Deck height

1930 said
Ok so can someone walk me thru the steps to finding where my compression is going to be at with this engine.

I can get the required measurements just need to know specifically what they all are thats needed.

I like the write-up above posted by Crazycuda but since my engine is still in the vehicle and is slanted I dont see how I am going to be able to get an accurate measurement of fluid.

I measured the bore and it is stock, as far as what I have read stock bore is 3.40. For some reason this one comes under that at 3.95 or so.

I can get the piston deck height in the A.M and I am confident I can CC the chambers on the head.

As far as I know that is all that is needed. Once I have these figures what can I do with them?

I understand there are on-line calculators but Id like to figure it the old fashioned way and understand my work.

I have been told with the way fuel is going that I will not want to shave the head any more than is necessary to attain a 9.1 ratio.

Now that I think about it if I decide to use the larger valves I have purchased isnt that going to change the volume of the chamber in the head.

Do I need to do this head work before I can decide how much to take off the head to increase compression?

I dont just want to remove a 100thou and hope for the best. Id like to know what and why things are being done.

Ok, here's what you need to know to figure out your compression:

Volume of combustion chamber in head.

Measure compressed thickness and diameter of "fire ring" on head gasket.

Volume above the piston to the top of the block when the piston is at TDC. If you have a flat top piston, you can just measure how far down the piston is from the head deck of the block, and then get the bore diameter. You can just use the stock stroke if you don't want to measure it, but measuring it will be fine.

Then I can walk you through the calculation or do it for you.

Also as far as measuring the volume of the cylinder at TDC while the engine is in the block, you can make a cover plate as I described in the link to my thread on how to check compression. Just put the fill hole to where it will be at the top of the block - even if it is not flat. A little "slant" is good also as it makes it easier to tell when the cylinder is full.