Thread: What Is Real Hp Of 67 390?

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Were They Understated Like The 428 When They Rated It At 335 When It Made More Like 400?

Back in those days they rated at "gross hp", which is at the flywheel, no accessory load. Today we rate at "net hp", which takes accessory load into consideration. As for the comparison to the 428 (as well as other high performance engines), there was no need to play games with the rating by "bragging" low, a version of Detroit poker (also known as sand bagging), with the possible exception of the '61 drag/track version. If anything, on the more mundane engines they may have even over rated them a tad just for grins (or marketing reasons). The 335 hp engines were moderate "performance" engines that were probably pretty close to the "reality" of the time. Of course, there will be those who will swear they had one that produced way more than that, so who am I to spoil their memories.

That's what I figured. Thanks Bob

yep my 66 gta390 cyclone make probably 700 hp--my 68 torino 428cj made 750----they just down rated them for insurance purposes---according to my insurance they probably were around 380--the 428 did have a lot more torque

My GTO's ran 9 second quarters right out of the Dealer.

Don

I thought someone said something about gross.

All original 1968 "S" Code convertible running through a C6 automatic transmission made 256hp at the rear wheels on a Dyno Jet chassis dyno in August of 2006. I owned the car at the time, the motor had never been out of the car or apart for that matter and had roughly 52,000 original miles on it.


Bill S.

Originally Posted by mrmustang

All original 1968 "S" Code convertible running through a C6 automatic transmission made 256hp at the rear wheels on a Dyno Jet chassis dyno in August of 2006. I owned the car at the time, the motor had never been out of the car or apart for that matter and had roughly 52,000 original miles on it.


Bill S.

About the same as the last GT 390 I had on a dyno, right at 270 at the wheels, engine was fresh but stock spec cam and a nice 3 angle valve job....


I'm going to get started on the 428 out of the '66 Bird one of these days, got it out, hot tanked and crack checked ok... Looks like everything will clean up very well at .030....But I'll probably get all carried away on it anyhow!!!!! Gonna take a bunch of torque to make that sled of a 'Bird run strong, it's a tank!!!!!!

http://www.youtube.com/watch?v=q_IYU...eature=related

Originally Posted by tango

http://www.youtube.com/watch?v=q_IYU...eature=related

I think you mistake the quest for a "stock" dyno record.

Originally Posted by jerry clayton

yep my 66 gta390 cyclone make probably 700 hp--my 68 torino 428cj made 750----they just down rated them for insurance purposes---according to my insurance they probably were around 380--the 428 did have a lot more torque

WHO ME OR JERRY ?

Must be talking about you Tango---I never had an engine that was dynoed---nobody ever built a dyno that had the capacity to go that high

I have been told that there is a difference between GROSS and gross HP---I always thought that a gross was 12 dozen or really off color jokes

That is some serious bench racing.

Never did any bench racing either

never could figure out a good drive system for a bench......