intake manifold question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

swtman · 06-24-2009, 11:36 PM

What is the purpose of an open center manifold? I have a 305 approx a '78-79 in which I just put in a new intake gasket and not sure if maybe I should have put in a restrictor in one side. What is this restrictor supposed to do? I have a newer 4 barrel manifold on it. Should I have put the restrictor in? Any help would be appreciated!

prostreetC-10 · 06-25-2009, 12:04 AM

I believe that the opening is usually for a carb with a divorced choke. Choke has a coil on the manifold and the heat operates the choke. The restrictor keep the heat from getting into the manifold. Problem is that many times, when you put the restrictor in, over time they burn out anyway.....it will be open one way or the other. This is my educated guess. Anyone else???

**GruntMoanCough** · 06-25-2009, 01:01 AM

Blocking these off will give some free horsepower by keeping the intake cooler but, for street use this will increase warm up time.

swtman · 06-25-2009, 01:53 AM

So it's ok that they are both open? It won't cause the manifold to over heat or anything??

**GruntMoanCough** · 06-25-2009, 03:01 AM

I don't think it will cause any problems.

mclairmo · 06-25-2009, 01:20 PM

It's ok that they are both open and might be best considering your location. This is how the factory did it to help with cold start warm ups. Allows warm exhaust gases to run under the carb to increase fuel atomization when cold. In cold climates, you need this. However, in warm climates, many hot rodders block this to help keep the intake charge cooler and denser for more power.

swtman · 06-26-2009, 12:10 AM

thanks for all the replies guys!!

06-24-2009, 11:36 PM	#1
swtman Registered User Join Date: Mar 2007 Location: Red Deer, Alberta,Canada Posts: 22	intake manifold question What is the purpose of an open center manifold? I have a 305 approx a '78-79 in which I just put in a new intake gasket and not sure if maybe I should have put in a restrictor in one side. What is this restrictor supposed to do? I have a newer 4 barrel manifold on it. Should I have put the restrictor in? Any help would be appreciated!

06-25-2009, 12:04 AM	#2
prostreetC-10 My Carbon Footprint Join Date: Oct 2008 Location: Orygun Posts: 5,527	Re: intake manifold question I believe that the opening is usually for a carb with a divorced choke. Choke has a coil on the manifold and the heat operates the choke. The restrictor keep the heat from getting into the manifold. Problem is that many times, when you put the restrictor in, over time they burn out anyway.....it will be open one way or the other. This is my educated guess. Anyone else??? __________________ A quick "pedalfest" *Still getting loose (carb test)* 496 Initial fire up video!

06-25-2009, 01:01 AM	#3
GruntMoanCough Registered User Join Date: May 2009 Location: Pemberton, BC Posts: 1,075	Re: intake manifold question Blocking these off will give some free horsepower by keeping the intake cooler but, for street use this will increase warm up time. __________________ My goal in life is to be as good a person as my dog already thinks I am - Unknown

06-25-2009, 01:53 AM	#4
swtman Registered User Join Date: Mar 2007 Location: Red Deer, Alberta,Canada Posts: 22	Re: intake manifold question So it's ok that they are both open? It won't cause the manifold to over heat or anything??

06-25-2009, 03:01 AM	#5
GruntMoanCough Registered User Join Date: May 2009 Location: Pemberton, BC Posts: 1,075	Re: intake manifold question I don't think it will cause any problems. __________________ My goal in life is to be as good a person as my dog already thinks I am - Unknown

06-25-2009, 01:20 PM	#6
mclairmo Registered User Join Date: Jan 2006 Location: Take Off Posts: 1,908	Re: intake manifold question It's ok that they are both open and might be best considering your location. This is how the factory did it to help with cold start warm ups. Allows warm exhaust gases to run under the carb to increase fuel atomization when cold. In cold climates, you need this. However, in warm climates, many hot rodders block this to help keep the intake charge cooler and denser for more power.

06-26-2009, 12:10 AM	#7
swtman Registered User Join Date: Mar 2007 Location: Red Deer, Alberta,Canada Posts: 22	Re: intake manifold question thanks for all the replies guys!!



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