compression

[my1946trk]

How much do I need to remove from my 1954 DeSoto 251 head at 7 to 1 stock to reach at least 8.5 to 1 , I have tried for a long time to find a 59 head at 8 to 1 stock but no such luck , so for economics sakes i will plane the head I have , I also have now a .435 lift cam instead of stock .375 so how much safe clearance top of valves to head am I allowed , This may determine how much I can remove from the head right from the get go , o well lets see what I can learn from you people , Thanks for now ,, Leo ,, myoldtrk ,,

[greg g]

Some where on the site there is a chart, but I took ,040 off my head and .010 of my block on my 230. My machinest estimated mine at about 8.4 and based on the compression test of 140 psi cold, that confirms that estimate. The 251 may differ slightly due to the increased compressable volume in the cylinder.

[Don Coatney]

I learned enough to do a bit of measuring and searching before I ask. Use a dial indicator to measure your valve lift and a hunk of clay on top of the valve to figure your valve to head clearance. Also here is a chart to help you with the math on your head milling.

[Don Coatney]

This might be of interest too.

[Rusty O'Toole]

As you live in Canada, if you can find a head off a Plymouth or Dodge car 1957 58 or 59 you will have high compression, they were 8:1 on the 230, higher on your engine. Then there are the Dodge trucks up to 1962. 55 and 56 cars about 7.5.

This trick will not work in the US as the Dodge and Plymouth head will not fit the DeSoto block.