I am putting together a LT1 with a forged bottom end a cam and a set of LE1 heads. My future plans for the combo was a supercharger but that'll be at least a year off. Any way my question is how much boost could be run through the motor on a forged bottom end with 10.5:1 compression? What would I have to do to safely run more boost? I am asking while the motor is out and I am in the process because the motor won't come out again until she blows. As well i don't want the motor to underperform incase something changes and I don't get the supercharger.

 

it can depend on what supercharger you go with.
However I know a few guys that do this sort of thing a lot. My experinnce with procharger p1sc intercooled super you can get away with higher compression if you stay at the suggested psi which is 8psi. Keep in mind that the higher the compression the higher chance of detonation this is what you must be carfull with. the safe bet would be to lower the compresion and if you take out the stock pistons (hypertectic)spelling. Put in the forged pistons and lower compression. I know guys with plenty of miles on their engine.
My question to you is how much of difference did you see with the gears?

 

I saw roughly 3 tenths in the 1/4 I guess. I put on the tires at the same time and resolved a spinning issue and picked up 5 tenths between the two. There was a thread talking about how there is no gain from the but I can't see 5 tenths on tires. I also had 2.73s stock.

The motor is getting forged pistons, rods, and crank. All of the parts are here but I was wondering if something needed to be changed for a future blower set up. Like I said before this thing isn't coming out again until it blows.

I just assumed an intercooled set up. I also was thinking of meth/water injection. Is that the maximum with the rebuild? Anyone ave any track/dyno numbers?

Thanks MC'SZ28.

 

With that compression, I wouldn't recommend more than 8 or 9 psi, and even then, some type of charge cooler would be mandatory, which you already mentioned anyway. If you are intent on keeping the 10.5 to 1 pistons I would plan on getting some heads when you put the blower or turbo on, TFS sells some for the LT1 with 62cc combustion chambers and they are only 1300.00 complete from summit. That would bring you down to 10.0 to 1 which is a little more boost friendly. Then agian, 8 psi of intercooled boost on a 10.5 to 1 engine might make all the power you want, another one of those depends on your goals type answers.

 

Why not drop the static compression to around 9 - 9.5 and run a cam with a high DCR. When it's time to install the blower, just swap over to a blower cam and you're set. You shouldn't loose much power with the lower static compression, but being able to run 12-14 PSI safely would make it worth it in the end.

 

Thats a very good point, You'll only lose 2 to 4 percent HP with every full point of compression, not a very big difference, and the ability to run more boost will definatly offset that

 

Not nearly that much - it depends where you start. IOW, going from 10:1 to 9:1 is a bigger drop than 12:1 to 11:1 (10% decrease in CR v. 8%). But in any case, even at the lower starting point the hp loss is <2% per ratio. Besides, that applies only to NA. There is minimal loss when under boost. I actually have the formula somewhere for change in NA hp with change in CR, I can find it if anyone wants the details.

Rich

 

So I guess most of the changes would be top end(less the pistions)? I would like to see the formula if you can find it rskrause. If I can get the numbers I am hoping out of the LE heads and cc503 cam I guess my target time would be low 11's with a blower. I don't want to get overly crazy, sure a 10 second street car would be bad *** but then things will break constantly. It is a car I'll drive to work and just to goof off with as well as taking it to the track. I'm not really set in stone about any of this so I want to keep my options open. It's just everything is here and paid for. I can deal with buying a new H/C set up when the blower comes I just don't want to do this rebuid crap again unless I have to. Thanks a lot fellas.

 

Sorry, can't find the formula. But I did find a table in one of David Vizard's books. But here are some repreentative numbers.

12:1-14:1 2.2% (1.1%/point)
10:1-12:1 2.8% (1.4%/point)
11:1-8:1 5.2% (1.7%/point)

Again, this refers to street NA combos. The effect is slightly greater if the cam is optimzed to the new CR. However, with pump gas and the rpm limits of typical components this is not often possible).

Rich