Thread: Boost pressure VS Compression for E85 T70 build........

Alright so a few questions here.

8.5:1 for L67
or
9.4:1 for L36

I can find either cheap enough and easily enough. I've always thought of higher compression as kind of "free" HP, so which block to go with?

I have a set of MLS gaskets already, use all the layers or leave one or maybe 2 layers out?

What about the heads, I plan on dropping a set of L67 heads I have off at a shop to have them checked out.

simple valve job, magna fluxed, new guides and seals, machined to prepare for a ST5 cam, and how about having the heads milled to jack up the compression?

Should I leave everything alone and use low comp block, all the layers of the MLS gaskets, and NOT have the heads milled?
or is it worth it to jack the compression up a little more around the 10:1 or higher for compression?

Keep in mind this engine will NEVER see pump gas only E85 and likely nitrous too. part of the reason to use the l67 heads is with a NA lower intake I will have an extra set of injector holes ready for nitrous. Its all going in a stupid light car so at the very least id like to make 500whp/500wtq is the goal.

Hoping the turbo guys will chime in on this.

Using 2 layers would get me to about 10.0:1 compression on a L36. Worth it to mill the heads a little?

In theory higher compression should make a more effecient engine and require less boost to make the same hp.

So if the car will never see pump gas can i get it up to maybe 11.0:1? not using stupid mega buck pistions to get the compression up so im basically looking for max compression with a L36 block, 2 layer mls gasket, and possibly milled heads.

even with only using e85 still go with the lower compression l67 block?

skip using the l67 heads or just run them and use a dry shot instead? shot would only be 75-100. i already have the zex dry kit. if i were to do direct id just need a few more odds and ends to convert it to wet.

as for the trans its gong in zachs old black caged gtp thats dow to about 2600#s. if i blow up the trans and destroy a 7/8s wih some good hard parts ill justsuck it up and switch to the 4t80 i refuse to cough up the cost of unobtanium gmr parts. i hope i can get a trans to survive beings the car is pretty light.

Right I understand the "shock" point but im hoping the weight will help keep a trans alive without unobtanium. If the trans doesn't survive I'll be forced to figure out a 4t80e, I cant justify spending 3kish for just a chain and diff.

The car doesn't need to make any hp records either. Im just hoping I can get it to shake down a 10.99 or faster.

So all in favor of the L67 full mls gasket kit and just get the set of l67 heads refreshed?

Basically everyone says low compression, E85, and crank up the boost.

Thanks for the heads up. I plan on taking my sweet time and chasing all the threads for the heads too and I'd like to gasket match the lim once I make up my mind. Think it will just be a lot bottom end and a na upper.

Thats what I was told to do by bill also. Thanks. Prep will be surgical clean. I sent email on some head studs but no response back yet. Besides 80# injectors and head studs pretty much all the parts are collected up, well piled up at gregs anyways..........

I wasn't considering custom pushrods? benefit vs cost? I didn't realize if I had the heads milled and used a partial MLS gasket I'd need shorter pushrods. Makes sense I guess, so then the question is throw a stock L67 together with a na upper? Or spend a little money on milled heads and 2 layer MLS to gain some compression? even more compression with a NA bottom end obviously.

Main reason for the MLS gaskets is id like to hit it with a bottle eventually. (speaking of nitrous stay stock bottom end with NA upper because it would be easy to duplicate if I chunk it on the bottle?)

Last anyone know if milled heads and 2 layers from the MLS gaskets would cause clearance issues?

Milling the heads makes them even more prone to twisting.