AMC 406 Stroker build

[BA_051]

Well my 360 was getting a little tired so I went on the hunt for 401 to drop in its place... Unfortunately, they are not easy to come by and not cheap... So instead of rebuilding my 360 with custom pistons, or spending a lot of cash for a 401 and more to rebuild it... I am building a 406 stroker from my '73 360 block... Just because I want to...

1973 AMC 360 block: Free
Vat+bore+hone+cam bearings: $250
1973 AMC Heads: Free
Rebuilt with 5000 miles on them (SS 2.02/1.74 Valves+hardened seats+bronze Guides)
Edelbrock RPM Air Gap: Free (on current 360)
Comp Cams 262XE and lifters: Free (bought for current 360 a year ago, never installed)

AMC 401 Crank: $400
Crank Grind: $200 for offset grind to 3.8" stroke + -0.010 on mains
Forged 4340 AMC 360 Rods + ARP bolts: $300
Forged Chevy 400 KB Pistons with rings (1.433" CH): $460
Main+Rod+Cam Bearings: $110
Full Gasket set + valley pan: $90
Hone SBC 400 wrist pin bore and press on new rods: $100

So a rebuilt, high compression AMC 360 stroked to 406 cubes totals...
$1910...
$550 for machine work
$960 for parts
$400 for a crank

Engine specs:
Bore: 4.125"
Stroke: 3.8"
Static Compression: 10.78:1
Dynamic Comp: 9.2:1
Deck Height:9.208"
Deck clearance: 0.000" (yes 0.000" without decking the block!)
3.8/2+5.875+1.433=9.208"

Cubic Inches: 406.26"

So I will post pics and more info as it goes together in the coming weeks!

OK so a few changes have occurred with pricing...
Vat+bore+hone+cam bearings: $230
Forged AMC Rods + Rebush: $300 + $160
Cam Kit, Melling MTA-1, $175
1.7 Roller tip Rockers + Hardened Pushrods + 7/16 Studs: $180 (THANKS RISTOW FOR THE ROCKERS!!)
401 Crank + Grind: $400 + $225
Full Gasket set + Brass Plugs + KB HyperEutectic pistons + rings + King Main/rod/cam bearings: $640

So that puts me at $2300... $400 over my initial estimate, But the Cam kit and 1.7 rockers/pushrods/studs Come to $350 and those were not in the initial estimate...

New Engine specs:
Bore: 4.125"
Stroke: 3.8"
Effective stroke: 3.66" (vs initial 3.16")
Static Compression: 10:1 (vs initial 10.78:1)
Dynamic Comp: 9.6:1 (vs 9.2:1)
Deck Height:9.208"
Deck clearance: 0.000"
3.8/2+5.875+1.433=9.208"

Cubic Inches: 406.26"

[mud89]

very interesting build !
Is it ok for the pistons valve reliefs, since they are note AMC ?

[BA_051]

From what I have seen, the reliefs are quite large and are a -18cc dish... I will check clearances from the valves and if they are to tight, I will enlarge the reliefs using a stripped head I have laying around...

It will be a few weeks before I get the crank (from a guy on the amc forum) so I have time to go over the block and get all my parts in. The max stroke I could have done was 3.890 with -0.060 rod bearings but that would leave no possible rebuild in the future... So I went with 3.8 and it worked great for getting rod+piston length.

[Full Size Jeeper]

What kind of H.P. and torque for this combo. Any idea?

[rocklaurence]

I regard to the crank, could you have offset a 360 crank to achieve the stroke and not needed the 401 crank? Plus, it was my understanding that you couldn't bore a 360 block that large w/o issues. But a very cool build. Mud Bull showed up in his Demon with a stroked 360 [406cid] yesterday

[BA_051]

my 360 block doesnt have the extra freeze plugs in the back and can actually be bored to 4.165 (stock 401) without issues. So this leaves room to to rebuild it later with 4.155 SBC pistons... And undersized rod bearings.
Stroking a 360 crank wasnt very feasible, Cast iron crank vs forged steel was reason enough for me to use the 401 crank... Plus:

390 Max stroke with STD 360 rod journal: 3.724"
401 Max stroke with STD 360 rod journal: 3.830"
The 390 is 0.106" less, the difference in stock stroke of the 2 motors.

And in terms of HP/TQ... I have no idea... A lot more than my tired 360 now for sure... Maybe if someone has a desktop dyno for some estimates...

[BA_051]

Well most of the parts are in... All the Gaskets needed, Pistons, rings, bearings, and Rods...
The rods were supposed to be for a press fit wrist pin, but i could literally press them by hand; so no good there! I sent them back for a set of floating rods with bushings already installed (for the same price) and they will need to be honed to the 0.927" chevy pin.

Just waiting for the crank to get here on the 9th... Ill get pics as soon as i get the rods back...

[Ghinmi]

It's so exciting, isn't it!

And in terms of HP/TQ... I have no idea... A lot more than my tired 360 now for sure... Maybe if someone has a desktop dyno for some estimates...

I would guess hp in the high 300s, torque... a bunch. What kind of fuel are you planning on running?

[SC/397]

4.125 bore in a 360 is very conservative. Should be a nice torque machine though.

[BA_051]

Yea I wanted to be a bit conservative on the bore... So I left it open for a rebuild in the future...

As for fuel... with the timing just right, it can run on 89 because of the cam... I havent decided yet...
Comp Cams XE262H
summit K8600
The k8600 has a bit more duration on both the intake and exhaust and larger separation... It might be a better match for this build...

Either will put the dynamic compression at 9.0-9.2:1 so I can run 91/93 octane fuel without issues...

[Strode]

Yea I wanted to be a bit conservative on the bore... So I left it open for a rebuild in the future...

As for fuel... with the timing just right, it can run on 89 because of the cam... I havent decided yet...
Comp Cams XE262H
summit K8600
The k8600 has a bit more duration on both the intake and exhaust and larger separation... It might be a better match for this build...

Either will put the dynamic compression at 9.0-9.2:1 so I can run 91/93 octane fuel without issues...

I have the XE262 in my 401. I like it, but I don't have anything to compare it to. I'm at about 9.1:1 compression too, and it has a nice torque line. I run regular gas just fine.



The Summit cam has a very bad reputation around here. The Melling MTA-1 has a good rep. I actually have a brand new MTA-1 that I bought in a box on the shelf. i was going to experiment with it and see how it compared, but I haven't gotten around to it.

I think you'd be happy with the XE262 over the Summit. And if you go with a 'smaller' cam, get the Melling (or equivalent, like the Edelbrock) and avoid the Summit cam.

[Ristow]

you couldn't pay me to run another 8600 cam.

i'd go a bit milder on the cam,and run 1.7 rockers. altho with your static compression you may run into issues with dynamic with a milder cam.

i had 9.5 comp pistons in my 401,zero deck at tdc,it would run 87 octane. altho,i did not cc them nor the heads to see what i actually had. i ran a mta1 with 1.7 roller tip rockers. i liked the combo.

[BA_051]

Such a wealth of information from you guys... I was leaning towards the 262XE...

How would the mta-1 with 1.7 ratio compare to the 262 with 1.6's? I am running 118-120 lbs seat pressure on my heads...

[BA_051]

Static Compression Ratio: 10.78:1
MTA-1 Specs, Intake closes 27 degrees ABDC

-Effective stroke: 3.66 inches.
-Your dynamic compression ratio: 10.42:1 .
-Your dynamic cranking pressure is 223.00 PSI.

XE262H Specs, Intake Closes at 57 degrees ABDC

-Effective stroke: 3.16 inches.
-Your dynamic compression ratio: 9.13:1 .
-Your dynamic cranking pressure is 188.48 PSI.

So I think the MTA-1 will be a little to mild for my build...

[Ristow]

the 1.7 rockers increase lift with nil effect on duration. how high are you going to be revving this? don't over cam for what you are doing. a big cam will give mopre punch higher in the rpms,but it will shorten the overall power band. i like torque right off idle and thru the rpm range so i go mild. your compression is going to limit how mild you can go tho.