Ptv
11-02-2008, 09:33 AM
#3
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I know claying is the only way to know for sure but I was wondering if there is a calculation to get somewhere in the ballpark before buying all of the parts. I have a good idea what cam and heads I would like to run(Thanks Predator-Z) but I am trying to figure out what rockers, pushrods and head gaskets to get.
11-02-2008, 05:10 PM
#7
FormerVendor
You can "ghetto" calculate what the normal P to V will be but it is not always 100% accurate and you woudn't know if you have good radial P to V clearance like Brad said above since that's not a thing that you can calculate. The radial valve clearance to the piston is soley due to where the reliefs are cut and just has to be checked.
If you want to estimate the regular vertical P to V you need to know your intake and eshaust valve's free drop in the head and your piston's valve relief depth and your piston's position in or out of the hole and your head gasket's compressed thickness. Then you also need to know the cam's lift at TDC when it is degreed in where it will be if you know that and your rocker ratio is you can see what it is approximately at TDC and it will be .030-.040 tighter than that where it's closest around 10 degrees away from TDC.
The best way is to degree the cam and then with a checking spring see how much P to V you have on intake 10 degrees after TDC and exhaust 10 degrees before TDC on the overlap phase. You can usually see the exhaust radial P to V right down the exhaust pirt at TDC with a light whereas the intake you can't really see so easy so you might clay that one.
If you want to estimate the regular vertical P to V you need to know your intake and eshaust valve's free drop in the head and your piston's valve relief depth and your piston's position in or out of the hole and your head gasket's compressed thickness. Then you also need to know the cam's lift at TDC when it is degreed in where it will be if you know that and your rocker ratio is you can see what it is approximately at TDC and it will be .030-.040 tighter than that where it's closest around 10 degrees away from TDC.
The best way is to degree the cam and then with a checking spring see how much P to V you have on intake 10 degrees after TDC and exhaust 10 degrees before TDC on the overlap phase. You can usually see the exhaust radial P to V right down the exhaust pirt at TDC with a light whereas the intake you can't really see so easy so you might clay that one.