AMC 360 w/401 Crank build up

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I have just begun another 360 build but this time I am installing a 401 crank and rods. This has been done before but, I thought that I would start a thread with plenty of photos as a reference.

Block Prep: (Before, it goes to the Machine Shop)

Pictured is the 360 block along side a 401 block. The beafiness of the 401 block webbing is noticeable. Also, the bottoms of the cylinders are notched for connecting rod clearance. So, the first thing I did was to add the clearances to the 360 block. I took careful measurements to determine where they should be and how deep they should be.


I also do the oiling mods including the internal oil line and I add oil drain back holes in the lifter galley.

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Block Prep: (Before, it goes to the Machine Shop)
One thing that I have noticed with most of the AMC blocks is that the oil feed holes to the mains are not drilled through 100% in to the lifter galley. They are like 75/95% the way through. So, I make sure to drill them all the way through.

This one may be over kill but, I never liked how the front cam bearing oil hole doesn't line up with the oil slot in the block. I usually file the bearing oil hole on a angle to line it up but this time I am doing it differently. I used my die grinder and just moved the hole towards the front a little so that there is a free path.


(I stuck the used bearing in place just so see of the passage lined up. It will be coming back out)

[tazjeeper]

nice work keep the updates and pic's comming.

[Ristow]

mine ran real strong,even with the spec flaws of the speed shop-that "did stroker AMC's all the time". and was getting real close to 14mpg overall doing it.


ran cool,and burned 87 octane no sweat.



who's doing the pistons?

[Greg Taylor]

Nice work, Rick. What's the final plan for this engine and what will it be going into?

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I can't use 360 pistons with the 401 rods due to the piston pin DIA. difference. I was trying to find stock bore Forged 401 (4.165") pistons but no one makes them nowadays. I sonic checked the block and it will handle the 4.165" bore and still have over .100" wall at the thinnest spot so, no problem there. I opted to have Bulltear make custom pistons for me at 4.155" bore with the 401 pins. This is the same bore size that I went with on the 383 stroker that I built with the +.030 400 chevy pistons. I had them put the common (less expensive) ring grooves in them so that rings won't be a problem. We are using the "502" heads which are about 60 cc and I want to end up at 10.0:1 compression ratio. The bottom line is that the pistons will be flat tops, fit a standard 401 piston pin, 4.155" bore with a slight dish to create a 10.0: compression ratio with a 60 cc head.

This combo ends up at a 399.18 cu. in. in a 360 block. Fun stuff!

[Greg Taylor]

Sounds like a nice combo, Rick. Are the Bulltear pistons full round dish or d-shaped dish?

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"Nice work, Rick. What's the final plan for this engine and what will it be going into?"

Thanks! This is a customer's engine going in to a Jeep project to play the in the sand with. It is your typical "here is a pile of parts, can you build a engine out of it?" type of project that I get. I have actually got 2 projects like this for Jeep guys. The other is a 390 block/401 crank project.

[Ristow]

i have stock bore 9.5 cast pistons in my 401. maddog racing carries them.

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Matt said that they will be "D" shapped. I will post pictures when I get them in like 3 weeks.
Yep, I buy from Maddog several times a month and use the cast 401 pistons where ever I can which are a nice product. The customer wanted forged on this one and I like conservative approach on the bore size as well as using the inexpensive chevy rings. 399 c.u. in. vs 401 c.u. in. won't make that much difference if any in this build.

[Heavy_Metal_Thunder_81]

Maybe I am missing something but if you're using a 401 crank, 401 rods, and boring it to right around 401 specs...why not just use the 401 block you had?

[dusty]

id wager the block was bored out quite a ways i've gone .060 before

but cracks happen too.

those are my 2 WAG's without knowing anything.

[austinaubinoe]

so are all AMC blocks the same? I know the 401 is really beefed up, but can a 304 be bored to a 401? Wouldn't you be worried making a 360 into a 401, I think that extra beef was there for a reason.

I was reading wikipedia and came across this: http://en.wikipedia.org/wiki/AMC_V8_...ment.22_blocks

anyone ever seen one? Sounds like a 360 thats even beefier then a stock 401. How much more do you think it actually cost to build the service block? Seems to be they would never fail, and could be rebuilt over and over!

[Ristow]

the cylinder walls tend to get too thin when a lesser displacement block is bored to a 4.165+ bore. even the 401 factory max overbore was only i recall .015".

going more than .030 over on a 401 is risky. i wouldn't even consider when for a few hundred more you can have a stroker with all the grunt and none of the heating issues.

when has anyone seen any AMC block fail?

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"Maybe I am missing something but if you're using a 401 crank, 401 rods, and boring it to right around 401 specs...why not just use the 401 block you had?"

The customer didn't have a 401 block. He just had a 360 and we were going to build a 383 stroker but, he found a 401 crank and rods. Basically, he didn't want to spend the money on a 401 block. I WAS going to bore his 360 to the 401 standard bore but no one makes forged standard bore pistons. So.... if I have to order special pistons anyway, I went with the 4.155 bore as a safety factor and because I can use less expensive chevy rings.

No, the blocks are not all the same. They DO have different jugs.

[Mark Wilde]

Originally Posted by Ristow

going more than .030 over on a 401 is risky.

I just mic'ed out the bore on my 401...appears to be .040 over.

edit: no wonder it runs so Great Googley Moogley hot!

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I have built some 390 and 401 blocks at 0.040" over with out a problem. I just built one at 0.60" over but, I sonic checked each bore before I did it. 0.030" is a good conservative approach if you don't have a sonic checker. The main thing with these blocks is to get the water passages clean. And I don't mean just hot tanking the block. The photo is how much junk I dug out of a 390 block AFTER it was in the hot tank. Most of this stuff collects around the rear cylinders. I use a long screwdriver and a flash light to dig it all out. Most of that crud is a mixture of sand casting and stop leak.

[jeepjseries]

[quote=SC/397]I have built some 390 and 401 blocks at 0.040" over with out a problem. I just built one at 0.60" over but, I sonic checked each bore before I did it. 0.030" is a good conservative approach if you don't have a sonic checker. The main thing with these blocks is to get the water passages clean. And I don't mean just hot tanking the block. The photo is how much junk I dug out of a 390 block AFTER it was in the hot tank. Most of this stuff collects around the rear cylinders. I use a long screwdriver and a flash light to dig it all out. Most of that crud is a mixture of sand casting and stop leak.

[78J-10]

Im currently building the same style stroker using a .040 over 360 block. Are the oiling mods a necessary for this storker to work? same with notching the bottom of the walls?

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I do the oiling mods on every engine that I build assuming that the customer is going to run them as hard as I do. The engine would run fine with out them of coarse. It is just good insurance to me. In this case, the guy wants the engine 7000 rpm capable.
I didn't install the crank in the block yet to see if the notches were necessary. I just assumed that they would be because it is close in a 401 in that area and I didn't want to have to grind them in there AFTER I got the block back from the machine shop. I measured from the deck surface down on the 401 block to determine how much to notch out.