85 T1 Engines....Unique

[85GLHT-Omni]

What's unique and what are the upgrade limitations?

From what I've found:

1. 287 G head...good and bad. Good for porting and flow, bad for limited pool of parts.
2. Dished G head pistons...unique to 84 and 85 model years...are there aftermarket forged parts available?
3. 6 bolt cast crank shaft...does this limit transmission upgrades (525 to a 555)?
4. Small spline half shafts
5. Skinny distributors and different HEP's.

Anything else?

[GLHS592]

1. 287 G head...good and bad. Good for porting and flow, bad for limited pool of parts.

There were probably quite a few more swirl head cars. I really don't know if the G head has any less parts availability.

2. Dished G head pistons...unique to 84 and 85 model years...are there aftermarket forged parts available?

The pistons are dished deeper than the later models. I don't know off hand if aftermarket forged pistons are available. However, the later model forged pistons were made by copying the specs of the stockers.

3. 6 bolt cast crank shaft...does this limit transmission upgrades (525 to a 555)?

Correct. No.

4. Small spline half shafts

This is the case for any 525 equiped vehicle.

5. Skinny distributors and different HEP's.

Correct. The logic modules were different too.

[cordes]

You can run any trans you want from any TD.
You just need a dist from an 86+ car.
Run 88+ auto trans omni axles for any trans other than an 525. Other options exhist, but this is what I did.
I would stick with the G head, and you can get forged slugs from www.turbosunleashed.com

[GLHS592]

Also, you can run the later pistons just fine with a G head. You will have to run the later turbo 2 style rods. You can get a set of them for $50 or so if you shop around.

[looneytuner]

small diameter head bolts.
Can be upgraded by machine shop.

[dwh4784]

Major one is the log style suck through intake, although it can be converted easy enough.

[GLHS592]

small diameter head bolts.

I forgot about that.

85 & older - 10mm
86 & newer - 11mm

[R/T]

[QUOTE=85GLHT-Omni]What's unique and what are the upgrade limitations?

From what I've found:
3. 6 bolt cast crank shaft...does this limit transmission upgrades (525 to a 555)?
QUOTE]

Only matters if it's an automatic trans - the flexplates are different.

6 bolt with 3 converter bolts
8 bolt with 4 converter bolts

On a 5 speed, the flywheels are basically the same - 6 or 8 bolt will work with any 5 speed.

[Una]

Anyone mention that '85 rods are heavy duty rods? Not the "lightweight" rods used on all 2.2 T1 cars from '86 up.. They're not floating pin, so you can't run readily available forged pistons on them, but so long as the stock pistons hold up, the rods are good to go.

[johnl]

Quote:
Originally Posted by 85GLHT-Omni
2. Dished G head pistons...unique to 84 and 85 model years...are there aftermarket forged parts available?


"The pistons are dished deeper than the later models."


Actually, the G head pistons have LESS volume in the dish because the G head chamber has MORE volume than the 782 head chamber. So, the combo of a G head with forged "782 spec" pistons yields a lower compression ratio.

I think it is safe to say that the general consensus is that a lower compression ratio allows an easier/safer balancing of piston/head gasket longevity/against high boost but at the expense of less off boost/low speed/around town performance. On the other hand, I read that some of the very best (precise fuel/EGT control) set ups have compression ratios that are 8:1ish.

[GLHS592]

Actually, the G head pistons have LESS volume in the dish because the G head chamber has MORE volume than the 782 head chamber. So, the combo of a G head with forged "782 spec" pistons yields a lower compression ratio.

Yep. My mistake. Thanks for the correction.

[supercrackerbox]

Don't forget you can always swap in an 86-88 crank if the six bolt thing becomes an issue. Although it shouldn't.

[85GLHT-Omni]

If I swap in a 555, I can just reuse my 6 bolt flywheel?

[GLHS592]

Yes you can.

[SwiftTech]

Don't forget you can always swap in an 86-88 crank if the six bolt thing becomes an issue. Although it shouldn't.

Unless you shear all 6 flywheel bolts off. But this only happened to me cause my shift linkage was out of adjustment and caused me to down shift to 2nd instead of upshifting to 4th at 95mph or so Doh!

[Tony Hanna]

Ouch! What kind of a noise did that make?

[SwiftTech]

a loud crunching/grinding noise. happend right at the end of the track and I had enough momentum to get it off without slowing things down for everyone else.

[cordes]

a loud crunching/grinding noise. happend right at the end of the track and I had enough momentum to get it off without slowing things down for everyone else.

I would say that is about the best case senario in that situation.

[85GLHT-Omni]

I thought of another quirk of the 85 Turbo engine:

If converted to a TII, you absolutely need a custom calibrated logic module. The GLHS, Stage II logic module will not work 'well' as the G-head requires much more agressive spark timing.

[Muertoloco]

could the 10mm headbolts handle 12#s of boost?