Strokin and AMC 401

Jeepin'Jesse

I am in the process of rebuilding the bootom end of my 1978 401. I have been reading on the net and heard from a couple of people that it is possible to stroke a 390 or 401 with a Chevy 400 6 inch rod. From doing my homework I see that the 401 rod is 5.858" long and I have found a set of Keith Black pistons that is listed as ideal for use with Chevy rods. Apparently you just have to drill out the wrist pins to .9292"? Is this good info and has anybody seen or had this done. I realize that this will be an expensive undertaking, but I am not worried about that. Somebody on another forum told me he wheeled with a guy who had done this and he called it a 445in. AMC and it made like 500 h.p.! Any help would be greatly appreciated.

tufcj

Look at this thread in the "how-to tech" area.

http://www.bulltear.com/forum/viewtopic.php?t=1473

A local machine shop has one that's bored/stroked to 430" using Chevy parts.

Bob
tufcj

Jeepin'Jesse

Hey guys, I found another article on a website about using 360 rods to stroke a 401. I check the stats and 360 rods are about .017 thousandths longer. Does anybody think this will make a noticeable difference? It should be the same as milling .017 thousandths off the heds, right? Also, 360 rods should bolt to the 401 crank as well, right? Thanks, Jesse.

tufcj

It will all depend on the pin placement in the piston you choose, the deck height, and the offset grind of the crank. You don't want to run your piston up past the top of the block, you need to give the top rings some room, and allow for piston and rod stretch at RPM. 360 rods have a 2.095 big end - 401 rods are 2.248, so the crank would have to be cut.

ol' school power

Jeepin'Jesse wrote
Hey guys, I found another article on a website about using 360 rods to stroke a 401. I check the stats and 360 rods are about .017 thousandths longer. Does anybody think this will make a noticeable difference? It should be the same as milling .017 thousandths off the heds, right? Also, 360 rods should bolt to the 401 crank as well, right? Thanks, Jesse.

Maybe I'm reading this wrong, but changing the rod and or piston doesn't change the stroke. As mentioned above, the crank has to be offset ground to accomplish a stroke increase. The different rods and pistons are used so it all doesn't stick out of the block once the crank has been modified.

radamx

OK what I did was to have the crank offset ground to a small block chevy rod size. 2.100 which took my 401 stroke from 3.68 to 3.825. then I bought 6 inch chevy rods and custom pistons. I 1/2 filled the block with block filler and bored it .085 over to 4.250 bore this gives me 434 cid . I have heard of useing a 400 piston but I just went with a custom piston to get what I wanted. you could also grind the crank to 2.00 small journal for more stroke. I am sure there are 50 different ways to do this .I was just shareing mine Good luck.

Lifted79CJ7

Sounds like a killer setup radamx. You have any HP or TQ numbers on that thing? What cam are you running?

radamx

I have the engine at the shop right now waiting for dyno time.
duration at .050 is 274-280
kinda big for most but I plan on running a lot of Nitrous
hopeing for 600 ft torque and 750 hp without Nitrous.

Dyno results

434 Indy 401-1 heads
motor pull

741.6 HP at 7500 rpm
572 ft torque at 5800 rpm

1st stage nitrous 200 hp

942.9 hp at 6800 rpm
851.0 ft torque 5700 rpm

2nd stage nitrous 400 hp

1162 hp at 7300 rpm
1000.8 ft torque at 5800

I think the header size was to big for the best power on the motor but they worked great on the Nitrous

Lifted79CJ7

:shock: Wow, that is going to be a killer!! I would just be happy with 400hp and 400 ft/lb!!

Elliott

radamx, Tell us more... is this stroked?

radamx

radamx wrote
OK what I did was to have the crank offset ground to a small block chevy rod size. 2.100 which took my 401 stroke from 3.68 to 3.825.
then I bought 6 inch chevy rods and custom pistons.
I 1/2 filled the block with block filler and bored it .085 over to 4.250 bore
this gives me 434 cid .
I have heard of useing a 400 piston but I just went with a custom piston to get what I wanted.
you could also grind the crank to 2.00 small journal for more stroke.
I am sure there are 50 different ways to do this .I was just shareing mine
Good luck.