LT1 E85 Compression Question

[jgardner]

So I've been running e85 in the TA for a while now and it runs great! This winter I'm going to be porting and polishing my heads. I know with e85 you can run a higher compression, and I'm just wondering if anyone has personal experience with how much. I've done a little research and have found some that state you could go up to probably 13.5. I'm thinking going up a point from 10.4 to 11.4 or even to 12 would be a good improvement without going overboard. Has anyone had experience with increased compression on the lt1 running e85? Also, I'm trying to figure out the best way to get the increased compression. Since I'll have the heads off, I was thinking of just getting them shaved a little. Thoughts? Thanks!

[Boost Addict]

I'm around 12:1 and running on 93 with no issues.

[jgardner]

Good to know thanks! How'd you get the extra compression? The thing I'm worried about is how much I can gain just by shaving the heads.

[farmington]

If you're sure that you will be running ONLY on E85, You should go up to at least 12.5:1. And no, just cutting the heads won't get you there. Only way to do this properly is new pistons.

[jgardner]

Ya I'm hooked on e85. Do you know what the safe amount would be to shave off the heads and approx what the compression would be? I'm planning a rebuild next winter so I can do the pistons then. It'd just be nice to take care of the heads while I have them off and reap the benefits during this summer.

[ThreeHonks]

if you shave too much off the heads, you will shroud the valves and have intake geometry issues

[Boost Addict]

Good to know thanks! How'd you get the extra compression? The thing I'm worried about is how much I can gain just by shaving the heads.

Pistons, deck height, heads, head gasket.

[kyleozzie]

my buddy has a 383 lt1 that runs on 93 that is almost 13:1

[jgardner]

Thanks guys! So I'm thinking I'll leave the heads alone, put a thinner gasket (should be able to get 11.1 by going to .026 gasket). That will tide me over until the rebuild next winter when I can change out the pistons.

[r1cefed]

Another issue with milling too much is that it can change the way your intake sits. Same with going with too thick of a gasket trying to lower compression for boost w.o pulling pistons.

Another option you might have since you are paying to get the heads ported anyway is too look into an aftermarket casting. Such as a Trick flow, Brodix, Dart. Since they cast their own heads they may be able to cut you some small combustion chambers and still have it work/flow fairly decent. Maybe not your 13.5 to 1 yet, but possibly more than you would get with your stock castings for now withough milling and changing geometry to much. I would maybe call and ask a couple of the manufacturers what they can do for your application vs a stock casting.

I am curious to see how this runs though. Please keep us posted.

[jgardner]

I'm actually going to be porting and polishing the heads myself so that wouldn't be an option. I'll have to do some test fitment with the intake and see what kind of an impact the different size gaskets would make (if any).

[masterfab]

just like boost addict said deck the block/head gasket can get you about 1/2 point/ and pistons. i would split the differance between decking the block and a thinner mls gasket. porting your own heads huh. word of friendly advice buy a cc beeker and make sure ever runner has the same cc runner when your done or you could throw your cumbustion off. like 2 cyl getting more air than the others. the crank will not like you at that point.

[r1cefed]

Combustion chamber is a touchy area. I wouldnt feel safe changing the shape of it myself and assuming they are all the same. Or that my new shape was better than stock. (Then again I am not an expert) But by polishing one different than another could change the way it dispurses the combustion. Most likely not in a good way. MOST of the time alot of R&D and flow bench/design time goes into making heads work. Hence why it is so expensive to have somebody bolt them down and run a CNC program on them.

I am not trying to be an ass and preach to you but I got this speech when I was thinking of touching up the heads for my current build. I wanted some light porting done and have the combustion chambers polished. Assumed it easily could have been done myself. I learned it is much better to have it done by a professional on professional equiptment to assure the flow/mixing of air/fuel is the same in all 8 cylinders. Even if what you are doing is minor.

Again I am in no way saying you are incapable of doing it yourself and making power with them. Plenty of people do it. I guess it is just how confident in your abilities you are. There is just alot to consider when it comes to effing with your heads. I would hate to see you have problems with it.

[PWND3r]

First off, my first question is... Are you running E85 on a stock pump and fuel lines with stock injectors? You do know that E85 will eat plastic and aluminum right? You also know that using E85 requires 10-30% more fuel right, and that E85 is not regulated so you're not getting E85 all the time?

With that being said; my old motor was a 385, with the heads milled down and the whole set-up it was about 13:1 compression and it was fine on 93 octane, but I occasionally mixed it with some 110 or some other type of higher octane. I usually experimented with fuel with that car. I could also spray a 100 shot on 93 octane. This was all done on a Walbro 255, stock lines and fuel set-up, adjustable regulator, and 42lb injectors.

Milling the heads will require you to mill the intake as well with the way it all sits. Unless you're trying to stay in a stock type class, it really wouldn't be worth the tear down. You'd be better off throwing some type of nitrous system on, it'd be easier, more bang for the buck, and you'd get more power.

Also please do not port the heads unless you know what you're doing. This will require a flow bench and someone with a very steady hand, if you're not using a CNC machine. You will have to do valve job if you port the combustion chambers and well as have the valve guides checked. If you're doing a rebuild next spring then I'd save all of this for then and enjoy the car until then.

[DETROITMUSCLE]

First off, my first question is... Are you running E85 on a stock pump and fuel lines with stock injectors? You do know that E85 will eat plastic and aluminum right? You also know that using E85 requires 10-30% more fuel right, and that E85 is not regulated so you're not getting E85 all the time?

With that being said; my old motor was a 385, with the heads milled down and the whole set-up it was about 13:1 compression and it was fine on 93 octane, but I occasionally mixed it with some 110 or some other type of higher octane. I usually experimented with fuel with that car. I could also spray a 100 shot on 93 octane. This was all done on a Walbro 255, stock lines and fuel set-up, adjustable regulator, and 42lb injectors.

Milling the heads will require you to mill the intake as well with the way it all sits. Unless you're trying to stay in a stock type class, it really wouldn't be worth the tear down. You'd be better off throwing some type of nitrous system on, it'd be easier, more bang for the buck, and you'd get more power.

Also please do not port the heads unless you know what you're doing. This will require a flow bench and someone with a very steady hand, if you're not using a CNC machine. You will have to do valve job if you port the combustion chambers and well as have the valve guides checked. If you're doing a rebuild next spring then I'd save all of this for then and enjoy the car until then.

What did that car end up running Joe?