Actual HP for an L-78

[old5.0]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chevy454</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: old5.0</div><div class="ubbcode-body">I would guess a showroom stock, assembly line built L78 probably made somewhere between 200-220 horse at the wheels in the real world. That said, pulling 375 to the wheels while maintaining a stock look shouldn't be hard in this day and age. </div></div>
I think that's too low...I would guess 250-300 @ the wheels, depending on the tune. Our 427/425hp did 370+ to the wheels rebuilt to as close to the way it would have arrived from the factory as possible...10.2:1 compression, didn't cut the heads/block, original crank/rods/manifolds, etc, etc. This would push our 3750lb Camaro to 106-108 mph depending on the air. </div></div>

Yeah, I could see something in the 250-260 range. My guess was completely unscientific based on personal observation.

That said, I think these engines are just begging for a custom cam. The square port BBC heads are excellent pieces that still stand up well 40+ years later. I think the power increase an otherwise stock L78 could see with only a modern, custom cam grind would be shocking.

[Chevy454]

The cam isn't the problem, ask any cam company (I've talked to no less than 3 about this very subject), the 143 cam is a pretty darn good piece. the problem (imo) is the huge tolerances from the factory...chambers 10cc+ too big, dome 6cc+ too short, deck clearance all of the place, etc, etc. As i said above, we did an L72 as close to factory as we could get it and it came in at 10.2:1...Scott Tiemann tore into an original L72 out of a Berger copo and it was a scant 9.8:1!

[Salvatore]

No need to dyno a street car and especially a show car motor. Whats the point? If the dyno on your motor says 475 hp, it does not mean much at a car show or on the street. Waste of time and money IMO.

[COPO PETE]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: [email protected]</div><div class="ubbcode-body">No need to dyno a street car and especially a show car motor. Whats the point? If the dyno on your motor says 475 hp, it does not mean much at a car show or on the street. Waste of time and money IMO. </div></div>
Quess I'm wasting all my time and money!
Peter

[old5.0]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chevy454</div><div class="ubbcode-body">The cam isn't the problem, ask any cam company (I've talked to no less than 3 about this very subject), the 143 cam is a pretty darn good piece. the problem (imo) is the huge tolerances from the factory...chambers 10cc+ too big, dome 6cc+ too short, deck clearance all of the place, etc, etc. As i said above, we did an L72 as close to factory as we could get it and it came in at 10.2:1...Scott Tiemann tore into an original L72 out of a Berger copo and it was a scant 9.8:1! </div></div>

Oh yeah, I don't doubt that at all. I know some NMRA Factory Stock class racers that have gone through hundreds of factory E7TE castings before finding a matched set with similar flow numbers and chamber volumes in the same neighborhood as the factory specs. But with the cam, I have to think there's power hiding there.

Look at this way. If you call Comp, for example, and order a custom grind, they'll be happy to sell it to you, but it's still based on lobe profiles already in their inventory. They may be willing to tweek the duration here or the lift there, but it isn't a true &quot;custom&quot; grind. It may be an improvement over an OTS cam, but you're still leaving power on the table. And it may genuinely not be much of an improvement over the factory 143 cam. A true, from the ground up custom is a whole different animal.

A little off topic, and I apologize, but I know of a 347 stroker small block Ford with a set of inline valve Canfield heads, stock 20* valve angle, Super Victor intake, Pro Systems prepped Holley, and a true custom cam that's making close to 700 horsepower at the flywheel. And it's only 10.5:1 compression, totally streetable, and makes a ton of torque, despite the big single plane and small displacement. The key to the whole thing is the camshaft.

I dunno, I'd like to see what an otherwise stock 396, or 427, could do with a true custom designed around the entire car.

[Chevy454]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: old5.0</div><div class="ubbcode-body">
Look at this way. If you call Comp, for example, and order a custom grind, they'll be happy to sell it to you, but it's still based on lobe profiles already in their inventory. They may be willing to tweek the duration here or the lift there, but it isn't a true &quot;custom&quot; grind. It may be an improvement over an OTS cam, but you're still leaving power on the table. And it may genuinely not be much of an improvement over the factory 143 cam. A true, from the ground up custom is a whole different animal. I dunno, I'd like to see what an otherwise stock 396, or 427, could do with a true custom designed around the entire car. </div></div>
Yeah, we're talking about the same thing...I had a place on the east coast recently cam doctor and log one of our blueprint camshafts, and we had this very conversation. Being the good salesman that he is he of course told me he could do a cam for me [just shy of a grand for dual lobe design + blank] and pick up a little power, and he's probably right...but he was quick to admit that the stock 143 camshaft was a pretty good piece for what we do. I doubt the gain would be some mind numbing amount, because the constraints of a stock engine and it's parts [that's what this discussion was in reference to] are pretty tight. Limited exhaust flow versus headers, limited ramp velocity of solid cam, limited induction from dual plane + 780 vacuum carb, etc, etc. On a full blown race engine where parts can be taylored to fit, then it's a different story, of course.

And I will say this: by simply adding some compression and pulling the retarding the camshaft 6 degrees, the stock 143 will peak higher and hang onto power a lotbetter than most would think... [img]<<GRAEMLIN_URL>>/wink.gif[/img]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: olredalert</div><div class="ubbcode-body">------Big thumbs up on the deck height variations, Rob. Theres a reason that so many chevy engines have been decked and it wasnt for higher than stock, as advertised, compression. Racers were just trying to get all the compression they were legally allowed to run. Bob H told me one time that when they checked the deck height on Red Alerts original LS6 engine that it was off substantially. Actually, he gave me a figure, but that #s gone. My old memory just isnt that good.......Bill S </div></div>
Most folks would be surprised at just how much diffeerrence there is from front to back on each bank! [img]<<GRAEMLIN_URL>>/sick.gif[/img]

[JRSully]

fwiw, when I had my 70 L78 engine rebuilt, it was comprised of the following: stock, orig block .30 over (now 408 CI),crank, dot rods, stock configuration 11:1 speed pro pistons, NOS 143 cam, uncut 291 heads/orig valve size, uncut 569 intake, stock 4557 holley, orig 2000 distrib (36 degrees all in @ 3k, headers,100 octane fuel: 421 hp @ 6k on the dyno

[COPO PETE]

I think that sounds resonable. If you had retarded the cam 6 degrees, put 40 degrees timing in and took it to 7000, you would have found the peek at around 6300 rpm, but maybe not with the 70 intake. Also, every dyno is different, and a hugh difference if you dyno in the winter or in summer on a hot hot day.
Peter

[Chevy454]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: COPO PETE</div><div class="ubbcode-body">I think that sounds resonable. If you had retarded the cam 6 degrees, put 40 degrees timing in and took it to 7000, you would have found the peek at around 6300 rpm, but maybe not with the 70 intake. Also, every dyno is different, and a hugh difference if you dyno in the winter or in summer on a hot hot day.
Peter </div></div>
Just as an FYI [your mileage may vary!]...our L72 liked 38 total, but you nailed the 6300 peak! [img]<<GRAEMLIN_URL>>/biggthumpup.gif[/img]

[olredalert]

------Big thumbs up on the deck height variations, Rob. Theres a reason that so many chevy engines have been decked and it wasnt for higher than stock, as advertised, compression. Racers were just trying to get all the compression they were legally allowed to run. Bob H told me one time that when they checked the deck height on Red Alerts original LS6 engine that it was off substantially. Actually, he gave me a figure, but that #s gone. My old memory just isnt that good.......Bill S