AMC 401 build up Q's

[ddestruel]

Im installing a 401, which already has set between the frame rails once. It is now out to have a another freshened up 401 installed.

The 401 that I bought for installing came with low miles & in pieces, with the Old school Edelbrock R4B intake, and a Crowler Cam spec'd at .521 and .534 lift and a really shitty valve job. The heads have a few broken spings and few bad valves, Hence the reason the guy did a teardown. And why i am freshening up. Also She came with .30 over 9.8:1 TRW Forged pistons & the heads are the big chamber 57/58cc Dog leg's.


Now that you know the Details What Im asking for is to Discuss the AMC 401:
PBB needs a page specific to the 401, so here it is.

I am curious to hear from the few on this page who have been running the AMC 401's, as they are not like a Chevy or Ford, so I dont want to hear about how i should have put a SB in 'cause it cheaper I'm hoping in the Jeep forum i can limit those responses.

I want to know what cam's your running, specs, if you made the jump to studs and 1.6 roller Rockers, (reason being these heads came with them). Im looking at a few cams in the .472 -.488 neighborhood 260 or so on Duration. Any thoughts comments concerns, don't want to cut my RPMs off too soon. what about Engle cams?

I'd love to hear Problems you've had when getting away from stock with these motors, especially on the trail & rocks problems, things you'd change and why. Stick or Auto, im running a stick. I had a 401 years ago and loved it, ive built an AMC 360 but didnt use enough cam on it, Ive heard that the 401 reacts even more differently to cams and engine mods, I have heard most outa box cams weren't enough for it. Most people dont have clue with AMC's.


Any tips or tricks with the 401, ive already got an aluminium radiator but there is more to discuss around that subject, i already have drilled the lifter valley and installed the oil flow improvement kit, what about better timing covers, oil pump kits and oil filter adapters, any performance models out there. I looked at the anti cam walking kit i dont think it's necessary. I also am debating drilling and tapping the timing cover to pipe a little more oil onto the distributor gear and timing chain but any thoughts on if its even necessary. The engine came with a DUI HEI setup thank god. 670 Holley Off road carb too.


I created this because I just couldnt find a good thread on the AMC 401, it seems like everybody touches on it or mentions it but there isnt any indepth tech and results. Starting this may yeild some good feedback and debates on AMC tech, specifically the 401



Thanks

Dusty



Yeah I know i could have posted this on FSJ or JU, i did read thier posts but 1. I'm not a member and 2. those guys seem to think that anything past a stock cam or even a V-8 in a CJ is too much and very few talked about the 401. And then the search everywhere is driving me nuts, I can't search for short words anymore, 401, AMC 401, 401 buildup, ect they all say search is too short. and it seems anything bigger is too specific killing me.

[JesseA]

AMCForum.net

These guys know their 401s.

[rock-rod]

Wow, where to start!

I recently pulled my old 401 out this winter after 8 years of extreme abuse. I have to say it was an excellent power plant and always provided me with more than enough horsepower and torque for any situation I was in.

My 401 was a 1973 model year pulled from an International Travellall. I built it with TRW forged 9.5 pistons and 58 cc dogleg heads. I ran a Crane HMV 272 series cam with .484 intake lift and .512 exhaust lift with 1.6 roller tip rockers. The heads came equipped with 3.8 studs from the factory, but I did replace them with some stronger studs from ARP. I originally ran a Torker intake and 670 cfm Projection, and it worked really well. The motor would spin up to 6,500 rpm with no problem- I did upgrade the valve springs. The bottom end was stock except for the pistons and a Milodon pan. I would say the motor produced about 380 hp and about 480 ft/lbs of torque. A 1971 401 from the factory with a cast iron intake and manifolds made 330 hp and 430 ft/lbs, so I feel with the mods done to this motor my estimate is pretty close.

I would say for you the R4B is a great choice. It really is the intake that all other AMC intakes are compared too. If you wanted something better, maybe the new RPM airgap would work better, but I don't think it would make enough of a difference to warrant the cost. As mentioned earlier I did start with a Torker, but I did switch to a Performer later on for better mixture distribution while running the 2bbl projection.

I highly recommend the Crane product. AMCs really like split pattern cams and the Crane fits the bill very nicely. You already have the roller rockers and studs, so no worries there. Just make sure you have top quality valve springs and retainers and make sure the builder uses the correct length push rods. Most aftermarket rockers sold for AMCs are really just rockers designed for a Ford or Chevy, so getting the pushrod length correct is key to a durable and quiet valve train.

There really isn't much needed for the bottom end. I would balance it, and that's about it. It already has a steel crank and rods- what more do you need? The main caps are huge, and the webbing is super thick. I guess main studs would help but I really don't think it's really needed unless you are running a blower or nitrous. The blocks are bomb proof. High nickle content means little wear in the bores, so all is good there.

About the only oiling mod I would consider is running a Milodon pan and pick up. You can do the oiling tricks for the timing cover and main bearing but once again, just how high are you planning to spin the thing? Run the aluminum radiator and highflow water pump and cooling should be fine.

I ran my 401 first with a T18, and then went to an 727 auto. I later switched to a NV4500 and the engine performed great with all three trannies. I prefer the automatic, so a low stall converter to take advantage of the off idle torque would be great if you went automatic. Just make sure you pick a good tranny. 401s are hard on automatics- I broke my 727 3 separate times with the 401. Each time cost me a tranny case and planet gears.

My one and only complaint was cooling. I was sometimes difficult to keep the motor cool when crawling. I am sure the main cause of this was the lack of a fan shroud. With the auto this problem was more pronounced. Idle creep is another issue. In low gear low range with an auto, you will need big brakes.

RIP my old 401. It died an unfortunate death when the block developed a crack on a cold night in Colorado. I still ran it for 4 years after that- leaking and all, and it finally gave up the ghost Oct '93 in Tellico.

[REDXJ4FUN]

Damn Rock-Rod you hit just about verything there is to say. I have a 401 in my 71 amx that just rocks and will run with Big blocks no problem . they realy do like more cam than chevys and fords with out lossing bottom end. if you realy can afford it there are some sweet roller cams out there that make it a monster but they are pricey( i just dumped 1200 in the valve train in my big block chevy ) hell if you wanted to you could sell the R4B for whta you can buy an airgap for and then you have the bungs on the intake for fool injection later. The 670 will srve you well.
ts kinda funny last year at the VA rock crawling championship a guy was running a TBI injected 401 and it didn't sound like it should have so I talked to him a bit and he was running a performer cam with is almost less than stock for a 401 and he had never realy tuned the TBI so I told him if he wanted I could work the tbi to clean up his flat spots and give him more punch, his reply "shit it already snaped 2 warn shafts and a ctm in a 60 whythe hell would i want more" ya got to love a 401

[rock-rod]

One thing I forgot to add about cam shafts and AMCs.

The lifters are large in diameter. They are the same ones used in Chrysler small blocks, and the large diameter allows for more aggresive ramping on the lobes. Thats why you usually see AMC cams advertised with more lift that say a Chevy small block- and both have identical cam phasing events.

I have always wondered if it were possible to retrofit late model chrysler roller lifters from their magnum motors to an AMC. Sure it would take a custom cam, but I bet it could be done and this would net a hydro roller cam

I would love to see someone build a 401 with the new Edelbrock heads and fuel injection. There was a build up going on in Car Craft, but I have lost track of the articles.

[ddestruel]

[QUOTE=rock-rod]
I'd love to be the one but $$$$$ i could buy another jeep for that money. I should have said that the rotating assembly was already balanced. Dont worry i intend to check it before i go to far. Thank you for the web pages and tips.

Sounds like a 270 duration isnt too much that makes this look like it is going to be fun.

Thanks Rock-rod and all you've been a alot of help just pointing some direction. I really was hessitant about where too much cam was with these but it sounds like they handle 260-270 Duration and the higher lifts .470+ quite well.



Im looking forward to firing this thing in the next month.

Thanks again

Dusty

[rock-rod]

The duration I mentioned was advertised. I think it came out to around 206 degrees intake duration at .050 lift. You could definitely tell the motor had a cam when it idled, but it was never a problem with performance off idle. Besides, with 400 cubes, one could stand to give up a few ft/lbs at idle for the huge gains up top. I also think if the motor were built strictly for off idle response then an automatice tranny would have serious issues holding up to it. In that case it would be TH400 time, or a well built (read expensive) 727.

The first 727 I broke stripped the rear sprag out of the case. The second one sent it's planet gears through the pan. The last one snapped hub off the front pump. Went to a NV 4500 after that.

Originally Posted by ddestruel

I'd love to be the one but $$$$$ i could buy another jeep for that money. I should have said that the rotating assembly was already balanced. Dont worry i intend to check it before i go to far. Thank you for the web pages and tips.

Sounds like a 270 duration isnt too much that makes this look like it is going to be fun.

Thanks Rock-rod and all you've been a alot of help just pointing some direction. I really was hessitant about where too much cam was with these but it sounds like they handle 260-270 Duration and the higher lifts .470+ quite well.



Im looking forward to firing this thing in the next month.

Thanks again

Dusty

[Beat95YJ]

Originally Posted by rock-rod

One thing I forgot to add about cam shafts and AMCs.

I would love to see someone build a 401 with the new Edelbrock heads and fuel injection. There was a build up going on in Car Craft, but I have lost track of the articles.

Edelbrock is in the process of switching their AMC dyno 401 over to EFI. Last time I heard it made 420+ hp and 470 ft-lbs of torque. They have since swapped in a bigger cam and re-run. I have no idea what it made with the new cam. As soon as the parts arrive I'll let you guys know what it makes.

[RickyR]

As said above, Rock Rod covered most of the bases.. I just wanted to add that my 401 is running just a no frills RV cam (don't know the specs sorry), and It develops more HP than I need.
One thing that wasn't listed above is an oil cooler. I am .060 over and haven't had heat issues yet.. I run a header style oil cooler in front of my radiator. This keeps my temps around the t'stat setting. I also use a Milodon 9 qt. pan with a remote spin on filter. I guess I have about 10 or so quarts of oil in my system.
I am running the 51cc heads and have a very high compression ratio, which means high octane fuel if I really want to run it hard. I'm sure a higher lift cam could make this a little more bearable on 93 octane, but for now I mix 114 with 93 to keep the pinging away.
Also tranny wise, I was running the T-18, but just went to a 727. You will have front driveshaft issues with the 727, so be aware of that.. If you do go auto, you can do a 2 piece front shaft...
I say let the Chevy and Ford guys just wonder what it's like to have raw brute hp from a basically stock small block..
Ricky...seeya...

[redramsport]

I was planning to use an AMC 360/Torque Flight 999 in my Jeep, but after reading this, the 401 is sounding more and more fun!! 450 ft/lbs in a Jeep has got to be a fun ride!!

But a 999 will never hold up behind a built 401, and it sounds like it will have some problems behind a built 360.

Rock-Rod, what all did you have done to your 727 to beef it up, if anything? And what did you do about the front driveshaft clearing the tranny pan? Although you might not have had any d-shaft clearance problems with the amount of lift you are running.

Also, anybody have any experience with a built 360? Figured I would probably bump the cam down a notch from what everybody is saying the 401 likes, would the 360 still have plenty of bottom end grunt that way, or is there something else that makes the 360 a completely different animal as far as cam selection?

[rock-rod]

Originally Posted by redramsport

I was planning to use an AMC 360/Torque Flight 999 in my Jeep, but after reading this, the 401 is sounding more and more fun!! 450 ft/lbs in a Jeep has got to be a fun ride!!

But a 999 will never hold up behind a built 401, and it sounds like it will have some problems behind a built 360.

Rock-Rod, what all did you have done to your 727 to beef it up, if anything? And what did you do about the front driveshaft clearing the tranny pan? Although you might not have had any d-shaft clearance problems with the amount of lift you are running.

Also, anybody have any experience with a built 360? Figured I would probably bump the cam down a notch from what everybody is saying the 401 likes, would the 360 still have plenty of bottom end grunt that way, or is there something else that makes the 360 a completely different animal as far as cam selection?

Yes, that kind of power is very nice to have. But it is very destructive on parts.

My first 727 was built stock. After I broke the sprag in that one, the builder installed a bolt in style sprag. That held up great, but later on a planet gear let loose and wiped out the whole damn tranny. I was trying to climb a ledge in Moab in second gear low range and did not quite make it. The jeep slid down while the engine was still spinning pretty high and as soon as the tires hit solid ground the whole thing let loose. The third tranny broke the hub on the front pump, but I think that was an error on the tranny builder. After that, I decided it was time for a more durable tranny so I swapped in a NV 4500. All three versions of my 727 had a Turbo Action manual/auto valve body and hemi servo lever. All had heavy duty clutches and bands. I learned after the first breakage never to wheel with the shifter in D, but to lock it in manual low when really giving it hell to prevent the sprag from breaking again. The reason why is when the shifter is in manual low, the valve body will engage the low/reverse band, and this combined with the holding power of the sprag kept it from detonating.

I did have drive shaft issues, but I did not have to run a two piece shaft. I was running a dana 300 with a spring over front, shackle reverse, and a low pinion front axle. I used a 2.5 dia front shaft with the slip/stub on the t-case end. The tranny had a mopar deep pan, and I notched the pan using 3.5 inch dia exhaust tube to form a sort of 'tunnel' to allow the driveshaft to swing with the suspension. It worked pretty well, but it was a PIA to get that notched out portion of metal to seal to the pan. I had welded it in there, but with my crappy welding skills I kept getting seepage.

401s are awesome motors. They do get expensive quickly. It's nice to see that the aftermarket is finally reviving support for these fantastic motors. I don't know why AMCs have such a bad rap- maybe it's just brainwashing from the big three. AMC V8s really enjoy a lot of technological advantages because they were the last to be design from the ground up. Chevy, Ford and Chrysler had already come out with their small block motors so AMC was able to take the best features of each and combine them into the new for '66 AMC V8. A lot of people think the oil system is stupid, but if it worked for NASCAR, then it will work for the public. Granted any oiling system in any american made V8 could stand mods to help them perform better for certain situations. Someday I am sure I will build another AMC V8. For now, the new 5.0 will have to do. For the record, the 5.0 is no where near the power lever of the old 401. Now I actually have to think about what gear to select while driving, where as before any old gear would do. I know I will miss the days of leaving the tranny in high gear and driving up the steepest hill when zero complaints from the old 401. It just pulled at any rpm- from 500rpm to 6,500 rpm.

[ddestruel]

Rock Rod why didnt you put another 401 together? instead of a 302?

I am going to run the NV4500 that i have behind the 401, just like you did glad to hear it worked well. We'll see how i do on parts $$$, Im glad to hear that the R4B is a good intake i was a little nervous.

Whats your thoughts on the Summit cams 8600 and the 8601 series. i have been told they have poor quality but i have yet to hear of any one who can verify this. Glad to hear the off idle isnt much of a problem with these longer D cams.

Thanks for all the info
Dusty

[redramsport]

Thanks rock-rod!!

After reading that, I think I may try to moderate my horsepower dreams a little bit and stick with something a little less destructive. If I keep the 304 and use the 999 and Dana 300 I have here now, I won't have to worry so much about breakage with Dana 44's and 35's. Since this Jeep is being built within the rules of the modified stock class, there is no need for it and hopefully it will save me a little bit of money (especially in the long run on axles parts and such)

Another question though, were you using the factory exhaust manifolds or a set of headers on yours? At that power level, I would think headers would help, but have heard numerous people say that the factory manifolds are fine. And, if you were to build it again, what would you do different this time around?

[newt]

If you are looking for another source of info, take a look at www.froadin.com That guy knows his AMCs.

BTW, I'm in the planning stages of taking my 401 from STOCK w/ very low oil press & 2 bbl MC carb to mildly built w/ TBI EFI. I'm really happy to see this thread while I'm in my planning stages.

How can I get my oil press where it should be? I've read that the after market timing covers are crappy. Any thoughts?

[ddestruel]

I'm Glad to see this thread having some really good constructive discussions, its definately giving me some insight into things that i otherwise would not have thought about.

I've pondered having a machinist bore out the oil pump holes and install partial sleves I wonder how that would work, thats the only way i can see to add material and bring the tolerances into closer #'s otherwise ive heard that the aftermarket covers are improving.

Dusty

[ddestruel]

Alright i looked at a bunch of cams, Schneider, Engle, Lazer, Isky, Comp, Crane, Summit and i finally went with a Howards cam

http://www.howardscams.com/page12.html

.479 lift with a .222 duration @.050 and a 114 lobe seperation. I'll let you know how I like it. Don Johanson (Howards kid)isn't grinding cams for them anymore but they still make a pretty good product. If i dont like it I will swap it out its not that hard to change Cams. Im hoping that the longer duration will take advantage of the 401's ability to move some air and yield the advantages of some increases in dynamic compression. Cross my fingers, the rest should be dont this weekend or first part of next week

Thanks for the tips and i hope this page proves useful for others when building a 401 as more info compiles

Dusty

[rock-rod]

Originally Posted by ddestruel

Alright i looked at a bunch of cams, Schneider, Engle, Isky, Comp, Crane, Summit and i finally went with a Howards cam

http://www.howardscams.com/page12.html

.479 lift with a .222 duration @.050 and a 114 lobe seperation. I'll let you know how I like it. Don Johanson (Howards kid)isn't grinding cams for them anymore but they still make a pretty good product. If i dont like it I will swap it out its not that hard to change Cams. Im hoping that the longer duration will take advantage of the 401's ability to move some air and yield the advantages of some increases in dynamic compression. Cross my fingers, the rest should be dont this weekend or first part of next week

Thanks for the tips and i hope this page proves useful for others when building a 401 as more info compiles

Dusty

That thing is going to sound pretty mean! Should have a real nice lope at idle. Are you going to do anything with the heads? With a cam like that, might want to think about a least cleaning up the exhaust ports a little.

[ddestruel]

DREMAL TOOL

I started on the heads last night taking rough spots off the CC's, polishing and the likewise on the pistion tops. also port matched the intake ports. Headers were already port matched on the exhaust side, so all i have left there is touching up the internal exhaust ports.

I am really hopeful that the lobe seperation on this cam at 114 will calm down the idle. The long advertised duration scared me at first though, but at least the .050 duration seems reasonible at .222. Im hopeful that this thing with the low lift long duration will work well as a torqy cam. I had a few friends run it through thier DD's just for curiosity's sake they said id only live from 1000-5500.

Howards had a grind similar to this for my 354 Hemi in my cj5 and somehow he was able to get the long duration low lift and still keep the idle down to a mild lope with a 112 lobe center on a .505 with 298 degrees adv duration.

[ken]

I'm running 401s in both my CJ5 and CJ7. They both have cams in the 264 advertised duration range, the CJ5 runs headers, the 7 runs manifolds. Both run 2 chamber Flowmasters and sound unbelievable! Power is about equal, which leads me to believe that with those cams (264s) the stock exhaust manifolds are pretty darned efficient. On my CJ7, I am on my 5th 999 auto tranny!!! Since this is my wife's Jeep, I've decided to rebuild it one more time and vow to keep away from driving it!! It is just so much fun to pull it down into first and stab the throttle!! The 999 doesn't like that though. I should stick with the T-18'd CJ5....kinda hard to break those!

Great thread. I like to hear from folks like you all who have had practical experience in hot-rodding the 401s. Also, if anyone has any info on hot-rodding 360s, I would love to hear it!

[87yj38]

Great info here. Not many people are aware of the inherant advantages on the AMC V8. I am shopping for a cam for mine now also. Many folks really like the Summit cam for the AMC's, but now that I am getting some other opinions, I am even more unsure what to get...

Rock Rod should do a Billa Vista type AMC V8 page IMO.

[rock-rod]

Originally Posted by 87yj38

Rock Rod should do a Billa Vista type AMC V8 page IMO.

Oh no, not me! Thanks though.

There is a guy in Perry Hall, MD named Ron Hash. He runs a shop called Perry Hall Power Equipment and he has built a number of super hot-rodded 401s with roller cams and 8,500 rpm capability. I learned a lot from him.

Anyone wanting to build an AMC motor needs to get a copy of Performance American Style. It is the factory produced hot rod book from AMC, and is available in reprint from various AMC performance shops such as American Parts Depot in Ohio or American Performance in Cocoa Beach, FL.

Also talk with Wayne Ellis in Edgefield, SC. He runs a shop called BeeJeep and knows a thing or two about AMC motors. Super nice guy. I think his number is 803-648-1983, but it's been a long time since I spoke with him so I am not sure if he is still in business.


Speaking about cams, there is a cam from Melling, part number MTA-1 that is a great RV type cam for the AMC V8. A 401 with one of these cams produced a lot of torque, and it also gives really good mileage.

[ddestruel]

When i was thumbing around for cams, ALOT of the companies out there that are grinding cams for AMC's have a generic take on how to spin one out for a AMC and most of thier ideas are across the board, i was really glad to read about how some people can verify that they have noticed the very defined differences between the same cam in different applications, 304, 360, 401 it just reinforces what i had been hearing that these motors are all very different animals and finding someone who really understands them and has ground specific cams that are tuned to the differences between these motors is hard to find.

Dusty

[redramsport]

I might have to run up the road and talk to the guys at Perry Hall Power Equipment. While searching around on the forum at Froadin.com, a guy by the username Hammer seems to know quite a bit about these engines, can't confirm that he knows what he is talking about, but it looks like he knows his stuff pretty well from what I read.

[YeeP]

What kind of compression ratios are you guys running on these 401s? I live at altitude and set mine up at 9.25 to 1. I havent fired it up yet, but am a little worried about pinging.


Ryan

[MC]

Teaser

2 of the best mods you can ever do to your oiling sytem besides keep clean oil in it are

1. install the lifter bypass
2. drill the mains and bearings to .337

A deep pan also helps

We dont ever suggest the timing cover external line to feed the dizzy gear. If you are ruining dizzy gears you have.

1. A oil pump problem
2. Improper oil hole orientation
4. Improper alignment of the camshaft drive gear and the distributor gear


Their are lots of issues witht the oiling on these motors here are just a few

1. The oil filter bypass spring fatigues over time allowing dirty oil into your engine.
2. The timing cover is cast 356 aluminum and the oil gets to the cover before the filter allowing particles to damage the cover (and the gears) resulting in a less efficient oil pump.
3. As the lifter and cam bearings wear the amount of oil that gets to the mains is lessened. (below is a picture of how the mains are oiled...only one feed line!)
4. The pressure bypass spring also fatigues.
5. New gears with nicks and really sharp edges cut away at the top and bottom of the cover causing scoring and making your oil pump less effective.
6. When you prime your pump with any material that has a greater viscosity than the oil you are running, Tiny particles of bearings and engine sediment find their way under and over the oil pump gears and cause scoring. The thicker or higher viscosity material will acutally cavitate around the axis of the rotational gear untill the engine is at operational temperature.

Major oiling damage occurs on start up, sustained RPM's and quick throttle pulses after sustained RPM's

The AMC forumula for bore and stroke is right on the money and these are really great engines in theory. they just need a little lovin'