K here's what am I wondering for all you tuners out there to give me advice please...

I Have a lt1 with a d1sc race kit on it with a 9 lb pulley and intercooler (the serpentine belt kit) And the longtubes from EM. when it warns up (gets hot boost seems to drop to 7 lbs so I am also considering on upgrading all the pulleys in the damn car to wider ones to try to eliminate some belt slip, but I digress.

The stock engine has 104K on it atm So I went shopping.

I have some nice stage II lt4 heads with a port matched intake in the garage next to the dana 44 and a lt4 knock sensor atm and am investigating my forged shortblock options now.

Now... the questions.

1. am I better off running low compression engine with high boost? or high compression with the pulley I have now on the SC

2. If I am better off running low compression with high boost what's the highest I can go on a 8.5 or 8.8:1 compression engine without having to get into water or methanol injection?

3. Should I get a F.A.S.T. ECM or can I still use my stock ECM just reprogrammed?

Please feel free to toss in you opinions so I can get more of a feel on how I am thinking this all through.

 

Definately drop that compression down. I would say in the 8's somewhere. You don't have to run an aftermarket ecm, but it makes the tuning and retuning easier, much more so if you've got an early LT1. You will always make more power with low compression and high boost than the other way around. You're gonna need some big dishes on those pistons.

 

Get the compresion down 8.5 or 9 to 1.with the lower compresion you should still be able to keep it on pump gas.You can tune this with the factory ecm it's not as acurate as a fast or gen 7 but it can be done.As far as the motor goes make sure you dont skimp on the parts (forged pistons,good rods,good crank)

 

okay yes that's what I been thinking I'm looking at all forged internals and looks like I can get to like 8.8 with the right JE forged sets... OKay then.... with that in mind... I'm wondering Eagle 4340 forged or cola and manley? what's the difference really? is it worth the extra grand to get a cola crank? or am I just as well off on Eagle/imported parts?

Also the question re. the water injection... what's the highest boost I can go w/o having to get into water/methanol injection on a 8.8:1 engine?

 

What kind of hp are you looking to make?I would use that to determ what crank and rods to use.I agree on the je pistons.I made over 700 hp with an eagle 4340 crank and a set of eagle 4340 h-beam rods.With a forged crank and rods you can run the clevite h brgs.You are also going to need a cam turned on a small base circle (if you plan on doing a 383).I think you are ok with the heads.If you already have a set of finished heads you can buy a completed short block(mti,morgan motorsports,rapid motorsports)it's a little more expensive but a lot less hassel

 

shooting for 600-700 hp. but will do more if boost will allow it w/o having to shoot water

 

here is what i would run

1.eagle 4340 crank 3.750 stroke
2.eagle 4340 h-beam rods (i would try and use a 6.00 rod but i think you might have to use a 5.7 or 5.85)
3.je,venolia,or srp pistons (i would set it up for as close to 9 to 1 as you can get)
4.clevite h brg.
5.custom comp or crane cam (turned on a small diamiter base circle)tell them its for a blower car and must be on a 114 lobe seperation and keep it a hyd. roller
6.comp r lifters (i think the number is 815-16 but dont hold me to it


I would keep the cam on the smaller size.I would spin my motor over 7000 rpm and the factory computer didn't like it

 

The best combination from the piston side of things would be a 3.75 stroke and a 5.850 rod. This keeps the ring lands thick w/out the necessity of putting the pin in the oil ring groove (which necessitates the need for a groove lock spacer). Take a look at bald turbo freaks new website www.baldturbofreak.com He worked with us to design a very trick set of 2618 alloy forged pistons for his monster and he's now selling these to others that run similar combinations. They will take well over 1000hp and have the durability to run on the street for a long time. These were designed to be "well mannered" as well and we built in quite a few special features to this end. I won't disclose these features, but you might be able to peel them out of Rick (btf). Good luck with your project!--Brian Nutter-Wiseco Automotive

 

If you are going to run that D1 you will need to drop the compression, to below 9:1 is prefered. You can run up to 6 PSI with the stock compression but you risk piston damage if it ever detonates. The stock cast pistons won't like detonation at all. Also you can run more timing in a engine with lower compression than you can the other way around. Dropping the timing 3 degrees will affect power levels considerably.

Definitely get a forged bottom end. Plenty of people use Eagle products without any problems. It is more a personal preference these days than anything else. Personally I prefer Lunati, or Callies for crankshafts, and JE or Ross for custom pistons. As Brian mentioned, the 2618 piston alloy is the choice for Nitrous and Blower applications. I typically ask that the ring land be located lower away from the top of the pistons to insulate them from heat. Brian mentioned BTF using a 5.85 rod combo so that the oil rings stay out of the pin area. Which is a good idea, I have also had good luck using 6" rods by just having the rings relocated lower. Using a 6" rod with the oil rings in the pin area poses no weakening of the piston. And for modest boost levels of up to 14 PSI I felt that the design was fine, plus I had the slight advantage of a better rod to stroke ratio. BTF is talking about making 1000hp levels, at hose levels strength requirements escalate for durability.

With modest boost levels controlling fueling with a stock ECM is easily done. Your main problem will be controlling belt slippage. I had a Prochaged LT1 C4 in for tuning the other day and while he had a 8lb pulley I never saw any more than 7 PSI. It made respectable power for a blown 9:1 383 on my dyno but its a far cry from 700. It did make about 430 at the wheels which translates to roughly 516 at the crank which is respectable. It had a mild cam in the engine with lightly ported stock LT1 heads. With better heads and a bit more boost I felt it could have made another 50Hp or more.