Stroking a 401

[Gremlin4ever]

Muscle Car Review, annual 2005 and is to be displayed until March 14, 2006


Get this issue fast! It has an AMC 401 build up with 498 lbs-ft of torque! Though it is at 4600 rpms it is a very interesting read.

[Briteblock]

You guys stroking to 3.850? Carrilo makes a nice rod that takes a small honda bearing like MC was talking about. I am at his shop and am a welder here...he has a 401 on a stand and I think its a stroker. MAybe with enough probing we could get him to give up all the info

[thigh19]

What about an offset grind to the Crank?

[J20]

I'm back and work continues on the bored/stroked 401. I'm building the run stand now. I want to run it in the garage first. I installed the Milodon external feed oil pan (one line), a dual remote oil filter, a Powermaster 140 amp alternator, a BeCool aluminum radiator with dual electric fans, a Flow Kooler water pump, a AGR power steering pumb and Super Box 2. The Edelbrock Pro Flow Multi Point EFI looks awesome, as do the classic finned aluminum Edelbrock valve covers, I do need to order the control chip from Edelbrock. I also finished the Dana 300 with a 4:1 gear set, 29 spline input and 32 spline outputs, do need a dual stick shifter. The NV 4500 is also ready to go with Advance Adapter AMC V8 complete bell housing kit. This combo just might move the J20 smartly down/off road.

[jeepsr4ever]

Loca l builder here has had GREAT luck getting 700hp on pump gas offset grinding a 401 crank and using these Eagle rods

CRS6000HJ 6.000" lightweight, 1.890" "Honda" journal, 570g $625.33

Thats 700hp with a small camshaft and not much tweaking, but thats stroking her .358"

Granted the crank will need to be ground ($600 MAX)
The rods will have to be bought ($625)
Custom pistons with lower ring lands ($800)

And this scenario will yeild 446CI at .030 IIRC

Now lets talk filling the block, over boring and sleeving + O-ring'n, 464CI at 4.28 bore.

[ericruhl]

The pistons could have been .015 taller, need to shave about that much off the top of the block.

About half of that .015 is a math error from this post.

3.82+ 6.00 + 1.275 = 11.095, not 11.102. So 11.118-11.095 = .023 deck clearance, .007" more than your expected .016. Any idea where the remaining .008" came from? Was the piston compression height off from your expected 1.275"? Sorry if I missed the answer in the thread, I didn't see it. And why did you shave the block, was it to recover the desired compression ratio?

I'm exploring options to follow in your footsteps ;) which is how I found this thread. I'm interested in offset-grinding the crank to increase stroke in combination with the 6" SBC rods to keep rod angle within reason, however I'm looking for a little more compression (~10-10.5). I'll call Wiseco to discuss a custom piston, but wanted to fully understand your build first. Currently I've come up with these numbers to get my desired CR:

Stroke = 3.820 (place holder for now, a spun bearing will limit my stroke options)
Bore = 4.190 (same as your pistons)
Head volume = 57.92cc (stock)
Head gasket volume = 11.34cc (stock)
Piston volume = 20cc
Compression height = 1.290 (1.275 + .015 from your build)

If my numbers are right, that yields 421 cu. in. with .008" deck clearance and ~10.5:1 CR. ??

Excellent writeup btw, thanks for sharing! :)

[J20]

I'm glad you spotted the error before start. This discrepancy was corrected by Wiseco when the pistons arrived. Did not have to shave block. I had 3.5 cc taken out of each combustion chamber to bring the compression ratio down to 9.3 to 1 and allow for larger than stock valves. I can't always get 91 octane gas. The piston dish could be made smaller and get a 10 10.5 to 1 compression ratio. I get some time off during the holiday and hope to start this engine on the run stand.

[ericruhl]

I had 3.5 cc taken out of each combustion chamber to bring the compression ratio down to 9.3 to 1 and allow for larger than stock valves.

Previously you mentioned "the new plan is to use a bigger intake and exhaust valve, .208 and .176". I'm guessing you meant 2.08 and 1.76, is that what you ended up with? The AMX valves were pretty close to that at 2.08 and 1.74 (assuming I read that correctly).

I get some time off during the holiday and hope to start this engine on the run stand.

Woohoo! Good luck! :)