TheOther77stang

Hey, I have a set of edelbrock performer head's w/ the large (2.02 in) intake valves, and I was wondering whether anyone knows whether they will work w/ the stock pistons in my 5.0. The engine was originally out of an '89 F150, but is running w/ a mustang 5.0 HO cam. I'm a bit concerned the large valves might run into the pistons, so I was woning if anyone knows, or knows where I could find out w/out actually pulling the heads off and trying.? Thanks.

nitrous_bob

stock cam and stock rocker ratio will work i am 99.99999% sure of

a little more lift and you'll have issues though.

Joel5.0

Lift has NOTHING to do with PtV......... FYI..... I've been working with a SC SN95, E-303 cam 4 degrees advanced (degreed) and 1.7 cobra rockers, 2.02 Edelbrock heads....... and no PtV problems (after checking, of course). The key ingredient is.... you have to check for PtV in YOUR setup.

mjr46

clay/play dough the pistons.. get a base line and go from there

nitrous_bob

so the valve opening more doesn't make a difference ?

really ?

how so ?????

mjr46

depending on the cam the valves are opening at a certain number of degrees before the piston ever reaches tdc.....I can't rattle the specs off the top of my head but a cam card will tell you often at what degree btdc the valve is fully open and so forth

nitrous_bob

yeah i was referring to the other comment , it does have something to do w/ it, itis not a completely unrelated topic

tyler72

Im not sure. I bought the total power package for my car and the heads came with 1.90 valves. Edelbrock says that the 2.02 valves will interfere with the stock pistons if you use their cam. However, A jegs head comes with 2.02 valves and they claim that it will work with stock pistons. I think its all just a big debate and I would buy 1 head gasket and install 1 head with a thin layer of play dough on top of the piston. Turn the motor over and then pull the head back off and look at the play dough to see how much clearance you have. If they are really close you might want to clearance the piston a little with a die grinder. Just make sure you do them all the same amount so that they remain balanced.

TheOther77stang

ok,I'm using a stock cam out of a 93stang right now. Thanks for your help,I wanted to make pretty sure they would work b4 I invested the money cause I don't have time to do a full rebuild w/ pistons and all now. Clearancimg the pistons won't jeapardize their structural integrity?

Joel5.0

It does, but not following the direct ".5xx" " lift relation....... PtV happens anywhere between 10° BTDC, TDC and 10° ATDC (TDC ±5° for most street oriented cams) in the exhaust-to-intake changeover cycle (overlap)..... and is totally dependent on the cam lobes profiles. The tappets lift at that point in the cycle could be anywhere between .050" - .100"........ if you plug-in the rocker ratio......they could be opened anywhere between .080" - .160" with 1.6 ratio...OR .085" - .170" with 1.7 ratio rockers...... the following piston vs. valves position should help in understanding it......



See how far away from the piston the valves are when they are at max lift?..... BTW..... you could have a .700" lift cam that would only have the valves opened at the same PtV lifts as a .480" lift cam during the overlap....... it all depends on the lobe profiles........ but not lift...... reason why you should always check.