Found this online. Says it's a 100% stock rebuild & dyno test.
375HP at 5800 RPM
Turn the speakers up and listen to it roar!
BTW stock fuel pump and drops to 3.9 PSI at 5800.

 

Those were the days if you did not buy a new Corvette with a LT1, good luck finding one that was not trashed! Love my 77 L-82 Corvette because that throaty motor brings me back to why Chevrolet was No 1.

 

I never did like dyno places that fudge the results on a 100% Blah, blah, blah motor. It's got headers, total free flowing exhaust (no Mufflers) and under driven water pump (note 1-1 pulley ratio) So to get only 375 hp seems like it wasn't built very well. Just blue printing and a quality balancing job in an otherwise stock build can exceed the factory specs. Put on modern springs without rotators and spring cups with multi angle valve and seat jobs is another plus

 

That is about 10 more than a new one plucked off the line at GM would make through headers.......
Unless the heads are worked on these.....that is about all it will ever make.
The DZ 302, the 327/365 and the LT- all made the same power as that is all the heads would flow.
The stock manifolds on the Vette and Camaro's murdered these numbers too......the large overlap cams installed in these all begged for long tube headers.

Jebby

 

Did i read that right? A bone stock 70 LT1 would make around 365 WITH headers? That would make the 370HP rating WAY overrated. I've read 360-370HP stock, actual crank gross HP, but 365 with headers is more like 340-345 without... which is way off.

 

Yep....and through manifolds even worse....the manifolds on the LT-1 had a 2" outlet......
GM assumed that you would put "day 2 " headers on these cars.......
Rode in a lot of these as a kid......with headers and timing they were a player.......without, they just made noise. To this day, you still get that ******* car show guy yelling about how he made 500hp with his and revved it to 8000 rpm on the way to work everyday, uphill through 5 feet of snow both ways.......
Bolt a real pair of heads on one (Which I have)....with NO other changes....and they make 420-425 horsepower just like that....that is how shitty the "camel back" head is......
The car in the Avatar (66' L-79) had 60 hours of port and machine work on the 441 heads to make the same flow numbers as an out of the box Edelbrock Performer belly button head.

Jebby

 

Thanks Leigh!

Call me crazy but those numbers look spot on for a bone stock 1970 LT-1 engine with 11:1 Compression and, certainly within a margin of error, since the reported published specs for this engine was/is 370 Gross HP @ 6,000 RPM.

The last fact ^^^^begs the question why the dyno operator stopped the pull at 5,800 RPM when the redline on these motors was 6,500 RPM from the factory and clearly on the video the HP was still climbing at 5,800 RPM when the pull was terminated. Another words, there exits the real possibility that this motor could have easily produced 380+ Gross HP if the pull continued to 6,500 RPM since we don't see when the HP production leveled off (6,000-6,200 RPM).

The other point to note is that Gross HP back in the day was done with open exhausts and either headers or open in this case 2.5 inch manifolds which would not change the Gross HP number on an engine stand dramatically with no pipes and no mufflers. Lastly, this engine in the video has a water pump hooked up and with a belt to the crank pulley which, again, would not be the traditional setup for a gross HP pull on a dyno stand for published HP results.

So you can see ^^^ that are a number of details here that imply that this was a pretty good number for a stock 1970 LT-1 (370 Gross HP). I did notice also that my rebuilt/upgraded L-82 355 with 10.2 compression, roller cam, AFR heads, and stock ported L-82 aluminum intake installed in my 78 with all the variables that are different than being on an engine stand revs much faster and, more forcefully, to 6,000 RPM than the engine in that video. Just an observation...

Here is the one description of GROSS HP:

​​​​​​Gross output, which in the U.S. is typically measured using the methodology laid out in SAE standards J245 and J1996, is the output of a ‘bare’ engine running on a test stand with no external engine-driven accessories (e.g., alternators or water pumps), free-flowing exhaust headers with no mufflers, and optimal ignition timing. Gross ratings are also mathematically corrected for standard atmospheric conditions. In other words, gross output represents a particular engine’s maximum output under ideal conditions.

 

Thanks for the feedback JBL-82. I agree it seems very realistic for a stock LT-1. I owned and raced one for 27 years and timed it many times. Always came up around that number. Qtr mile speed was between 102 and 106 depending on tune. 60 fts were always horrible, like 2,5, it was a stiff street / autocross car.

And I also agree 100% with Jebby that a new set of modern heads offers significant airflow and HP improvements with almost no downside, vs 50 year old technology. Cylinder head airflow was really in it's infancy back then, and made significant improvements in the 80s & 90s. The only downside to the modern heads is to the must-be-original numbers matching crowd. Modern heads have almost zero driveability downsides, (unlike cams), and significant HP on the upside.

To really enjoy (experience) the 70s well-if-its-bigger-must-be-better (cylinder head) mentality, you must drive a 69-70 Boss 302 sometime. That cylinder head was so ridiculously big on that engine the car almost stalled if you let the clutch out at anything under 4000 rpm. What a joke on the street that was. Lots of burnt clutch smell. The 302 DZ ran much stronger. Just highlights how little everyone knew back then.

 

TWO INCH...??? I thought that was just the later 350's...??? Jesus... whats the point? I understand the 'they're just gonna put headers on it...' (hello 426 Hemi...) mindset... but not everyone does/did. Hell, there are some very good reasons not to put headers on. What the hell were they thinking? Is not the rest ov the exhaust 2.5"? How much money could those smaller manifolds possibly have saved them?

Thats as bad as a 440 Mopar. Stock, they were dogs... every single one save the 69 1/2 only A12's. You think Chevy overrated their engines? They threw every engine dyno trick in the book at the 440 Magnum to get that 375HP rating. But if you bolt headers on...??? Jesus Christ...

I've only been learning about the Chevy smallblock for a few months now... aside from hearing about them ad-nauseum from my Chevy friends for 30 years (and not really listening). I was shocked that the SB heads were so universally maligned. I was led to believe those sacred 'camel humps' were amazing. Exhaust aside... thats the first thing i'd remove if i got a SB Corvette.

Guess thats why the bone stock LT1's didnt really run any great 1/4 MPH... you know, for their numbers.