Do the TRW forged pistons have more valve clearance potential than stock hypers?

[5spd GT]

Speed Pro has a forged piston kit (stock replacement style) from TRW. Do they have deeper valves reliefs and wider?

If my valves clear my stock 93 hyperuetic pistons would that not mean with everything else equal that the TRW's would clear if not more? Any insight?

It seems that the TRW forged pistons give a 10.13:1 compression ratio (IIRC) with 58cc cylinder heads. I was wanting to shoot for lower 10's in static compression.

Thoughts?

 

[DMAN302]

Dave take a look at these wiseco forged slugs..I used them on my block and the valve reliefs are pretty usable, the part number is PT012H3. Summit has them on their site, price is pretty good, take a look and I hope this helps.

 

[5spd GT]

Thanks Derek, those look good $500 bucks is a bit steep but not out of the question. It was showing the compression is about 9.1:1. with a 62cc head. I was looking at something maybe with a bit more compression if possible...

 

[ms93gt]

If they are the -4 vavle reliefs then the answer is no. They are just that, stock replacements but yet forged. Sorry bud.

 

[txstang84]

heres a thought-with the cash you could save buying the trw's, or sealed power, or speed pro-whoever the hell puts their tag on them now-you could probably take them somewhere and have them flycut for big lift and big valves. See the thing is, most of the compression ratio differences are based on deck clearances. the trw's (#2488's) are pretty much carbon copies of the forged slugs that came in the 87-92 5.0's. This makes sense if you read the underside of a stock 5.0 piston-they were made by TRW. But getting back to the subject, most piston mfr's make their pistons so they won't completely come up to the deck-about 0.008"-0.012"...to account for the possibility of the engine being rebuilt needing to be decked...
The stock ones, as well as the #2488 TRW's come about 0.003"-0.004" out of the hole. This is the reason for the differences in cr's with aftermarket pistons.

 

[Rick 91GT]

Here's what I get with a 0 deck block, Probe 4cc flat top, 58cc head, .039" gasket What cc are the TRW's?


Bore Size: 4.030
Gasket Bore: 4.100
Piston Top Land Dia: 3.995
Stroke: 3.000
Connecting Rod Length 5.090
Compression Height: 1.600
Deck Height: 8.190
Ring to Top of Piston 0.250
Gasket Thickness: 0.039
Valve Notches Volume: 4.00
Dome Volume: 0.00
Volume Head: 58.00
-------------------------------------
:COMPRESSION RATIO: 9.790
-------------------------------------



calculation variables:

Piston to Deck: 0.000
Crank Throw: 1.500
Vol. Above Top Ring: 0.90 cc
Piston to Dec Vol.: 0.00 cc
Gasket Volume: 8.44 cc
Volume Clearance: 71.34 cc
Cylinder Volume: 627.08 cc
CID: 306.014


(notes/messages)

× Piston Flush with Deck

 

[txstang84]

i think they're 2.7cc reliefs Rick...pretty small

 

[Michael Yount]

How much clearance did you have before?

 

[5spd GT]

Looks good Rick That'll work...

Michael - Well we all know that story, I didn't get the most accurate reading but visually I know it was over .080...just under a tenth of an inch. I looked at the thinnest part of the clay and it seemed alright...I'm going to check it this time and get a "real reading".

 

[65ShelbyClone]

Speed Pro has a forged piston kit (stock replacement style) from TRW. Do they have deeper valves reliefs and wider?

Oh god no! They have tiny reliefs. With my combo I had to notch them even more. Seriously, the valves were around .010" from the pistons. The eyebrows were deep enough, but just not wide enought for 1.90/1.60s and my cam.

 

[Michael Yount]

I didn't remember David - I was hopful you had numbers you could use -- and then compare depth of reliefs on the pistons, in/out of the hole - etc., and calculate where you'd be with the new pistons. But it sounds like you're gonna have to make a commitment to the new pistons one way or the other -- and then make them work if you need more clearance.

Have you torn the motor down already? If not, you can still take measurements (drop valve and in/out of the hole on the piston) that will help you know where you'll be with new components.

 

[5spd GT]

I didn't remember David - I was hopful you had numbers you could use -- and then compare depth of reliefs on the pistons, in/out of the hole - etc., and calculate where you'd be with the new pistons. But it sounds like you're gonna have to make a commitment to the new pistons one way or the other -- and then make them work if you need more clearance.

Have you torn the motor down already? If not, you can still take measurements (drop valve and in/out of the hole on the piston) that will help you know where you'll be with new components.

Taking out engine tomorrow

I removed everything myself on wednesday down to just where the heads/block are the only extremities remaining. I just have to unbolt the driveshaft and tranny mounts and it is ready to pull out.

 

[Michael Yount]

If the heads are still on and the cam is still in, then it's not too late to do drop valve measurements and check current p to v. That may help you with your parts ordering, and may allow you simply calculate new p to v based on changes you make David.