401 differences

[Coondawg]

are there any differences between the jeep 401s and the amc 401s? I've got a lead on a 401 from a javelin, would like to put it in my 89 waggy.....

[mdill]

AMC changed the crank snout in ~72 to the new style on all engines.
So pre that time you need to buy/machine (from where ??) a crank adapter.

Mike D.

[AMX factor]

If the 401 from the javelin is a true 401 Javelin, grab the car and sell it. It'll finance your FSJ project. Oh and send me the tranny out of it!

[Kali]

coondawg how in the heck did you find a 401 in new hampshire?!?!?!

[Coondawg]

Well, It's just the motor, and its down south, where my waggy is....

[Ristow]

i don't think the 401 ever had the old crank flange.wasn't it '70 when that changed?

[Coondawg]

Guy says its out of a 73 or 74, so I think it will be fine....

[dusty]

73/74 not enough of a difference to bother you.

buy that baby stuff a decent cam in there.

like .480 or more lift (they love .500) and at least a 270 adv dur with a 218-226 dur @.050 will yield a nice rpm range right into the mid 4000s and low 5ks and a 112 lobe sep will give you decent idle. you may never need the rpm but why not have it if you ever want it, the bigger cams dont rob you of much if any low end on a 401 so take advantage of it. performer intake and holley 670 with an hei and you'll be rockin

[mdill]

i don't think the 401 ever had the old crank flange.wasn't it '70 when that changed?

If my memory is correct, 70 is when AMC changed the deck height, and the 343->360 2??->304 but the 390 stayed for one year, then I think it was 72 the crank flange changed, but that is from memory.

Mike D.

[Ristow]

yeah,sounds about right now that you say it,i can't remember either.

[fulsizjeep]

Was it really the crank flange or was it the harmonic balancer that was different including 3 holes for the pulleys instead of 4 on the newer ones? Will e has an old style 401 in his Waggy. He got a aluminum pulley for the Waggy belt system from BullTear right?

[Ristow]

the flange was changed,when the t/c 727 replaced the b/w automatics.

[Coondawg]

I've got the summiit 8600 on my 360 now, barely been ran. Should I go a step up with the cam?

[dusty]

Heres a cut and paste of something i posted awhile back. the 8600 is a great cam but if its in a good running motor i wouldnt rob it. its nice having a spare motor even if it is loose just in case things go ary heres some numbers thatmay or may not help you. most of these motors were fresh so the rings were just seating up and tuning wise we didnt do much tuning on the dyno. definately they all picked up a little more power after being dropped into the rigs and tuned on over the next few days and weeks


i have engine dyno print outs that show exactly what i am describing that the 401 will produce the same amount of power (or close to within 10-20 hp or ft/lbs) at 1500-3500 rpm just like the 256 and the 260 but with a much bigger cam and with the bigger cam and right duration you can gain from larger peak torque and hp, as well as a broader operating range. giving you more power when you want it and more rpms when you are glad to have them.


Ran a HMV 272 and it worked very well in my old 401. I ran 9.5 forged pistons with '73 model heads and the motor made awsome power- on the order of about 371 hp and about 483 ft/lbs.

It would also rev to about 6,500 rpm. There was a little chop in the idle, but nothing annoying or difficult to tune. I ran this motor with both an automatic tranny and a manual tranny, and it worked well with both set-ups.

all of these had fair compression ratios that said my buddy took a stock bore 401 with 150k miles honed it polished the crank put std bearings and the stock pistons with new cast rings a howards .479/.479 292/292 adv dur 222/222 dur @ .050 114 lobe sep cam in with stock bridged heads a holley 600 and a torquer intake with 1 3/4 tube headers and that thing runs circles around alot of 401's ive seen built.. alot can be said for careful tuning and getting lucky too.

AMC 401 .030" Over
Bore: 4.195"
Stroke: 3.68"
Compression: 9.6:1
AMC 502 Heads Stock 2.025" 1.68" Valves
670 CFM Carb
Dual Plane performer
Small Tube Headers w/ Mufflers
PAW version of the summit K8601 Cam

RPM HP TQ
2000 156 405
2500 198 416
3000 241 422
3500 295 431
4000 341 453
4500 360 432
5000 351 371
5500 336 330
6000 302 274

_________________

401 .030" Over
Bore: 4.195"
Stroke: 3.68"
AMC 6090 Heads mildly ported 2.025" 1.68" Valves
800 CFM Carb
Dual Plane Intake - airgap
large Tube Headers 1-3/4"tube w/ Mufflers
crower solid 292 cam
CR 10.5:1

RPM HP TQ
2000 161 413
2500 210 432
3000 259 441
3500 314 462
4000 365 469
4500 400 475
5000 429 451
5500 439 412
6000 420 367



same as above but with a single plane torquer intake and a little more tuning/ timing..... couple of factors could have influenced this run that day it was about 10 years ago.

RPM HP TQ
2000 153 387
2500 207 426
3000 260 448
3500 318 473
4000 359 491
4500 421 498
5000 468 496
5500 486 468
6000 472 429

401 w/ stock bore and stock heads, 9.5:1 comp, air gap dual
plane intake, 650 cfm TBI, and small tube headers. comp 260h cam and the Crower 276HDP
>

comp 260h
>
>RPM HP TQ
>2000 169 387
>2500 210 398
>3000 236 412
>3500 271 433
>4000 319 397
>4500 292 354
>5000 271 307
>5500 246 268
>6000 231 202
>

Air gap matched to a holley 770
>Crower 276HDP
>
>RPM HP TQ
>2000 166 427
>2500 210 442
>3000 259 453
>3500 310 465
>4000 339 445
>4500 331 386
>5000 328 344
>5500 311 297
>6000 279 244



401 9.8:1
R4B 750 Holley
Mildly ported 090 heads
.500/.512
222/226
270/274
112 lobe sep

We should have spent more time tuning on this one but back then time on the dyno was spendy. when tuning on it in the rig it picked up a fair amount more on the top end with some recurving of the dist and larger secondaries In all honesty after a few months if i had taken this motor out and re run it i think it would have come close to 400hp


RPM HP TQ
2000 178 418
2500 214 427
3000 251 449
3500 301 478
4000 346 489
4500 369 443
5000 347 381
5500 316 338
6000 279 284



rarely does my motor see over 5k but having it pull hard right up into 4500-4800 rpm range when passing is right on the money. the 401 because of its large bore and stroke is a very versitile motor and is often under built.

pick and choose carefully. remember my ability to tune or inability to tune on the engine dyno impacted these numbers also the solid cam numbers are from a friends motor

Food for thought

[82Waggy]

Having compression to match the duration of the cam and gears to get you into the correct rpm range are the key.

If staying with stock compression and/or stock gears (2.73 to 3.31's), you probably will not obtain results similar to Dusty's (he was running 9.5 -10.5:1cr in those examples and some pretty high gear ratios as I recall).

A Comp XE256H10 dyno'd over 400ftlbs from 2000-4400rpm, 428ftlbs at 3400rpm, 200hp at 2500 and 348hp at 4800rpm with 9:1cr, a Holley 670 and Edelbrock performer manifold.

So as you can see, long cams are not necessarily the holy grail of making power.

Figure out what your useful RPM range is and cam/gear accordingly.