I have a 1970 LT1 that made 360hp stock. I took it to the machine shop to get hot tanked and a valve job. The engine has not been bored. The only only things that I am changing is the cam and intake. I even have the organal carb that just got rebuilt.

Here are the stock specs
.
Casting # GM P/N Description
Block 3970010 4 bolt main, suffix codes: CTB, CTC
Crankshaft 330550 Forged steel
Heads 3927186 63.995 cc, 2.02/1.6 valves, screw in studs & guide plates
Cam 3972182 3972178 symbol: (1) square Solid lifter - 0.458(I)/0.484(E) lift, 317I/346E duration
Pistons Domed type - yields 11.0:1 compression
Intake 3972110
Carb (A/T) 3972120 Holley List 4490, 780cfm , 4150 series - 4BBL

The cam I am using is a Comp cam XE294H- 0.519 I/ 0.523 E Hyd flat lifters. I am also using there recommend spring kit -986-16.

I am using a RPM Performer Air Gap intake.

What do you think my horsepower gain is going to be?

Thank for any help you can give.

 

None, you might actually make the advertised 360hp now. Those heads are really holding you back.

 

Back in 1970 the HP ratings where in gross HP. Net HP was probably around 310-325HP. I agree with ME Leigh, you are probably making around 360 net HP now.

 

I doubt the net would even make 300. Not only that there are some other issues. We dont have leaded gas anymore. Octane is different too. You should just junk the heads and start over. 11:1 is way to high to run on iron heads, nowadays. Pistons gotta go too, that or get some bathtub chambered heads (that probably wont flow worth a damn).

 

Hes running a huge cam, so he might be able to get by, if he runs the highest grade gas available, and never goes WOT.

I sure as hell wouldn't run it, that motor is worth a far amount to a collector, or restorer.

 

Boy, does that bring back memories from the early 70's. Most of that stuff, except a small journal 327 block, steel 283 crank, 12.5:1 TRW forged pistons, Torker intake. Absolutely no guts below 2500 RPMs, but definately hang on after that. Sold it in '78 when unleaded and regular became all that was available.

Why not a set of Sportsman II Lites? Aluminum, 72cc chambers - just what the doctor ordered.

Of course, flat top pistons and doing a home-port on the 186 heads would probably be cheaper.