Tech Tips

Building 360's and 401's

Ok, here it is the first installment of what I know about building AMCs.

1. The three manuals to own are Haynes "Jeep wagoneer& Pickup" My favored manual, Chiltons Wagoneer/commando/Cherokee/Pickup, good but not as many pictures and "Performance American Style" available from American Performance Products, this manual is the original factory "hot rod manual"
and well worth the price if your an AMC owner.

2. The catalogues to get are Performance Automotive Wholesalers, Summit, and The American Performance Products catalog.

3. Decision time! If you Have a rebuildable 401 I would definitly do so, if on the other hand you have a 360, "and I know that I'm going to get grief for this" with a TH400 you might consider a small block Chevy and a
transmission case swap, believe me it's still cheaper to drop in a Chevy-if, that is your doing the work yourself. That being said the build up for 401s and the 360, is identical, the 401 is just a far superior engine in terms of the materials used in it's construction as well as performance and is thus well worthy of a rebuild. the 360s are not bad engines, but AMCs cost considerably more to build do to scarcity, than do Chevys. but you decide on your own...This should set up a month's worth of discussion Ha Ha...

4. More decision time, how much money do you want to spend? Forged pistons are really not needed for weekend trails, but if your building a really serious truck you might consider them. If you live in an emissions area you will either have to keep your stock manifold or buy a compliant prformance one. The stock non-adjustable rocker arms work fine, but again for a really serious truck you will want adjustable rockers (roller rockers really). The same goes for stainless valves or just steel valves. Etc, Etc...

5. Unfortunately not a lot of material is available on AMCs to help with these decisions, but there are tons of articles on other buildups of the "Big Three" so use them as a guide...

6. I am going to assume that most of you are going to build a motor using similiar parameters as mine 1. Financial 2. Improved performance (mainly torque) and gas mileage 3. longevity 4. Nothing too exotic... That being said you can build the engine based on your manuals, but these are my recomendations:

1. for our purposes use cast pistons with moly rings
2. use an "RV" cam lots to choose from, but for our needs not extremely critical. They all improve the low end torque...
3. Edelbrock Performer Manifold With or without EGR. With Egr if you live in an emissions area.
4. Use the two oiling improvement kits from American Performance Products. Drill and tap the holes prior to hot tanking, and any other machine work.
5. Drill your lifter gallery per the 500hp on pump gas article at download this article.
6. Don't use the paper aftermarket intake gaskets, they may say hi performance but they don't say long life... instead carefully cut the middle out of the "bathtub" style steel gasket and use it, all you need are essentially the pieces that seal the ports. If your going non-EGR then you will want to block the EGR ports with a piece of fairly heavy guage steel say 16 guage (not a piece of coke can)
7. I highly recommend that if you own an air compressor ( and you really should if your doing a re-build) that you buy one of PAWs inexpensive porting and polishing kits.
8. use the kit to de-burr you block and heads.
9. Use the kit to "clean up your heads" you don't have to do a full port and polish (that's a job best left to the pros) but you can certainly clean up the casting flash, and radius the intake and exhaust ports as well as smooth out the combustion chambers. AMCs seem to have a lot of residual flash etc.Use Performance American Style as a Guide. DON'T go overboard! Now have your heads done...
10. The oil pump bottom plate can be " cleaned up" using a piece of wet dry sand paper on a piece of glass, do this if there are grooves in the surface, use about 400 grit caborundum paper with water.
11. Carefully inspect the timing cover for oil pump related wear, and water pump corrosion. Best case scenario replace it. They are expensive.
12. Use a Hi performance water pump, with a back plate on the impeller, I got mine from Summit. An over-bored 401 will run hot.Make sure that the Impeller rivets do not make contact with the housing, do a dry assembly (with out gasket sealent prior to final assembly) you may need two gaskets for proper clearance.
13. Stock exhaust manifolds work fine, are easy to install and are quiet you don't need headers. do use that Porting kit you just bought to grind down the air injection ports. weld the ports shut and grind them all the way if your going non-emissions.
14. Do replace your rod bolts. I used Milodons, about half the price of ARPs. Your rods will have to be resized. I used the port & polish kit for some minor de-burring. Have the rods magnafluxed and shot peened.
15. Balance your engine! AMCs are externally Balanced, so if your going to put a 401 in something that has a four speed make sure that you have your flywheel prior to the re-building process. Make sure that the machine shop you use knows that your balancing, don't let them talk you out of it. The pistons and rods should not be assembled prior to balancing. Most shops do not balance in house, you will save a few bucks if you transport the parts and pay for the balancing yourself. The crank, rods, pistons, flexplate or flywheel, and the harmonic balancer, plus one set of rings and the bearings. I recommend and have seen a few members recommend Doug's balancing. I had a flex plate and flywheel matched to my motor just in case...
16. Stock ignitions are ok, but Jacobs seem to the number one choice for Jeep owners. My next upgrade.
17. Quadra-jet far superior to Holley or stock carburetion for off-road (more controversey) but a whole different book. You can get a custom built one from Jet performance. Prior to assembly obtain the carburetor and an adapter plate, I used the porting kit to clean up and radius the adapter to manifold seams best case scenario--- fuel injection probably Edelbrock or a 350TBI from GM (another argument for a Chevy engine) anyway if you can run a Quad do so, it's a pretty easy swap, you will loose air cleaner clearance, use a dropped base filter. This also a good excuse for a body lift)
18. Paint your lifter gallery with Rustoleum.
19. If you can afford it run a deep/ high capacity oil pan.
20. I got most of my engine kit plus porting kit, engine cleaning brushes as well as various assembly lubes and sealants from PAW. As well as the manifold. I obtained my flywheel and a few small parts from Amercan Performance. I got the water pump from Summit. A new dipstick tube came from a local Jeep dealer.
21. Do not order your engine kit prior to sending the engine to the machine shop! You may assume that a stock engine will only need a .030 over but that may not be the case. some may need a .040 or even .060. go with the least that you can to avoid problems. Ditto for your crank shaft, many cranks do not need to be machined.
22. Do have your heads surfaced.
23. Save and record the placement of your bearings at dissassembly, notice the wear patterns. You May or may not need to have your block line honed based on the wear patterns.
24. If you've gone this far do have your heads rebuilt with new guides (bronze), new valves and springs etc. Do any head work ie. porting prior to having them built, make sure the builder has AMC experience as these are not adjustable valves, and as such must be set up after seats have been ground,
to proper clearances.
25. Be informed, organized, clean and cautious. Check all your torques twice, and pay special attention to seals and gaskets. I believe this engine should put out between 325 and 360 horsepower, net. And tons of torque, pretty safely. IE you won't blow it up.

Good luck

I hope I answered as many answers as I could, Please check your manuals for most stock technical questions.