piston valve clearance
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Mountain Pass
Joined: Dec 2005
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piston valve clearance
I have dooe c heads that have been milled even with the valves got em cheap i have a factory flat top piston came off of a 86 5.0 , supposely has 512 lift on the intake without the rockers installed to put a thin peice of stirofoam like come with a burger about thick as a nickle and turned the motor and it left a very lite indention on the stirofoam (didnt have puddy on hand) and im wondering do yall think i'll have a clash
FTE Legend
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From: Ottawa, Ontario
Valve clearance is about cam duration as much as valve lift, because it really doesn't matter how far the valves open when the piston is at the bottom of the hole. You need to assemble the complete valvetrain for at least 1 cylinder and rotate the motor through a full cycle to determine if there is a clearance problem. You also need to disassemble a lifter and stuff it solid so you get an accurate reading of what happens when the motor is under oil pressure.
Last edited by Conanski; Jan 10, 2008 at 10:25 PM.
Hotshot
Joined: May 2003
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From: south louisiana
Problem with styrofoam is it doesn't stay compressed. Your mix of heads, cam and pistons with no valve reliefs spells dissaster with it running. The reason those pistons didn't need reliefs was the valves in the heads used with em were 1/8" farther away from the deck. They're sunk deeper into the E6SE heads.
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Mountain Pass
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Hotshot
Joined: May 2003
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From: south louisiana
E7's will not change anything enough to clear those pistons. All you're gaining is a slightly smaller valve as far as clearance goes. Headgasket spacer shims? Never heard of them. Thicker head gaskets can gain you clearance but at the cost of a lowered compression ratio. Do the job right and change pistons.
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I'd change the pistons or keep the cam small enough... you might be ok with 500 lift but like what was stated its the duration that matters although they go hand and hand... big lift big duration...
if you can use heads that have not been decked and use the thickest gasket you can find....then try and keep the preload to a minumummmmm..lol the more preload on the lifters the more the valve will open if you miss a gear and float the valves... 1/8 to 1/4 turn max..
and you should have at least .100 clearance on the exhaust and .080 on the intake...
if the heads are off grind some reliefs in the pistons....just make a template and grind away just need to do the exhaust... most cams for sbf will have a higher lift and longer duration on the exhaust side thanks to the wonderful heads they made...
if you can use heads that have not been decked and use the thickest gasket you can find....then try and keep the preload to a minumummmmm..lol the more preload on the lifters the more the valve will open if you miss a gear and float the valves... 1/8 to 1/4 turn max..
and you should have at least .100 clearance on the exhaust and .080 on the intake...
if the heads are off grind some reliefs in the pistons....just make a template and grind away just need to do the exhaust... most cams for sbf will have a higher lift and longer duration on the exhaust side thanks to the wonderful heads they made...
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Mountain Pass
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do they make studs for roller rocker that will screw in to the existing bolt holes that are on the factory heads instead of getting them machined im running out of time we race jan 23 golden isle speedway
Hotshot
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From: south louisiana
Originally Posted by leftystar
do they make studs for roller rocker that will screw in to the existing bolt holes that are on the factory heads instead of getting them machined im running out of time we race jan 23 golden isle speedway
More Turbo
Joined: May 2003
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Ditch the styrofoam idea. Do it right. Mock up a full valvetrain, and test it right. Thats a lot of lift for 1.84 valves on a stock 86 piston though. It might clear depending of duration, but I would not bet on it. I just swapped in a cam with 544 lift, and I am running a HO shortblock with valve notches, with the same heads as you with 1.94 valves, and I hit. I had to lay the eyebrow back a little. So learn how to check it, and do it right, or stick with stock. Or risk it...
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