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What intake manifold gasket do I need? LT-1 heads on 350

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Old 09-04-2010, 11:04 PM   #1
arcticcatmatt
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Default What intake manifold gasket do I need? LT-1 heads on 350

Hey guys, I already ordered up the wrong gaskets and wasted 40 bucks.

I have a 350 small block with 71-72 LT-1 75cc heads casting number is 3973487. Here is a picture

I just got these gaskets in

http://www.summitracing.com/parts/FP...n/?prefilter=1
There is no center hole which I think is exhaust for EGR function if I wanted to use it. And its too tall, can't get valve covers on.
and they do not fit even though they say they are for a small block chevy. Now I see in the text that it won't fit an LT-1 setup so I am having a hell of a time figuring out what I need.

Help please! THANKS

Last edited by arcticcatmatt; 09-04-2010 at 11:55 PM.
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Old 09-05-2010, 01:08 AM   #2
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Quote:
Originally Posted by arcticcatmatt View Post
Hey guys, I already ordered up the wrong gaskets and wasted 40 bucks.

I have a 350 small block with 71-72 LT-1 75cc heads casting number is 3973487. Here is a picture

I just got these gaskets in

http://www.summitracing.com/parts/FP...n/?prefilter=1
There is no center hole which I think is exhaust for EGR function if I wanted to use it. And its too tall, can't get valve covers on.
and they do not fit even though they say they are for a small block chevy. Now I see in the text that it won't fit an LT-1 setup so I am having a hell of a time figuring out what I need.

Help please! THANKS
Stock gasket with the open heat crossover you want fel pro FPP1256 if you want the stock size gasket with a blocked heat crossover you want FPP1204. both gaskets have the same 123 x 199 runner size. The gaskets you bought if there from summit simply send them back. If your in a hurry most auto parts stores will have fel pro gaskets.

Last edited by Little Mouse; 09-05-2010 at 01:38 AM.
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Old 09-05-2010, 09:06 AM   #3
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Since the LT1 engine has a 'reverse' flow cooling system, can that setup use a typical intake manifold for a carb versus the injection system the LT1 came with ???
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Old 09-05-2010, 05:01 PM   #4
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71/72, LT1 heads pictured did not have reverse flow, fuel injection.

Last edited by Little Mouse; 09-05-2010 at 05:09 PM.
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Old 09-05-2010, 05:54 PM   #5
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Since the LT1 engine has a 'reverse' flow cooling system, can that setup use a typical intake manifold for a carb versus the injection system the LT1 came with ???
71-72 did not offer fuel injection or reverse flow cooling.
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Old 09-05-2010, 07:47 PM   #6
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My 'bad' - I had my wife's '95 SS Impala on the brain. The engine is called 'LT1' and it features reverse flow cooling to run a little more advance with the computer.

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71-72 did not offer fuel injection or reverse flow cooling.
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Old 09-05-2010, 09:57 PM   #7
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Thanks little mouse. I will check that out. It appears the center is not cut out though?

This is for a supercharged engine so I am told I need the metal center gaskets.

I am confused what you others said. These heads were designed for fuel injection? What is reverse flow?

I looked up the casting number 3973487 and the internet told me 71-72 LT-1 heads, thats all I know. This was a drag car I am converting to be more streetable. I took the dual carbs and NOS off.. it is keeping the blower and the new holley blower carb and hilborn scoope are going on as soon as this stupid intake is figured out

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Old 09-05-2010, 11:40 PM   #8
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Coolant flow was reversed thru early-mid-90's 5.7L 'LT1' engine and 9C1 engine. The additional cooling facilitated more advance through the systems computer and the result was a fine running engine that would rev really fast. I believe the Corvette LT1 in that era had aluminum heads and/or aluminum block, but don;t quote me. The SS Impala and 9C1 was all iron. All this on 89 octane. You could 'tune' the engine to run even better by tricking it into using 93 octane, installing cooler t-stat, freer flowing air intake, headers + 2.5" exhaust, etc. It was a sleeper of a big car. We had two SS Impala's and one 9C1 - they are truly neat cars.

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Originally Posted by arcticcatmatt View Post
Thanks little mouse. I will check that out. It appears the center is not cut out though?

This is for a supercharged engine so I am told I need the metal center gaskets.

I am confused what you others said. These heads were designed for fuel injection? What is reverse flow?

I looked up the casting number 3973487 and the internet told me 71-72 LT-1 heads, thats all I know. This was a drag car I am converting to be more streetable. I took the dual carbs and NOS off.. it is keeping the blower and the new holley blower carb and hilborn scoope are going on as soon as this stupid intake is figured out
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Old 09-06-2010, 08:00 PM   #9
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Measured a the ports tonight with my dials. 1.19 x 2.10. The gaskets little mouse said I need are 1.23 x 1.99 according to the website. Sounds like he is correct. I am hesitant to order them because the center port square isn't knocked out in that picture.
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Old 09-06-2010, 08:12 PM   #10
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Many of the intake gaskets have that small hole in the center exhaust crossover or come with a little 2 piece stainless plate to install and restrict the amount of exhaust that flows thru there. My usual thing is to get gaskets that are 100% blocked or cut a thin piece of stainless and put that in there. But I'm trying to keep all the heat I can out of the intake.
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Old 09-07-2010, 09:29 AM   #11
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^ Gotcha. I may do the same, considering I don't drive in winter and this is a supercharged car I have enough heat to deal with.

Here is a picture of the gasket that came out of it. These fit no problem with those valve covers. So I need a set of these whatever they are.
[IMG][/IMG]

Last edited by arcticcatmatt; 09-07-2010 at 09:35 AM.
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Old 09-07-2010, 12:57 PM   #12
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Just ordered these http://www.summitracing.com/parts/FPP-1604/
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Old 09-07-2010, 04:00 PM   #13
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They look like the Felpro gasket you'll get when you go to NAPA. (If you look very closely, you should see: "This Side Up" on on side of the gasket. Did yours not have the metal restrictor in the center cutout?

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^ Gotcha. I may do the same, considering I don't drive in winter and this is a supercharged car I have enough heat to deal with.

Here is a picture of the gasket that came out of it. These fit no problem with those valve covers. So I need a set of these whatever they are.
[IMG][/IMG]
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Old 09-07-2010, 07:57 PM   #14
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Quote:
Originally Posted by arcticcatmatt View Post
Measured a the ports tonight with my dials. 1.19 x 2.10. The gaskets little mouse said I need are 1.23 x 1.99 according to the website. Sounds like he is correct. I am hesitant to order them because the center port square isn't knocked out in that picture.
If you have an accurate top to bottom measurement on the head. FPP1205 is 128 X 209. without looking it up doubt it has the heat crossover.
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Old 09-07-2010, 08:25 PM   #15
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As TimAT wrote ... cut your own Xover block from thin shim stock ... you can add that to an OE replacement-grade intake gasket & go racing; No problem. Glue shim to heads w/ silicone ... then install gasket as usual. Do NOT use aluminum shim; Al Will burn thru sooner than later.

-add-
above is commonly used in restricted circletrack motors where both OE iron heads 487 etc & EB performer 2101 intakes are mandated. Cheap replacement grade gasket w/ a homemade shim is fine ... I run some rtv around the coolant & aircharge ports too.

Last edited by jackson; 09-07-2010 at 08:34 PM.
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