im building a E-85 nitrous motor and want to bump up the comp. i figure if i get around 13ish to 1 i will be safe. i also have a set of 64CC 225 dart heads. is it possible to get this without milling the heads to hell? also by milling the heads, will that effect anything minus the obvious? im guessing its going to have to be a custom made piston, but any imput is thanked.

 

Thinner head gasket, but then that could be bad with the added compression. And when raising compression by either of those methods, you would want to watch PTV with whatever cam you decide to run.

 

yea no doubt. it seems hard to find out any info with all the people ive talked to. id want to run a bigger cam also...

 

If I had better knowledge of engines I could help more. I only know basics sadly. I know 59cc heads really bump compression, and you can still run a nice cam, like a ms3 I believe, but IIRC the comp from 5.3s end up being like 11.5 or something. Thiner head gasket, like .040 or thinner, but then you could blow out a weaker gasket with the higher comp, and potentially run into PTV like I said. You have a cam decided?

 

nope. all i have right now is maybe those heads, i could go to a diffrent head i guess? a set of oliver billet rods, and a nice crank, and block of course. i have a set of tea stage 2 5.3 heads on my current motor? id rather go to a aftermarket cast maybe? id figure out the cam after the pistons i think.

 

Aftermarket cast are slightly taller than stock, reworked heads aren't they? Could those give you a little more room if you were to mill them for more compression?

 

see thats what i don't understand. wiesco makes a piston that would work with those darts, but id have to mill them to get it to work. i don't really want to mill the hell out of them, but im not afraid to. i just don't know what effect milling a head so much has on it.

 

Only effect that I know is running into PTV issues. There are tons of people on this site that run milled heads, and have held up fine.

 

milling them .10 or so shouldn't be bad, my 5.3 heads are milled, but i was told to try and get comp like that i would have to mill .20-.30 off the head. thats where im leary..

 

Understandable. And once milled, no going back. If you can mill like .10 off, check PTV with clay,mill .05 off again, check, ect ect, that might get to where you want to be, and within a safe margin. You have access to a shop, and that can do this kind of work?

 

Milling the heads beyond say .042" can really affect the flow numbers. Any milling affects the flow numbers, but anything under .030" is not significant enough to justify the gains to be had with higher compression. Unfortunately, that will still require a domed piston to get above 13:1. If you want to make it easier, Wiseco makes a +5cc domed off-the-shelf piston which will be useful (I'd recommend setting the piston out of the hole @ .010"), then add a .040" Cometic, and mill to 58cc Chambers (.036" milled). That would give you 13.0:1 static compression with a .030" quench area.

As far as a thinner gasket, you want to do that first. By tightening the quench, you decrease the likelyhood of detonation by improving the burn throughout the combustion process. This is important as you add "squeeze" the air/flow mixture harder - you want there to be a very effective burn. Also remember that higher octane fuel burns slower but more completely. If you want to build your motor for gas or E85 or whatever, focus on NA power first, unless you are making a drag car that will see huge shots of nitrous. You aren't going to blow the gaskets (unless you have a huge shot of nitrous or boost - but then the heads will lift as well).

Optimize for NA through the proper quench/gasket selection/deck height/milling. Don't worry about the milling. Piston-to-Valve clearance may be a problem, depending on the cam, but a simple way to get a ballpart estimate for that is to:

First determine the freedrop (.150" on a stock LS1 - don't know on the Darts, but they should have that information) and then use this formula: Freedrop - piston depth (should be positive if the piston is above the deck) - how much the heads are milled - needed clearance + gasket thickeness = lift clearance at TDC. Comp gives you the tappet lift @ TDC for 106 ICL and 110 ICL for their lobes. To determine tappet clearance, you multiply that number by the rocker ratio (1.7). As long as your lift clearance at TDC is larger than the Comp requirements, you should be okay. But always measure to make sure.

 

wiesco makes a off the shelf piston with a 12cc dome i guess? in theroy i would only need a 64CC chamber to get to 13 to 1? i guess im confusing myself here maybe.

 

thanks a bunch sir. i do plan on spraying quite a bit thru it, 200-300?? im just trying to use e85 to my advantage becouse its so easy to obtain where i am. why build a 10 to 1, when i can go 13 safley, ya know? i haven't bought any head yet, or pistons, just looking at those heads, and trying to figure it out, anymore input you offer would be thanked again.

 

That is the kind response I was hoping would come in. Nice post Jake.

 

E85 would require you to change out the seals in fuel system (at least according to Nissan back when I had an 04 Titan and was trying to get it E85 compliant... 11mpg with $4+ gas = ugh). On the LS1, I imagine you'll have to do that as well, but it shouldn't be that hard or expensive.

I've also heard debates on a flat top piston vs a domed piston and for me, I'd rather keep hard edges out of the combustion chambers as they can lead to hotspots. With a huge shot of nitrous, those hot spots could cause some headaches. But, if the piston is designed to handle it (and most reverse dome pistons, like the Wisecos are), they do a really do a good job of eliminating those hard edges. I believe the off-the-shelf Wisecos can handle a 250 shot without any problem as they also 2618 alloy and have some nice features. You can upgrade to H-11 tool steel for the pins and go with some hellfire stainless NPR top rings to help. A solid rod is also necessary. For a budget and a good trade off in weight vs power, the Compstar H-Beam Rods with ARP 2000 bolts are a good choice. I've seen and heard of some of the expensive I-Beams twisting.

I would run a dedicated fuel system on a 300 shot, and go with a progressive controller. Maybe 100 shot followed by a 200 shot (both direct port). That way you can run C16 or propane in the secondary fuel system and really be safe. Limit the amount of nitrous to whatever Wiseco recommends.