PI swap help

Darkhorse97

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Hey all, need some advise on some work I am about to do to my 97 with an auto. I am doing a PI swap complete with stage 3 comp cams with beehive springs . I was doing some research and hearing that it will not work because of valve to piston clearance. Not sure what the best plan of action is here. I have the heads completely assembled. Want to up the power NA but am I screwed without having to cut reliefs in the pistons ?
 

apsmith49921

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You probably won't have piston to valve clearance. Which means your stuck with 2 options. New pistons or New cams

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Silver95bird

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it sounds like you're not well researched. best options here:

1) get smaller cams. PTV is much better, and so is performance below 4000.
2) degree your cams. you should be doing this regardless with any aftermarket cam.

the larger the cam, the more you give away on the bottom end. then the give away is compounded by having to retard the cam timing to make the intake lobe clear the piston.

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96blak54

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Definitely gonna have ptv clearance issues!

Some folks have success hand carving valve reliefs into the pistons. You really only need about .065" depth and its all cut out on the piston dish edge, so its not alot of carving really.

Some have took a valve, made it into a cutter, or used a sanding disk stuck to the face and used a bare head as the cutter guide. Ran a power drill on the valve cutter to achieve valve reliefs exact location.

Their are companies that make the exact tool i just described. Looks like a long stem valve that has little cutting edges and again, must use the head as a cutter guide.

While you ger all this work done, send your cams back to comp and have the regrind the exhaust opening 20° later.
 

apsmith49921

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Bottom ends are the same in both cars. Shouldn't have ptv issues

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lwarrior1016

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The piston dishes are different between pi and npi, but the lip around the outside of the piston is what contacts the valve and it’s the same between the two. Pi cams in an npi engine does not have clearance problems.
 

96blak54

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Nasty cams can be ran with npi heads with no valve contact problems.
 

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