Checking P to V clearance
01-26-2005, 02:44 PM
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Checking P to V clearance I am going to be installing a G5X3 in with PP stage II heads with a 114 LSA. I have not found a straight answer so I am going to swap it in. Once the cam is in if there is no clearance issues the motor should turn over by hand without stoppping right? If it stops I'll need to flycut the pistons. Is this an ok way to check or do I need some special tool to check instead? I know there are other ways to check but if this way works why not.
01-26-2005, 03:13 PM
#3
the reason this method wont work is because theres no positive valve retraction on a conventional pushrod motor.
in otherwords, when the valve is suppost to close, it doesnt always do it instantly along the backhalf of the cam ramp.... sometimes it lags behind... it has mass, and the spring can only close it so fast....
so when the motor is spinning, the valve may be down farther as the piston comes up...
because of this, you need a gap larger then just enough to turn it over... the best way to check is still the clay on the piston, turn motor over, and measure test.....
just dont use playdoh as it expands when compressed, giving false readings... modeling clay is best.
in otherwords, when the valve is suppost to close, it doesnt always do it instantly along the backhalf of the cam ramp.... sometimes it lags behind... it has mass, and the spring can only close it so fast....
so when the motor is spinning, the valve may be down farther as the piston comes up...
because of this, you need a gap larger then just enough to turn it over... the best way to check is still the clay on the piston, turn motor over, and measure test.....
just dont use playdoh as it expands when compressed, giving false readings... modeling clay is best.
01-26-2005, 03:42 PM
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im looking to use the same cam w/afr 205s. you should have clearance if the heads are not milled. answer to other question no u cant just roll over the motor and hope it turns over than youre fine. what if the valve only had .001 clearnce it would still roll over but as soon as you fired it up bye bye.check out a few of the threads in the last couple of days there was some info on p/v clearance.good luck
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lots of people say its more accurate than clay
01-26-2005, 08:45 PM
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Steve, you shouldn't use pre-load when checking, it could give you a false reading. Unless they arel totally solid. It would be better to use a solid roller lifter and adj pushrod set to zero lash. Of course dial indicators are best, and I think everybody would say its more accurate!
Last edited by SLED28; 01-26-2005 at 08:51 PM.
01-26-2005, 09:18 PM
#10
Originally Posted by SLED28
Steve, you shouldn't use pre-load when checking, it could give you a false reading. Unless they arel totally solid. It would be better to use a solid roller lifter and adj pushrod set to zero lash. Of course dial indicators are best, and I think everybody would say its more accurate!
01-26-2005, 09:39 PM
#11
A test spring is about as strong as a wound up paper clip...i because the spring inside the lifter is WAY stronger than the test spring is...it's just barely enough to hold up the weight of the valve...as a result, you should really set no pre-load at all, just go to zero lash...pre-load might cause the valve to open on the base circle of the cam, and thus never close, and thus be that much closer to the piston than it'd ever actually be.
You're right guys. Sorry for the false info.
I deleted my post. Anyway, I guess I had more clearance than I thought. Last edited by Steve H.; 01-26-2005 at 11:32 PM.