Question: 1966 Corvette (Early RPOL72 427CU 450HP at 6400RPO)

[2010corvette]

Hi,
Question to ask C2 Corvette aficionados.
Read some stories about the reduction in horse power ratings on the L72&36 engines early 1966 Corvette production, but it's not clear why.
Anyone know the real reason for lowering the L72 engine from 450HP@6400RPM to 425HP@5600RPM.


:thanks:

 

[Hib Halverson]

To appease "safety" nazis and the insurance industry.

 

[Vettehead Mikey]

There was no actual reduction in HP, just what was written on the air cleaner sticker.

 

[Tom Bryant]

If I recall the early sales brochures listed the 450 hp rating. Then after pressure from the insurance industry the rating was reduced to 425. I have read that dealers were supposed to replace the 450 stickers on the air cleaner lid with 425 stickers but I can't say if there was an actual recall or not. I suppose 425 was acceptable since the biggest engine the year before was 425. Crazy.

Tom

 

[2010corvette]

Thank You for the replys to my question.

 

[motorman]

back in 66 when i tried to sell my 66 450 HP 427 corvette anyone who wanted to buy it the insurance payments a month were more than the car payments.

 

[Tom Bryant]

I wanted a solid axle back then. I graduated HS in '66. The insurance for even a 10 year old Corvette was a grand a year for someone my age. That was a hard one to cut considering wages at that time. My new '67 442 was only $320. a year.

Tom

 

[2010corvette]

Thank You for the interesting replies
Back in July 1966 ordered 1967 Corvette Sting Ray Convertible 194677S100560. When the Corvette arrived at Curhan Chevrolet in Randolph Massachusetts, the dearlership informed that I couldn't take the Corvette home until September 29, 1966. This was a waiting period of three weeks and the Corvette was hidden inside Curhan Chevrolet until Sepember 29, 1966 (Sept 29, 1966 was show date for 1967 Chevrolets)
Just before September 29, 1966 found I could not get insurance due to the L36 engine and inspection sticker due to the N11 exhaust in the State of Massachusetts.
My father actually put the Corvette in his name so I could drive the Corvette. I was just shy of 21 at the time.
The dealer finally put inspection sticker on the windshield.

PS: I have owned many Corvettes. The first two were previously owned. 1960 Hondrus Maroon 283CI 270HP 4 speed and 370 posi axle, 1962 Roman Red 327CI 250HP 4 speed and 336.1 posi axle,
1989 Coupe Z51, 6-speed, 354.1 posi axle and loaded, 1999 Coupe Z51, 6-speed, 342.1 posi and loaded, and C6Z51, 6-speed 342.1posi and loaded stored with 14,000 miles.

 

[bundies]

1966 427

Hi,
Question to ask C2 Corvette aficionados.
Read some stories about the reduction in horse power ratings on the L72&36 engines early 1966 Corvette production, but it's not clear why.
Anyone know the real reason for lowering the L72 engine from 450HP@6400RPM to 425HP@5600RPM.



Having owned a 1966 427 since Dec. of 1969 I've seen alot of articles on the horsepower change. The 396 of 1965 was 425 horse so it only followed that when they up the cubes to 427 they showed the horsepower as 450.
At that time the school boy street racers were every where (me included). The insurance companies were playing catch up and of course over re-acted. My insurance actually went down because I went from a 1967 GTO (considered to be the choice of boy racers) to a Corvette considered to be a more adult car. But the insurance companies were having a field day with the manufacturers if you can't insure it, you can't get financing, and if you can't get financing (as a young man) your probably not buying a new car. Around the same time (1966) GM put out many edic's. One that no car was to have better then a 10:1 weight to horsepower ratio. The other was that only sports cars could have multiple carburation. I think they kind of slipped the Corvette under the mat lowering the stickers to 425. If you show the weight as a little over 3200 pounds your still under the 10:1 but it looks like an effort. Plus again some insurance companies like mine USAA considered the Corvette to be a more adult responsibly owned car. (yea right) Any way the second edic is why all of GM's cars that had multiple carb's in 1966 lossed them in 1967, GTO, Riviera grand sport,etc. Then the Corvette that hadn't had multiple carbs since the dual quad 283 gained trips in 1967.

 

[willyfast]

Did GM fib about H.P.?

Hi,
Question to ask C2 Corvette aficionados.
Read some stories about the reduction in horse power ratings on the L72&36 engines early 1966 Corvette production, but it's not clear why.
Anyone know the real reason for lowering the L72 engine from 450HP@6400RPM to 425HP@5600RPM.


:thanks:

By your noting the two RPM's it is obvious you know H.P. is simply a calculated number based on torque and rpm. So GM really didn't have to 'cheat' in arriving at the lower H.P., they just used a lower RPM on the DYNO pull to compute H.P. Wonder...Do you think they really fooled the safety NAZI's and Insurance industry?

 

[JohnZ]

By your noting the two RPM's it is obvious you know H.P. is simply a calculated number based on torque and rpm. So GM really didn't have to 'cheat' in arriving at the lower H.P., they just used a lower RPM on the DYNO pull to compute H.P. Wonder...Do you think they really fooled the safety NAZI's and Insurance industry?

Yes, they did - they just picked a different point on the curve as the rating point - I have the Chevrolet Engineering Change that revised the advertised hp and released new air cleaner stickers on all big-blocks in all car lines in July of 1965, and the stated reason is "Management Direction". They did the same thing for the '67-'69 Z/28 302 engine - they advertised 290hp @5800 instead of 345hp @ 6800.

 

[Hib Halverson]

I've known about the original 450-hp rating for the L72. I new the Z/28 was underrated, just not by how much. That it was 290 at 5800 and 345@6800 gives you and idea of how "peaky" that 302 was.

John, does any information you have give the actual power/torque ratings for the L88 and the ZL1?

 

[JohnZ]

John, does any information you have give the actual power/torque ratings for the L88 and the ZL1?

I've never seen anything officially published by Chevrolet, but one of the dyno techs at Tonawanda said the L-88's and ZL-1's consistently showed over 500hp, and the guys who designed/developed those engines (Dick Keinath, Denny Davis, Bill Howell, and Gib Hufstader) were at our NCRS "Horsepower Wars" seminar last November, and agreed that 560hp was reasonable with the "Heavy-Duty" over-the-counter under-frame headers and 4" open sidepipes (made for Chevrolet by Kustom Equipment in Flint, Michigan).