View Full Version : Performance AMC blocks

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10-29-2005, 03:28 AM
What we need now is brand new, cast iron, performance engine blocks, heck Shafiroff is casting SBC blocks with a +1" deck height, MC ought to be able to do the same for us! :lo1l:

11-08-2005, 12:21 PM
That would be nice.

An all new AMC cast iron block with lots of meat so that we can take advantage of the large bore spacing. In my dreams I can see 500 cubic inch AMC motors in every Jeep and AMC car.

Of course this new block needs to sell for 1/2 the price of a new Indy aluminum block and have options for increased deck height and crank to cam bore spacing so it can go with a huge custom stroke crankshaft.

I want one.

11-08-2005, 01:51 PM
Heck, I'm not even worried about making large displacement, the AMC V8 is a small block, after all. But I would like to see something with a little more deck height and be heavy duty enough to withstand sustained high rpm operation. You getting this, MC? :mrgreen:

11-18-2005, 12:45 PM
...and what exactly do you think is wrong with the 401 block design??

What do expect to achieve with the taller deck??

What do you think is so great about 500 cubes?

In case you didn't know, there was a ProStock racer named Shirley Shanahan (spelling?) back in the 70s, with '70s technology, that was turning 9.8 sec @ 139 MPH with a 2500+ lbs. AMX and an iron headed iron 360 inch AMC. Somewhere around 720 HP.
That's around 2 HP per cubic inch. Not too shabby for a stock-block, stock-headed, carbureted engine with a points distributor and no nitrous.

* 9.89@139MPH, 2520 lbs.
* 401 + .022" (4.187")
* Moldex 401 crank de-stroked to 3.26", 6.19" SBC rods, 302 SBC brgs.
* Piston specs????? (probably SBC)
* Offset guides, 2.165"IN, 1.86"EX,
* .628" lift, 324 duration.
* Pair of Holley 750 Double Pumpers.
* 40 lb. flywheel, 5.12:1 gear.

My '69 AMX was going 9.88 @ 128 with a 401/automatic and a single carb, no nitrous, and iron block & heads. That's well over 600 HP.


11-18-2005, 12:49 PM


11-18-2005, 01:08 PM
Nothing is wrong with the factory block but it is only good for a limited amount of cubic inches.

I am running 9.80's now at 135.5 mph with a factory 401 block and Indy SR cylinder heads....so I am running faster and at a higher mile per hour than your example you are giving.

Why would I want the cylinder block you ask.....because I want more cubic inches than a stock block can supply. Cubic inches is horsepower and torque.

There is no replacement for displacement....and I want all I can get.


11-18-2005, 01:21 PM
...and, there was a fellow named Mark Donohue who drove a Penske AMC to several TransAm championship titles, with iron AMC block and heads.

And there was a fella named Bobby Allison who raced NASCAR's top series with iron AMC block & heads. Underfunding allowed only one win, as I recall, but the AM engine went 500 miles at 8000+ RPM for at least a couple of seasons.

There was also a guy named Breedlove who drove an AMX with iron heads & block to 106 speed records, including a 189 MPH top speed record. In the early seventies. Carbureted & points ignition.

The AMC design is hard to improve on. All the aluminum "race" heads available, and fully ported & prepped iron heads still make as much (or nearly) power. Definately not cost effective horsepower gain to buy Edelbrock or Indy heads. The Edelbrock heads won't even take as large a valve as a stock head will.

About the only notable weak point is in the oiling system. That should be adressed in any high output build anyway. Waiting to see the Bulltear dry sump pan rite now.

11-18-2005, 01:37 PM
Shirley Shahan (Drag-on-Lady) ran an SS/AMX. These had specially prepped 390s, bored .030 over. They ran a cross-ram intake and dual quads. The heads were also highly modified with 2.080 intakes and 1.74 exhaust valves (even square ports). Still respectable with an all iron engine.

The Drag-on-Lady race car may be on display at the 2007 AMO show in Denver, and do some passes at Bandimere. We're still working out the details.


11-18-2005, 01:50 PM
First of all, you are not playing by the same rules that the example was, 70s ProStock. Very limited rules, only 360 cubes, stock chassis. Limited ancient tech. 2500 lbs min. No NOS.

Second, more cubes does NOT equal more HP in all instances.

Increased bore size actually makes peak HP go DOWN, while increasing torque.

The only benefits of more cubes are:
* You can use larger valves if you can build some heads with more distance between the valves (good luck).
* More torque.
* If you are going to use NOS, turbo, or supercharge, you don't need to rev as high to make th big numbers (like a small cube engine)

Smaller engines (can) rev higher than bigger engines and HP is made at higher RPMs. (why do you think the 302 Z28s were fast?) The limit is when the bore gets too small for the needed valve sizes. That's why the Japs went to 4 valve heads. I think there's several hundred front-wheel-drive four-cylinder cars that would make you load up and cry all the way home. I think they are in the high sixes now. So much for comparing apples to oranges.

The example of my AMX is a 3000+ lb stock chassis car with bolt-ons, and NO NITROUS, no non-amc rods, pistons, block, or heads. Adding 350 HP of nitrous could bring that ET down to the high 7s or low 8s, with traction & gearing dialed in.

I noticed you did not reveal how much your car weighs, or if it has a tube chassis, or how much NOS you are using, what rod/piston combo is. It would be faster with a smaller engine revving higher.

11-18-2005, 02:02 PM
Argue with HRM!!!
December 1971, Hot Rod magazine

Look at what AMCs up to...again. Shirley and N.L. Shahan trade in their successful SS/D AMX for a team of all-AMC small-block Pro Stocks
By Steve Kelly *

One of Shirley Shahans brighter qualities is that when she steps out of
her race car, onlookers are often set to wondering how such a pretty, pert and fetching young lady is able to be at least as good as her male competitors. One of the reasons is that her car is well-maintained by her husband, H.L. Shahan. H.L. is the only moniker most racers know him by, and the initials certainly dont stand for "Hard Luck". Back in 1965, Shirley took the H.L.-prepared Super Stock Plymouth to a Winternationals eliminator title. When the pair switched over to American Motors products in 1969, it wasnt long before Shirley established new D/Super Stock records; and when they were broken, Mrs. Shahan set new marks for the same class in 1970. While Shirley is able to effectively get grease under her fingernails, she has found it best to leave the super-wrench work to H.L. And now, with a Gremlin and two Hornets running as a promotional
effort for AMC dealers, H.L.s work has been aided by the talents of Paul Phelps and Louie Wlosinsky, both employees of Landrith Corporation, a small race car prep shop near Detroit. Dave Lan+ith, former manager of Hurst Performance, just happens to be one of the organizers behind the promotional program for the AMC dealers.

The AMC-dealership-backed drag team is meant to be a means of impressing potential customers in,each of the 21 American Motors sales zones. Naturally, a good amount of help was rendered by the AMC engineering department to make sure the cars perform as well as possible. The efforts have been rewarding. Best time-so far-on a Hornet is a 9.89-second e.t. and a speed of 139.52 mph. The Gremlin cant get close to the Hornets, its best performance being a 10.01-second e.t., with a top speed of 137.20 mph. One of the advantages the Hornet body has is its longer wheelbase and greater rear overhang, which help to get the car off the line quicker, due to more and better weight transfer to the
rear. Ironically, when the cars are run "below weight" (i.e., below NHRA Pro Stock minimum), neither car runs equal to the times turned in at their legal Pro weight. The Gremlin can run with a weight of 2220 pounds, and the Hornets, owing to a lot of "metal thinning", come in at ten pounds less. Legal NHRA weight for the 360-cubic-inch-displacement American Motors cars is 2520 pounds. The Gremlin is used most often as a match racer for special outings, and the Hornets are put to work as showcase match
racers and as entrants in national events.

Except for wheelbase and body configuration, the Shahan cars are identical. The chassis work is quite refined. Front suspension is coil-spring-type, with each spring specially wound from .238-inch-diameter wire in a three-inch-wide coil. The left rear spring has five leaves, while the right has six. Each rear spring is 1% inches longer than stock, and theyre moved inward, for an increase in car height and also for tire clearance. The leaves now are shackled to the sub-frame rails, rather than bolted to their sides. Rear spring rate, at the wheel, is 145 pounds per inch on the right, 135 pounds per inch on the left. No traction bars are employed, and the rear axle housings are super-tough Danas with 9%-inch-diameter ring gears. The housings are narrowed 6% inches. Rear gears are 5.12:1,
axles are from Henrys Machine and Detroit Lockers are used. The only change made to the front end, besides the new coils, is shortened upper A-arms so that each car rides with 7%-degree positive caster, meaning that only the outside edge of each front tire is pushed against the track. Shocks are Hurst/Gabriel, the rear ones located aft of the axle housing.

Steering units are from a 65 Corvair (aluminum box), and there are lots of wheel turns from lock to lock to negate chance of driving a crooked "straight" line by accident. Air-heart disc brakes are fitted all the way around, front rotor diameter being 9~/y inches and rear 11% inches. Each car has a Line-Loc, but this is used mostly to warm up the rear
tires in the staging area. The brakes are one of Airhearts "Pro Stock Kits", and the saving in weight is 16 pounds.

A stock six-cylinder model drive shaft has performed with no sign of twisting and no breakage. Transmissions are Borg-Warner Super T-10s, modified by Doug Nash and equipped with Hurst changers. Between each engine and gearbox is a 10'/y-inch Schiefer clutch (Borg & Beck style) and a 40pound steel Schiefer flywheel. Rellhousings are Lakewood hydroformed steel safety units.

The chassis have been highly detailed for the cars ten-second workouts, and the engines have been well-built by H.L., working closely with the AMC engine wizards in figuring out a few new techniques. For instance, only the concave surfaces of the intake ports were polished. The convex surfaces were left in stock finish. Factory tests showed a drop in horsepower when the entire port was mirror-polished. Even though the engines measure 360 cubic inches, they dont share bore-and-stroke specs with stock AM 360 V8s. The bore now is 4.187 inches, an increase of .107-inch, and the stroke is reduced by .18-inch to 3.260 inches. The crankshafts are by Moldex, made from 401 AMC VS forgings, and have been Tuftrided. The journals have been cross-drilled for better oiling, and Federal-Mogul F77 bearings are used.

Bottom ends are reinforced with Milodon 392 Chrysler four-bolt-style main bearing girdles adapted to fit. (Reportedly, the switchover is fairly easy.) Compression is close to 13.7:1, and a new-design dome Venolia piston is now in use. Rod length, center to center, is 6.190 inches (stock is 5.875 inches), but this is not a Chevy rod despite its same length.
Twelve-point, 7/16-inch rod bolts are used on the shot-peened and polished, forged-steel Carillo rods that use bearings "adapted" from a 302 Chevy V8. Crane roller lifters run on cams of the same make, lifting .628-inch at the valve. Opening duration is 324?. Offset valve guides are used in order to use larger-diameter valves. This is a tricky maneuver, but worth the time and labor. Intake valves are 2.165 inches across; exhausts measure 1.860 inches, come from TRW and are suspended by dual (inner damper) springs by Crane. The 1.6:1 ratio rockers are Crane-made, forged-aluminum and needle-bearing-bushed. The relatively high compression dictated 0-ringing the heads.

The likeable Mrs. Shahan hasnt been spending much time at home, nor has she been taking very long to traverse the 1820. No doubt a large number of her drag racing foes would prefer that she stay home with the laundry and cleaning, but chances of her trading a gear-shift handle for a vacuum cleaner are remote.
Rear weight bias for both Hornet and Gremlin should be about 54% to the rear for cars to run equal with same weight.

BELOW-Interior is free of nonessentials. Its furnished with a blonde and S-W gauges.

ABOVE-Intake manifold is individual-runner type, specially fabricated by AMC. Two types of Holley carbs have been used: 4500 I-R and 4700 series double-pumpers. The 750-cfm-size double-pumpers work best at present time.
LEFT-Arrow indicates frame rework so that springs could be moved in for tire clearance and chassis lifting. Note the gusseted housing and Airheart discs.
BELOW-Shirley does her own wheel-lifting thing with 9.89 Hornet.

11-18-2005, 02:06 PM
I am defintely not saying that you can't make power with iron AMC OE stuff, you can.

But it is a proven fact that if you want to make lots of power there is no replacement for cubic inches. You don't see modern pro stocks running small cubic inch engines do you ? No....they run as many cubes as legally possible in their class.

Another thing is making reliable horsepower. You have to spin a small engine hard to make as much horsepower as a larger cubic inch engine.

As far as the Iron heads outflowing the race oriented (not edelbrock) Indy 401-1 or Brewer heads....they are not even close. The 401-1 Indy heads flow right at 400 cfm and the Brewer heads even more than 400cfm.

That much head flow needs more that 400 cubic inches to take best advantage of it.

A fully worked AMC iron head can be made to flow around 300 cfm or so but that is with a HUGE amount of work that is not cost effective compared with the Indy 401 SR (stock replacement) head. The 401SR (stock replacement) head can be made to flow around 350 cfm with a max port job. But they will flow 300 or so cfm with just a moderate cleanup of the ports. By the time you payed for a professional to max out the Iron head you would have more money in it than a set of Indy SR heads cost.

If you want an AMC Iron head to flow more than the 300 cfm ballpark the only way to do it is with the cut them up...section out multiple castings and weld the pieces together tricks like Wally Booth did. Again not cost effective with modern Aluminum race oriented castings on the shelf for sale.

11-18-2005, 02:16 PM
I am not going to debate you. I don't like typing that much.

You are stuck in the old technology days of the early 70's. There is a lot more available than that now !

I am not going to be stuck in the 9's forever. Next year I am planning on running in the 8's with no power adders whatsoever and I am going to do it with 500 cubic inches and big flowing cylinder heads. And I will do it realiably turning a lot lower rpm's than a smaller motor.

No I don't run any power adders what so ever...no NOS, blower, or turbo...it's motor only....405 cubic inches with a flat tappet solid lifter cam. My car is a backhalfed Spirit that weighs in at 2840 pounds. And I built it all myself !

11-18-2005, 03:13 PM
Not stuck in the old technology days, not hardly.

But I am very proud of what the AMC designers created and I like to display it for all to see. Anybody can burn up bucks like the bowtie or ford guys have to.

I guess it just depends on what you are wanting.

Looks like you are going racing, while I am going street machining.

A low ten street AMX is fine for me. Having it all AM, and using "period pieces" (like the Ultra Ram, R4B, & Street Ram) is icing on the cake.

The 401 can put out around 600 HP with AM heads, crank, block, rods, & without any high buck mods, and stand up to around 1000 HP when sprayed. That get's you into the 9s before spray.

The thing you are getting from more bore is more torque, and at a lower RPM, as the horsepower decreases, and at a very high cost (if using Indy heads or the Indy block). That's all I'm trying to say about that.

Any Dyno program (most are pretty reliable) will show that the HP goes down as the cylinder size (or stroke) goes up, all other input variables remaining the same. The power band goes down (to a lower RPM), the peak torque reading increases, also at a lower RPM. The opposite is also true, to extreme RPMs that are unreachable. Tho I do know a guy who ran his all AM AMX over 9000 RPM (he never made a full pass w/o blowing something up).

Personally, I stay away from any special combos made up from Chevy or Indy parts, etc., and stay with what AMC designed so well. The fully ported Indy SR heads flow only slightly better than fully ported AMC heads until the valve is over .600" lift, and then they get a bigger advantage. Pretty expensive per HP cost. Especially when you figure the added expense of lifting the valve to .800" or more. I'd rather save that money and put it towards the other AMX, or any of a thousand other areas it can be spent.

But then, I like "old technology" AMXs, too. Nothing like a stock appearing motor, that puts out 600 HP (950 if sprayed), to show to the boys after dusting them.

Not arguing with you, we all are here because we like AMC. You are using aftermarket & I like factory. So be it.

11-18-2005, 03:21 PM
Not arguing with you, we all are here because we like AMC. You are using aftermarket & I like factory. So be it

I couldn't agree with you more !

I wish you the best of luck blowing away the Fords, Chevies, and Mopars with your AMC.

I love the look on the other guys faces when an AMC beats them !

Have a good one !


11-19-2005, 03:17 AM
Boy...I sure didn't mean to start a fire there :mrgreen:
I would just like to see a solid, performance oriented, stock dimension (maybe a little more deck height, for improved rod angle, not more inches), cast iron block. Face it, guys, when you are racing,sh!t will break sooner or later, and the supply of blocks is far from inexhaustible. With all of this renewed interest in AMC, I see the supply of 401 blocks drying up quite soon. Even those blocks are only good for 750 hp (or less) in sustained operation, such as in the roundy- rounds or road racing.
We need a solution that is more practicle than $4200 aluminum blocks. :-|

John Martinez
12-07-2005, 11:17 PM
Larry Wycoff, is getting in excess of 800 HP out of stock block sleved and bored to 440 slug. He is using MOdex crank with 4" stroke. He get like 440 cubes or a little more. At 8500 rpm he is putting out in excess of 800 HP no adders.

But larry is going to go Blow Alchy and he will be using a 550 cu in hemi to get there. Even though Indy has offered him an alum block he feels more comfortable with the hemi platform due to past uses and aftermarket knowledge. This will be dropped into his tube chassis with AMC body.

Good luck to both of you. You both are doing AMC proud. Now if hankrod pumps up the turbo all bets are off.

12-07-2005, 11:44 PM
Now if hankrod pumps up the turbo all bets are off.


12-07-2005, 11:45 PM
We have a guy here locally that runs a 1400hp AMX. I think it may be the fastest AMX I have ever seen. He has a blown Hemi in it and probly 80K into his motor. I think he is still married as well :?:

12-11-2005, 08:39 PM
A stock replacement block in 401 would be excellent!

Then I could just get a new block and go standard bore with the new pistons and rings instead of searching for .010 or .020, dang I hate going .030 :smile:

12-12-2005, 04:58 PM
Dang somebody beat me to the punch. I was thinking that the last time I checked 401 wern't that plentiful. I would be nice to get a cast iron block that you didn't have to roll the dice on. No more having to dig thru junk yards you could just pick up the phone order one. May be even start under bore and have the buyer machine what bore they want. Just and Idea or maybe I'm 111!!! .

12-15-2005, 09:33 PM
Since chrysler bought amc, wouldn't they be the ones to ask? Maybe the service replacement block?

12-16-2005, 04:15 AM
I somehow don't think Der Chrysler is interested in reviving the AMC V-8. They want us to buy their POS "Magnum" 360 crate motors. Personally, I'll switch to Chevy long before I will ever run a small block Dodge. 8)

12-22-2005, 07:07 PM
I somehow don't think Der Chrysler is interested in reviving the AMC V-8. They want us to buy their POS "Magnum" 360 crate motors. Personally, I'll switch to Chevy long before I will ever run a small block Dodge. 8)
What I ment was to find out if they still have the molds for the 401's, or the service blocks. If they won't make them, then someone else could. Someone could also make a semi finished forged crank, then the rod journals could be ground to any engine or stroke spec.

12-23-2005, 06:11 AM
Sorry for ranting there, what I meant to say is that I suspect that DC would destroy that tooling rather than let someone make products that would compete with what they are trying to sell, despite the fact that most of us would opt for something other than Dodge small blocks in the absence of AMC engines

401 Pacer
08-05-2007, 11:37 PM
Sorry for bringing this long dead thread back to life (no, not really), but some points to ponder.....

Tall decks and long strokes increase piston speeds (but decrease rod angularity). Something to watch out for. Haven't done the math, so this may be a non-issue, just rattling everyone's cage when it comes to "more is better" (it isn't always).

Didn't Mother Mopar release a 401 service block recently?

08-06-2007, 09:12 AM
No service block and only rumors of interested parties. I think the ultimate block would be a thick cylinder wall block with 4 bolt mains on at least the middle three mains and a little better oiling program with the ability to bore out to 4.375 yet you can start with a stock 304 bore.

09-09-2007, 08:26 PM
No service block and only rumors of interested parties. I think the ultimate block would be a thick cylinder wall block with 4 bolt mains on at least the middle three mains and a little better oiling program with the ability to bore out to 4.375 yet you can start with a stock 304 bore.

jeeps4ever. I agree with your statement. That type of block would be perfect in todays world. Also, with todays metallurgy, a much stronger block. One more thing I would add would be to add more material to the block to able to drill deeper into the block for the head studs to avoid distortion when clamping the head one. Todays pro-stock motors are like that. old_and_rusty

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