What do you think of this engine, estimate some HP

454 + 0,30
10,25 compression
Edelbrock Performer RPM rec port heads
Comp CAMs hyd roller extreme Marine 11-451-8, 230/236 @ 0,50 - 0,547/0.547 @ 0,50
Holley 870 vacuum street avenger
Stock LS6 intake

Thank you

 

I'd loosely guess 425-450hp.... Depending on the actual heads you end up using (runner size). The intake is the bottle neck...and that cam isn't doing you any favors either. You don't mention if you are running headers or manifolds but that's another factor.

Heads too big, cam too small, intake WAY too small...

If you haven't already bought the parts, I'd re-evaluate some of it but....if you already have it, then run it and see...

 

Yes I know the engine isnt a good match. But it was in the car when I bought it.
It has hooker super competition headers.
For now there is a Air-gap intake, but I want the stock Hood so going to change the intake to stock LS6.

 

Does someone know What RPM range the stock LS6 have?

 

The RPM air gap is really the perfect manifold for that combo. You’ll easily lose 30+ hp going to an LS6 intake...


A stock 70’ LS6 engine made peak power at 5600 RPMs, had a redline of 6500. Despite the fact of having rectangular port heads and a significant 242*@.050 cam, they actually make a lot of bottom end torque and it comes in pretty early..... (likely due to the intake manifold).

Your current cam isn’t “bad”, it’s just not likely a good match for rectangular port heads....that said I’m sure you’re still capable of making 450hp with the RPM air gap intake.

 

I think the cam and LS6 intake match pretty good, but it should have been oval port heads to be correct, but then the LS6 intake dont match...

 

That cam and that intake do not match at all.......the only thing that intake was designed to do was to clear the hood.....nothing else......it was never used on any other car.
Look at the LS-6 intake for a Chevelle........Chevrolet got that one right, it is almost identical to the L-88 intake.......there is a reason it sits high.
The Vette LS-6 is a cork......and I would not go backwards so you can run a stock hood.

Jebby

 

his current hood is wrong color and has a major light leak with an air filter sticking through it. and the car came with untouched matching paint orig hood and wiper door, etc. i can see his point.

 

Yes, I have the original BB hood with correct color.
Im not going to race this car, it should be a cruising machine.
If I want to race I can put this in, but then I need another hood...haha, a 69 2nd edition L88

 

Your combo isn't much different than mine... but I haven't put mine on a chassis dyno, so I can't 100% accurately estimate the power mine is making, but in talking to the previous owner, who claims to have built and raced some BBCs when he was younger and doing more racing, he figures it is close to +/- 500hp. I wouldn't think yours would be much behind, if at all. I enjoy how mine drives at lower speeds, has plenty of low-end TQ and pulls really strong from 3000-5500rpm, at which point I can tell it flattens out a bit. Having a 6-speed transmission with close gearing helps, too.

468ci
10:1 CR
rect port alum heads
LS6 intake
240/250 @ .050, .570/.570 lift, 110 LSA cam
Hooker long tube headers with 3" exhaust from header collector all the way back
Holley 750 DP carb, mech secondaries

When I get bored with it, I will get an L88 hood, painted to match (my paint is a solid 8.5-9 out of 10, and my stock hood looks fantastic), and install an RPM AirGap intake for the extra +/-30hp that ajrothm and Jebby say is there (and I agree with them). Or... yank it all apart and build a new engine...and a rear-end... and a ...

 

An original LS6 Chevelle did indeed run the pancake intake, but I am sure many of them did not stay on long. Ironically the '70 L78 396 Chevelle still ran the nice High Rise intake. (They switched SHP engine options mid-year).

The flat intake was designed for the lower hoodlines of the 68 vette and 70 Camaro. All prior SHP BBC ran the high rise intake, including the C2 Vettes. That's another reason the 68-69 C3 Vette did not have a Holley car'b L72 427 option, it wouldn't fit under the hood. The L78 '70 Camaro was the only L78 with the flat one, while the '69 'maro had the high one.

And yes it probably did cost 30 HP. But all original LS6s (from 70 Chevelles) have been dyno'd at 435, 455 & 485 HP, with 510-513 lbs tq. with stock exhaust manifolds too, and those A-body ones were another real cork, they cost more than 30HP, maybe 40-50. So headers help a lot, and carb & distributor tuning really helps these a lot as well. With headers, or a better intake, or both, these were 480-500HP+ engines.

I would estimate your motor to be in that range, with headers, 460-490 HP.

 

The 70’ LS6 Chevelle intake is the same intake as on the 71’ LS6 vette. They were all pancakes. An L88 intake is considerably taller and wouldn’t work with the cowl induction hood/air cleaner on the Chevelle.

 

Factory redline was 6500 rpm. GM originally planned the LS6 for cars other than the Chevelle, like the Corvette and the Camaro but gas, insurance, and other factors were putting an end to street high performance cars so these flat intakes were used on the Chevelle with a spacer to get the air cleaner up to the cowl hood.
Now let me just say this. I agree with everything fellow members have said here except remember, most the the HP numbers are achieved at an rpm not normally seen on the street. So the downside of the flat LS6 intake is not really that much worse than the "high rise" version at lower rpms. I agree, if you are at lower elevation 450 hp is probably a realistic number.
Good luck with your combination.

 

Ok, this makes sense and something I wanted to discuss in another thread, but never really got around to it. I'm more familiar with forced induction setups that make tons of TQ at all rpms, as soon as the throttle is cracked open...and when you mod them, you typically see gains that are consistent and flat across the entire useable rev-range. "Power/TQ under the curve" is what matters, especially on a street car, so if the LS6 intake gives up +/-30HP from say 5800-6500rpm over a pancake LS6 intake, but only 5-10HP from 3500-5000rpm, then it really isn't effectively as big of a loss. Peak HP, sure it is down power, but average HP it is much less. It would show up if racing, I understand, but the power lost under the curve isn't that great... as you said, only in higher rpms, which would be in a racing environment.

30HP loss from 3000-6000rpm is a different story, however.

 

Great answer from you guys 😃

If you would buy another hydraulic roller camshaft to pick up some power, witch one do you think fit my combo?
I know mine is a marine cam, I dont know how it is different from a car camshaft, from What I understand there are plenty of carengines with that marine camshaft.

 

I stand corrected......learn something everyday.......strange they would make the cowl unit work with the L-78 396 high rise and not the LS-6........
The more I learn about GM back then.....the more I realize that they really didn't have their s%&t together.....

Jebby

 

Here is an important consideration on camshaft selection. Often times less is more. Don’t just look at the numbers but where they occur. A broad flat torque curve is better for a street car. Also consider the entire package when choosing. Example rear gear ratio. If your going to change it take that into account. Lots to think about here

 

From what I understand from the Chevelle guys the cowl hood worked just fine with the hi-rise L78 intake. And the LS6. That year the L78 was listed as a SHP engine option. In mid year, Dec or Jan ? IIRC they just suddenly switched that option to the LS6. If you remember GM had a 400 cubic inch ban and lifted it in 1970. So is it ironic that this engine magically grew Cubic inches in Jan of '70? And in the meantime it was just called SHP? And when the 454 SHP was released there was almost no info about it. But in their infinite wisdom since this exact engine was "supposed" to go into the strike delayed 70 Camaro, (another combo that never happened anyway), they made the exact engine capable of fitting under the lower Camaro hood, and then had to put a stupid looking 1" or 1-1/2" metal spacer on top of the carb, (under the already existing cowl inducted air cleaner), for it to reach the cowl hood in the Chevelles. First time I ever saw that piece of back yard engineering I almost died laughing! That stupid adapter is actually a treasured part in the Chevelle crowd. My all original 70 Z28 LT-1 Camaro just barely fit under the hood, much like a C3 Vette. It absolutely would have taken the pancake intake for the L78 or LS6 to fit.

 

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Since you already have it in your car, I'd say leave it. I'll bet it runs great as is.

That looks like a XM-284R right? Actually not a bad street cam at all. Pretty close to LS6 specs. 2200-5800 rpm range Should work well with LS6 intake. Just a little bit less LC than some of the car cams and a little more lope in the idle. It's actually one of the ones I was looking at. Should have decent idle and decent vacuum for vette vacuum system. If you go with more cam, it is going to get less streetable very quickly, you'll lose the bottom end TQ very quickly, and you'll need that high rise manifold even more to get the power out of a bigger cam. To get the revs out of a bigger cam you would need the very expensive HR lifters and more rear end gear.

OTOH if you just want a little more torque, especially low end TQ, you can just advance the cam a couple degrees pretty easily. If you want to "test" to see if you really want a bigger cam, and more HP upstairs, try retarding the cam a couple degrees.

 

I talked with an old friend today that is a Chevelle Guru and he confirmed what others have said here. The L-78 was the SHP option in the early 70 model year. The LS 6 option was slated for the Camaro and Corvette but never made production for those models. The LS6 released in mid year production was put in the Chevelle / El Camino with the flat intake because that is how it was designed and built and the only mod necessary for Chevelle production, was that stupid looking spacer to meet the cowl hood height, which was selling very well.
At least that is what he told me how he remembered it, and it sounds logical.