1972 LT-1 engine question
Thread Starter
Instructor
Joined: Sep 2005
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From: Marvin N.C.
1972 LT-1 engine question
I know that the '72 LT1 was rated at 255hp., but I've been told that they actually were a lot higher hp but lower rated due to insurance regulations. Can someone tell me what was/is the actual hp output. I'm trying to find out how it would compare to a 327cu. or 350cu. engine w/350hp. Would the difference in say 0-60 or the quarter mile times be much different with all things equal ? The '68 vette I'm interested in with the '72 LT1 isn't local so I can't drive it to compare, and would appreciate any thoughts.
Thanks
Thanks
Team Owner
Joined: Sep 2006
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From: Westminster Maryland
Hi T,
The 70 LT-! was the stunner at 370 GROSS horsepower.
The 71 LT-! was rated at 330 GROSS horsepower, one of the biggest differences was a sizable decrease in compression ratio.
The 72 LT-! was rated at 255 NET horsepower, but was basically the same engine as the 71 LT-!.
If it's a real LT-! engine, even from a 72, it's quite a nice sb factory motor.
Lot's of people claim to have an LT-! engine because the engine in question was in a garage next to an Lt-! once. Seriously… many claimed LT-! engines don't have the Lt-! parts.
The suffix code on the engine stamp will at least tell you what this engine started it's life as.
Regards,
Alan
The 350/350 was rated in gross horsepower so you can do the math to see how it would compare to the 72 LT-!.
The 70 LT-! was the stunner at 370 GROSS horsepower.
The 71 LT-! was rated at 330 GROSS horsepower, one of the biggest differences was a sizable decrease in compression ratio.
The 72 LT-! was rated at 255 NET horsepower, but was basically the same engine as the 71 LT-!.
If it's a real LT-! engine, even from a 72, it's quite a nice sb factory motor.
Lot's of people claim to have an LT-! engine because the engine in question was in a garage next to an Lt-! once. Seriously… many claimed LT-! engines don't have the Lt-! parts.
The suffix code on the engine stamp will at least tell you what this engine started it's life as.
Regards,
Alan
The 350/350 was rated in gross horsepower so you can do the math to see how it would compare to the 72 LT-!.
Le Mans Master
Joined: Dec 2003
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From: Fremont CA
Like Alan has already covered how the motor was tested on the SAE dyno test was the main difference in a 71-72 LT-1. Owning both a 70 and 72 LT-1 the big difference is in bottom end torque and you will find that it is quite common for a 71/72 LT-1 to have been ordered with 4:11 gears by a dealer who was savvy enough to know the low compression was going to hurt performance. Hot Rod did a quickie 1 page test of a 72 LT-1 and actually coxed a 13.96 second 1/4 mile ET but not the 102 MPH trap speeds you will commonly see in a 70 LT-1. I had that issue years ago but haven't been able to locate it in years. The 71/72 LT-1s performance can be quickly upped with substitution of the crappy open chamber heads and when I wrenched in the 70s we commonly swapped 292 " turbo " heads onto these cars with great results.
Team Owner
Joined: Jan 2006
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From: Crossville TN
'71 & '72 LT-1 engines were lower compression than the '70 engines and I believe the cams were a little less agressive. The 'redline' RPM rating on the '71 and '72 cars was specified at progressively lower numbers. That doesn't mean that those engines wouldn't wind higher than 5800 or 5600, respectively; rather, GM specified those RPM's so that the rated HP would be lower BECAUSE of insurance 'issues'.
The '71 & '72 engines were essentially the same...although rated with different methods (Gross vs. Net power); but they weren't up to the likes of the '70 LT-1 engine.
The '71 & '72 engines were essentially the same...although rated with different methods (Gross vs. Net power); but they weren't up to the likes of the '70 LT-1 engine.
Thread Starter
Instructor
Joined: Sep 2005
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From: Marvin N.C.
Thanks for the responses, however they lead me to ask another question and that is, why is there no mention of a '68 327/350 engine ? Is there a major difference in its performance vs the others ?
Drifting
Joined: Dec 1999
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From: Reno nevada
TQ is the key and not some questionable HP numbers. TQ and ci run hand in hand, so the 327 with all equal parts will fall behind the 350.
The highest HP small blocks of that era are more fiction than fact when it comes to performance. Myth busters........ I have a highly improved .030 overbore in mine.
Like somebody said above the big block higher hp models or 454 are the way to go for performance
The highest HP small blocks of that era are more fiction than fact when it comes to performance. Myth busters........ I have a highly improved .030 overbore in mine.
Like somebody said above the big block higher hp models or 454 are the way to go for performance
Team Owner
Joined: Jan 2006
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From: Crossville TN
The '68 327/350 hp (L-79) was a very nice engine. It was the basis for the L-46 and following LT-1 engines. If that engine and the L-46 were set up perfectly and put in vehicles that were tuned specifically for them, I'm not sure which would win a 1/4 mile drag race. The L-46 would have more torque; but the L-79 would wind farther with a longer power band, and likely have a bit steeper rear gear in its car (which would balance with the better torque of the L-46).
Both would be a LOT of fun to 'experience', IMO.
Both would be a LOT of fun to 'experience', IMO.
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From: Southbound
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FWIW: Zora Duntov always felt the optional 350hp smallblock was the most reasonably priced performance option for the Corvette during the years it was available. You got a lot of bang for less than $200. He tried to save it for the 1971 model year, but the bean counters hosed it.
Last edited by Easy Mike; Apr 20, 2014 at 12:13 PM.
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From: Sierra Foothills CA
I followed the LT1 closely because I bought my avatar car new and it came with the 1970 LT1 in it. As stated already, the only change for 1971 was a drop in compression from 11:1 to 9:1. The new rating method accounts for the additional power drop in 1972.
My memory tells me that they all used the same camshaft, and that is supported by the info contained in this link. LT1 internals were the same whether in a Corvette or a Camaro- http://www.nastyz28.com/camaro/z28lt1.html
The 1970 LT1 lists peak power at 6000 RPMs, the 1971 and 1972 both list a power peak at 5600 RPMs. Redlines were all 6500 RPMs except for a 1972 LT1 with air conditioning, where it was lowered to 5600 RPMs due to belt limitations. This info comes from Vette Vues Fact Book of the 1968-1972 Stingray by M.F. Dobbins. I could only speculate as to why the rated power peak differs after 1970.
My memory tells me that they all used the same camshaft, and that is supported by the info contained in this link. LT1 internals were the same whether in a Corvette or a Camaro- http://www.nastyz28.com/camaro/z28lt1.html
The 1970 LT1 lists peak power at 6000 RPMs, the 1971 and 1972 both list a power peak at 5600 RPMs. Redlines were all 6500 RPMs except for a 1972 LT1 with air conditioning, where it was lowered to 5600 RPMs due to belt limitations. This info comes from Vette Vues Fact Book of the 1968-1972 Stingray by M.F. Dobbins. I could only speculate as to why the rated power peak differs after 1970.
Last edited by Les; Apr 20, 2014 at 12:51 PM.
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I just drove an all original 327/350 a few weeks ago 4 speed with gearing that had it going 65 mph@ 2800 rpm.
They run nice like an economy car. Just not a lot of get up and go, but I was never impressed with the C-5 Z06 with it's 405 HP. I always found my self driving with my foot to the floor hoping for more.
They run nice like an economy car. Just not a lot of get up and go, but I was never impressed with the C-5 Z06 with it's 405 HP. I always found my self driving with my foot to the floor hoping for more.
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Le Mans Master
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From: charlotte north carolina
The Parts and Illustration Catalog shows the same part number (3972178) for the 1970-72 350 Special High Performance engine's cams(the Hp rating isn't mentioned, but there are different listings for the HP and Sp. HP engines). The 1969-70 High Performance and 1973-80 Special High Performance cams was 3896962 for the 350ci engines.
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From: allentown Pa.
HW motor
TQ is the key and not some questionable HP numbers. TQ and ci run hand in hand, so the 327 with all equal parts will fall behind the 350.
The highest HP small blocks of that era are more fiction than fact when it comes to performance. Myth busters........ I have a highly improved .030 overbore in mine.
Like somebody said above the big block higher hp models or 454 are the way to go for performance
The highest HP small blocks of that era are more fiction than fact when it comes to performance. Myth busters........ I have a highly improved .030 overbore in mine.
Like somebody said above the big block higher hp models or 454 are the way to go for performance
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From: altered state
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