Actual HP for an L-78

[olredalert]

----Hey Bill,,,Somebody at GM thought that your basic engine combo was good for 425HP back in 65 in a Corvette. Of course, that was probably under optimum conditions on GMs dyno, but if its bragging, thats as good a place to start as any. After 1965 and early 66 I think GM started to sandbag a bit for two reasons. First; Insurance. Second; Various racing entities.....Bill S

[66 L78 ragtop]

I have GM paperwork dated Aug 65 showing that the L78 produced 425 @ 6200 RPM. The down rated horsepower occurred in 66: 375 @ 5600 RPM

[Bill Rose]

I guess brag wasn't the best word to use. I've had that horse power question a few times, and I wasn't sure how to answer it. Thanks for the help with this guys. Next time I build a motor, it's going on a dyno before it goes into the car. I'd still like to get some numbers from a freshly built stock L-78, and see how it compares to the numbers from GM, 40 yrs ago.

[PxTx]

If you want to talk about HP, just have the car chassis dynoed. They'll be able to help you with a corection factor for drivetrain loss.

I think it would be preety cool if you can get it to make 375 WHP. Just depends on how bad you want it.

[old5.0]

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.

[SSRSBOB]

Called my engine builder. They vary, he has done many. Usually in the 415-435 range. Many head and block castings are better than others, core shift, etc. That's why no two L78's make exactly the same power. it's generally a range.

Bob

[XXXGoldL34M20]

just tell everyone that it is <span style="color: #CC0000">425 H/P</span>
my buddy with an L78 1970 Chevelle does and no one ever questions him.

[Chevy454]

<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.

[Keith Tedford]

Roger Huntington was a pretty on the ball guy back then.

Auto journalist Roger Huntington wrote an article about what these engines actually put out, and here is the list. The figures are for gross HP though, I have the list of net HP ratings too.


Engine------------------Advertised----Rated----------True
------------------------HP @ RPM---- Torque@ RPM-- HP @ RPM

Buick 455 Stage 1-------360@5000----510@2800------420@5400
Camaro Z/28 302--------290@5800----290@4200------310@6200
Chevelle 396 L-78-------375@5600----415@3600------400@5600
Corvette 427 L-88-------430@5200----450@4400------480@6400
Mopar 340-4 bbl---------275@5000----340@3200------320@5600
Mopar 440-Magnum------375@4600----480@3200------410@5400
Mopar 440 Six-Pack------390@4700----490@3200------430@5600
Mopar 426 Street Hemi---425@5000----490@4000------470@6000
Mustang Boss 302--------290@5800----290@4300------310@6200
Ford 351-4 bbl Cleveland--300@5400----380@3400------340@5600
Mustang Boss 351--------330@5400----370@4000------360@6000
Mustang 428 Cobra-Jet---335@5200----440@3400------410@5600
Mustang Boss 429--------375@5200----450@3400------420@5600
Oldsmobile 455 W-30-----370@5300----500@3600------440@5600
Oldsmobile 350 W-31-----325@5400----360@3600------350@5800
Pontiac Ram Air 400------366@5100----445@3600------410@5600

[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.