Ballpark HP for my 401 help please

[Magical_Merlin]

I have a 77 401 bored .060 over
9.5:1 Pistons
Comp 270H cam
Howell EFI
502-1 casting heads, mildly ported/polished.
Also has been fully balanced, including the clutch pak.

Anyone have a ballpark HP number for this configuration?

If you need more details, let me know.

[Lenni AMC]

I would say easy 450 hp maybe 500+ ft of tourqe

[fifesjeep]

Toss on some aluminum heads... I'm wondering if the EFI will choke it at the higher rpms...

[Old Rugged Crosser]

Lenni-- Magical_Merlin would have to do some of his magical tricks to it to really achieve those numbers!

The most potent 401 from the factory was put out in 1971 : 401-4B(Early) 335 h.p. @5000 torque: 435 @3400 10.2:1 comp. 4.165 x 3.68 bore & stroke.

It takes a lot of work to get beyond that.

[Lenni AMC]

I disagree and here is why. There is not so much trouble going for 1 hp per cui with a relatively small budget just read the many articles from Hot Rod magazine like this one here http://www.carcraft.com/techarticles...ild/index.html
Here you can see a fresh build 360 engine but stroked to 370, I realize they are doing somethings that maybe our 401 buddy isin´t doing like longer rods and alu heads but he has more cui and that gives a lot.

I´m not a big fan of these edelbrock alu heads because they don´t flow much more than stock AMC heads with a mild porting job also you can see they are not running a big cam here but getting 437 hp that´s impressive. the cam they are using is not so different from the calm that our 401 friend is using..

And finally the compression ratio is higher on the magazine engine that this one but here´s something I have realized a lot of people think the compression ratio is making a BIG change in horsepower and tourqe output but this is what is really happening from the stock 8,4:1 to 9,5:1 compression there is a lot of difference both in power output and MPG but from 9,5:1 to 10:1 there isin´t really maybe something in MPG but a few hp

For example I saw and article couple of years ago and they where having this trouble with a drag engine that had 15:1 compression ratio and turned out 860 hp but the guy who bought it wanted to put it in his street car so he could drive it so they desided to lower the compression ratio from 15:1 to 11:1 and dynoed the engine after the change and it turned out 820 something hp so here you can see the higher you go with the compression it makes less and less affect.

Maybe my numbers are of 20 hp or even 30 but The 401 motor we are talking here is a EASY 420++ hp in my opinion but maybe you know something I don´t ?

Best Regards Leonard from Iceland = )

[fifesjeep]

Build it, dyno it and post a picture and or video of the results... actual/visual facts will put the guessing to the waste side... BUILD IT, and it will show us. ;)
I'm going with 434hp 468ft-lbs of torque

[Magical_Merlin]

I dont have any way to dyno it. I am just wondering what the ballpark figure could be.

I just read this article also.
http://www.carcraft.com/techarticles...nes/index.html

[fuzz401]

300 to 350 HP to the ground
380 to 425 FT.- LB. torque

[Old Rugged Crosser]

That my friend, is much more realistic.

By the way Fuzz how are the eyes?

[Dusty]

300 to 350 HP to the ground
380 to 425 FT.- LB. torque

since i dyno'd mine in a similar combo, id say fuzz is pretty darned close. the howell tbi EFI holds you back. tbi has its limits on hp production 330 hp is about tops for most good tuners with spark control. 350 is a select small group. i am 9:1 with more lift than the comp cam and my numbers were pretty solid


401 - 30 over
Decked, align bored and balanced
10/10 crank, resized rods, all ARP bolts
Forged 9.1:1 pistons
Lunati 58501
Advertised Duration (Int/Exh): 256/262
Duration @ .050 (Int/Exh): 213/220
Gross Valve Lift (Int/Exh): .484/.507
LSA/ICL: 112/108
Cast 502 heads (Mild Port match) w/ roller tip rockers
Edelbrock dual plane performer intake
ported exhaust manifolds
670 TBI GM injection 85lb/hr injectors HEI distributor

On a chassis dyno rear wheel numbers it put down the 292 hp @ 4900 rpm 389 ft/lbs @ 3500 rpm it had a similar 351 ft/lbs at 2000 rpm and carried numbers at and above 354 ft/lbs all the way to 4000 rpm. red line is 5500 rpm and it spins hard on the street to 4500-5000.
As you can see the above are rearwheel numbers, assuming 10-12% parasitic drivetrain loss it should be in that 315-330 hp 420-440 ft/lbs range.
The shop that put it on the rollers called it out with correction factor as 331 hp @ 4900 rpm 443 ft/lbs @ 3500 rpm it had a similar 393 ft/lbs at 2000 rpm and carried the same 400 ft/lbs all the way to 4000 rpm. idles smooth at 500 rpm red line 5500 rpm spins hard to 4500-5000.

I think thier correction factor estimate is a little high but 292 /389 at the rear wheels was pretty respectable. I expect this motor to be around for quite a few years.


cracking past the 1 hp per cube becomes a game of cubic dollars. i usually end up about about .80 hp per cubic inch on a mild street rig build for an engine capible of 5000-5500 rpm and less and that number seems to always be obtainable, past that the supporting hardware costs rise significantly. I've built some healthy 401's with 400 hp 450+ ft/lbs but after then cubic investment goes up exponentially from the 1 hp per cube threshold. alot of people claim 400 hp+ motors but few ever have put them on a dyno to prove or disprove thier performance. Remember all the chevy guys who love to claim they have a 400 hp+ 350 cubic inch motor in thier pickup truck that supposedly cost em $1500 to build and runs on 85.5 octane with gobs of low end torque. my engine is probably realistically a flywheel output rating of 310-320 hp / 415-425 ft/lbs which from where i stand and with what im driving these days doesnt bother me one bit, its a heck of alot more than 90% of the guys on the trail these days have. it might be more it might be less but those are flywheel guestimate numbers that dont mean much since i never ran it on an engine dyno........ its all about when the rubber meets the road and what finally makes it to the ground it what ultimately defines your engine


Heres an engine with the size up from me cam with actual dyno numbers
http://www.ifsja.org/forums/vb/showthread.php?t=121315


If i had it to do over again i probably would run a single pattern Engle cam ground with a touch more duration maybe a 216 or 218 at .050 but overall i love the mild manners of this motor it never ceases to perform when it needs to