12.89:1 CR...doable? E85 maybe?

[2.8/3400 1985 Camaro]

Alright guys, I'm not getting much help/info/testimonials over on TGO, so has anyone successfully run 12.89 CR or higher on a gen 1 or 2 block? Or can at least tell me if they think it is viable or not? And what potential issues there will be other than detonation, or I'm also thinking about running E85 for 100+ octane, anyone converted to run it that knows what I would need to do?

[geoffinbc]

Pump gas NO unless it has a wild cam. E85, or Propane no problem.

[1988GTU]

Probably doable with pump gas with meth injection. Or pump gas and retarded timing.

[torq455]

assuming the bearings can handle it. i know a guy on here that had 12.5 CR with the stock oil pump. ruined the rod bearings over time.

[geoffinbc]

The stock oil pump has nothing to do with the bearings lasting. The problems was more likely due to detonation

[Superdave]

one of the domesticcrew guys had a hybrid with like 12:1 scr and a Crane H272 cam. I seem to remember him running it on regular pump gas.

like betterthanyou said though, it depends on the cam.

[2.8/3400 1985 Camaro]

I'm getting a solid flat tappet from crower with a 3-7k powerband and 8k+ redline. 248* int and 250* exh @ .050 lift, and .501 gross lift on intake, with .511 exhaust.

If someone could explain the below thing or tell me what # it is from those above that would help in that i could find the dynamic CR.
"Intake Closing Point (degrees)ABDC @ 0.050 lift plus 15 degrees"

[Superdave]

you won't be able to drive that on the street.. that cam has 79 degrees of overlap. It will have to idle at 1300 RPM.

[2.8/3400 1985 Camaro]

How will it do with that kind of CR though, well enough for to run pump gas?

[IsaacHayes]

Well, with a huge ass stall, or 5spd it might be drivable with that idle.. LOL... manual you could just slowly let out the clutch without touching the pedal probably.... hahaa

IVC ABDC spec you need to get from crower..

With that much overlap, it should bleed off a ton of compression I would think.

[geoffinbc]

Over lap does not tell the whole story. Pressure bleed off depends mostly on the IC event. The later is closes the more pressure will bleed off. You do not necessarily have to have a lot of overlap or duration to bleed off cylinder pressure.

[Superdave]

IVC (ABDC) would be 48.0 @ .050

[2.8/3400 1985 Camaro]

Well where is the issue with driving that on street exactly? I mean yeah, 1300 rpm would be a really high idle speed, but what effect does that have on driveability exactly?

[2.8/3400 1985 Camaro]

That would put dynamic CR at 11.363:1, I'm assuming you already added the 15 degrees into the 48. Now I don't suppose anyone knows the DCR on stock gen 1 2.8? or the cam's ICP?

[Superdave]

no, i didn't add the 15.


That's a race only cam. Probably circle track, sandrail or for a '660 powered boat. Under normal driving it's going to need a pretty high stall converter, your brakes and other vacuum driven accessories will barely work and probably non-stop tuning. Since it's a mechanical cam it's also going to be noisy and you'll have to adjust the rockers a few times a year.


I run a pretty extreme cam in my 3500, trust me.. if you enjoy driving the car go with something a little more tame.


I think something like the Lazer cams 2700122 would be a better choice..

3rd up from the bottom: http://members.shaw.ca/betterthanyou...haft_guide.htm

It depends on what heads you are using as well, that much cam on gen1 or gen2 heads is a waste of time.