Too much lift?? Not enough piston to valve clearance??

There is a math equation to figure out your lift but damned if I know what it is, math was never my strongest suit. I'm sure theres some Stangers on here that know how to figure that out.

I don't know off hand what the size of the E7 head valves are, they may be small enough that you can get by. If you can't figure it out don't risk it, I'm going to be doing a H/C/I/TB/Inj/MAM/etc... change soon so I researched the ways to measure Piston to Valve clearance. Check this website out if you end up having to measure.

you will have to much lift and not enought clearance you will need to have the pistions fly cut or a different cam you shouldnt run much over .500 lift with the stock stuff, and the stage 1 cam is a .512 lift

Can't speak for sure as I didn't put my engine together, but I am running a Stage 1 cam with stock heads and do not have a problem. I don't have 1.7 ratio rockers though, and don't know whether or not my pistons were cut at anytime.

according to summit, that cam is .499 intake and .510 exhaust with 1.6 rockers.

take that number and plug it into the equation:

cam lift x rocker ratio = valve lift

.312 x 1.72 = .537 intake
.319 x 1.72 = .548 exhaust

I don't believe you'll have a problem with piston to valve clearance, but you will have a problem with coil bind. The stock valve springs are not designed for that much lift so you'd have to change them. You'd be safer running this setup with 1.6 rockers and using TFS springs that are designed to fit the stock head without machine work....

Larry

Lots of interesting stuff here. First of all, the cam you've selected is designed to be used with other mods to the engine. It will likely make the overall performance of your stock headed engine worse, not better. Your stock valve springs probably won't properly control valve motion with the lobes on that cam - which means you'll probably experience valve float before you get to enough rpm to see any power increase. Additionally, with the 1.72 rockers, you may have a spring bind problem. That should have been checked before engine assembly. I think you would be much better off saving your cam install until you have the proper heads, intake and exhaust mods and then select the cam to match your components and your power requirements, usage of the car, etc.

As for clearance, it's a function of a number of things. With stock heads and valve sizes - and the piston reliefs, you'll probably find you have enough clearance. But the ONLY WAY to know is to measure it on your engine. There's a site listed above and I'll list another below. And, the way you posed your question, you seem to have a fundamental misunderstanding about what causes piston to valve interference (it seems others in the thread do as well). Peak lift has nothing to do with p to v clearance - the pistons are way down the cylinders when the valves are open to peak; no clearance problems ever at peak. Clearance is an issue during overlap - when the piston is passing through tdc between the end of the exhaust stroke and the beginning of the intake stroke as the exhaust valve is closing and the intake valve is just opening. So, commonly changed things that impact clearance are 1) heads with larger valves than the piston reliefs, or with valves positioned differently than the stock piston reliefs (tfs) 2) heads that have been milled 3) blocks that have been decked 4) different pistons from stock 5) cams with earlier opening intake valve timing or later closing exhaust valve timing - usually this means cams with more duration, more overlap or tighter LSA's. Because of the dimensional differences of every engine, when you start to measure things in hundredths and thousandths, no two engines are the same - even two with the same components. So other's experience with clearance in their engines won't tell you anything about yours. You have to measure to be sure. If you decide to run the cam with the stock heads - you're dealing with #5 above. If you change the heads later you add #1 to the list of reasons to measure your clearance.

You may find that you start it up and nothing bad happens. All that means is that you got lucky. You may still find that if you miss a shift and over rev it, that exhaust valves will hit the pistons. People may say it was fine in theirs, you should be ok. You take a big risk if you act on that. Just so you know the risks you're facing. Good luck with it.

http://www.geocities.com/jjonibones/PVC.html

I run a f-303 with stock shortblock over .100 of clerance on both valves and on each heads, i used the modling clay method.

the f-303 have .512 of lift on exhaust and intake.

Bock - great that you measured; but the lift has nothing to do with your clearance. 93Stang - put the stock cam back in it till you take it down to do the heads. Then I know it will be alright; unless you're willing to measure clearance, you're just guessing.

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