Head Gasket Specs

[HalfdollarMayflower]

All,

Been a while since I've had a chance to post (medical issues, but that's a different story)...I'm in the final planning stages for a rebuild & need some measurements to help me decide what I want to do.

Motor is a 1950 P20 code (218), stock bore & stroke, never been touched as far as I can tell. She will be getting a .020 overbore and I'd like to have the block decked & cylinder head milled.

With a straightedge and feeler gauge, I have calculated that the deck clearance is 0.016" (piston sits 0.016" in the hole at TDC). This is contrary to a post stating that another (early) 218 had a deck clearance of 3/32", but the decks might have gotten shorter over the years...who knows!

Cylinder head is stock - I've read somewhere around 85cc and stock static compression ratio for this engine is 7.0:1.

By my calculations, decking the block 0.030" will make the piston stand proud of the block by 0.014" (.016 - .030 = -.014).

Decking the block in this manner has obvious advantages; it will bump the compression ratio slightly by reducing the 'quench' or 'squish' area and create more turbulence in the combustion chamber (so I have read), all of which leads to increased power!

I'd also like to mill the head somewhere around 0.050" to 0.060", but need a couple specs before I can get everything nailed down.

First, does anyone know the compressed thickness (or thicknesses) of head gaskets for these motors? I have heard 0.065, but surely someone knows for sure...this measurement is critical in determining my quench distance and static compression ratio.

Second, for you guys who have milled heads, do you have cc measurements of your combustion chambers after milling? Using some of the more refined compression ratio calculators on the net, I come up with a chamber volume of 85cc stock and approx. 75cc with 0.050" milled off...does this seem close?

Thanks!

Gary

[HalfdollarMayflower]

Somebody's gotta know the compressed gasket thickness...Fel-Pro p/n 7564C, Victor p/n 1059. Can't find it on the web, parts manual or Fel-Pro's website....

[Don Coatney]

I got .073"

[HalfdollarMayflower]

Thanks Don...what brand & part number is on the gasket?

[Don Coatney]

Thanks Don...what brand & part number is on the gasket?

No idea. This was the head gasket I removed from the 218 engine that was in my P-15 when I bought it several years ago.

[HalfdollarMayflower]

Thanks again Don...spoke with Mr. Asche tonight, he says that all flathead gaskets he's come across measure about 1/16.

Additionally, he says these iron heads can be milled up to 0.125" with no valve intereference, provided a stock lift cam is used. Deck is safe to mill at least 0.020", although he mentioned that famed modified/stock car driver Cotton Owens told him he went as much as 0.040". George seemed a little concerned about cutting into the valve seats that far, as he's never decked a block other than to freshen the surface...any thoughts on this?

CC'd my head tonight...comes in at 85cc's, so it's bone stock-untouched. I estimate that milling 0.060" off the head will reduce the chamber size by approx. 12.5-13 cc. Milling 0.050" should reduce the chamber volume by 10 cc...maybe someone will find that info useful.

I'm going to try to cc my old head gasket tomorrow...might be useful helping to calculate static compression ratio. It measures in at 0.070" in thickness, manufactuer unknown.