BlueSix

Ok, this isn't something i'm looking to do tomorrow. I'm bored and can't find an answer to my question by searching. Car is a 2004 GTO. There are 15K miles on the stock short. I'll be using American Racing headers, off road mids, and probably a magnaflow cat-back. I'd like to do an AFR 205, comp xer 228/232 110 LSA combo, using the factory LS6 intake until i can afford a Mamofied FAST 90. Any opinions on how high i can go on compression with the 105 octane fuel? I was thinking around the 13:1 range, maybe shoot for a DCR slightly above 9:1. Anyone think I'd have detonation problems? How much would the AFR's have to be milled to achieve the desired compression? What gasket would be best? Cometic? .035? .040? Would I have any PtV issues? Is it possible to get the compression as high as i want with the stock short?

I understand the additional fuel requirements when using E85. I would switch to E85 before the h/c swap.

BlueSix

I might also consider the TSP terminator heads, I've seen good results with those heads and the cam i want.

Dragula

iTrader: (5)

Check into ETP heads as well. I think they have a 11.5* valve angle that could lesson the P to V clearance issues.

I'm interested in hearing what people have to say about this. I hope your DCR can be higher than 9:1 with E85.

BlueSix

Does anyone know how high we can take the DCR with e85?

VORTECFCAR

iTrader: (2)

I'm in Minnesota and have considered the same thing. I would feel safe at 13:1 on E85. The source escapes me , but I read that 14:1 is reasonable on E100.

I too would worry about piston to valve issues. I wonder how a short duration cam on LSK lobes would do in a 13.5:1 E85 LSX. That would be ~2.X point bump in dynamic compression for most of us big cam users.

Side track-> It wouldn't cost much to mill the heads and throw an '02 LS6 cam in

The wheels in my head can't hook the Himalayan torque

BlueSix

Bump for us high comp dreamers.

VORTECFCAR

iTrader: (2)

Just do it blue six, or I will. I've got an old man truck cam in the mail and a set of '98 heads I could home port and mill the **** out of. Should I do it?

Irocss85

iTrader: (1)

well, not sure about the rest of your questions, but .040 is the thinest you want the head gaskets on stock shortblock. most LS pistons will be about .006" OUT of the hole. meaning, with a .040" cometic, you end up at .034" quench height. just about optimum. any thinner will cost you alot in terms of flame travel and quality inside the combustion chamber. so consider the .040 your starting point.

also, IMHO, thats a very humble cam to run high compression with. it'll work just fine if low end torque is what your after, but why hold yourself back if you dont hvae to? although, I guess if you have to mill alot off the heads, you're duration #s and ICL will be restricted by the lesser clearance.

and on that note, I verymuch agree with the ETP 11.56deg. heads as they will lend to clearance but if you mill alot, you'll still need to flycut the pistons, even with a mild cam.

but if you do go down this road, please share all that you figure out as you go.

BlueSix

The cam may be humble, but low/mid range power is what i'm looking for.

BlueSix

Go for it. I may get some stock 243's and mill them down and find a used cam in the parts for sale section. It'd be a cheap way to just "try it out" before i go all out.

VORTECFCAR

iTrader: (2)

Exactly, I'd be building for grunt to 6300 rpm or so. I don't have the funds to be building an all out setup

Don't count on me doing anything like this in the next week or anything. But I might start cruising the classified ads for specialty items. A set of milled 243s with 918s would be pretty sweet.

BlueSix

Anyone know how much would have to be shaved off of a 243 head to get above 12.5:1? Possibly using a single pattern cam, tr220 or something similar, would there be and PtV issues when keeping the lift under .570?