LS9 Head Gaskets

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Oct 12, 2010 | 12:08 PM

koji777

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From: Bossier City LA

LS9 Head Gaskets

I've got a 408ci LS1..... iron block. My bore is 4.030

Mycar is turbo charged S91

Will LS9 head gaskets work well for me?

Thanks!!!

Oct 12, 2010 | 12:12 PM

Big_Bird_WS6

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yes. 6.2 LS9 is 4.062

and ls9 gasket will go up to 4.075

Oct 12, 2010 | 12:25 PM

JAX04

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From: Indy

I couldve sworn that i read they are a 4.1 gasket??

Oct 12, 2010 | 01:12 PM

Gonoma

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From: Easley, SC

Quote:

Originally Posted by JAX04

I couldve sworn that i read they are a 4.1 gasket??

Im fairly certain that they are 4.100" as well either way they will work on your 408 OP

Oct 12, 2010 | 02:20 PM

Big_Bird_WS6

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****. now that you guys say it. it might be a 4.100. either way you are fine. run it. lol.

Oct 12, 2010 | 07:51 PM

Mike454SS

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Umm...anybody going to mention thickness/quench/compression ratio?

Oct 12, 2010 | 11:21 PM

Big_Bird_WS6

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Quote:

Originally Posted by Mike454SS

Umm...anybody going to mention thickness/quench/compression ratio?

thickness is same as all of gm gaskets. .51

and compression is based off of more than just gaskets. a lot more

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Oct 13, 2010 | 09:59 PM

Mike454SS

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From: South Windsor, CT

Quote:

Originally Posted by Big_Bird_WS6

thickness is same as all of gm gaskets. .51

and compression is based off of more than just gaskets. a lot more

A LOT more? Deck height, compression height, piston dome/dish/valve relief, chamber volume (don't forget the volume of the valve faces...I've seen Ferrea ship different volume valve faces under the same PN), bore, stroke, and gasket bore/thickness...the OP didn't really say much other than that he has a 4.030" iron 408...nobody asked what heads, nobody asked if the block was zero decked and if so, what the piston tops look like...so my point was...rather than saying "yeah run those gaskets" maybe people could say "what are the rest of the specs on your engine?"...most GM gaskets are 0.051" and most STOCK gm bottom ends put the pistons out of the hole ~0.010" giving you very close to 0.040" quench...when you go to a built bottom end, I'd find it more likely that they were "in the hole" on paper, and the machine shop most likely milled the engine deck down to "zero" with the pistons...not always the case, but seems to be the most common...so then an off the shelf GM head gasket opens the quench up a lot...

I'm not trying to pick a fight...but there is a LOT more to head gasket selection than just "yeah, GM uses them with boost so go for it"...especially when it's a big bad built stroker that probably has a good amount of cash invested in it, and will have air forced into it, most likely with a fairly high HP/TQ goal...

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Oct 13, 2010 | 10:08 PM

wilson34

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From: Pittsburgh PA

^thank you

Oct 15, 2010 | 03:37 PM

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koji777

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From: Bossier City LA

The block has been completely gone through.... All I ca say is that I had Cometic gaskets, and the heads are Patriot stg 3 72cc. The comp ration on the build sheet said 9.5:1

I know this is not an actual measurement, but the Cometic head gaskets are a 16th of an inch by dial caliper.. don't know what they are compressed.

Thanks for any help and input!!!

Oct 15, 2010 | 09:43 PM

#11

Mike454SS

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From: South Windsor, CT

Calipers aren't accurate enough for thickness (could measure bore diameter with them though)...are there any part numbers on the gaskets that could be translated back to specs?

Oct 17, 2010 | 03:24 PM

#12

koji777

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From: Bossier City LA

no markings on the Cometics to give me a clue. Builder is no longer in the bizz...... don't know what size the Coms were other than a 16th with dial caliper

Oct 17, 2010 | 07:11 PM

#13

Mike454SS

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From: South Windsor, CT

Then at this point, you need to use a depth micrometer (borrow if necessary) to measure if your pistons are at zero deck, or in the hole, or out of the hole, and how much...then you really should also measure the displacement of their valve reliefs and of your chambers on your heads before you buy head gaskets.

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