Big Block L-72 Question.

**MosportGreen66** · #1 10-07-2003, 04:26 PM

Hey Guys,

What was the difference between the early production L-72 with 450HP (in my Vette) vrs. the later production L-72 with 425 HP. I am guessing the cam was different but I am not 100% sure.

Thanks.
-Dan

**Stefano** · #2 10-07-2003, 04:42 PM

Same cam, same engine, Corvette to Corvette, just a different rating.

Remember the first L-78s(396s)in the Corvettes were rated at 425hp and the new 427s certainly had to have more HP [img]/ubbthreads/images/graemlins/burnout.gif[/img]

Chevy454 · #3 10-07-2003, 06:41 PM

According to the Chevy by the Numbers book, the '66 had more cam duration, different heads w/slightly larger combustion chamber in the head, and a different intake than the later L-72s. Kind of nit-picky stuff, and I honestly can't say if any of it makes any difference. [img]/ubbthreads/images/graemlins/dunno.gif[/img]

Keith Tedford · #4 10-07-2003, 07:34 PM

A friend worked on the line in the fall of '65 when the first L72 "B" body cars came down the line. For a short time they had 450 hp decals. Then they were changed to 425 hp. Through the early sixties all the manufacturers were playing a number oneupmanship game. It appears to be more of a numbers game than anything else. Perhaps reality finally set in as the new ratings were more in line with actual output. [img]/ubbthreads/images/graemlins/burnout.gif[/img]

**MosportGreen66** · #5 10-07-2003, 10:39 PM

I had the Corvette at a local show this past weekend and a guy with a Mosport Green 425HP coupe asked me what the difference between the engines were. I told him, honestly, just don't know.

Thanks guys.. I knew someone out there would know the answer. I did not know that the original 1965 Corvettes had L-78 engines. Chevrolet did a good job with the changing of the HP ratings; got me.

-Dan

Enoch · #6 10-07-2003, 11:55 PM

I have restored 5 '66 Corvette's w/ L-72's Serial #'s from under 1000 tru 20,000. No difference in any parts of the motors were found. I have heard 2 stories as to the reason for the 25 hp "de-tune".
First Insurance reasons.
Second Chevy execs. knew the L-71 was coming out the following year and they thought it wiser to go back to 425 and go up from there than up from 450 with the rating of the L-71. Also at this rate the L-S6 would have to have been rated around 500 hp.
As a side note all 5 motors were run on the dyno after stock spec rebuilds and they all made between 470-480 hp and 480-500 ft lbs of torque.

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