401 towing motor?

[fsj1978]

Hey guys, this isn't going to be happening for quite some time, but I was wondering what parts/pieces you'd select for building a 401 with the following considerations:

1) Cruise rpm of 2500-3000 (presumably a sweet spot to get best MPG?)
2) Shift points of 4000
3) Regular unleaded fuel

What parts would you choose and what kind of HP and TQ numbers (ballpark) do you figure you would get?

Thanks and have a GREAT Day!

[maccj5]

ive built many amc engines and am currently building 3 401s one for 69 m715 one for 1973 cj5 and one for spare ive found that its best to build a stock bottom end with no more than a performer/rv cam eldelbrock performer intake, headers and msd ignition ive never dynoed one but 300 hp is not unreasonable with a good spreadbore carb/750 cfm square bore holleys seem to kill power ive tried a carter competition 750 cfm on a 304 built this way and can fog 33 12.5s in a 73 cj5 but its no good off road quadrajets are great for these engines just my opinion i also think high compression is great for horse power but at a higher rpm than is usefull
for offroading or pulling power just my 2c

[dusty]

401's love extra lift close to .480 lift with no mods. summit 8600 is a great basic cam for stock pistons with a 401.

The edelbrock cam is WAY too small for a 401 especially witht he shift points you are talking about


I opened up and polished my combustion chambers just a hair on my next motor, also opened up exhaust and port matched intakes. it has speed pro pistons though i wish i had gone with the KB's my compression ratio is 9.6:1 i have a 5.12/.512 lift cam at 226 dur @ .050 274 adv on a 112 lobe seperation running a air gap intake a holley 670 and hei ignition, with a 5 spd.


Current motor is a 401 bored .030 over with speed pro forged pistons and a 9.6:1 CR i have the crane HMV272 .484/.512 218/228 dur @.050 272 adv dur on a 112 lobe seperation with a performer intake shorty headers and a 3" exhaust. i run HEI and currently a holley 670 though i also had a edelbrock 750 on here before. the holley 670 picked up a little snap to it and has served me quite well, the 750 had just a little bit of a dead spot off the line (very minute) but it also needed the offroad kit and i already had the 670 sitting in my garage so hard to argue.


That said the jeep has 33's and a nv4500 and at one time 3.54's though now it has 4.10's since i swapped to a j10 rear axle. it tows a trailer regularly around 6000 lbs. with the 3.54's in direct which is the gear i spend most time in when towing i cruise right at 2500-3000 rpm when i down shift into third to pull a steep hill it gets right up there in rpms to 4000+. This combo has proved to be a great balance of power, towing ability and hp.


Sweet spot for best mileage would be keeping with lower rpms

i average 9 mpg when towing and get 12-14 when empty. i cruise the road in od empty at around 2000-2400 rpm. though it can cruise at 1800 in od with no problems either. it has power off idle all the way up to 5000-5500 rpm which i dont think ive ever seen over 4500 rpm yet but it pulls hard off the line all the way up.

honestly if your going to run 3.54's id say take a look at that comp EX268 grind, if you like a little more rpm with shift points in the 4k -4500 id look at the hmv272. I have no detonation problems with my higher compression pistons and once i recurved the distributor that helped a little more. i did have to jet up the 670 though it was under jetted.


Engle makes some great cams for amc motors, they know how to take advantage of the performance these motors are capible of.

you are in chino ca right? you will have smog to contend with so that may be an issue there are ways around that but thats for pm. if you are ever in norcal bay area or sacramento get a hold of me you are more than welcome to take it for a drive and see if the power is what you are looking for.


for stock pistons and an rv grind look at the engle s or howards had a 479/479 222/222 dur @.050 114 lobe sep cam that works really well with stock compression in a 401. nothing extravigent but rpm wise 5k is about all shes got

[mark j]

I just had my 401 built for durability and torque. The shop that did it has dyno sheets on about 20 401's they've done over the years with HP #'s ranging from 300HP to 708HP . The 708HP was on the dyno when mine was in the shop with a $20K build price. Back to the topic- of the 401's built similar to mine the HP #'s were in the 325 range with about 390 lb/ft torque. Basically- it has an elgin cam with a grind compareable to the summit 8600 that has been degreed. The rotating assembly was balanced. I think these engines are a great platform for reliable power. The 401 in my j10 is amazing stock. I can't wait to get this built 401 in the 89 waggy.

[dusty]

FOUND A COUPLE OF ENGINE DYNO PRINTOUTS FROM YEARS PAST. BEST I CAN TELL THE ENGINE COMBOS TO HP PRODUCED SPECS ARE PRETTY CLOSE TO ON THE MONEY. I HAD A REALLY HARD TIME READING THE OLD DOT MATRIX PRINT OUTS. READ EM ANALYSE EM AND SCRUTINIZE. REMEMBER ALL HP NUMBERS VARY ON ABILITY OR INABILITY TO TUNE THE MOTOR AND ALSO NOT ALL OF THESE WERE MY MOTORS.

MOST OF THESE WERE DYNOD AT AN ENGINE SHOP IN SPOKANE WA IN THE EARLY TO 90'S OR IN GREATFALLS MT AROUND 1996- 2000.



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 319 381
>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 166 367
>2500 210 392
>3000 259 413
>3500 310 421
>4000 339 439
>4500 331 396
>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 178 398
2500 214 427
3000 251 449
3500 301 478
4000 346 489
4500 369 443
5000 347 381
5500 316 338
6000 279 284