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View Full Version : Did a compression test tonight.

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1ViciousGSX
03-23-2006, 01:19 PM
Why would the cams affect it in a negative way? Wouldnt the extra lift and duration allow more air in for higher compression results?

Not saying you said the cams would affect it but since you refered to it as being a possibility I was kind of curious.Late closing of the intake valves will reduce compression at cranking speeds.
tim
03-23-2006, 02:25 PM
Yeah, I was thinking about that a little more last night after I posted. I would think though that the late closing of the valve would be offset by the extra lift and it wouldnt really affect compression much.

Maybe not, it just seems to make sense to me.
CDeutsch
03-23-2006, 04:05 PM
I did a compression test before and after changing cams. My numbers were 10-20psi lower with Crower Stage IIs.
1ViciousGSX
03-23-2006, 08:05 PM
Yeah, I was thinking about that a little more last night after I posted. I would think though that the late closing of the valve would be offset by the extra lift and it wouldnt really affect compression much.

Maybe not, it just seems to make sense to me.At cranking speeds, lift has no real effect. The air flow is way too slow for lift, duration or port velocities to make a difference. It's only mechanical closing of the valve in relation to the piston's travel that will change compression at this point.
tim
03-23-2006, 08:19 PM
That makes sense too, thanks.
Onefast99gsx
03-23-2006, 09:11 PM
Makes sense to me too. Thanks for that additional input on this subject.
joesushi
03-25-2006, 10:43 PM
I did a compression test before and after changing cams. My numbers were 10-20psi lower with Crower Stage IIs.

Hey Chris! I recently just had a head put together by a friends shop. It's got used valves but all checked out ok, crower II's, titanium retainers, and upgraded springs. How did the crower's perform for you?

PS sold that galant yet?
CDeutsch
03-26-2006, 07:48 AM
Hey Chris! I recently just had a head put together by a friends shop. It's got used valves but all checked out ok, crower II's, titanium retainers, and upgraded springs. How did the crower's perform for you?

PS sold that galant yet?

They're better then stock. I probably should have them degreed to maximize performance.

Still have the galant, someone is looking at it today. :)