Northstar Engines and System Technical Discussion Discussion, headgasket thickness?! in Cadillac Engine Technical Discussion; Does anyone happen to know what the stock/factory headgasket thickness is by any chance? Thanks in advance........
Not in the service manual or alldata. Most stock graphite/metal sandwich gaskets are something like .080" - .100" new, .040" - .050" compressed. For a Northstar, which has minimal deck clearance (.017"), that .040" in the quench areas is the source of the "cold carbon rap". The absolute maximum head cleanup cut is .007", so GM doesn't want compressed gasket thicknesses to get too thin.
You might get in touch with Cometic and ask for their MLS thickness for a Northstar. MLS gaskets do not, for all practical purposes, compress.
OK, it took 34 seconds - The Cometic MLS for Northstar is .066" new. Around $175 each.
Automobile(s): 98 eldo/KD54 w/N37,T96,QA1,D55,DS3,U1Z. U3R next
Re: headgasket thickness?!
I had researched the Cometic MLS gaskets and saw the .066 listing.
I called a vendor and asked what was the stock replacment thickness and he stated the .066 was the replacement. Yet, that got me wondering was the stock gasket the same thickness? How do I know for sure that I'm not lowering/ raising my compression without a reference number to go by?
I figured with all the headgaskets being done now and before me that this topic had to come up.
FelPro (Federal Mogul) and other gasket makers will stick darn close to the stock engine designer's compressed gasket thickness specs. You really need to change gasket thicknesses radically to make any significant compression ratio change.
An off-the-shelf FelPro gasket set, bought in January, for one of my (1970 ?) 455 Olds engines comes out at exactly the 1970 compressed specs for a 10.5:1 engine - .040". BUT, we don't want a working marine engine to run at 10.5 or 11:1 so we use dished pistons to lower the CR to < 10:1.