[mustang283]

The last person that had my 1991 mustang 5.0 put a 331 stroker kit in it, x303 cam, explorer intake, and left the stock heads on it.


He said there are SRP forged flat top pistons with valve reliefs in them. If this is true, if I put some trickflow TW ported to 180cc heads on it, will the pistons be fine? Will i have to notch them anymore? or flycut them?


Thank you!!

[cindys_sn95]

if they are SRPs, they have good reliefs. but with the TW heads i would double check to make sure.

[89coupe]

You gonna have to check the PtV clearance anyways.

Generally because the the Twisted wedge valve angle and placement , you end up more PtV clearance that you would with an Inline valve head with the same Valve size. Im assuming the SRPs have an adequate valve relief depth, but what im not sure of is the radial clearance of the relief on the Piston

The heads are worth getting no doubt about it.

[mustang283]

man i read something that twisted wedge can not be used with those pistons. this sucks. i hope its not the case!

I read you have to get the srp pistons made for the twisted wedge heads...

[89coupe]

Some aftermarket companies make a piston with standard and twisted wedge valve reliefs.

TFS claims you can use their TW heads on a Stock 86 block which the pistons have no valve reliefs.

Regardless Check.....

[mustang283]

If I had the standard reliefs, is there still a good chance it will all work?

And to check ,you put clay in the head and turn the engine over with a wrench and then take the head off and look at the clay?

[89coupe]

Originally Posted by mustang283

If I had the standard reliefs, is there still a good chance it will all work?

And to check ,you put clay in the head and turn the engine over with a wrench and then take the head off and look at the clay?

Not sure if it will work, just have to check.

Clay method is perferred. But you need the correct Pushrod Length first. And the twisted wedge heads will require Push Rod length checking..

Twisted wedge style pistons have the valve relief moved more toward the center of the piston. If there is a problem, it may not be the radial part of the relief, it may be in the heel of the relief. If you look at a picture of the way the valve reliefs are on a standard typ piston, you will see the radial part, then you also see part where the relief and the top of the piston meet. id figure thats where the problme will be if there is one.

[mustang283]

should i just reuse the pushrods that im using now? The guy threw in pushrods should I test it using those or mine?

And how do i measure the pushrod length?

[MUSTANGPAT93]

I would go with a 6.750 pushrod. Trickflow makes a set so you can use them with stock pistons. You should be alright using the heads but i would use the clay its a easy inexpensive way to check piston to valve clearence.

[mustang283]

should i still use themwith my aftermarket pistons? how would I measure the pushrod length? thanks everyone for your help.

[89coupe]

You need a pushrod checker. Comp Cams sells them. Kit comes with 2 checkers and some Light pressure springs to install in place of the valve springs. Checkers can get bent when using springs with High pressures

[mustang283]

which length checker should i get, there the ones under 20 dollars right?

There not stock pistons. my title got changed, but there not stock pistons. they are flat top SRP pistons with valve reliefs for the 331 stroker motor.

[89coupe]

Probably the 7701 Push Rod Checker. They sell a whole KIT. Two Checkers and two light checking springs. Thats what I recommend getting.

[mustang283]

Okay, so I get that, and my heads. I put the heads on and test the pushrod length. If its good. Then I do the clay and check piston to valve clearence?

And if Both check out good then i can bolt them on right?

Are there any places that go into detail with pictures how to do the pushrod test?

And would I have to buy new ones if there too short and cut them if there too long?

[mustang283]

I can't seem to find those pushrod checkers. I found this

COMP Cams: Hi-Tech™ Checking Pushrods

its only 20 dollars. Would those work? If I somehoe got some old weak springs?