Red Line of a 401?

fivequarter

Haven't had time to check around and I am about finished installing the 401 into my GW. Want to use a tach and would like to know the red line of a 401 so as to pick an appropriate tach maximum display, i.e 6000, 7000 or 8000 RPM tach. Thanks.

tufcj

Factory redline on my 390 is 5500 RPM. I'd imagine that a stock 401 is the same. If it's balanced and machined right, it will rev higher. I had a well built 304 in my CJ that I mud bogged with, and routinely revved it to 7000. Bob tufcj

fivequarter

Thanks. I will probably go with an 8000 RPM tach. That should give me about even scale on each end of the RPM range.

wizzard

i have a 401 out of a 71 ambassador sst. 7000 is no problem that's where i put the red line on the sun tach. but mines a car engine in a cj5.

Goose

Uhhhhhh Shuudder.. I hear valve float rod stretch and other mayhem in the future..

Holeshot

7000 is childs play for a prepped 401 or 390, bursts to 8500 should be no problem with forged pistons, a good oiling system, and a properly assembled shortblock.

SwampRat

It's probably possible, if you want a short-lived engine, but it's not very realistic that there is gonna be very many 390/401's actually peaking Horsepower at 8500 RPM out there...

Holeshot

OK swampRat, why are you following my every post and trying to make me out to be wrong? You're not one of those FAMCFORUM rejects, are you?

I'm getting tired of it.

Who said ANYTHING about PEAKING HP at 8500 RPM???

I said BURSTS to 8500. And that won;t hurt a good 401 one bit.

Which gets you far enough PAST peak to make your next gear catch the fat part of the power band.

It's really QUITE simple, get it?

You must be too used to those off-brand, throw-away engines from GM & Ford.

SwampRat

lol, your next gear is supposed to catch peak torque, not peak horsepower! If you think a engine like a AMC will live for a extended period of time while hitting RPM's at 8500, your wrong.

jeepsr4ever

You guys need to simmer :idea:

Holeshot

That would be a FORGED crank, twit. Shows how much you know about AMCs!!!!

Holeshot

Here's a Dyno2000 run with Wally Booth's destroked 401 specs, and the valves reduced to 2.08 & 1.74. He actually used 2.14 & 1.90 with offset guides.

fivequarter

Holeshot, That is a very impressive setup. It is far different than the near stock rotating assembly in my 401. The destroke must have a significant effect on the RPM limit. Is that a custom crank? The rods must be custom as well? The induction on that motor can pull more than twice the air my EFI can.

Holeshot

Destroking has a MASSIVE effect on the RPMs at which the engine makes power. Smaller engines can rev higher, so long as the reciprocating assy can take it and the induction/exhaust can take advantage of the higher revs. That is why the Jap cycles are using 4 valves per cylinder, some revving to 15,000 RPM (some go higher), and making around 150 HP (some make more) from 65 cubic inches. That is rougly equal to getting 700 HP from a common sized production car engine. Most of them went to at least 4 valves per cylinder back in the late 70s to early 80s. Those kind of revs used to be reachable only by the 2-strokes. I've heard of AMCs going into the 9000s. Of course, a drag engine is only there for a portion of a second. Actually probably goes through the 8000s in a second or so, it could be calculated mathematically. Custom AM V8 cranks are available from many of the crank makers, for a price. Using aftermarket rods (H-beam) from a smallblock chevy application is very common and quite easy. The rod change is pribably more for the very few extra ponies to be gained with a longer rod, rather than any weakness of the original forged rods. The 401 crank can also be turned WAY down, clear to Honda 4 cylinder size (1.8", I think). Lots of people also use pistons designed for the chevy 400 smallblock. If not using flattops, the valve reliefs will be in the wrong place, so use flattops and have the valve reliefs milled to your heads. Isky will rent (or sell) you a tool to do your own, using the valve guide for center. I prefer the near stock rotating assy route. Custom one-offs are quite harder to duplicate if or when they fail. And there is nothing wrong with the AMC design that oiling system mods won't cure. 600 HP w/o NOS is enough for me. And revving past 7500 is not needed to make that 600 HP. There are much bigger numbers available when destroking and upping the redline, but that gets expensive and into the non-AMC parts installing. I don't know how tight you are spinning your 401, but even a fresh, tight, stock-block 401 with big-tube headers, a Torker, and at least 850 CFM, can go to 7500, if there's enough cam and valvespring to keep the valvetrain from floating. Most of the cam makers have grinds for AMC that go to 8000 or 8500. Gotta go chase the 3 yr old...bye

SwampRat

You aren't gonna convince me of much with some dyno software.

Holeshot

I don't give a damn if I convince you about anything!!! The question on this thread was the redline of a 401. 8500 RPM is the answer, with a prepped shortblock and mods to open up the breathing. If you are offended by the robustness of the AM V8, maybe you should go find a chevy board to give your advice. Don't blame me for your ignorance. Now you can go find another thread to dog the users. Contact Motion Software Corp. while you are at it and tell them how much more you know than they do. Maybe they will offer you a job "fixing" their software. 111!!!

SwampRat

What is the point of talking about a redline of a engine anyway. 8500 RPM, sure a engine can rev there if you miss a gear and possible survive once or twice, but one a engine is not gonna make power there anyway so there is no point of having a engine go there. If you think your gonna build a AMC engine for use such a circle track that will consistently run 8500 RPM's with only a "well-prepped" factory short block your wrong, just making sure people don't think you are correct. They might as well hire me to edit their software because true hot rodders know that a computer will never be 100% able to predict the power of a mechanical device. There is expections to every rule, what if your dream engine on your dyno software makes 900 Hp N/A @ 10,000 RPM's, that program doesn't even take into consideration the rod length and piston weight and oiling system and valvetrain ect, ect that would be required for a engine to rev that high, but it tells you your engine can make that much horsepower!!!

Holeshot

Who in the hell uses a 401 for circle track? NOBODY!!! Shows how much you know!!! The AM V8 is actually used more and more in drag racing, where 8000 to 8500 may be the shift point. CompCams sells over the counter cams for AM V8 that they advertize revving to 7500. And that's with .672" lift. I have seen real serious AMC cams with over .800" lift. My 390 still revved well over 7300 with 2 broken valve springs and a flattened lobe from the spring shrapnel, 8200 when fresh. Production 390~401 rods are good to 8000 RPM. The Edelbrock Ultra-Ram was designed to rev up to 9000 RPM and use a pair of Dominators for 2300 CFM. The dyno software assumes that the operator is knowledgable enough to know the basics. Maybe not in your case. You came to the wrong place to try to degrade the AMC V8. Run along.

SwampRat

Alright, your big bad self has won, your right. I'm done. Sorry to get you in such a shoving match, but I never thought I degraded the AMC engine at all. I was using that as a example, you don't need to take a shot my knowledge because I used a engine with a "well-prepped" stock buttom end as a example. But I can see you routinely look for ways to do that. See ya.

Holeshot

Just a tidbit of info for those interested...

The Torker is designed for 3500₇₅₀₀ RPM.

http://www.edelbrock.com/automotive/man_amc.html

I don't think they would still be selling nearly 40 years later if there wasn't some AM V8s turning 7500 (at least).

The AMC V8 is getting MORE popular, nearly 40 years after being designed, with Indy Head Service, Edelbrock, Herman Lewis, and others coming out with hardcore engine parts, maybe more now than ever.

The Torker I took off my 390 was extrusion ported, used a 2 inch open spacer, 900 CFM of Holley double pumper (heavily worked "Carburetor Shop" 850), and put out 518 HP on the HotRod chassis dyno they hauled around with the Hot Rod Magazine "Power Tour". The car went 11.2 @ 122 with big street radials all around, BIG sway bars (F&R), stiff gas shocks for the twistys, thru the mufflers & tailpipes.

Here's the 484 HP & 500 ft/lbs. tq. 401 (low compression, little cam, small exhaust valve, 950 CFM Holley) that the Chevy lovers at CarCraft Mag built (they didn't even paint it the correct color!!!):

here's what they said about the heads:

"flow numbers were 279/210 cfm at 0.700-inch lift at 28 inches of water. Those are big ports for a cast-iron street head."

they also said:

"with an available four-bolt main kit, you can go to 700 hp and 9,500 rpm"

I'm thinking that short of the 4 blt. kit, dowelling the caps & using a girdle may be effective, but why skimp if you want 9,500 RPM?

I think they said they used cast pistons, and I don't think they used "zero-gap" or "gapless" rings, loss of HP, they used stock exhaust valve size, loss of HP, & they started out with 10₁ pistons but then increased the chamber volume a bunch, 11₁ final comp ratio would have been way better, another loss of HP.

They could have easily ended up with over 550 HP with a more radical cam, zero-gap rings, 1.74" exhaust valve, 11₁ final CR. Why no velocity stack??? What else did they overlook??? & why??? Could easily go over 600 in the car with cold air rammed down it's throat. Could it be Rambler envy??? The dreaded BigBlock Blush?? The smallblock squirts??? ick!!!

To those who like to argue, you may find an email addy at:
http://carcraft.com/ of the person who did the dyno runs & wrote the article.

No need to argue with me.

You may also want to do a search for "Tony Zamisch" and take a look at his "Great White" Javelin that went 216 MPH with over 600 dynoed & naturally aspirated HP from his AM V8.

Thanks, Tony Z, this image is using your bandwidth. I didn't think you'd care.

If I have mis-stated any AMC specs, I'm sorry, I'm human, and the memory may not be as sharp as it once was.