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Discussion Starter · #1 ·
Ok i am stumped, did hks overlap these cams like what crower does with their 276/284 combo? Reason i ask is that with hks 272's my motor had 130psi for compression 6800ft. Now with the 280's its at 92psi all 6. Yes cams have been shimmed and all. I am curious if anyone else got the same readouts?
When I had the crowers 276/284 combo my compression was almost exactly the same at 90ish psi.
Thanx
 

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Shawn Davis
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I must be missing something. Why would changing your cams effect your static compression? The test is performed with the valves closed and the cylinder effectively sealed. Why would the timing of these events (unless there was no overlap) effect your compression?

S.
 

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Tuning focused...
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bigger cams always tend to loosen up some compression, interesting the big change from 272 to just 280s it has to be something.

I have arond 130 Psis with 272 as well with my built motor, went down from 175 psi on stockers...
 

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Discussion Starter · #4 ·
If there is overlap where it sucks in a bit of intake air while on the exhaust stroke then the compression would go down. I was curious if hks made these 280's to do that very thing.
Nothing else has changed on the car so the only thing I can point it to would be the cams.
 

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Maybe we can calculate the overlap on the 272 vs the 280 cams via the camcards. That would give you an indication.
 
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