Paul L

Apples and oranges perhaps. The L-82 is the hydraulic lifter version of the solid lifter LT-1. If you stripped off the cat con from the L-82 and added true dual exhaust, would HP (expressed as net) come close to the 1971 LT-1 net HP of 330?

MotorHead

The 71 would have been rated at Gross HP and the 79 is Net HP. The difference is that the 71 would have been rated at what it would pull on a engine dyno with stepped headers and forced induction and not accessories dragging it down. This was the optimal performance of the motor, a few years later it was decided that this was not a fair way to advertise the power of a car and they decided to rate it with all the accessories and stock exhaust connected. This was Net HP.

Now there is a debate on how much HP the engine loses to the accessories etc. but my humble opinion is about 15 % so the the 320 Gross HP 71 is still much more powerfull than the '79.

Hope that helps :D

Paul L

Thanks, I had the title bass-ackwards :bb . So in your opinion the LT-1 is much more spirited than a de-neutered L-82? I do wonder since the cams and compession are basically the same. The solid lifters do give a bit of a boost on the revs but much else?

page62

Hmmm...food for thought. Due to the fact that I have a de-neutered engine, perhaps I could change the L-82 logos on the hood to LT-1*, or perhaps LT-1a

Or maybe not... :p:

dman535

Keep in mind that you also have different intake manifolds, different carburation and ignition timing. There is also another factor to consider, most LT-1's were not air cars, many did not have power steering and ran steeper gears. Given all those factors I would see a LT-1 to be much more spirited than an L-82 car.

Paul L

It is a thought! Just look at the facts:
1970 LT-1 - 370HP (gross)
1971 LT-1 - 330HP (gross)
1972 LT-1 - 255HP (net)
1973 L-82 - 250HP (net)
1974 L-82 - 250HP (net)

You could conclude that the solid lifters are worth only 5HP! Look at net between 1972 and 1973. These data are from the Corvette Black Book.


[Modified by paul79, 10:12 PM 9/26/2002]

Paul L

Thanks Derek. I do not have A/C and have 3.55:1 in the rear. Of course most LT-1s had 4-speeds.

SharkAttack

I always heard (never proved) the '71 and '72 LT-1 engines were the same, just rated differently.


[Modified by SharkAttack, 8:40 AM 9/27/2002]

Paul L

The comparison was between the 1972 LT-1 (net) and the 1973 L-82 (net). Only 5HP difference. Here is more for thought. This is Road & Track specs for a 1979 L-82 with smog equipment.

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Paul L

The comparison was between the 1972 LT-1 (net) and the 1973 L-82 (net). Only 5HP difference. Here is more food for thought. These are Road & Track specs for a 1979 L-82 with smog equipment.



Same magazine specs for an early 1970s LT-1 without cat con and the like. It is slower from 0-60! GM did some pretty nice smog work in the late 1970s.




[Modified by paul79, 10:55 PM 9/26/2002]

MotorHead

Two more things to consider besides the Gross to Net change was the smog eqipment they started putting on these cars in the early 70's, I remember test drving a 1973 RoadRunner 383 that had a 4 speed and I could not get the tires to spin, needlessto say I didn't buy it.

Also for 0-60 and and 1/4 mile times you have to take into account what tires they were running at the time, a 435 HP big block on bias ply 70 series tires is not going to be too quick :D

Rowdy Rat

Paul,

General Motors listed both SAE gross and SAE net horsepower figures for the 1971 model year so it is very easy to make the camparison and answer your question. The 1971 Corvette horsepower ratings are as follows:

ZQ-3 - 270 (gross)/210 (net)
LT-1 - 330 (gross)/275 (net)
LS-5 - 365 (gross)/285 (net)
LS-6 - 425 (gross)/325 (net)

As you can see, the 1971 LT-1 has a good 50 horsepower on the 1979 L-82... Not to mention that the LT-1 is going to be a couple hundred pounds lighter as well.

You can also see that the 1971 ratings are not the same as those for 1972... They were NOT the same engines with a different rating system. Distributor and carburetor changes are responsible for most of the variation between the two years.

Regards,

71coupe

I read something a while back the stated LT-1's were under rated by GM. Most '70 LT-1's were pushing over 400 horsepower at the motor.
'71 models-?
More food for thought.

DeenHylton

Don't forget that most engines dropped compression ratios between 1971-73. All Mfgs. across the board (Chev, Ford, Chrysler) went from 10.5-11.0 : 1 down to 8.5-9.0 : 1 with each full point of compression worth 10-15 HP.

Robert N

The 70 LT-1 was under rated and the horsepower is closer to the 400 based on my findings as well assuming a 20% loss through the drivetrain.
The 71 was probaly under rated as well as it was stilled a stronger motor than the 70 L46 with 350 hp.

The solid lifter set up, as well as the larger cam, carb, intake, heads, and compression all played a part in the power difference. The compression (if I remember correctly) dropped in 71 and again in 72, accounting for some of the hp drop. There were other significant changes that affected power as well.

Paul, as for the times for the 70 LT-1 from 0-60, I have seen them listed in most reports from low 6 sec to low 7 sec times. The car should easily do a mid to high 5 sec 0-60.

In my opinion, an LT-1 is more spirited as you put it.

The other note regarding the LT-1s - they were built for speed and di not hit peak power till the 6000 rpm area.

e3pres

I've driven both. The LT-1 is such a better engine. It's all in the heads.

Cali,68,L-79

Paul I'd have to see the cam specs myself but my engine builder said the cams are completly different. The bumpstick in the 70 was much larger "since the cams and compession are basically the same" My first Vette was a 70 LT-1 convertible and completely stock. It had way more HP/ ***** then my L-82 even after all the mods I've done on the L-82.

David

silver79

Paul i agree with you that the LT-1 and the L-82are very close the differnce is brobably the weight of the cars.The 71 should be at least a couple of hundred pounds lighter

Paul L

I guess that I have always been puzzled by the allure of the LT-1, compared with the L-82, when the performance specs do not seem very different. It would be intriguing to drop a cam and solid lifters in a late 1970s L-82 and see what happens (compared to the hydraulic).

Robert N

Add the holley carb, high rise dual plane intake, large valves and you essentially get an LT-1. If the LT-1 was one of the most potent, well designed SBs, then why buy a ZZ4 rather than build a modern LT-1? With the better technology today, you could take a stout 4 bolt 350 block, modern heads with the same sized valves, modern radical cam, headers, intake and carb and build a wicked engine.

Paul, the specs are similar. It does not make sense to me why the LT-1 is much different than the L82 on paper. Driving one answers that question.

To me it is similar to driving a Z06 and comparing it to the LT-1. The Z06 is faster, more nimble and more comfortable, but the feel of the LT-1 with its raw power is intoxicating. Something to do with computer generated, monitored and controlled HP VS brute strength.