TWO AMC MOTOR BUILD EXAMPLES

AMC-8
Your Jeep's engine, not a movie theater
Photography by Marlan Davis, Norm Brandes

American Motors Corporation put V-8s in lots of vehicles, from Matador police cars to Gremlins. The company's V-8s ran the gamut, including the 290, 304, 343, 360, 390 and 401; however, Jeep folk are mostly concerned with the 304, 360 and 401 versions because, from 1970 through 1991, that's what came in your V-8 Jeep.
The Jp Magazine staff has been wanting to build up an AMC 360 or 401 (don't waste your time building a 304) for quite some time, and we still may get around to it. But for now, we're going to lean on the Hot Rod magazine boys on the 10th floor for some tips and tricks on building up an AMC V-8. Although the AMC 390 Hot Rod built isn't a 401 and it's on the hotter side of what an off-roader would build, the buildup offers lots of good tech any AMC-ophile will benefit from. When Jp finally gets off its lazy butt and builds its own 401, you can bet we'll employ some of these tricks, but with a little less compression and slightly different cam specs.

Christian Hazel
Rotating Assembly
Both 390 and 401 engines have stock 4.165-inch cylinder bores, but at 3.574 inches, the 390's stroke is 0.106 inch shorter than the 401's 3.68-inch stroke. All AMC cranks have 2.747-inch-od main journals, but rod-journal sizes differ. The 290 through 360 cranks are usually nodular iron and have 2.09-inch rod journals, while 390-401 cranks are made of forged steel and have 2.248-inch journals. Properly prepared, the externally balanced, forged-steel stock cranks are plenty durable and can handle just about anything you can throw at them. This engine's 390 crank was turned 0.020-under on the mains and 0.010-under on the rods. Federal-Mogul trimetal 34-groove bearings are used to ensure adequate oiling. The crank was also balanced with Mallory heavy metal to permit use of a neutral-balanced, SFI-certified ATI balancer, as well as a Centerforce neutral-balanced 40-pound flywheel drilled to accept a diaphragm clutch (AMCs came stock with Long-style clutches).
Brandes says AMC engines are not compression-sensitive, and he has run stock cast-iron heads at 11.25:1 without spark-knock on premium pump gas. Aluminum rejects heat better, and Indy revised the backside of the chambers for better quench -- so Brandes saw no problem running over 11.5:1 with the proper pistons, chamber shape and camshaft. Hypereutectic pistons were just fine for this dual-purpose street/strip engine, because in Brandes' view, their heat-rejection characteristics at low-rpm are better than with forgings, which helps increase a high-compression engine's detonation resistance. However, off-the-shelf piston availability was a problem when this engine went together.

Rather than depend strictly on the strength of the standard oil system's hydrodynamic oil wedge, Brandes had the crank cross-drilled (as indicated by the red wires inserted through the oil holes) to provide constant oiling through all 360 degrees of crank rotation.

The 390 and 401 engines have forged rods (most other AMC engines use cast rods). Due to the change in deck height from '69 to '70 models, there are two different length rods: '68-'69 390 rods (left) have 5.790-inch center-to-center lengths, while the '70 design (right) is 5.858 inches long. AMC factory-forged-rod failures are rare; just rebuild the big-end and remove any excess flash.

Indy closed up the rear-chamber wall between the valves to yield superior quench. The KB piston (right, compared to the old Speed-Pro replacement forging, left) has a step that keeps the mixture out of the chamber's dead area, while the large flat dish area uses the whole chamber for a good burn. The result is a tumble-and-swirl-promoting 0.030-inch quench.
About the only readily available, mass-produced high-performance piston was a step-dish KB Pistons 401 hypereutectic casting, which has a shorter compression height (CH) than a proper 390 piston. But installing the 401 pistons with a 390 crank would normally place the pistons way down in the holes at TDC, causing a drastic loss of compression and quench. Brandes' multiprong solution: 1) Mill the existing 401 pistons (PN KB392) approximately 0.035 inch, reducing the 1.51-inch compression height and -17.3cc dish volume to 1.485 inches and 8 cc's, respectively. 2) Heavily mill the late tall-deck block deck to yield a 0.015-inch piston-above-deck height. 3) Install a 0.040-inch-offset bushing in the late 5.858-inch-long rods' piston-pin ends to obtain a final 5.898-inch center-to-center rod length. The bushing doesn't excessively thin the rod's small end because the KB pistons are designed to use smaller 0.927-inch-od small-block-Chevy piston pins. By the time you read this, KB should have a dedicated long-rod 390 piston designed for use with either a bushed long factory rod, or (if the crank's rod journals are machined to 2.100 inches) commonly available aftermarket 5.85-inch-long Chevy rods.

AMC 360 Engine Build - 370-Inch 480HP AMC

Parts List Combo One
Part PN Source Price
AMC Block N/A Pick Your Part $89.00
Performer RPM Heads 60119 Edelbrock $1,519.90
Air-Gap Manifold 7531 Edelbrock $272.95
Distributor 8523 MSD $353.88
Connecting Rods 2-ICR-6000-2000 Scat $379.00
Rings 5525 Hastings $160.43
Small Cam 17-UH4-UH9 Lunati $185.00
Intake Gasket 800G Mr. Gasket $11.95
Head Gaskets 8266PT-1 Fel-Pro $22.69
Engine Gaskets KS2002 Fel-Pro $63.99
Spark Plugs R5671A-9 NGK $20.00
600 DP Carb 0-4776C Holley $299.88
Shorty Headers 65912 Edelbrock $363.39
Plug Wires 31199 MSD $74.88
Rocker Arms 133021 Ford
$167.31
Oil Pan 30260 Milodon $315.95
Oil Kit 24050 Milodon $270.39
Pistons Custom Lunati $750.00
Valve Covers AMC Indy Cylinder Head $255.00
Rings 2M5524 Hastings $160.43
Engine Bearings AMC 360 Clevite $116.29
Pushrods PR750S Elgin $19.04
Water Pump AMC 360 Chrysler
$45.17
Balancer AMC 360 Chrysler $72.40
Oil Galley Lines N/A Earl's $35.20
Timing Chain AMC 360 Chrysler $48.99
All Labor Performed by JMS Racing Engines, jmsracing.com
Blueprint Block $450.00
Weld Rods $98.00
Assemble Short-Block $250.00
Offset-Grind Crank $250.00
Balance $175.00
Total $1,223.00
Big Total $7,296.11

Full article can be found at:
http://www.carcraft.com/techarticles/ccrp_0601_amc_360_engine_build/index.html

Building an AMC Brute
500 lb-ft and 484 hp From the Ugly American
By Douglas R. Glad
Photography by Bill Tichner

Want sick power from a basically stock engine? Try a 401. Using factoryheads on the portly 4.170-inch bore, you can build torque where itcounts and still make good power on top with a reasonable cam, goodvacuum, and off-the-shelf parts. In the case of the buildup we'reoutlining here, the payoff was 484 hp at a streetable 5,600 rpm andnearly 500 lb-ft of torque at 4,600, with more than 450 lb-ft from 2,500to the horsepower peak.

With the help of JT Payton at Payton's Performance, Holley MarketingManager Bill Tichner did all of that. His goal for the 401 was to use asmany stock parts as possible and create as much power as possible whilestill maintaining at least 13 inches of vacuum for an aftermarket fuelinjection system to come later. The performance key to this engine is heavy port work on the iron heads, attention to the oiling system, and a couple of other tricks we will outline in this story. This engine’s destiny is to be stabbed into an AMX, and with a little shot of spray, lift the wheels at its favorite track.

The Block
The practical limit of the plebian AMC 401 is about 500 hp at 7,500 rpm.The main caps will begin to walk above that, so limit these engines tohealthy street mills if you want to keep the price down and use stockparts. Just because we're interested in this kind of thing, we foundthat with an available four-bolt main kit, you can go to 700 hp and9,500 rpm for the full-race Chihuahua. Whee. But this is a streetengine, so Tichner used a post-'70, tall-deck block bored 0.030-over for4.195 inches and used the stock two-bolt main caps with big-block Chevystuds from ARP.
We'd recommend using the stock bore if you can. Payton's says the highnickel content in these blocks makes them resistant to wear, and0.030-over is on the limit of the 401's block design. So if you don'thave to bore, hone it and move on.

The Rotating Assembly
Lots of goodness here. The stock rods and crank on all AMC 390 and 401engines are forged from the factory. To keep them working, Payton's shot-peened the stock 5.85-inch rods to relieve stress and used a pressed piston pin for street durability and low bucks. For full-tilt mills, Payton's uses a 6-inch Chevy rod and turns the rod-bearing journal down to 2.100 inches from the stock 2.248 for reduced cylinder-wall loads and 7,500-plus-rpm capability. Taking no chances, they use ARP rod bolts as well.
The 401 crank has a 3.68-inch stroke and is more than manly enough with just a polishing of the journals and chamfering of the oil holes to live. It's worth mentioning that the '72-and-later 401 crank had a Torque Flite 727 flange, so look for the casting number 812-0510 or you will have to modify the flange to get it to work with a modern automatic.
We asked a couple of builders about off-the-shelf pistons and got head scratching and thinking but no part numbers. This engine uses a custom Lunati aluminum-alloy forged flat-top for future use of race gas and nitrous. At around $640, it is the most glaring expense on this engine. The slugs have a 1.48-inch compression height with two 17-degree valve eyebrows spaced 1.590 inches apart with a total of 11.23 cc's of relief. With a 0.043-inch thick gasket, 0.020-inch deck clearance, and the 64ccheads they're good for 10.0:1 compression.

Cylinder Heads
There are Indy and Edelbrock heads available for the AMC, but Tichner wanted to use the stock dog-leg heads. The cork in their design is the intake runner and the exhaust-port-to-header match. Payton's put in about 11 hours of work to cut the stock valve seats and fit a set of2.08 intake and 1.625 exhaust valves and raise the intake runner. Payton’s machinists are careful to avoid the intake floor, because past experiments found that changes there actually hurt airflow. Extensive work in the combustion chamber was performed to unshroud the valves and open the chamber from 58 to 64 cc's. This was also helpful in reducing the compression on this engine to run on pump gas. The final flow numbers were 279/210 cfm at 0.700-inch lift at 28 inches of water. Those are big ports for a cast-iron street head.
Dyno Chart
RPM HP TQ
3,500 309 464
3,600 322 471
3,700 331 470
3,800 338 467
3,900 346 466
4,000 356 467
4,100 366 469
4,200 378 473
4,300 394 481
4,400 409 489
4,500 423 493
4,600 436 498
4,700 445 497
4,800 450 492
4,900 454 486
5,000 457 480
5,100 461 475
5,200 467 472
5,300 472 468
5,400 478 465
5,500 482 460
5,600 484 454
5,700 483 445
5,800 474 430
5,900 469 417
6,000 469 411
On the exhaust side, the rough casting was cleaned up and the headerswere port matched to the heads. Early Super Comp 17/8-inch full-lengthheaders for the '68-'74 Javelin/AMX and '74 Matador need to have theflange opened up a bit to match the exhaust port, but new headers ofthis design should already be modified to fit.

Carb And Ignition
This engine was built with the future installation of Holley's Commander950 MPFI kit in mind. It has a single-plane manifold and throttle-body included. For the dyno run, Tichner used a manifold that is similar in design from Herman Lewis Racing and a 950-cfm Holley HP Series mechanical-secondary carb. The cfm might seem a little much, but this engine is going into a light AMX that will likely see more WOT on the track with a plate of nitrous than street cruising. According to Payton’s dyno sheet, the A/F ratios were correct for this size carb on this combination.
MSD offers both a standalone ready-to-run distributor and the Pro-Billet that requires an MSD 6-, 7-, 8- or 10-series ignition to operate. Both come with a vacuum advance and replace the stock points stuff. Tichner chose the Pro-Billet and a set of Autolite AR52 racing plugs to spark itall.

Cam and Valvetrain
The cam was a sacrifice to get some vacuum at a loaded idle. It is a Lunati hydraulic flat-tappet grind with 230/235 degrees of duration at0.050, a valve lift of 0.0523/0.0540, and 108 degrees of lobe separation. The full-kill cam is also a Lunati grind, but it uses a solid lifter and has 249/259 degrees at 0.050 and 0.579/0.598 lift with the same lobe separation angle. It will sacrifice more idle quality and vacuum but would likely crest 500 hp on this combination. The rocker arms are aluminum rollers made for a Ford 260-351W but useable on the090 and 993 castings with Lunati springs with 105 pounds of seat pressure at 1.80-inch installed height.

The AMX
Ultimately, the engine is destined for Tichner's AMX. We'll let him tell its story.
I have a Torque Flite 727 that I got with the 401 out of the donor'73 International Travel-all, but I am not sure if I will build it or something else at this point. I still need to build the rear-end to handle the power as well. I know I want 3:55 gears and probably a 2,500stall since the torque comes on immediately from this motor. The car was originally a 390-cid car. I bought it with a 290 and then put ahigh-compression 360 in it during college. Now it has the 401. I am going with the multipoint EFI so the factory hood will be able to close. You can't get this kind of power out of an AMC and keep it under thestock hood with a carb."

Tips and Tricks
It's no secret that the AMC V-8 has a failing in its lubrication system. Oil from the pickup travels through a passage on the oil-pan rail into a pump with an aluminum housing that tends to wear, then to the filter, and finally to the main oil galley. It's nowhere near good enough for even a stocker, in our opinion. The solution is the Milodon single or dual pickup that bolts directly (and conveniently) to a Milodon deep-sump oil pan. It bypasses the stock restriction and nearly double soil flow to the filter and mains. Payton's adds a filter before the oil reaches the pump gear in conjunction with a direct-oil feed from the main galley in the lifter valley to the rear main bearings, because on a stock AMC, they're the last in line and tend to fail during high-rpm use.
Stock AMC oil-filter adapters are made of aluminum, and the pump-gear face rides directly on the housing and wears it down. Fortunately Speed Pro sells a replacement kit for the oil-pump gear assembly and pressure spring, and we've seen the 340/360 Mopar service replacement housing being used for 390/401 performance applications, so look to Jeeps fort his part.
Payton's Performance AMC Engine Build Specs

Part Mfr. PN
Block AMC Stock
Main studs ARP 135-5002
Main bearings Speed Pro 4950 M
Crank AMC Stock crank
Rods AMC Stock (5.858)
Rod bearings Speed Pro 8-3385CP
Rod bolts ARP 114-6002
Pistons Lunati custom
Rings Speed Pro R-9349 35
Pin AMC Stock
Pan Milodon 30260
Oil line Milodon 24050
Oil pump Speed Pro 224-51285
Timing cover AMC Original
Cam Lunati 31799
Cam bearings Speed Pro 1401 M
Lifters Lunati 71963
Springs Lunati 73126
Rockers Lunati 84161
Valves int. Milodon 45027-8
Valves exh. Milodon 45047-8
Heads AMC 1973
Head gasket Fel Pro 8266PT1
Headers Hooker 7103-1
Intake Herman Lewis Racing call
Intake bolts ARP 414-2001
Carburetor Holley 0-80496-1
Distributor MSD 8519
Spark plugs Autolite AR52 Racing
Fuel pump Holley 12-802
Valve covers Payton's Performance call
Damper ATI 917943
Crank pulley Moroso 64100
Water pump Milodon 16270
Timing chain Milodon 15000
Oil line to rear main:
3/8 NPT to 8-AN, straight Earl's Performance 820108ERL
3/8 NPT to 8-AN, 45 deg. Earl's Performance 824508ERL
Perform-o-Flex hose Earl's Performance 403008ERL
Payton's Performance
www.paytonsperformance.com