stupid question, but when did the compression ratios drop?
Race Director
Joined: Apr 1999
Posts: 15,127
Likes: 476
From: NM
Re: stupid question, but when did the compression ratios drop? (Bilyk)
1970 had high compression and gross HP figures
1971 had lowered compression and both gross and net HP figures
1972 had low compression and net HP figures
1973 added hardened valve seats
and
1975 added cat converters
The lower compression and hardened valve seats were getting ready for the upcoming unleaded gas and cat converters.
tom...
1971 had lowered compression and both gross and net HP figures
1972 had low compression and net HP figures
1973 added hardened valve seats
and
1975 added cat converters
The lower compression and hardened valve seats were getting ready for the upcoming unleaded gas and cat converters.
tom...
Safety Car
Joined: Jan 2000
Posts: 4,143
Likes: 0
Re: stupid question, but when did the compression ratios drop? (Bilyk)
For base engines :
1970 - 300hp 350cid - 10.25:1 comp.
1971 - 270hp 350cid - 8.5:1 comp.
1972 - 200hp 350cid - 8.5:1 comp.
The reason for the hp drop from '71 to '72 (to my understanding) is that BHP was now measured at the rear wheels instead of at the 'flywheel'....
However, I'm not sure why there was only a 30hp decrease from '70 to '71 when the comp. was so darn low.... you'd think it would be greater (maybe the '70 motor was more like 325-350hp) :chevy :seeya
1970 - 300hp 350cid - 10.25:1 comp.
1971 - 270hp 350cid - 8.5:1 comp.
1972 - 200hp 350cid - 8.5:1 comp.
The reason for the hp drop from '71 to '72 (to my understanding) is that BHP was now measured at the rear wheels instead of at the 'flywheel'....
However, I'm not sure why there was only a 30hp decrease from '70 to '71 when the comp. was so darn low.... you'd think it would be greater (maybe the '70 motor was more like 325-350hp) :chevy :seeya
Race Director
Joined: Aug 1999
Posts: 10,073
Likes: 1
From: Toronto
Re: stupid question, but when did the compression ratios drop? (verskel)
verksel, almost right on the horsepower rating strategy.
Pre-72, Gross hp was rated with the engine on the dyno with no accessories attached. Now the SAE Net rating is the engine on the dyno with ALL accessories attached.
There are no companies that rate the horsepower at the rear wheels. Kind of hard to sell a Mustang GT with 210 'Rear wheel HP' when the V6 Camaro has 200 'Flywheel HP'.:lol:
Pre-72, Gross hp was rated with the engine on the dyno with no accessories attached. Now the SAE Net rating is the engine on the dyno with ALL accessories attached.
There are no companies that rate the horsepower at the rear wheels. Kind of hard to sell a Mustang GT with 210 'Rear wheel HP' when the V6 Camaro has 200 'Flywheel HP'.:lol:
Burning Brakes
Joined: Mar 2002
Posts: 803
Likes: 0
From: South San Francisco CA
Re: stupid question, but when did the compression ratios drop? (Bilyk)
I was going to guesstimate early '70s. But, why do that when we so many knowledgeable people on this forum. Way to go....guys!!
