Just bought a AMC 401... Any ideas???

[1976JeepCJ7]

Hey guys, I'm new here to the forum and I'm looking forward to hearing all of your ideas. I just bought a completely stock amc 401 from a 1977 J10 to put in my 76 CJ7.

block 3-198951
head 3231475-1
holley 1850-4 600 cfm

I've got the wide ratio T18, a Dana 300 with 4:1 gears, and 4.56 gears at the axles. This CJ7 is going to be for rock crawling and trail riding mainly, but I don't have a rig or a trailer to get it there, so it's going to have to be able to keep up with the club members on the way to the trail (70 mph). The engine currently has a 600 cfm holley carb on it. I took the heads off and did an inspection and everything seemed to be in pretty good condition. It has a ridge at the top of each cylinder so boring it out is a must. I've never done an engine rebuild so right now I'm kind of intimidated because of all the different options. I don't care about having 400+ hp or anything, but I don't want to have any regrets either. I mainly care about the torque curve at low RPMs and about how reliable this thing is going to be. All of that being said, my budget is about $3000 for the rebuild and swap into the CJ. Any ideas on pistons, camshaft, intake, carb, exhaust, rings, lifters, oiling mod, bearings, rockers, etc??? I know this thing as been done to death but it seems like most the other threads are looking for high hp at high RPMs.

[northplainsdrifter]

I don't have much experience with rebuilding, but what I did notice is that with 4.56 gears and trying to do 70mph, you'll be really turning high rpms! Let alone driving 70 in a CJ! That would scare the crap out of me!

[1976JeepCJ7]

It would scare me too don't get me wrong, but I just want to have that capability. I looked at the gear ratio calculator and with 37" tires and at 70 mph with my setup it's right under 3000 RPMs. With 32" tires it's at about 3500 RPMs. I guess my point is, I don't want to be topped out at 55-60 like I was with the 258. Eventually I will have a tow rig and I won't care about high RPMs, but until then.....

[tufcj]

A near stock rebuild will give you everything you need in a CJ. Go with a good RV cam with lift just under .500" and LSA around 110 degrees. Spend some money on a quality valve job and some polish/port work. AMC engines like to breathe. The 600 carb might hold it back at high RPMs, but throttle response will be crisper than with a bigger carb. I'm running 37" tires with 4.27 gears, and sometimes it isn't quite enough on long hills in the mountains. I've done 400+ mile road trips in mine, at 75+ MPH on the highway. In a well built rig, it's really not scary at all.

On second thought, you really don't want a 401 in a CJ, so send it to me, and I'll put it in my Rogue.

Bob
tufcj

[rollbar]

I'll trade you a perfectly good running 360 :)

[1976JeepCJ7]

plus cash???

[rollbar]

It wouldn't run because I didn't have the tac wires connected, but with help from these guys, we narrowed it down.

Still not 100% complete w/the build.

[Dusty]

if you want simple thats going to idle strong and be reliable

you'll be fine with the 256XE but it is small for a 9:1 401. there is alot to the lift with amc's, , the larger diameter lifter in the AMCs is advantageous because it allows you to use the higher lift capabilities without having to increase duration. my 9:1 401 with the lunati cam .484/.507 213/220 dur @ .050. idles at 500 rpm and will snap to 5k without issue Similarly Engle really takes AMC cams and motors to their limits with the high lift, .500+ with very short durations. lift allows the fuel and air in duration sets your rpm range. Comp makes a nice cam but the last couple of engines that have thrown on the dyno's i am pretty much a believer in Engle's cams with Lunati running a close second.

We can all throw out numbers at you your setup sounds identical to mine, hope you don’t have tera low gears in that dana 300…..

Couple of examples here’s Donwags build and dyno numbers.
401 - 30 over
Decked, align bored and balanced
10/10 crank, resized rods, all ARP bolts
Cast stock style pistons with head 9.1:1
CC XE256
Edelbrock heads (ported and polished) w/ roller tip rockers
Edelbrock performer intake dual plane (heads and intake port matched)
Edelbrock shorty headers
Holly Truck Avenger 670
MSD ProBillet and 6AL

Results after the build including dyno
“The idle is just a little rough, lopey, lopey” 550 rpm idle Very mild lope almost not noticeable

it made over 400ftlbs from 2-4200rpm with peak torque of 428 at 3400 and 348hp at 4800 on the engine dyno.

Second motor is mine running TBI im in it close to 3k but that’s exhaust, repairs to the TBI and aluminium radiator and lots of messing around with things I could have avoided.

401 - 30 over
Decked, align bored and balanced
10/10 crank, resized rods, all ARP bolts
Bulltear 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
RPM Range: 1200-5500
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 rear wheel numbers
assuming 10% parasitic drive train loss it should be in that 315 hp 420ft/lbs range. the shop that put it on the rollers called it out 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.

You can end up splitting hairs with cams, a well tuned system makes a world of difference, if i had done headers i might have picked up another 5-10 hp and another 15 ft/lbs and the TBI was probably robbing me a little on top end performance think we had a defuel issue above 4500 rpm but as you can see your cam choice is going to put you pretty close to the lunati only sacrificing rpms and a little. though the motor with the 256ex had edelbrock heads which have better port velocities. The motor with the edelbrock heads could have taken advantage of a higher lift cam with similar duration numbers and pulled another 30 ft/lbs out of that motor without trying. You are going to be happy this engine regardless will have fantastic off the line snap.... it might lack a little top end but like i said i think you are splitting hairs to regret your decision you know best what wioll be a good fit on the engine and seat fo the pants is everything. a 214-216 dur at .050 is sure nice for well mannered


For some other cams to look at

Engle
.489/.489 254/254 adv 209/209 dur @ .050 112
.501/.501 260/260 adv 214/214 dur @ .050 112
.538/.538 272/272 adv 224/224 dur @ .050 110
I love this one. way big but i like how they throw in there very heavy tow aka tractor pulls Mdium hot street, very heavy tow. 9.0 to 9.5:1 compression. Powerband 2000-5800 RPM, id actually love to run this one in my next motor
IN .594/.594 298/298 249/249 108°

Comp Cams
Magnum grind
270H
.479/.479 270/270 adv 224/224 dur @ .050 110/106
Extreme energy
.477/.484 256/268 adv 212/218 dur @ .050 110/106
.493/.500 262/270 adv 218/224 dur @ .050 110/106


Lunati
.484/.507 256/262 adv 213/220 dur @ .050 112/108
.507/.527 262/268 adv 220/226 dur @ .050 112/108


For a given duration it seems that Engle pushes the limits of the amount of lift possible with a hydraulic lifter equipt motor. They are all good cams fun to look at em side by side and then take into consideration the cam timing. mind blowing

If i didnt have the lunati i would have had one ground with cam .520/.527 220/222 dur @ .050 on a 110 or 112/108 with an advertised duration of 262/264 or .516/.524 218/220 something like that for my 9:1 401 but i was trying to emulate the build that i posted above my build. Then again that’s splitting hairs and there are already good cams out there. Engle will argue as will a couple others that amc's flow so well on the exhuast side that single pattern cams are more than sufficient. i knew the lunati i chose would work and i wanted a super low rpm stable idle.... i have been able to adjust things down to 400 rpm and keep it running there and actually had it barely sustain a 250-300 rpm idle with the TBI system but currently idle is set at 550 with no stall saver programming

[jeepcj7304]

what exhaust are you running I like the sound of it

[Dusty]

dual 2.5" pipes with flow master 2 chamber mufflers stock cast manifolds ported out as much as i could