Author Topic: CCR work sheet  (Read 1246 times)


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CCR work sheet
« on: May 11, 2011, 05:41:46 PM »
I worked up a corrected compression ratio work sheet for the 350. The spreed sheet will give you an idea of the CCR of what you have and what the changes are or effects of propossed changes. This one is for stock base gasket only.

Enter your bore 80 for 80mm ect
Enter your storke 68
Enter 125.4 for rod or your rod used in case of long rod
Enter you head volume in cc's
Enter head gasket ID
Enter head gasket crushed thickness
Enter the deck, the distance from piston crown edge to top of cylinder
Enter the piston dome volume Use bore x 0.17475 for a wiesco that will get you close.
Enter the distance from top of the cylinder to the top of the transfer ports ( if ports are all diff than average the number)
Enter the distance from the top of the cyliinder to the top of the exhasut port.

This wil give you a corrected compression ratio and will also give corrected degrees of port open via piston positions and blow down degrees. Thenn you can look down the chart and see what a ex open port change will do to CCR and blown down degrees.

This is important to log as you over bore a cylinder due to the ports roof gets lower as it is over bored due to it's at an angle. It will alos raise the CCR due to the bore is larger and the effective stroke has changed. The blown down timng also chages as the the top of the exhasut port roof lowers.

IF you enter all the correct information you can  have an idea of this effect.

First you can change the bore  than the efficitve stroke or head gasket thickness in combonation with the others and see the results. This is not an quide to use as it's just Back Yard Hacker math. But it will give you an idea how the engine is effected. This will also remove some of the guess work involved.

Remember this is CCR only and MSV is also effected which is another sheet and topic.

Tip: the stock CCR of a stock post recall ody is 6 to 1

Some have some fun and play with the spreedsheet. I'll do my best to ansawer any question as they arise. I then will add to this sheet as we look at the durations, mean line for time area and angle area for power bands.

I have locked up the sheet for now so any one can play with changing up the calculations.