For a racing class that requires pre 74 American production iron block and heads, with a 370 cubic inch limit, naturally aspirated, where maximum power is everything, how do you think a 4.25 x 3.25, high rpm Hemi would work out? I already have a set of iron heads that will flow 420i 315e. The Wallace calculator says these heads at this cid will make 900+ horse at 10,000 - 11,000 rpm. How high can this size hemi reliably rev, assuming all the best stuff?

What has been done like this already?

How would you build it?


Thanks, Joel

You would have to talk with either Ray Barton, or Charlie Wescott about this type of stuff, as SS/AH engines are turning those kind of RPM's.

John Hagen / Charlie Malyuke B-Block Pro Stock baby Hemi

There are a couple of engines still floating around. But I don't know if they are for sale or how much. It would be expensive to fix or duplicate.

Sounds like one of those classes where the deepest pockets win.

Also, no welding is allowed other than repairs. So I couldn't convert a low deck block. It would have to be a Hemi block.

Maybe a guy could convert a low deck without welding? I'd have to take a closer look

You're a smart man. You know darn well it takes more than money to win. The whole purpose for this class is to keep costs down by eliminating aftermarket blocks and heads, NASCAR motors, blowers, nitrous, turbos, and all that expensive stuff. But any real racing cost money.
Here's a topic that you will appreciate more:. bucks down racing

I’m pretty sure I know what your thinking is on this Joel.... you need to focus on one thing at a time.

One thing at a time? That train left about 40 years ago

Does that work though? Not sure if you are allowed the same mods but thought I read SS/AH hemi heads were something like 30k.

Those have a lot of welding/epoxy I believe however.

Are you allowed to do anything similar or need to keep original port locations?

The other possibility is the G1 354/392 Hemis....We have a couple of them around here in the gasser AA class running in the 4's in the 1/8th mile....Blown of course, but they rev them up there real good. They were supposed to come out with a new 392 G1 Hemi block last year, but it seems that's not happening. That would have been the direction I would have tried. You would need to call Oddy on his setup, its a wicked 4.8 car....

So if I were to attempt it with a G2, I would say a low deck Hemi block would be where I want to start if that's even possible. Wasn't one of the new block manufacturers making a block that could be machined as a Hemi or a Wedge? If he has a Low deck, that would be awesome. Use a billet center weighted crank, and go from there....Its the block that will be the issue I think...Barton already has the high rpm rocker train figured out, so its a great place to start with a SS/AH that's de-stroked...

One other thing....Lets just say you built it, and it worked, and you won a race....They would ban you as fast as they could.

I think the only thing that works to really hold costs down is a claiming rule like they have in circle track.
I've seen bracket racing cars that I'm sure are a strong six-figure operation.

from my efforts in my drag week hot rod coupe, I've learned a lot about the drawbacks of the first gen Hemi in naturally aspirated, mainly a small bore that hinders breathing. I know in naturally aspirated, it's a lot easier and cheaper per horsepower to build a Gen 2 Hemi.

It needs to be a production block, no aftermarket blocks. One thing I'm getting clarification on is if the Mopar performance iron replacement Hemi block is allowed.

What bore and stroke are you looking at?
I remember the destroke 366 C.I. Pro Stock gen 2 Hemi not running that good compared to the other longer stroke 426 hemi motors being used back then
I'm thinking a 4.310 bore with a short enough stroke to make your goal with ultra light good pistons may fit your needs

Late 70’s technology :

.030” over standard Hemi block, 6.96” NASCAR rod (can you say heavy?), standard 3.48” Direct Connection crank, DC race piston @ 12.5 to 1 (can you say heavy?) with Dykes rings, stock street Hemi heads port matched and bowls cleaned up, .750 roller, Rat Roaster manifold, auto trans, 10.5 x 30 tire. A/SM. Ran 10.30’s at 133+. Never could hook it up, but it ran out the back door like a freight train turning it 8500. Never broke anything and it was raced a lot.
This same package we went to a tunnel ram with 2 dominators, ported the heads - I think they flowed 350-370 back then, at 3400 #’s in B/MP went 9.70’s.

Current technology, light Diamond pistons, light rods, better valve gear, better intake, scrapper, who knows what that is worth.

You're at the bottom of the learning curve. Very little tune-up data crosses over.

That's why I'm asking.

Good info, thanks

Porting and milling of heads OK, epoxy OK, no brazing or welding on heads or block. Block can be decked up to .125.

What induction system is allowed, sheet metal ? Carb rules ?
Vacuum pump allowed?

That A/SM motor used a single 850 with choke tower in place.

By the way, I have one set of new .030” pistons and rods from the backup motor we never built. I also have good used 3.48” crank, full radius fillet if you want to try and build one on the cheap (cheaper).