Actual HP for an L-78

[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]

[JRSully]

Those '70 569 pancake intakes aren't as bad as everybody thinks and I think this has been hashed about in another thread. Interesting concept on retarding the cam 6 degrees and bumping timing to 40.? Might be time to shelf the orig engine and build that CE block I got laying around...

[Chevy454]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRSully</div><div class="ubbcode-body">Those '70 569 pancake intakes aren't as bad as everybody thinks and I think this has been hashed about in another thread. Interesting concept on retarding the cam 6 degrees and bumping timing to 40.? Might be time to shelf the orig engine and build that CE block I got laying around... </div></div>
Search this site for &quot;compression map&quot;...that is how you propertly determine your cam timing [particularly IVC]...ignition timing is determined by burn rate [chamber design, port velocity, dome height/design, etc], ie, the slower the burn rate the more ignition advance you need.

Just for grins, I've attached a dyno sheet from last week of our Pure Stock L72...stock untouched intake/exhaust manifolds, Crane blueprint Gm143 cam [retarded 6 degrees]. There's a slight *lull* down low where the carb is transitioning, but we're running out of time so it will just have to do.