hammy5454

I would say that his trap speed was pretty consistent with his ET although, that is one blazing fast, stock LT-1.

I once took my BMW M3 to the track and recorded a best of 13.1 at 110 mph. Same, same.

Mike Ward

Net horsepower is measured at the flywheel but with all accessories along with stock intake and exhaust.

All factory HP and TQ numbers are specified to be at a given RPM. Compare your numbers to theirs at the same RPM for greater accuracy.

7t9l82

gross horsepower is on a dyno with no accessories.
net is on a dyno with all accessories smog equipment and complete factory exhaust.
the 71 was down a bit from the 370 h.p of 1970.
i know several L-82 cars ran 14.2 quarter mile times with little work, sounds like something was wrong with your tune up.

none of the numbers you quoted were ever rear wheel horsepower.

hammy5454

Thanks Mike, for the clarification on NET hp ratings. As I stated, I wasn't sure how it was calculated.

As far as your other comment, I feel a bit taken aback. I feel a 13.82 @ 103 mph for a pure stock car on F70 bias plies is nothing to be ashamed of and a good representation of the car's capabilities. I doubt there was anything "wrong" with my tune up. My car typically ran among the top 25% or so of the pure stock cars entered and in a MuscleCar Review article which compared a dozen stock small block musclecars, mine was one of only two that broke into the 13s. The rest ran mid 14s which again, is nothing to be ashamed of and typical of the performance of those original cars.

A 14.2 ET from an L82 with only "some" modifications? What were the mods? More than just a perfect "tuneup" I'm sure.

Anyway, my times were real.

For the record, I've always disliked talking to bench racers at Cruise Nights who probably never even took their cars to the track but, assumed they ran low twelves, etc. cuz they "felt it" in the seat of their pants. Just sayin'.

cv67

believable. Had a 70 Z/28 same thing different manifolds I believe. Even with ported heads and a larger (similar to a comp 282s) it wasnt 400hp...maybe with longtubes. Good running motor but a 13 sec car at best.

6T5RUSH

Have to agree with Barry's70LT1 and LT1kid.

Although mine is not a true '70-'72 Corvette LT-1, I have to jump in here and also comment along with hammy5454 on my favorable experiences using a replacement LT-1 intake, camshaft and lifters on my .060 over 327. I'm running factory ramshorns with a stock 2818-1 585 cfm Holley. The dual pattern, flat tappet solid lifter LT-1 camshaft really woke up this small block. Rockers are stock 1.5 stamped, steel Chevy.

Here's a video I took of a Dyno Run on a Mustang Dyno back in 2011 where the tech had to get out of her at 5,500 r's cause she was leaning out (had told him to take her to 6,500). This 2nd run shows she pulled 296 rwh. ENJOY!



Realize I'm far from factory stock for my 327 but I did achieve real performance improvement with my stock 461 iron heads that were "breathed on" heavily by a pro cylinder head guru, Jeff Kobylski...RIP.

I too used the 15 lb. nodular iron flywheel and have what I call the "best of both worlds" exhaust system...both factory side exhausts AND a complete, mandrel bent, 2 1/2" with an H pipe and shorty Dynamax mufflers under car system.

My point to this post is the old school flat tappet factory camshafts and the LT-1 in particular with a "stock" engine compartment look achieves great performance. Love that solid lifter sound!!

hammy5454, I too participated at the Pure Stocks and have to agree that Bob Boden and Dan Jensen do an outstanding job of putting together this program. My best, test and tuning at Milan was 13.4's at a 104...that with a lot of tire spinning...street radials, Muncie wide ratio 4 speed and 3.73 posi.

Jim
In God We Trust!

cv67

Wouldnt happen to be the brother of Dave owner of the balance shop in Reseda ca?

dmaxx3500

then we need to start some new ones,what do you got

7t9l82

first of all i didn't say there was anything to be ashamed of, with stock tires and stock everything you aren't far off. the LT-1 required some tinkering and some tires with some bite. people make the mistake of saying these cars were never on par with the new cars and that isn't fair my gosh look at the tires today there is probably a half second right there maybe more and hydraulic lifters and a computer to constantly adjust everything.the LT-1 liked a bit looser valve adjustment and more timing fatter jetting and you had to have headers or you weren't getting anywhere. and they liked to rev so a gear was in order. thats the way we used to run them but we considered that stock.

as for the L-82 cars shim head gasket good dual exhaust distributor set up and carburetor work. 3 55 gears and thats what we got.

and i totally agree on bench racing know it alls.

and actually i confused myself i was thinking yours was a 70 not a 71, and that made a big difference.actually the71 LT-1 and later ones ran just a tad better than the L-82 , so yes you are correct thats not to bad. sorry i missed that point.

Jebbysan

An LT-1 will never make more than 360-370 horsepower without porting the heads....it just can't......

But the great thing about the LT-1 is the fairly flat torque curve....
370 horse is nothing to sneeze at.....

Jebby

jb78L-82

This question about the LT-1 has come up many times in the past and here's how I break it down:

The first problem with any comparisons is the whole Gross HP versus Net HP issues. By switching to Net HP ratings in 1972, the manufacturers were faced with a PR nightmare comparing pre 1972 Gross HP engine ratings to 1972 and on Net HP ratings. In some ways, this dilemma is amusing even today when I read about crate engines rated at 425 HP etc, with the only problem is that those numbers are Gross HP, not NET HP, which is the relevant HP number today and really no where near that mark in the real world of NET HP ratings. Fortunately, GM's switch from Gross to Net HP ratings in 1972 does provide some useful information for the question being asked.

The LT-1 350 was offered in C3's from 1970-1972, with the 1970 350/370 Gross HP one being the only one that is somewhat unique with 11:1 compression and solid lifter cam, as I recall. The 71 LT-1's dropped to 330 Gross HP with the only change being a big compression ratio drop from 11:1 to 9:1 (coincidentally the same as the coming 73 L-82 @ 9:1) and also used a hydraulic cam instead of the solid lifter cam. All 3 LT-1's used a Holley 4150, no difference. The 1972 LT-1 and the 1971 LT-1 are exactly the same engine, the only difference is a gross HP rating in 1971 and a NET hp rating in 1972. The NET HP rating for the LT-1 in 1972 was 255 HP.

Using some VERY basic analysis, the change from Gross HP rating to Net HP on the LT-1 from 1971 to 1972 resulted in a 23% reduction in the HP between the 2 rating systems.

The 73 L-82 and the 71/72 LT-1's are all the same motor. The 73 L-82 was rated at exactly the same Net HP as the 72 LT-1-no difference. The only significant performer of the LT-1's versus the future L-82, as stated previously, is the 70 LT-1.

Lots of published numbers on the LT-1 one but here is one:

1970 Engines:
350 V8 300 HP
350 LT1 V8 370 HP
454 LS5 V8 390 HP
Performance:
350/370 LT1: 0-60 in 5.7 seconds, ¼ mile in 14.2 seconds

1971 Engines:
350 V8 300 HP
350 LT1 V8 330 HP
454 LS5 V8 365 HP
454 LS6 V8 425 HP

1972 Engines:
350 V8 200 HP
350 V8 210 HP
350 LT1 V8 255 HP
454 LS5 V8 270 HP
Performance:
350/255: 0-60 in 6.9 seconds, ¼ mile in 14.3 seconds

As noted previously, with better modern tires, the 70 LT-1 should be able to crack high 13's in the 1/4. As noted earlier as well, the later L-82's can also get into the high 14's as expected since the net hp ratings would be 225-255 with 73/74 and 78-80 being the better years. The difference in the 1/4 times is primarily slightly less HP versus the 71-74 cars (LT-1 and L-82) and more weight in the latter 70's cars. Interestedly the 78/79 L-82 4 speeds would run 6.5 0-60 (compare to the LT-1 above). If you look at the 70-80 LT-1/L-82 at a Macro level it all fits together and makes sense.

Just looking at the numbers and performance we know, I would guess that a 70 LT-1 rated at 370 Gross HP would actually be producing about 290-300 NET HP in today's world.

Hope that helps!

69autoXr

All LT-1's were solid lifter cams, never hydraulic. Not to mention high rise intake and Holley carb. So, not the same motor as 73 L82, which was rated 250 net vs. 72 LT-1 255 net.

20mercury

Couple of questions please:

1. this is likely a dumb one, but the C6 LS3 must be in net hp? So if the LS3 is advertised at 430hp, that must be net?? So gross might be around 500hp to be comparable to 1970 ratings?

2. I believe all of the L-82's from 73 thru 80 were very similar. So if you changed out the exhaust on even the 75 and 76 L-82, you should get similar results as you describe for the 78/79/80 L-82's???

I guess I did not realize that the L-82's are not that far behind the LT-1's (for 71&72 anyway).

Mike Ward

Plus different heads, ignition curve, smog system, etc etc.

Not many performance parts in common between and LT! and L82.

cv67

Check the different tech sections all corvette motors were grossly underrated

jb78L-82

Thanks for the clarification on the solid lifter cams. Obviously the high rise intake and Holley carb were were only worth 5 HP from the 72 Lt-1 to the 73 L-82, 255 net hp versus 250 Net HP, which is not surprising since the L-82 intake and Qjet are pretty good as well. That to me is no real difference. Same for heads, ignition curb etc.

jb78L-82

Not really true. The main performance parts between an L-82 and LT-1, especially the 71/72 LT-1 and the 73/74 L-82 are very similar if not the same-forged crank, 9:1 forged pistons, 4 bolt mains, etc. The main difference which is obviously minor is the cam-255 Net HP versus 250 Net HP. If you believe the folks on the forum, the Qjet was/is better than the Holley. The L-82 aluminum intake is also very good. The smog equipment differentiation between the LT-1 and L-82's does not become significant until 1975 when the true dual exhaust was eliminated and the terribly constrictive cat becomes mandatory on all cars. Strip a 78/79/80 L-82 of all smog equipment, add 2.5 duals, and the performance is real close to 71/72 LT-1-they are basically the same motor with some minor variations that have minor performance impact.

My 78 L-82 4 speed with zero emissions equipment, 2.5 duals, and a Holley 4175 recorded 233 RWHP, NOT Net HP, Not Gross, on the dyno. The internals of the engine are bone stock along with the L-82 aluminum intake. You can back into the Net number any number of ways, but there is no denying that 233 RWHP is quite a bit more than a 72 LT-1 at 255 net HP (remember the 71 LT-1 at 330 Gross HP is the same motor as the 72 LT-1 rated at 255 Net HP). No getting around that fact.
The 0-60 times referenced above from the LT-1 and the late 70's L-82 further confirm the similarity.

jb78L-82

1. Yes all horsepower since 1972 is Net.
2. Strip away all smog equipment on an L-82 and maximize timing for performance and the L-82 really wakes up.
3. Most of the Folklore surrounding the LT-1 stems from the 1970 LT-1 with 11:1 compression and the 370 GROSS HP rating. After that the differences between the LT-1 and the much maligned L-82's is really a very small performance difference, especially stripped of emissions and adding 2.5 inch duals.

Mike Ward

Aside from pistons none of those contribute to performance which was my point. We could argue that the block was the same too as were the timing cover, oil pump etc. etc.

'73-'77 have a cast iron intake, same casting number on L48 and L82.

The ignition timing and curve, inhibition of vacuum advance as well as carb jetting on the early L82s is a major handicap but was required to meet smog regulations.

All of this needs to be taken into account when attempting to regain early '70s performance.

6T5RUSH

cuisinartvette,

Not certain if Jeff had any family members out on the left coast.

Jim
In God We Trust!