with limited production they used the Eddy intake , for 70-71 Mopar cast there own intake in iron

[r15303]

Thanks for the info.  What is the advantage to blocking the passage?

[GoodysGotaCuda]

Keeps unecessary (depending on your climate, and carb setup) heat, out of the intake manifold. Cooler the intake manifold, cooler the air charge going into the engine. Cooler air is more dense, more air you can get into the cylinder, the more 'boom' 

[dodge freak 2]

Cooler air has more oxygen than hot air, more oxygen means the carb can be jetted richer and it burn.

But I can even hear the motor pick up rpms when I first start it for the day. When my foot is steady at around 2000 rpms after 20-30 seconds it climbs 300-400 more rpms-as the intake starts getting a bit warm. After I hear it change, its ready to go. Thats it, no more than 1 min I wait, even now in winter.

 I believe when its close to around freezing outside, my motor makes more power with the exhaust heat open than close. Even if I drove it for a 1/2 hour.

I recall how after the car sat like getting gas when the exhaust heat was block and I then drove it, the first run was faster than the second or third. When I pop the hood open the intake was ice cold. Thats why I went back to a heated intake and afterwards I notice no change in performance.

Maybe if the motor had like 11-1 compression it be different,   

[Chryco Psycho]

most of these cars are no longer operated in cold climates so heating the intake is redundant & can cause fuel boiling problems in the carb

[AMXguy]

My new six pack set up has the original old choke style, by blocking the heat passage off is that going to make the choke way to slow to come off? can I just adjust it real light or maybe I should just block it open?

[dodge freak 2]

most of these cars are no longer operated in cold climates so heating the intake is redundant & can cause fuel boiling problems in the carb

You are right, today was nice-I thought-upper 30's or 2-3 C--but I seen not 1 "old" car, mines just 30 years old. But I did see 2 motorcycles ! Thats crazy I think, I had my heater going good and all the windows rolled up tight.

For your choke, it need to be electric-if you feel you need it.

You still can get a heat barrier to keep the carb cool in the summer if the intake is heated, mine stays cool while driving it but the intake is super hot-in the summer.

I don't think theres much HP to be gained-10-15hp by keeping the intake heat block but it sure makes the car more enjoyable to drive by keeping the intake heated.

Just MOI

[FJ5_440]

For me, the power gains are not the reason for blocking the crossover.  The "New" gas we have now is.  With the crossover open and no carb spacer, I could literally hear the "reformulated" gas boil out of the carb after shutting down and having the heat soak set in.  Besides that, it burns the paint off of the intake in the crossover area without the blockoff.

[Chryco Psycho]

adjusting the choke very light or adding an electric assist is nessisary with teh crossover blocked

[ted]

whats the felpro part # with it blocked for a 383/400?

[Chryco Psycho]

1214 for B / 1215 for RB