Choosing pistons to complement GT40P heads

Capri306 · 10-20-2005, 02:42 AM

Hey all. It's been a while since I've actually started a thread here in the Windsor Power Forum, but it feels good to be back in the motor-building mood.

To the chase: I'm rebuilding the near-200k-mile engine in my '87 Notchback. It's old, tired, and has some rod knock. Not content to settle for a stock rebuild, I'm looking to maximize its potential, but within my limited budget (I'm a college student).

This rebuild will consist of my block punched over 0.030-in., GT40P heads (completely stock, no alterations), Explorer/GT40 upper & lower intake manifold(s), Dynomax or MAC headers, some variant of CompCam, with my 'personally tweaked' AOD backing it up. Okay, nothing in there too special, but that's what I'm working with.

The car already has 3.73 gears, Mass-air conversion, E303 (which will go away), an aluminum driveshaft, MSD 6 box, 65mm TB, 2200-stall converter (this too might go away), huge-ass radiator, underdrive pullies, off-road H-pipe (w/ tabs), Dynomax equal lengths, Flowmasters....you get the idea. All it could pull was 14.3's, but at least it was consistent.

Biggest mistake was the mismatch in cam and torque converter.

My question regards the choice of pistons for this rebuild. Unfortunately, this also brings the variable of compression ratio into the equation. I won't mind using premium pump gas at all, but I don't want to have to run timing at 6°BTDC, either! I'm thinking around 10.5:1 will be just about the limit for a reliable daily driver with iron heads and pump gas. I need this motor to have a pretty flat torque curve, due to the variety of driving conditions I'll be using it in (particularly city driving), which is why I'm favoring the higher compression ratio. I need a blessed union of driveability and oh-my-God-I-just-crapped-my-pants feel at WOT.

If it helps, I believe my stall will be in the neighborhood of 2800 to 3000, but this will depend upon the cam.

My gut is telling me to call up Probe and pick their brains a bit. If not, just to go flat-top Speed Pro w/ Total Seal gapless rings.

Has anyone experimented with various piston types on these heads with good results? Jeff Chambers?

10-20-2005, 02:42 AM	#1
Capri306 Moderator Join Date: Sep 1998 Location: Grand Rapids, Michigan, USA Posts: 1,001	Choosing pistons to complement GT40P heads Hey all. It's been a while since I've actually started a thread here in the Windsor Power Forum, but it feels good to be back in the motor-building mood. To the chase: I'm rebuilding the near-200k-mile engine in my '87 Notchback. It's old, tired, and has some rod knock. Not content to settle for a stock rebuild, I'm looking to maximize its potential, but within my limited budget (I'm a college student). This rebuild will consist of my block punched over 0.030-in., GT40P heads (completely stock, no alterations), Explorer/GT40 upper & lower intake manifold(s), Dynomax or MAC headers, some variant of CompCam, with my 'personally tweaked' AOD backing it up. Okay, nothing in there too special, but that's what I'm working with. The car already has 3.73 gears, Mass-air conversion, E303 (which will go away), an aluminum driveshaft, MSD 6 box, 65mm TB, 2200-stall converter (this too might go away), huge-ass radiator, underdrive pullies, off-road H-pipe (w/ tabs), Dynomax equal lengths, Flowmasters....you get the idea. All it could pull was 14.3's, but at least it was consistent. Biggest mistake was the mismatch in cam and torque converter. My question regards the choice of pistons for this rebuild. Unfortunately, this also brings the variable of compression ratio into the equation. I won't mind using premium pump gas at all, but I don't want to have to run timing at 6°BTDC, either! I'm thinking around 10.5:1 will be just about the limit for a reliable daily driver with iron heads and pump gas. I need this motor to have a pretty flat torque curve, due to the variety of driving conditions I'll be using it in (particularly city driving), which is why I'm favoring the higher compression ratio. I need a blessed union of driveability and oh-my-God-I-just-crapped-my-pants feel at WOT. If it helps, I believe my stall will be in the neighborhood of 2800 to 3000, but this will depend upon the cam. My gut is telling me to call up Probe and pick their brains a bit. If not, just to go flat-top Speed Pro w/ Total Seal gapless rings. Has anyone experimented with various piston types on these heads with good results? Jeff Chambers? __________________ Capri306, Moderator The Mustang Works Online 1979 Mercury Capri 1987 5.0L Mustang LX Notchback 1993 5.8L Eddie Bauer Bronco

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