How big a cam will make power in an LT1

We're in the process of building a max'ed out LT1 engine. The goal is: maximum power from the stock-style LT1 block, intake, and heads. So far, here's the plan:

4.030 x 3.875 = 395 cid
11.8/1 compression and 6" rods
AFR 210's, bowl blended with short-turn work
Ported LT4 intake
Shaft rockers
Large solid roller cam

Similar dirt-track builds have netted us 600-640 fwhp, so we'd like to get over 600 with this one.

For the cam, I started out with a proven dirt-track solid roller: 262/268-106, +4. Since the LTX intake doesn't have much ram-tuning effect, I closed the intake valve earlier. The spec's I came up with are 258/268-106, +6. The problem is, I've never heard of anyone using a cam that size in an LTX. Most people with solid rollers stay in the 240 - 250 range.

Does anyone have a guess as to how this cam will work in an LTX?

Thanks,
Mike

It sorta sounds like you want this to run on pump gas? If not, and it really is a max effort engine, then bump that compression up a bunch.

The LT1 in my car, admittedly not a street application but with stock compression and cleaned up head castings with stock runner volumes, supports a 274/281 @ .050 Comp grind. Most of the other parts would be comparable: high stall converter, lots of rear gear, shaft rockers. The manifold is not stock but the throttle body is stock. I'm fairly pleased with it since it does essentially what it was designed to do.

c.

AdioSS, it doesn't have to be a pump gas engine. We concluded on that compression ratio because that's about tops for flat-top, 2 valve relief pistons. Wanted to stay away from the nasty combustion chamber shape associated with domes.

cnorton, that's interesting. Yours sounds like a Stock Eliminator setup. What kind of power does it make / what does it run in the quarter?

Thanks,
Mike

It has waaay too much cam for a Stocker. It's a Super Stock combination. Best ET was at 3000# at the Pomona Fairplex, 9.89. With a better tune-up it ran 9.97 at Las Vegas. I believe that it's capable of 9.70's in decent air.

c

It has waaay too much cam for a Stocker. It's a Super Stock combination. Best ET was at 3000# at the Pomona Fairplex, 9.89. With a better tune-up it ran 9.97 at Las Vegas. I believe that it's capable of 9.70's in decent air.

c
what kind of RPM did that combo turn?

At sea level with 100" roll-out radial slicks it crosses at about 8300. Typical speed at that ET is about 133-134. My logbook is in the trailer so I can't give you an exact number. Legit MPH is occasionally hard to get because the nose of the car can trip the speed lights. When that happens it usually shows a speed of 137+.

c.

Mike I run a very small dome and had no problems with the combustion chamber shape.12.5 CR on a 54 CC head. I do have the piston 15 thousands in the hole though.

I've never heard of anyone using a cam that size in an LTX.260/266 @ 0.050", 0.688"/0.688", 112 lsa. (http://home.gci.net/~jimlab/images/Engine/Delivered/Cam_card.jpg)

640+ horsepower (http://home.gci.net/~jimlab/images/Engine/Delivered/Dyno.jpg) in an 11.4:1 397 LT1 with a Hogan's intake and AFR 215cc RR heads.

Cam Motion recommended the following cam for my LT1:

R2707-2858-13+4
Small Base Circle / Hot Lash .024
Intake 270@.050 / .689 (1.6)
Exhaust 284@.050 / 688 (1.6)
Lobe Center 113
Centerline 109

Considering using it in my upgraded 392 LT1 (4.010 Bore, 3.875 Stroke), that will have a Super Victor, LE Ported AFR 227s and approximately 13.1 compression....and being squeezed 300+ with a NOS Double Cross Bar Plate.

Dave

Cam Motion recommended the following cam for my LT1:

R2707-2858-13+4
Small Base Circle / Hot Lash .024
Intake 270@.050 / .689 (1.6)
Exhaust 284@.050 / 688 (1.6)
Lobe Center 113
Centerline 109

Considering using it in my upgraded 392 LT1 (4.010 Bore, 3.875 Stroke), that will have a Super Victor, LE Ported AFR 227s and approximately 13.1 compression....and being squeezed 300+ with a NOS Double Cross Bar Plate.

Dave


That should be a fun set-up be sure to keep us posted.