i know externally they are very different...do both motors have the same crank and pistons....i know the crank is the same stroke, i'm wondering if its a different material (forged vs cast). rods are the same in every 60* V6, so that just leaves pistons. if u have any info on this i'd appreciate it...

selling 3.1 TDC project (check my sig...)

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Eric
'87 GT 5-speed Gold/Tan NOW with a 4.10 4-speed <- edit broke 4.10 back to 3.65 4-speed
3.1 TDC + other goodies F/S $900 (no ECU or harness) PM or email for more info....

The block itself has a .1" higher deck height that they used to help lower the compression. The piston are cast aluminum with a steel reinforcing ring that are made by Mahle and are still available(I can get the part#). The crank is supposedly a regular crank that is rolled to help harden it. Besides those three points there isn't really anything else. I wouldn't worry about getting a TGP block as there are other ways to lower the compression. I would have to say use a regular block and buy custom forged pistons from Ross. The pistons are the weakest link in the whole setup, and they'll be the first to go.

[This message has been edited by skalor (edited 05-09-2003).]

quote Originally posted by skalor: The block itself has a .1" higher deck height that they used to help lower the compression.

Where on earth did you hear that? I find that extremely hard to believe. Does it also use a different lower intake and pushrods?

I think that the turbo engine has 8.4 compression vs 8.5 for the regular engine. The crank has a different part number. I've heard a couple of different stories about what's different about it which makes me think that people don't really know what's different and are just spreading rumors.

You can probably find people who know more here: http://discussions.gmforums.com/forumdisplay.php?s=919e5de10432b16cd18344e673508ee0&forumid=515

or here: http://discussions.gmforums.com/forumdisplay.php?s=919e5de10432b16cd18344e673508ee0&forumid=263

or on various W-body sites around the web.

[This message has been edited by Will (edited 05-09-2003).]

http://www.netavalanche.com/tgp/viewtopic.php?t=81&highlight=different+pistons

I found it on TGPs boards as I've been going on them for 2 years know. Like I said though I wouldn't worry about the block as there are much better ways to lower compression more effeciently.

An NA 3.1 has a compression ratio of 8.9 while the turbo 3.1 engine has been seen to be either be 8.7 or 8.8.

I suggest you do a little searching on the forums listed below, as we get asked this question a lot.

The TGP boards are as follows: http://www.w-body.com/forum/index.php http://www.netavalanche.com/tgp

Also, the TGP uses a Mellings high volume oil pump. I can get the part # for that and the pistons if you need them.
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1989 Pontiac Turbo Grand Prix(the 'other' one)
1989 Pontiac Turbo Grand Prix(the 'nice' one)

[This message has been edited by skalor (edited 05-09-2003).]