What compression ratio were the Gen IIs?

[Doward]

Just what the subject says Gen II was 88-94, yes?

[WhiteRaider]

According to the family tree:

1987: 8:9:1

1993: 9:6:1

[Doubt_Incarnate]

88-94 iron heads still existed, and were diferent. i think 3.1 iron head motors were supposed to be 8.5:1, and im not sure about the 3.4's

[Guest]

ALL (N/A) GenII engines were 8.9:1. GenII was from '87 to '94. The J-body was the only car in '94 to retain the genII design, the rest of the line went to the genIII in '94.

FYI, genIII is 9.6:1

Doward, are you copying my set-up?

[Doward]

LOL, might be going something like that.... Gen III topend + Gen II rotating assembly + big arse turbo + '749 ecm?

I've started working on a LIM for it, too. LOL, THAT is going to be the fun part!

[SappySE107]

94 lumina was also gen 2.

[Guest]

94 lumina was also gen 2.

Good to know, other W-body models went to genIII though, correct?

[Guest]

LOL, might be going something like that.... Gen III topend + Gen II rotating assembly + big arse turbo + '749 ecm?

I've started working on a LIM for it, too. LOL, THAT is going to be the fun part!

Do yourself a favour and go genIII pistons, I wish I had.

Gives you 9.6:1 SCR (must use an .060" head gasket though, due to genIII pistons coming .020" proud of teh deck surface).

I'll be going to 9.3:1 with the .040" head gasket, when I put the new top end on.

Yes, I'll be switching to a 749 for my dizzy project, seems to be more support for the Sy/Ty .bin from enthusiasts, than the TGP code.

[Doward]

I would, but I'm going to be running TGP (Mahle) pistons... I want the lower compression

[Guest]

I would, but I'm going to be running TGP (Mahle) pistons... I want the lower compression

Do you already have them?

[gpse3400]

GEN 2
2.8- 8.9:1
3.1- 8.8:1
3.1T- 8.7:1 (doubtful though)

GEN 3
3100- 9.6:1
3400- 9.5:1

[Guest]

GEN 2
2.8- 8.9:1
3.1- 8.8:1
3.1T- 8.7:1 (doubtful though)

GEN 3
3100- 9.6:1
3400- 9.5:1

Where the hell did you get that from?

2.8 = 8.9:1
3.1 = 8.9:1
3.1turbo = 8.8:1

genIII

3100 9.5:1 and 9.6:1 Depending on year/source
3400 9.6:1

[Doubt_Incarnate]

In all actuallity, thats just the advertized CR. from what i've read in other posts is there is as much as a 2cc difference in combustion chambers for the same type of head, or maybe even in the same head. so one car or even cylinder might have 8.9, and another 8.7 and yet 9.1, or perhaps even up to 9.8 on the newer ones. and then still the cc of the pistons dish, i'm sure there are variances everywhere. you'll have to figure out the cc's everywhere to get the truth about the CR for your specific car.

[Guest]

In all actuallity, thats just the advertized CR. from what i've read in other posts is there is as much as a 2cc difference in combustion chambers for the same type of head, or maybe even in the same head. so one car or even cylinder might have 8.9, and another 8.7 and yet 9.1, or perhaps even up to 9.8 on the newer ones. and then still the cc of the pistons dish, i'm sure there are variances everywhere. you'll have to figure out the cc's everywhere to get the truth about the CR for your specific car.

Yes, advertised SCR is an average, just like the "1.5:1" stock GM rockers, which can vary from 1.32 to 1.64:1.

[Guest]

D

Yes, I'll be switching to a 749 for my dizzy project, seems to be more support for the Sy/Ty .bin from enthusiasts, than the TGP code.

GEttigna dizzy to work with that gen 3 intake is going to be fun. good luck with that.

I have already mocked it up. its not going to happen.