Need Head Gasket Help
Thread Starter
Safety Car
Joined: Jun 2005
Posts: 3,841
Likes: 0
From: Inver Grove Minnesota
Need Head Gasket Help
I need to bump up my compression ratio. In order to do this I was going to switch to a .015 compressed thickness gasket which would only be 3.2cc of volume which should bring me up about a half a point. I called Fel-Pro and they told me I can't run a .015 thick gasket on the street since that is not what it was intended for. Is this guy just reading what the book says or is he actually right.
Racer
Joined: Apr 2004
Posts: 401
Likes: 0
From: IL
Have these on my built 327, using aluminum AFR 180 Eliminator heads. Got these #1094 before they were officially out from the hiperf engineer who designed them.
Surface finish is a concern, these aren't to be swapped with just anything. Surface finish must be ideal and machined within a range (sorry don't have Ra spec handy) in order to seal. Composite gaskets are a little more forgiving in this regard.
Plus aftermarket heads usually have a thicker deck surface and have little to no head deflection (bending) when torqued. This ensures compression of the emboss beads in the gasket. Also the thicker deck surface aids in compression of the wire c.o. ring that under the armor in composite #1003 head gaskets.
Bottom line, depends on the hardware your using. Stock heads, use the o.e. gasket. Even the #1003 sometimes don't seal on stock heads because of head bending. The ring doesn't compress and prevents clamping of the body/coolant ports and can weep coolant.
Check out this site for general catalog specs.
http://www.21cgt.com/FMWebCatalog/default.htm
Surface finish is a concern, these aren't to be swapped with just anything. Surface finish must be ideal and machined within a range (sorry don't have Ra spec handy) in order to seal. Composite gaskets are a little more forgiving in this regard.
Plus aftermarket heads usually have a thicker deck surface and have little to no head deflection (bending) when torqued. This ensures compression of the emboss beads in the gasket. Also the thicker deck surface aids in compression of the wire c.o. ring that under the armor in composite #1003 head gaskets.
Bottom line, depends on the hardware your using. Stock heads, use the o.e. gasket. Even the #1003 sometimes don't seal on stock heads because of head bending. The ring doesn't compress and prevents clamping of the body/coolant ports and can weep coolant.
Check out this site for general catalog specs.
http://www.21cgt.com/FMWebCatalog/default.htm
Thread Starter
Safety Car
Joined: Jun 2005
Posts: 3,841
Likes: 0
From: Inver Grove Minnesota
I have Holley aluminum heads:
http://store.summitracing.com/partde...5&autoview=sku
Would I be better off going a different route?
http://store.summitracing.com/partde...5&autoview=sku
Would I be better off going a different route?
Last edited by JustinD; Aug 14, 2007 at 03:28 PM.
Thread Starter
Safety Car
Joined: Jun 2005
Posts: 3,841
Likes: 0
From: Inver Grove Minnesota
They are some sort of dished piston on a 4 bolt main block with the factory deck height. It was a gm performance crate motor bought in 86, or at least that is what the guy told me that I got the car from. Which could be absolutely wrong since he was dumb enough to blow the stock engine. It has a .041 thick on it now.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Me thinks you should pull the heads off & check this stuff before you decide on a gasket. Get us a down in hole measurement and pics of deck surface & piston tops.
-edit- unless they are truly needed, I'd suggest heads without heat Xover. Unless truly needed, suggest blocking both Xovers at head with a thin steel shim. FYI, some chokes are dependent upon Xover but can be modded.
-edit- unless they are truly needed, I'd suggest heads without heat Xover. Unless truly needed, suggest blocking both Xovers at head with a thin steel shim. FYI, some chokes are dependent upon Xover but can be modded.
Last edited by jackson; Aug 14, 2007 at 04:36 PM.
Veteran
Joined: Oct 2005
Posts: 1,284
Likes: 81
From: Nashville, TN
Me thinks you should pull the heads off & check this stuff before you decide on a gasket. Get us a down in hole measurement and pics of deck surface & piston tops.
-edit- unless they are truly needed, I'd suggest heads without heat Xover. Unless truly needed, suggest blocking both Xovers at head with a thin steel shim. FYI, some chokes are dependent upon Xover but can be modded.
-edit- unless they are truly needed, I'd suggest heads without heat Xover. Unless truly needed, suggest blocking both Xovers at head with a thin steel shim. FYI, some chokes are dependent upon Xover but can be modded.
There is no point in buying anything until you get the heads off to know exactly what you are dealing with. There are plenty of this and that guys out there that have no idea what they are talking about and this kind of sounds like the guy you got it from if he can't produde a receipt for what he put on it.
If he THINKS its a GM crate engine in, then there are a wide variable of ranges of what is actually on it. Also you really need to know your camshaft timing to really judge what CR is good and what is too much for safe street operation on pump gas.
NCM Grand Opening Veteran
Joined: Sep 2005
Posts: 20,979
Likes: 384
From: South of giving a damn
St. Jude Donor '11, '17
You'd be better off pulling the heads (like the others stated), verify the components & then consider shaving the heads for your CR increase. Holley website or tech support should be able to tell you max amount that can be safely removed from the head. You can then decide on the proper head gasket, which will provide the proper amount of quench.
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