71 454

[Kap142]

Hey guys who can enlighten me as the the HP and compression specs for a 71 454 w/ a Q jet 4 brl?

OK Black Book shed some light 454 with steel heads produced 365 HP with a 9.0/1 compression ratio.

My question is this. If the gross BHP rating had still been used in 72 roughly what would the HP been listed at with the slightly reduced 8.5/1 compression ratio?

Question 2 is my BB has been bored .030 over and is running a mild cam. Carb is stock Q jet and manifold is also stock, as are exhaust manifolds and such. What would be a reasonale guess (without dyno) as to HP now?:shrug01:

 

["Backyard Mechanic"]

454
The big-block was expanded again for 1970 to 454 in³ (7.4 L) with a 4.251 in (108 mm) bore and 4 in (102 mm) stroke. The 1970 Chevy Corvette LS5 version of this engine produced 390 hp (291 kW) and 500 ft·lbf (678 N·m), and the LS6 engine was rated at 450 hp (336 kW). It is generally accepted that the LS6 was substantially underrated (a common practice at the time to avoid undue attention from insurance companies) and actually produced well over 500 horsepower as delivered from the factory.

A 465 hp (347 kW) and 490 ft·lbf (664 N·m) version of the 454, dubbed LS7 was also designed but never went to production. However a handful of LS7 intake manifolds were produced and sold by a handful of Chevy dealers as performance parts. The LS7 was later offered as a crate engine from GM and advertised at 500 hp.

Power began falling off after 1970, with the 1971 LS5 producing 365 hp (272 kW) and 465 ft·lbf (630 N·m), and the LS6 option coming in at 425 hp (317 kW) and 475 ft·lbf (644 N·m). Only the LS5 remained in 1972, when SAE net power ratings and the move towards emission compliance resulted in to 270 hp (201 kW) and 390 ft·lbf (529 N·m). The 1973 LS4 produced 275 hp (205 kW) and 390 ft·lbf (529 N·m), with 5 hp (4 kW) and 10 ft·lbf (14 N·m) gone the following year. Hardened valve seats helped allow these engines to last much longer than the earlier versions, even without the protection previously provided by lead from fuel. 1974 was the last year of the 454 in the Corvette though the Chevelle offered it in the first 1/2 of the 1975 model year. It was also available in the full size Impala/Caprice until model year 1976.

GM continued to use the 7.4 L 454 in their truck line, introducing a new Vortec 7400 version in 1996.

 

["Backyard Mechanic"]

http://www.nastyz28.com/bbcmenu.html

 

["Backyard Mechanic"]

http://www.geocities.com/MotorCity/Downs/3000/cmspec.html?200724

 

[72ragtop]

Ken, i remember reading theres a 35% reduction between the yrs due to rear wheel and all accessorys being utilized in 72. which would take 365 down to 270hp
Depending on cam (mild) anywhere from an extra 10 to 50 hp. And if heads where shaved when engine rebuilt. u could be back up to 9.0 comp. which isnt going to make much of a diff in hp.
Happy Holidays to all

 

[Kap142]

Ken, i remember reading theres a 35% reduction between the yrs due to rear wheel and all accessorys being utilized in 72. which would take 365 down to 270hp
Depending on cam (mild) anywhere from an extra 10 to 50 hp. And if heads where shaved when engine rebuilt. u could be back up to 9.0 comp. which isnt going to make much of a diff in hp.
Happy Holidays to all

Thanks Ken,

I was more just plain curious then anything else. :shrug01: This girl has more (white knuckle) horse power then anything I've ever owned.

And thanks Rob for the specs.:thumbsup: I guess if I ever want an accurate rating I'll come off of the tune up price and get with Greg or Rextreme, have um tune and dyno. Then I'll really know.

Even if they said I had an 85 HP VW engine I'd still love it. Besides that it tickles my b*lls when I drive. After all what more can one ask?:lmao::lmao:

Merry Christmas all and God bless

 

["Backyard Mechanic"]

You have to remember that big blocks are known for tq rather then hp,if any motor has been bored,then you will get more tq,when you stroke a motor out you get more top end hp,in most cases.I think Goldie is just perfect the way she is.:thumbsup:

 

[Kap142]

Thanks Rob,

I really don't see much modification coming. Your the only bro who has driven her and I greatly respect your opinions.

God bless and Merry Christmas