I didn't think p/v clearance was gonna be an issue with my new pistons...

[stangboy]

This weekend I rebuilt my motor. I started Friday evening after work and I would have finished last night but when we were checking p/v clearance we ran into a problem. The valve was hitting the piston right at the edge of the valve relief. So, my rebuild has come to a skreeching hault. I thought most aftermarket pistons had valve reliefs big enough to clear at least a 2.02 valve. I don't remember where I heard that before but now I know that its not true. The thing that puzzles me is that a friend of mine told me when he saw my pistons that he has the same exact pistons except his are .030 over. He has Edelbrock performer RPM heads w/ 2.02 valves and he has a Trickflow stage 2 cam (.542/.563 lift). I have an F303 cam(.512/.512 lift) So, now I have to get my pistons notched.

 

[zenboy99]

Its not only the lift of the cam, its the cam timing events, duration, lobe design, etc.

Trick Flow told me that my FTI cam wouldn't clear, but I had well over a tenth of an inch on the intake and exhaust side.

 

[Joes95GT]

Cam timing is key.

Which valve is hitting? I assume the intake valve? What are the valve timing events @ .050" lift? You may be able to retard the cam assuming your valve timing isn't too far out of wack.

Joe

 

[stangboy]

The intake valve was hitting but I don't even think it was at max lift yet. I installed the cam straight up(dot to dot). My timing chain set has the marks on it to retard or advance the cam 4* either way. But the thing is that the valve is actually bigger than the valve relief. If the valve actually fit in the relief I wouldn't have an issue.

Here's how we checked. We put the #1 piston about an inch before TDC, put some clay on the piston, bolted the head down, installed the pushrods and rollerockers, then I started to turn the motor slowly. By the time the piston got all the way up I couldn't turn anymore. So, we pulled the head off and looked at the clay and saw that the valve was hitting right on the edge of the relief coming out of it some which tells me that the valve is bigger than the relief. We tried it without the clay just to see if it would make a mark on the piston so we could see exactly where it was hitting and how much of it was hitting. So, do you think I should maybe retard the cam or something? As for the timing events, I really don't know.

PLEASE HELP!!!

 

[zenboy99]

If the valve hits, it will usually hit at 20-30 degrees of crank rotation, not at max lift.

 

[Joes95GT]

Try retarding the cam 4*

Joe

 

[GTJake]

With a retarded cam and 185's on a 302, that car isn't going to wake up till 4k rpms or later. Might want to try a smaller cam if that's an option.

Jake

 

[TMC]

excactly what pistons are these?

 

[stangboy]

.....ok.......So, uuhh, whats the average cost to get pistons notched and can they do it with my shortblock assembled?

 

[stangboy]

excactly what pistons are these?

These : http://store.summitracing.com/defau...rt&searchtype=both&part=TRW-L2488F+&x=12&y=12

 

[stangboy]

Well, getting the pistons notched is gonna cost me $120. I'm gonna re-clearance the pistons and valves to see exactly how much clearance I need and I'm gonna see if I can find a thick head gasket. I'm crossing my fingers.

 

[TMC]

OK, that explains it. Those TRW pistons are pretty much a stock Ford piston that they expect to only use 1.84 valves with at the Max. So, yes, you'll need to cut the pistons to clear your 185's. Sucks but there really isn't any other way around this.

 

[stangboy]

OK, that explains it. Those TRW pistons are pretty much a stock Ford piston that they expect to only use 1.84 valves with at the Max. So, yes, you'll need to cut the pistons to clear your 185's. Sucks but there really isn't any other way around this.

DAMMIT!!!! I guess that would explain why the rebuild kit was so cheap. I thought those damn valve reliefs looked kinda small. You think I'll be ok with thicker head gaskets?? because I don't have the extra money to get that done.....and I don't have the time or patience to tear the motor down again to get the pistons notched again and then put it back together.

 

[95snoozer]

These : http://store.summitracing.com/defau...rt&searchtype=both&part=TRW-L2488F+&x=12&y=12

trw = stock pistons

 

[Joes95GT]

Well it looks like you have a few options.

1) Use the stock cam.
2) Spend the money and get the pistons flycut
3) Dremel the pistons and use a thick headgasket, risking the integrity of the piston, and killing compression.

Joe

 

[TMC]

No, a thicker gasket wont work for you. You'll only gain ~.020" with a thick gasket and it will kill compression.

TEA rents a jig and tool to flycut your pistons while still assembled in the shortblock. I'd give them a call and see how much it is to rent that.

 

[stangboy]

No, a thicker gasket wont work for you. You'll only gain ~.020" with a thick gasket and it will kill compression.

TEA rents a jig and tool to flycut your pistons while still assembled in the shortblock. I'd give them a call and see how much it is to rent that.

I just emailed TEA. Thanks for that info, TMC.

 

[stangboy]

I decided I'm gonna go ahead and pull the pistons back out and take them to a machine shop to be flycut. I'm looking at about $150 to get that done. Hopefully I won't have to worry about clearance anymore. The only problem is that its gonna be another week or 2 that I'm gonna be down.

 

[SBC RACING]

reply

If i were you i would sell those pistons on ebay and put the 150 you were gonna spend on flycutting those pistons with the money you make on ebay towards a good set of forged pistons like SRP, JE, Ross.

 

[mo_dingo]

Yeah, you can get forged pistons for under $300. Might as well with this glitch you encountered. I remember seeing some selling for $250-270 if I remember correctly.

It wil be strange though. Forged pistons, stock rods.......Sigh.
Scott