Need head gasket help

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Apr 4, 2014 | 04:55 PM

Jc803

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From: Lexington, SC

Need head gasket help

I've been trying to research and find out what head gaskets I need but everything is so confusing. I've got a LQ 408 with AFR 225 heads. Can anyone tell me what I need. I'm mostly confused about what bore size to get. And I bought the car with this bottom end so I dont know how much it was bored

Apr 4, 2014 | 06:26 PM

Darkman

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It is presumably a 4.03 bore with a 4.00 inch stroke. With the AFR 225s you will need at least a 4.125" bore gasket.

Last edited by Darkman; Apr 4, 2014 at 06:34 PM.

Apr 4, 2014 | 10:40 PM

Jc803

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Damn glad i read this before i bought ls9 gaskets. Why is it a 4.125? Just curious, I'd like to learn this stuff so I'll know next time. I read somewhere that guys want .030 more than the bore. So wouldn't i need at least a 4.060 assuming the bore is .030 over

Apr 5, 2014 | 12:45 AM

COSPEED2

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They recommend them on their site, but we have sold smaller gaskets than this for them. I cannot tell you why they recommend such a large gasket really.
In theory you COULD use a 4.040/.050/even .085 gakset, but I would contact AFR just to make sure. they can tell you the real reason.

Seems to be such a large area of quench lost using that large of a gasket.

Apr 5, 2014 | 06:45 AM

LS1MCSS

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I have 4.120's on my 418 with the AFR225 heads.

Apr 5, 2014 | 08:56 AM

Jc803

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Oh ok, so the reasoning is because you go by which is bigger, the heads or the bore, and in this case you guys are saying the heads are bigger, it doesn't have anything to do with the bore. That's how i take it.

Well if all three of you say run a 4.12x then I'll take your word for it

Apr 5, 2014 | 09:26 AM

Darkman

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Quote:

Originally Posted by Jc803

For what it is worth, the recommendation of a 4.125" gasket for the AFR 225s originates from Tony Mamo/AFR and has to do with the size of the chambers. There are numerous threads on the need for larger gaskets on AFR heads - e.g. https://ls1tech.com/forums/generatio...re-gasket.html. Like coSpeed2 suggested, you might want to call AFR to verify that this is still their recommendation.