Which is the better combo 1970 454 or 1971 454?
 

I have a 1972 chevelle SS body that I plan on making into a stocker. What do you guys think is the best combination choice with an automatic trans
- 1970 454 450 h.p. weight break- 8.58 and 3688 Lbs
- 1971 454 425 h.p. weight break- 8.57 and 3599 Lbs

Both motors can run the 401 aluminum heads according to the stock car classification, but the 401 head isnt listed on engine bluprints for 1971, only for corvette.

Any info or comments is appreciated

Re: Which is the better combo 1970 454 or 1971 454?
 

70 402 is nice.

Re: Which is the better combo 1970 454 or 1971 454?
 

I have seen a couple of the iron head 450HP 1970 cars run well. that's a pretty decent factor. The only big difference between that and the 427/425 is about 0.240" of stroke. The 427/425 is pretty popular.

Re: Which is the better combo 1970 454 or 1971 454?
 

The 71 402 has better head choices and a little more ex lift, but I think it gives up a tiny bit of compression.
A real quick glance (hope I didn't overlook anyone) at Nitro joes Stats and I only see the '70 402 being run by a few and no '71-'72's being flogged.. that coud keep you safe from HP.
Alan, I think that '71 iron headed 425 HP engine gives up compression from the '70 450 HP.
I didn't figure it, but the dome comes over .200 down , but the head cc is 2 or 3 tighter.
humm, Just looked at the '71 classification guide and they show a 420 HP factor for the iron head and a 430 factor for the " A" head in the Chevelle listing. Yet in the Specs they have a "C" on the '71 specs for the Alum head in corvette only... ??? I wonder which way it is. That '71 402 fits in the middle of the 11.0 -11.50 so I would think it could move up and down classes pretty easily. It might be able to move to 3, just have to do the numbers.

Re: Which is the better combo 1970 454 or 1971 454?
 

Adger, I was comparing the 1970 454/450 to the to the 1966-69 427/425. The two biggest differences, with iron heads, are the 0.240" more stroke and the 1.880" exhaust valve the 454/450 gets. The rest is very similar.

Re: Which is the better combo 1970 454 or 1971 454?
 

If you're open to something other than a Big Block,the best combination index wise for that body is the 350 like Katie Sepanek runs in I/SA. Rated at 270 hp in a Chevelle body and 278 in a Camaro. Just a thought.

Re: Which is the better combo 1970 454 or 1971 454?
 

x2 Danny, and a hell of a lot cheaper to build.

Re: Which is the better combo 1970 454 or 1971 454?
 

Go ahead and do the 1970 LS6, it's 12.5 + to 1 (measured) instead of the 71's 10.7 to 1 and C-12 is cheaper than C-11, LOL. Plus, you would be at the height of Chevelle power and you sound like a top of the BBC food chain guy to me.
I would love to see this car built and go in the 9's.

Tracy