Originally Posted by 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.

Originally Posted by MN-Brent

wiki:
LT-1
Years: 1970–1972
The LT-1 was the ultimate 350 cu in (5.7 L) V8, becoming available in 1970. It used solid lifters, 11:1 compression, a high-performance camshaft, and a 780 CFM Holley four-barrel carburetor on a special aluminum intake with ramhorn exhaust manifolds and a low-restriction exhaust to produce a factory rated 370 hp (276 kW) (the NHRA rated it at 425 hp for classification purposes) and 380 lb·ft (515 N·m). Redline was 6500 rpm but power fell off significantly past 6200 rpm.

The LT-1 was available on the Corvette and Camaro Z28.

Power was down in 1971 to 330 hp (246 kW) and 360 lb·ft (488 N·m) with 9:1 compression, and again in 1972 (the last year of the LT-1, now rated using net, rather than gross, measurement) to 255 hp (190 kW) and 280 lb·ft (380 N·m).

Originally Posted by hammy5454

Hi all,
Well, this comes from my personal experience as well as what I can recall reading in magazines in the seventies.

First, we all know that hp ratings were a joke back in the day. They were either under rated for insurance reasons (428 CJ = only 335 hp?) Really? On the other end of the spectrum, we have the mighty mouse
L79 327 rated at 375hp and the LT-1 at 370 hp (doubtful on both counts).

Here's what I have. I purchased a 1971 LT-1 Corvette in 1985. It was in need of a lot of TLC but, everything was there and it was a perfect candidate for restoration. I took it to our local track early on. It was an oil burner and it smoked like a train but, I wanted to get a baseline. My best ET of the day was a disappointing 15.12 @ 91 mph!

Next off to my local chassis dyno where it recorded an astounding 219 hp! Ha!

Well, I seem to recall some road tested ETs from Car Life, Road and Track and Hot Rod magazines. I recall a 14.09, a 14.36 and a 14.45 as some of their ETs, all at around 101 mph. So, I knew the car had potential.

After I had the car in the beginning stages of restoration, I began to participate in the Pure Stock Drags sponsored by MuscleCar Review Magazine in Mid Michigan. (Special thanks to Bob Boden and Dan Jensen BTW, for getting me started).

Anyway, to complete an already long story (sorry) ... after a few years and with the car 99% restored, I recorded a best ET at their event of 13.82 @ 103 mph. This was on a stock (.030 over) rebuild with smog pump intact and on original style F70/15 Firestone Wide Oval bias ply tires. The only upgrades were that I had the heads massaged with a 3 angle valve job and a bit of polishing AND the addition of a 2 1/2" SS exhaust. Otherwise, this car was bone stock. (Stock exhaust manifolds, 3.70 rear end, etc.)

Now, back to the chassis dyno where the car recorded 292 hp at the rear wheels.

If you recall, back in 1971, they started rating hp as GROSS (at the flywheel with no power accesories attached, etc., etc.) and NET (which I believe was at the rear wheels as on a chassis dyno.)
The LT-1 for '71 was factory rated at 330 hp GROSS and 275 hp NET.

So, in conclusion my slightly higher hp rating (due to minor modification) and my slightly quicker ET and higher mph makes complete sense. Also, the factory NET rating of 275 hp was probably pretty accurate.

I DO really miss that car however, my 2014 Z51 Vert which I have on order will hopefully, ease that heartache!

Thanks for listening! Comments?

Originally Posted by stuartc53

My pleasure to listen. What you say makes sense. We are whipping a dead horse, as some members have said, but CF is built on Vette guys and gals just chatting about whatever comes to mind regarding their cars.

The 1970 LT-1 was quite a performer in its day. But by today's standards, its a slow poke. Now that I am 60, its still plenty fast for me.

Originally Posted by chevymaster1972

I love small block chevys and believe the LT-1 to be the crown jewel to chevys small block arsenal. But from what I read the 71-72 LT-1's are identical, 330 Gross hp for 71 and 255 Net hp for 72. I love old chevy engines be it small or big block.

Originally Posted by 427Hotrod

Here's some dyno testing that will shed some light on all of this. It's not perfect...but as good as you're likely to find.

http://www.hotrod.com/techarticles/e...t/viewall.html


JIM

Originally Posted by F4Gary

Wow! My 72 makes more HP than the 70!

359 vs 353.

Hmmmm....

Originally Posted by bashcraft

Where are you seeing specs for a 72?

Originally Posted by F4Gary

72 was the same as the 71.

Originally Posted by bashcraft

True, they are, but you know that dropping the compression 2 points and keeping everything else the same is only going to lower the hp, right? There's no way it would go up.

Originally Posted by jb78L-82

70 LT-1 had 11:1 compression and solid lifter cam (370 GROSS HP). 71/72 LT-1's had the same compression (9:1) and are the same motor, just rated differently, 71- GROSS (330 HP)/72 (255 NET HP). BTW-the 73/74 L-82's (250 Net HP) are also VERY similar to the 71/72 LT-1's. What this all comes down to is that the 70 LT-1 with the higher 370 GROSS HP had a halo effect on the lesser LT-1's for the uninformed. The L-82 which debuted in 73 did not benefit from the halo effect of the LT-1 name even though the 73/74 and beyond all the way to 1980 L-82's are essentially the same engine as the later LT-1 with emissions, timing differences, exhaust, and carb calibration. Correct those differences and a L-82 will make the same power as the later LT-1's.

Originally Posted by AirBusPilot

Interesting dyno comparison between the LT-1, L-82 and low compression 71 LT-1. Despite the drop in compression, the 71 LT-1 made the most HP, due to superior air flow of the heads. While at first glance, there appears to be a minimal difference between the lo-comp LT-1 and L-82, that is not the case.

http://www.superchevy.com/technical/...g/viewall.html

http://www.superchevy.com/technical/...g/viewall.html

Originally Posted by scottyp99

I think the L82 can be most closely compared to the L46 engine, it's pretty much just an L46 with less compression.

Scott

Originally Posted by stuartc53

I have owned a '77 L 82 4 speed and several early 70s LT-1s. There is really no comparing the two. The LT-1 is much faster. They both had 3.70 posi axle ratios. The '77 L 82 is good performer, but nothing like a '70 LT-1.

Originally Posted by 1968-72 Corvette PR

Hi to all.

All of us C3 Corvette knowers know that the 1970 LT1 is rated at 370hp, and that the LS5 of that same year is rated at 390hp.

I believe that the 370hp rating of the LT1 is a factory lie, another case of an engine being underrated by the factory, and that the true hp of the LT1 is closer to 400hp. If this is the case, then the LT1 is probably a bit more powerful than the LS5. Is there any fact to this ? Do any of you know ?

Another thing. Of the 1287 LT1 Corvettes of 1970, only 25 were built with the race-ready ZR1 package. Was the LT1 in the ZR1 any different from the normal LT1 ? Did the ZR1 have a little bit more hp than the normal LT1 ?

Also, did the LT1 have L88 components ?

Wanting to know.

Best regards,


José, from Puerto Rico