Oh is it HIGH RPM Race only? (just picking!) But if racing was just about winding the Pee out of it, i guess we'd all be racing honda S2000's, I never equated a lack of rev cieling with a lack of track performance Plenty of stock eliminator cars don't rev all that high. But you're right Mark, if you've got the heads, go for it! A question was asked about how I defined durability..not meaning to go O/T, but I responded and I stand on my limiting the LONG (>4") stroke stuff mainly to mid rpm torque motors, but i'll build whatever a customer wants but I'll be up front with what I see as limitations.

I'll tell you what though, I met a really cool guy from south carolina while I was up at the Bristol Mopar show last fall. ronp was there and others, I'm sure they'll remember it.

416 in a 69 cuda fastback, automatic, 3.91 gears maybe? full exhaust. clicking off 7.50's in the 1/8th letting the trans shift itself at maybe 5000 rpm. This guy gets it and the car was deadly consistent for bracket racing. Embarrassing a lot of trailered open header cars too. Silver with the black 340 stripe...sweet ride and very impressive. He was racing, cutting pretty nice lights too, went several rounds in as I remember.



turning a big arm small bore small port (relatively) torque motor into a HP motor by spinning it up tighter ain't the way I'd do it but opinions vary, i'd rather build a 370-ish motor with whatever heads you would put on your 'big boy' and I'd just gear it deeper and wind it up tighter. High piston speeds and long strokes CAN wind up high but they're going to be less efficient hp/cube than a shorter stroke motor. Beyond peak torque your motors rate of acceleration (rpm gain per second) slows...in other words the friction losses start to act like a brake on the crank and the longer the stroke the bigger the brake. do a long stroke and short stroke comparison in any decent engine simulation software and you'll typically see (same heads, cam, cr, etc) that the frictional HP losses have a higher rate of rise per 100 rpm and it's more or less linear...the the higher you rev the steeper the rise of frictional loss.

If I want a 420+" motor for racing I'd much rather punch a siamese block to ~4.20 and use a 3.79" stroke but up to 4" seem to work really well and it's a preactical build (unlike a chevy withthe rod/cam interferences). take a 451 low deck big block at 451 4.375" x 3.75" and then build the same off a 361 based 454 using a small 4.125" bore and a big 4.25" stroke...which one do you think will make more hp at 7000rpm? Piston speed at 7000 4375 vs 4958 ft/min, that's almost 10 feet per SECOND more of rings scraping up and down the bore with worse high rpm geometry. I know 511's have 4.25 arms and bad rods too but they also have a much bigger piston pushing down on them and bigger valves to feed them.

Using a 4" bore and putting in a 4.25" stroke is great, fantastic actually for a broad flat torque curve, but you're basically close to the same bore and stroke as a 455 Oldsmobile (also not known as a free revver), with a much shorter rod.

I've built a lot of 4+" stroker small blocks and when you spin one over on the stand with the short 6.1-6.2 rods and really the rod angle as it spins (it's a lot easier to examine on a smal block than a deep skirted big block you almost WANT to keep the revs down.

I'm not saying you can't I just try to build a motor around what I feel is it's "natural" geometry, a low revving e-head 4.25" motor is a slam dunk and is NO SLOUCH EITHER. By 'natural' it means it's not at a crank speed where it's fighting itself and effectively "taking it out on the block". I think even RyanJ (I know a bit but he's probably FORGOT more than i'll ever know about A motors ) said the 4+ stuff is better suited to lower revs.

I've built and worked on SB fords as well which have (on average) both A LOT better and greater variety of affordable big flowing heads than us mopar guys. the big 4.17-4.25" stuff just doesn't run or hold up as well as the 3.70-3.93" stroke motors spun ~400 rpm higher with both 9.2" (Cleveland) and 9.5" Windsor Decks, you can want them to but they just don't. And I'm talking 370-380cfm Chapman/roush heads not too many years removed from state of the art NASCAR induction and roller cams. How many AFFORDABLE mopar heads are there like that and don't also need a ton of valvetrain upgrades. It's just to me a matter of practical packaging, the few extra cubes for a race motor to me ain't worth it. Guys do and go fast and that's cool but I bet they've got high caliber heads (not ported e-heads) and never back to backed with a comparable big bore short stroke longer rod combo with the same or similar cubes.

As said in another thread, racers with BIG heads want to work those heads to their max if they want the most power, it some cases longer (than optimum) strokes are the most affordable way to get there, and durability (inthe long term sense) isn't a priority, to a lot of hard core racers a short block is expendable...where his heads may not be

Another way to define durability is generally if you keep max piston speeds below ~4000-4200 ft/min and use good parts the motor holds up better/longer than motors that routinely spin higher. with a 4.25" arm that crank speed is around 6200, and there's nothing wrong with that I like the idea and I'm thinking about getting one myself