AMC 401 Build Options and Questions

JeepScrambler

Welp, I finally found a 401 V8 to take the place of my 360 V8 I have in my '85 CJ8 Jeep Scrambler. The 360 only has a couple thousand miles on it since I rebuilt it but I have been wanting to put a 401 in the Scrambler for some time. The 360 has a 670 cfm Holley Truck Avenger, performer intake, Harland Sharp 1.6:1 roller rockers, hedman headers, and a crane cam but I cannot remember the specs on it. This engine is then going to go in my '84 CJ7. Here are the current drivetrain specs on my Scrambler: -NV4500 5 spd -Atlas II 4.3:1 Transfercase -Dana 60 front axle, 5.13 gears, Detroit locker -Dana 70 rear, 5.13's, Detroit Locker, narrowed to front width -40"x13.5"-R17 Goodyear MT/Rs Since I already have my '84 CJ7 built for the trails and rocks, I mainly use the CJ8 during the summer for trips to and from the lake although it is built (yeah, it gets babied)! It is about a 30 mile trip to the lake and another 30 back and I also do some interstate and other longer highway trips. Since I do run it on the highway the majority of the time with sustained higher RPM's (2200-2600) would I need to address any of the oiling issues? I am not sure of the timing cover condition on the current engine so should I just go ahead and pick up a new timing cover to prevent any future headaches? Any other oiling upgrades/parts y'all would recommend (oil filter adaptor, pushrods to increase crank oil, different cam bearings, different oil pump, Crank scrapers, etc)? Since I am going to to a complete rebuild on the engine would I be better off buying a complete rebuild kit or should I buy the parts I need separate? If I buy a complete kit, who has the best prices and quality? If I buy the parts separately, what pistons (I am wanting to stay on pump gas so nothing over 10 to 1), cam (I have read many prefer the summit part # K8600), and other parts with their part numbers do y'all recommend? Could I actually come out with significantly more power for only slightly more money if I buy the parts separately? I will be running a Holley Truck Avenger carb, performer intake, and a set of shorty headers (anyone have suggestions on a set I should run?) Would I benefit much from running roller rockers on this engine as well? If any body has any more info to throw at me let me know! I am wanting to build this motor right(avoiding current and future oiling issues to extend engine life) with a significant HP increase while still keeping it somewhat streetable(at least as streetable as a Scrambler on 40's can be!!!) Sorry for the long post!!!

JERSEYJOE

Welcome to the forum. You have come to the right place to find a talented pool of AMC motor heads to help. I also have a CJ 7 wit ha 401 as well as a J-20 that I just completed a 401 for. You can't go wrong with a stock type rebuild. Keep the cpmpression at 9.5 to 1 or lower to be able to use regular. You can still make 400 hp and lots of torque. I am running an Engle cam in mine with the Harland Sharp rollers. The performer is good as is the Holley 670. Oiling mods can be limited to the reduced ID cam bearings, a mid plate, new cover or as wild as you want including dry sump ect. Really not needed for what we do. Wait for some of the senior guys like MUDRAT, FUZZ 401 and TUFCJ to respond with detaled recommendations. MC our host can supply everything you need.....

Dusty

Keep in mind if you ever plan to go to Throttle body injection. like the howell system that certain cams and intakes will give you headaches. but then again in the fuel injection arena i am not the one to ask i have screwed my last two builds listening to the wrong advice and wrong info ...... ishould have stuck to carb'd motors. they always ran well but the ability of going from sea level to 10000 ft without any need for carb adjustments has been nice. no more on trail adjustments :!:

JeepScrambler

Jersey Joe, are you running 9.5 to one compression pistons in your 401? Are you running 91 octane without any problems? If so, where did you purchase them from and do you have a part number? I am leaning more towards buying the parts individually so I can get different came bearings and such I need through this site. Dusty, I have thought about a TBI system but have heard several people complain they are not getting the maximum HP with a built 401 and a TBI system. Have you had any trouble with yours? Also, which cam would you recommend that would work well with both a carb or TBI? I still love the simplicity of a carburetor is another reason I keep steering away from a TBI system; well that and the initial cost of one! Thanks for the info so far! :lo1l:

JERSEYJOE

THEY ARE KEITH BLACK PISTONS. IF YOU WANT TO RUN 8.5 TO ONE THE STOCK TYPE CAST ONES ARE FINE FOR A MILD MOTOR. SEE THE KB WEBSITE. MAKE SURE YOU TELL THEM WHICH CC HEADS YOU ARE USING. THE EARLY ONES WITH THE 58 CC CHAMBERS AND NON-BRIDGED ROCKERS DO NOT HAVE HARDENED EXHAUST SEATS AND FOR EXTENDED STREET MILES YOU NEED TO HAVE THE SEATS REPLACED. I AM ALSO RUNNING AN ANCIENT EDELBROCK WATER INJECTION SET UP AS EXTRA INSURANCE. I LIKE TO RUN 91 OCTANE BUT IT WILL WORK WIT 89. I HAVE RUN THIS EXACT SETUP PREVIOUSLY AND MY CURRENT J-20 PROJECT IS STILL IN THE BUILD STAGE.

Dusty

JeepScrambler wrote
Jersey Joe,
are you running 9.5 to one compression pistons in your 401? Are you running 91 octane without any problems? If so, where did you purchase them from and do you have a part number? I am leaning more towards buying the parts individually so I can get different came bearings and such I need through this site.

Dusty,
I have thought about a TBI system but have heard several people complain they are not getting the maximum HP with a built 401 and a TBI system. Have you had any trouble with yours? Also, which cam would you recommend that would work well with both a carb or TBI? I still love the simplicity of a carburetor is another reason I keep steering away from a TBI system; well that and the initial cost of one!

Thanks for the info so far! :lo1l:

I wish i could tell you the cam to run but i am at a loss, i ran a howards 479 lift 222 dur @ .050 292 adv dur on a 114 lobe sep and it was great with a torquer and 600 holler double pumper, took the carb off ditched the headers, went to manifolds single 2.5" exhaust and the TBI and this motor became full blown turd. i am currently emailing back and forth with mc on this one. i totally botched my last two efi motors. i seriously wonder if i am loosing velocity with the TBI kit over my old holley double pumper. i really like the TBI at times because it will never die but the lack of bottom end power and mid range sucks. WOT is what my old mid throttle used to be. i imagine its a combination of issues i screwed with exhaust, headers and then added TBI all in one weekend, i dont normally do that all at once but i scored the tbi for 800 and i had header issues and i wanted to quiet the rig down from the dual 3" pipes and i had a jeep trip actually my bachelor party in 6 days to go on so it was done.

i'll get back to you when i find a winning combo till then i can only offer my wild ass guess. which is i think i need to find a cam that maintains higher vacuum especially with the big 670 tbi unit that they send you to maintain bottom end snap. i suspect a cam like the lunati cam i cam looking at with the sharp ramps. high lift and cam even timing like it is will lend itself to dynamic compression, and will keep up vacuum and combined with the performer intake over my torquer i hope to increase velocity to a point where the bottom end power will return to my rig. Right now my 304 2bbl powered cj 7 walks all over my 401 powered cj7 in ever aspect but idling ability. the 401 with the TBi will idle over anything but the rest sucks.

i'll keep you posted.

heres what i am thinking this go around
Advertised Duration (Int/Exh): 256/262
Duration @ .050 (Int/Exh): 213/220
Gross Valve Lift (Int/Exh): .484/.507
LSA/ICL: 112/108

8.5 pistons
58 cc heads
stock manifolds ported out
dual 2.5 exhaust
performer intake

I am still concerned that i am cutting my motor off at its knees with too small a cam but we'll see. what sucks is the fresh short block i have is a .030 over motor with the forged speed pro 9.8:1 pistons on 58 cc bridged heads. I really think that i may source some lower compression pistons but then that means i have to tear down a perfect good already setup short block..................... SO you can see my dilema

otherwise my current motor is a std bore stock compression motor with the howards cam, 58cc early heads, manifolds, torquer intake..... that needs machine work. the other motor is a cheaper option but how i setup it up is yet to be decided. i like the idea of lower compression in a trail rig. but i may have to take what i already have and make it work

one of the more balanced motors that a buddy and i built was a 9.8:1 with comp cam 270H an airgap intake and a 770 holley though he later changed to the 670 and a performer for better results towing with a th400 but with the t18 in his cj the 770 and air gap had no problems. but overall a great engine holds 20-21 inches vacum with that 670 performer held 18 in with the 770 and the air gap. but weight was an issue the cj 5 was light and had small tires the cherokee chief he put that motor into had a th400 33's and weighed alot more so it needed the changes. remember you are building a jeep. keep it simple with cj's and lighter rigs we've always been able to get away with a little more cam and drive around it but big tires heavy rig i error on the safe side.

shorty headers the only ones i know out there are edelbrock's otherwise i just run manifolds anymore. i've grown tired of header headaches and the heat they create. i used to try and squeeze every last pony out of the motors. now i just do a mild port match on the manifolds and the heads, clean up the exhaust ports. a good valve job witha performer intake and i live with a motor that idles at 500 rpm and that will spin down the road

JERSEYJOE

Call me old fashion but I like to run combinations that are tried and true. Stock heads with minor throat and bowl cleanup, Performer rather than a Torker. The cam I like to run in 401 Jeep motors than need low end torque but also some HP for towing is the ENGLE 5054 which is .501 lift int and ex and 214@.050 with 112 lobe centers. Perhaps the split pattern one that Dusty mentions is a bit more aggressive and would also work fine. I always resist the temptation to over cam any Jeep that needs road manners. AMX's and Spirits are another story.

Dusty

i am hoping with my build up that with the 9.8:1 pistons the longer exhaust duration might help some otherwise i have always really like the engle grind that jersey joe pointed out. i would be inclined to run that if i was going with stock compression. probably could have gotten away with it on my higher compression but i was a little detonation shy

JeepScrambler

Hey thanks for the info guys! I appreciate it. I, finally got my 401 here a couple of weeks ago. I'm going to have the machining work done to the block, crank, and heads sometime later next week or the following week. So far here are the following oiling upgrades I plan on doing(I plan to get the parts through bulltear):

-pushrods with .015 smaller feedholes
-cam bearings (increased pressure setup)
-midplate

A couple of other questions:
-which oil pump would y'all recommend, the AMC "HRC" oil pump gears, or the (HP) Oil pump kit through bulltear?
-are the pushrods with the smaller feedholes compatible with guideplates?
-would 9.8:1 compression pistons be to much to run on pump gas or should I stick with something under 9.5:1?
-I think I have my cam choices narrowed down, either the ENGLE 5054, comp cam 270H, or the summit K8600. Just have to decide which will work best for my setup?

Again, thanks for all the help and info so far!
Here's a picture of the 401 and the Jeep CJ8 it will be going in:

Sorry, pictures of the '8 are over a year old, they don't show the warn 9.5ti winch mounted, the rear end (dana 70) narrowed slightly to match the front dana 60 width, and decals on the windshield removed! I need to get some updated photos:

jeepsr4ever

Look at the body on that one! :shock:

ironman_gq

not sure but are BOTH the small hole pushrods and bearings neaded? I was under the impression that it was either one or the other. Hopefully MC will chime in

JeepScrambler

If they are both not needed which would y'all recommend, the smaller hole push rods or the bearings? Also, I was thinking with my Jeep, since it is geared so low and the Jeep the Jeep is usually running at rpm's above idle, would I benefit from running an edelbrock air gap intake over the performer intake? Or should I just stick with the performer? Would there be much of a notable difference? One another side note, I got the engine to the machine shop to begin some of the machining work. The cylinder walls do not have any ridge on them at all so I'm hoping they will just need hone the walls so I can still be at standard bore to allow plenty of room for a future rebuild. Jeepsr4ever, yep the body is and has always been completely rust free! My family has owned the Jeep since 1990 when we bought it with 33K miles where it was used primarily to drive around our trails on our ground in the sandhills, haul firewood, etc., it rarely left 4-Low and was garaged every night. I did the frame off build about 7 years ago when the CJ8 had 44K miles. And now it has just over 48K. It spends it winters in a heated warehouse and comes out only during nice weather! But when it is nice I drive it as often as I can! Lots of sentimental value with this Jeep since we have had it since I was four years old.

ironman_gq

If you can I would go with the bearings cause it opens up the options for different pushrods if you ever decide to do anything with the heads or mill anything.

JeepScrambler

Ironman, thanks for the reply. I will be going with the cam bearings. I have a question about the rocker arm studs. I am having the heads machined for the 7/16-14" base and milled down 0.375". Is there any benefit to running rocker arm studs with the upper portion 7/16" or should I run the 3/8". I have searched on summit racing for rocker arm studs and there are many different choices (brand, length, etc.) Which ones do you guys prefer? I plan to run Harland Sharp roller rockers with the 1.6:1 ratio. For my build would the 1.7:1 rockers benefit me at all? Thanks for the help. :t:

ironman_gq

If you use 1.7's you need to make sure you wont have any coil bind in the valvesprings and make sure you have clearance for the valves so they wont hit a piston

JeepScrambler

I believe I will just be sticking with the 1.6:1 roller rockers. Would I be better off running rocker arm studs with 7/16" or 3/8" upper portions. Will the 7/16" studs be notably stonger? I am having the heads drilled to accept the 7/16-20" studs and machined down .375". What is the effective stud length you have all gone with to allow proper set up and adjustment of the rocker arms with the .375" machining? One more quick question: are the non -small holed push rods listed on the bulltear site hardened for use with guide plates?

AMX69PHATTY

On the '70 heads with no guideplates and Harland Sharp 1.6 ratio 7/16 stud rockers I used ARP #100-7101 for sbf. If buying new Roller Rockers and Rocker Studs, and have not bought them yet, why not go ahead and get the bigger 7/16 studs and matching rockers ? As "insurance" ? Wouldn't think the cost difference between 3/8 studs & rockers and 7/16 studs & rockers would be that much. If cost difference is a lot, then it would be a tougher decision. Larger studs just provide higher valve train stability when using beefier springs and more radical cams and higher rpm's. Since I was buying both new anyways, I went ahead and bought the 7/16, but they were used in original screw in stud type heads, so I'm not sure what specs are needed for modified bridged rocker heads, overall length, bottom thread length, length above hex, and top end threaded portion length. Studs do gotta be right so the lifters can be properly preloaded without running out of thread and the poly-lok bottoming out and running out of adjustment (studs too long), or not enough thread engagement of poly-lok on stud (studs too short). Stud length also effects where the socket head jam screw ends up sitting in the top of the poly-lok.

fifesjeep

I used the 7/16" 1.7 Harland Roller Rockers on my heads... The machine shop figured it all for me... They insured proper geometry etc. I didn't have the studs for the 1.7 Rollers but the shop had the ones I needed... I get back to land today... I can look at my reciepts for some part numbers etc etc. With my set-up there is no binding etc... After the shop milled the bosses (roughly the thickness of the stud nut & guide plate added together)... they drilled and tapped the bosses and when they did they went into the water jacket... Not an issue (IMO) as everything was sealed and I have been running it like that for over 2 years, no leaks etc.

JeepScrambler

Hey, yeah if you could get me some part numbers and possibly some of the specs that would be great!!!

JeepScrambler

Its been a while but I'm finally getting back to working on the 401. I'm getting ready to select the pistons to use in the engine. I am wanting to keep the compression ratio around 9.5:1. The block will be bored .030 over. Does anyone have any piston recommendations that will keep me at that compression ratio? I was looking at the KB354-030 but I have heard these require a bushing in th wrist pin. Would I be better off with forged pistons or Hypereutectic aluminum? Also, what rings should I choose, cast iron or moly? And where is a good source to buy these rings from? Thanks for all the help! :t: