Time differences at quarter mile only tell a small part of any story and were problems with very poor tires for the time period trying to launch cars from a dead rest. From a 40 mile an hour roll a 70 LT1 would just walk off leave all the L/82 stuff with ease. I out ran a lot bigger displacent tq motors with my 302. Why because i was smart enough to catch them rolling along where tq not needed nearly as much. While they were low rpm having to shift there car I was in same gear still pulling hard. Low rpm engines are a joke. Bottom line both the L/48 and L/82 did nothing but hurt the vettes reputation it had once gained as a performance car. Built lots of motors using gm parts and about every cam they ever used including there off road cams. Its only sad that the L/82 only thing you could get. The LS4 the exact same engine you got in a pickup even to the cam only difference between two vette got better exhaust manifolds engine was a total dog. My new 73 had 4000 mikes on it when i pulled it down only thing reused the two bolt main block, oil pan, oil pump, dist. Flywheel and balancer. When it went back together it was a 7600 with power engine. An engine built to make power to 7600 and one built to 4500 rpm massive difference regardles of any displacement used and with the 454 it would annilate the lousy tires at any rpm you liked to run at lol.

 

Are you sure of this figure? By my calculations that's about a 22-23% difference from gross to net, I thought it was in the area of 10-15%, but I could be wrong...

 

Yup..the 71 and 72 LT-1 are almost exactly the same motor:

"here were other options for '72 Corvettes. The LT1 was relatively rare and the ZR1 was nearly as rare as they come. The LT1 V-8 was a high-performance 350-cid small-block. It used a 9.0:1 compression ratio and a Holley four-barrel to churn up 255 hp at 5600 rpm and 280 lbs.-ft. of torque at 4000 rpm. Other LT1 goodies included a forged steel crankshaft, solid valve lifters, a high-performance camshaft, an aluminum intake manifold and a 2.50-inch diameter dual exhaust system."

The 1971 LT-1 was 330 GROSS HP and the 1972 LT-1 (same engine) rated by GM as NET HP was 255 NET HP which is a difference of 75 HP going from Gross to Net HP. 75/330 Gross HP is 22.7%!

I agree that I use most of the time going from gross to net 12-15% reduction in the numbers and Gross to RWHP about 25-30% reduction but you cannot argue with GM's published numbers. Most likely the 71 LT-1 rated at gross HP was NOT 330 Gross HP but inflated for marketing reasons..the 255 NET number is much more reasonable based on the engine specs and car's actual performance.....but either way the Gross to Net HP change in ratings was a 22.7% reduction....

 

Might not be all the diff. You back total advance off 2° and you lose about 25 hp. It is still there, but not until you re-tune.

 

Good possibility^^^^^^^^.

If timing was different for the 1972 LT-1 and derek is correct , you would add 25 to 255 NET HP and you are at 280 NET HP. The 50 hp reduction from the 330 Gross HP number (50/330) is 15.2% reduction which is more likely the real number in that case....

Either way, the point here is that the 71/72 LT-1's and 73-80 L-82's are all pretty much the same motor with the same non emissions performance potential. Remove the cat and 2-1-2 exhaust, headers, no AIR pump and other emission non sense like EGR, add performance timing and remove idle jet limiters on the carbs, and all of these motors were pretty decent performers. Add a performance carb tune and roller tipped rockers and these motors were VERY match to the 71/72 LT-1 and very close to an L-46 350 Gross HP motor. My 78 L-82 4speed with 3.70 gears non emissions was a pretty good performance car with the OEM L-82 motor...VERY GOOD in fact.

BTW-Not to bring up another sore point for some on the forum, BUT the mid 60's SMALLER 327 V8's actually made more power than the larger 350/350 GROSS HP L-46...Shocker! Magic number was 360 GROSS HP......from a smaller V8!

 

The difference in the L-82 camshaft was it was ground 2 degrees retarded. Changing to a different timing chain with advance keyways or an offset bushing made them functionally identical
A free flowing exhaust, timing and carb improvement and it ran very well.
The NHRA factored the L-82 at 315 h.p. one would assume with the noted changes.
My old 78 pacecar with those changes headers and some light headwork , automatic, ATI convertor 3:55 gears never met a ,70 LT-1 it didn't like. It was so far ahead at half track the LT,,-1 couldn't make it up horsepower isn't the entire story.

 

Oh😁 I may have had 1.6 roller rockers. On that car too.

 

In my AIM, it lists both net and gross hp. Net is 255 and gross is 335. Don't know why it isn't 330 like the '71.

 

72 was the year they went to net ratings.

 

Yes, I know.