Posted By: MNobody
Figuring Piston to valve clearance, help......... - 08/16/12 12:07 AM
Ok, Ive got a 318 with a .528 solid running .026 lash on all. I'm trying to check the piston/valve clearance without the stock adj.rockers on. with the piston at TDC and the head sitting on the block with no head gasket, moving the valve up and down between the seat and the top of the piston i've got approx .165 of movement and i'm confused, very confused lol. Thanks!
Posted By: MNobody
Re: Figuring Piston to valve clearance, help......... - 08/16/12 01:02 AM
Thanks Guy's, the short block is still assembled in the car. I've got Ross 10:1 's w/valve reliefs, .090 down in the Ho and i'd like to shave these 72cc chambered 360 j-heads down to gain back some compression. Think i can take take .040 off them and use a.025 head gasket safely? I don't have a dial indicator, cam and lifters are still in the block i measured .352 lift at the solid lfter x 1.5 =.528 but then i got lost....
Posted By: GO_Fish
Re: Figuring Piston to valve clearance, help......... - 08/16/12 02:05 AM
Your heads are off. I just put playdoh on top of a piston, bolt the head on loosely, get your lifters set where you want, then slowly turn the motor over by hand. Pop the head back off and take a utility knife and slice a cross section of clay across the middle of each valve. You will be able to measure your actual clearance, then add for your compressed head gasket and subtract for your milling, then you have your number. You could do this on multiple cylinders for a higher comfort level if you want.
Posted By: MNobody
Re: Figuring Piston to valve clearance, help......... - 08/16/12 03:18 AM
Thank you! turns out with the gasket in place .046, i only have about .015-.020 on the intake and about .050 on the exhaust. Taking .040 of the surface could have been a problem....
Posted By: 5spdcuda
Re: Figuring Piston to valve clearance, help......... - 08/16/12 03:45 AM
Ideally you should have at least .100 on the intakes and .125 on the exhausts. You can get away with less, but if you get any valve float it may not be very pretty.
Posted By: 383man
Re: Figuring Piston to valve clearance, help......... - 08/16/12 03:58 AM
The clay will work fine. But you have to have the timing chain on and in time and the valves adjusted. You will want to check both the intake and exh all thru the overlap period the exh/int stroke. As long as you turn the eng over a full 360 degrees you should get a reading. I use a light spring under the valves when I do it as that way if I have one that I feel is close I will bring it up to that spot and then put a dail indicator on the valve and push the valve down until it hits the piston to get a very accurate check. Ron
Posted By: MNobody
Re: Figuring Piston to valve clearance, help......... - 08/17/12 05:32 AM
Why is that? Oh the head gasket measures .050 i measured in a bad spot before. Fixed a couple valves and lapped them all in, gonna put her back together with the same kind of gasket's it had.
Posted By: MNobody
Re: Figuring Piston to valve clearance, help......... - 08/18/12 06:05 PM
Must be the reason they went with a mechanical cam, I can't believe this thing run's as good as it did with 8.17 comp and i won't even get into what i found with the heads. Needless to say they are getting the ports cleaned up and i lapped the valves, new heads in the near future. Gonna put her back together with the same thickness gaskets as it had with hopefully no surfacing. Guy told me he ran .026 lash on all the valves, i'll loosen them up to .028 just for grins and giggles. I look at it this way, they beat the crap outta the 318 at the track trapping at 7,000. I beat on it every time i take her out, and the only issue i found so far is bad workmanship done on the heads with leaky valves.