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Forced Induction This section for the traditional Pontiac V8

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Old 01-10-09, 03:59PM   #1
gtofreek
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Default Valve spring setup for boosted applications

Thought I would pass on how we figure out how much valve spring to put on boosted applications, for those interested.
We start by finding out what the cam manufacturer suggests for spring pressures. Usually this info is on the cam card but not always. This is for roller cams. I would not use this for flat tappet cams as lobe failure may result.

Then we measure the diameter of the backside of the valve from the inside edge of the valve seat.

Then we subtract the valve stem diameter off of that number. In Pontiac's case, .341".

Now multiply that number by 3.1416. This will give you your valve area.

Now multiply your valve area by the number of lbs. of boost you plan on running. This is how much seat pressure you should add to the spring pressure the cam manufacturer recommends.

Example: Let's say your running a 2.11" intake valve. The seat is .040" wide and the top of the seat is set .010" down off the outside edge of the valve.
This would put the bottom edge of the seat at a diameter of 2.01"[2.11"-.02"[for the .010" down off of each of the outside edges of the valve]=2.09"-.080"[for the seat width x 2]= 2.01" for the inside seat diameter.

Now we subtract the stem diameter of .341 from the 2.01" = 1.669".
1.669" x 3.1416[PI] = 5.2433304
Now, if your running 8 lbs. of boost, you would multiply 8 x 5.2433304 = 41.9466432 lbs. extra seat pressure. Or 42 extra lbs. seat pressure to round off. Just showing the math is all.

This is to help the valve stay seated under boost.
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Old 01-10-09, 09:53PM   #2
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Ooops! I goofed, this was not supposed to be a sticky. Maybe a mod can move it to the forced induction section.
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Old 01-10-09, 10:16PM   #3
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I think it's good for it to stay here, Paul.
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Old 01-10-09, 10:24PM   #4
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ACTUALLY, I stuck it since I liked the info


Sorry to freak you out.

Good info though.
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Old 01-10-09, 10:46PM   #5
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Thanks, I thought I posted to the wrong section.
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