Greg88

Hey Guys,

I have been tossing around the idea of trying to get a little more HP/Torque out of my LT1. Been thinking about a supercharger but with my current set up, I am about 11:1 compression, which would mean different heads etc just to get the compression lower.

I guess the other option would be doing something different to my current engine to run N/A? I would love to see around 500 rwhp. I am about 400 rwhp currently, just want a bit more. I am just not sure what direction I should go in, being most realistic with the money spent. Here is my current set up:

1993 LT1 Block

Short Block

Bored .030 over = 355ci
Mahle Forged domed 5CC Pistons
Eagle 6” H Beam Rods with ARP Bolts
Stock Crank cut and polished
Melling High Volume Oil Pump

Heads/Cam/Intake

Lloyd Elliot Custom Grind Cam
223/230 .565 Lift 112LSA
LS7 Lifters
Cloyes Timing Set
Comp Pushrods
AFR 190cc (Ported Flow 294/208 CFM)
60cc – 2.05/1.60 @.600
Crank 99893 Double Valve Springs
ARP 7/16” Rocker Studs
ISKU Adjustable Guide Plates
Comp 1.6rr NSA 7/16”
Ported Intake
58mm Throttle Body
30 LB Ford SVO Red top Injectors
ATI Super damper Balancer and Hub
Pace Setter Long Tube Headers

11:1 Static Compression

Thanks for the input!

JakeRobb

I'm no expert here, but if you wanted lower compression to go FI, you could also change to a dished piston to increase combistion chamber volume.

Alternatively, there's always nitrous. Seems like your build is a pretty good starting point for some giggle juice.

Good luck on your build!

Injuneer

If you are after 100 HP at the wheels, you'll need to add about 125 HP at the flywheel. That's a very low boost S/C or a relatively small shot of nitrous.

With regard to the heads, does "AFR 190cc (Ported Flow 294/208 CFM) 60cc was 65cc" mean you started with 65cc combustion chambers and the heads were milled to produce 60cc chambers? If so, are you sure you're at 11:1 with 5cc valve reliefs. Or did I completely misunderstand what you meant there? Or is it a 5cc dome, which would work out closer to 11:1?

Greg88

With regard to the heads, does "AFR 190cc (Ported Flow 294/208 CFM) 60cc was 65cc" mean you started with 65cc combustion chambers and the heads were milled to produce 60cc chambers? If so, are you sure you're at 11:1 with 5cc valve reliefs. Or did I completely misunderstand what you meant there? Or is it a 5cc dome, which would work out closer to 11:1?[/QUOTE]

Yes sorry. They were 65cc and milled down to 60cc. I purchased the engine complete so this was out of my hands! Also it's a 5cc domed piston.

I've thought about nitrous with the higher compression engine but I live in Canada and the laws are strict on nitrous. Also I like the thought of FI or NA because it's constant power!


Just not sure what the heads/rotating assembly are capable of at this time!

Greg88

I have a local D1SC forsale and I have my engine out for some TLC work. Could someone help me with the CR if I put -20 dished pistons in the setup provided above? I am sorry but I don't know exactly what all the numbers are that I need to find out the compression ratio. I would like to see 9-9.5:1 for a supercharger (I think). I am not sure what the thickness of the head gaskets are but I will be changing them anyways. Thanks in advance!

Greg

Injuneer

Good calculator, with diagram showing required info

- bore
- stroke
- gasket thickness (compressed)
- deck height (need that from the builder if you don't know it)
- piston top volume (see note on ”+" = dish; "-” = doepme)
- combustion chamber cc's

https://www.rbracing-rsr.com/compstaticcalc.html

They do ignore head gasket bore diameter, but that is minor. Typically it's larger than the block bore, say 4.125" stock.

I put in your bore, stroke, piston dish, and combustion chamber cc's, assumed 0.029" for the compressed gasket, and 0.020" for the deck height and got 9.02:1

I wouldn't go any lower than that. But you need accurate dimension for the gasket and deck height. Buddy of mine was over 800 HP on 383ci, with a blower and 9.5:1 static.

Greg88

Ok thanks! Maybe a -16 dished piston would bring it up to closer to the 9.5:1

Thanks Fred!

Zspoiler

You have to run a dished turbocharger/blower piston.with 8:1 compression to run any kind of supercharger.I have run super chargers for years,And my 1979 Z-28 RS is supercharged with 500 HP plus.The engine is a 377 cubic inch small block built from the ground up to do so.

Injuneer

I can only tell you what the CR was in George Baxter's 383 LT1 (in 3,800# 97 SS convertible) that held the LT1 record at 9.04/155 MPH back in 2001-2003. 1,125 HP at the flywheel. The LT1 aluminum heads (including aftermarket), reverse flow cooling and high precision ignition timing/reduced spark scatter allow a higher compression ratio. That's why stock LT1's left the factory at 10.5:1, capable of running on 87-octane fuel (92 preferred).

The LSx guys run 9.0 to 9.5 as well, with no problems.

Greg88

I know this is an old thread. I just got the motor back together and determined that the static compression ratio was 10.3:1. I am seriously contemplating putting a SC on the car. Running this compression. Only running 7-8lbs of boost from a P1SC. Am I crazy or is it def doable!? I am not sure if the 30lb injectors could handle the extra load? Would obviously need to upgrade the fuel pump to maybe a 255?