ready to have 401 short block built, need advise.

willysworker

I have a orig. 401 short block ready to rebuild. I want a mild RV type build for my Willys/Wagoneer 4x4 project( http://www.cardomain.com/ride/2451568 ) which has a tired short block AMC 360. My replacement 401 block is stripped, cleaned and been OK'd with inspection. Jones engine in Spokane will do machine and short block assembly. I'm going to do the rest.

Here is my question? Machine shop says only pistons available for 9/1 comp. are 30 over. I'd like to go 10 or 20 if possible but need a source for these pistons. I'm planning on using stock 401 heads.
Also, what is the best low rpm cam. I have Edelbrock cam, roller timing, intake manifold and carb. on my current 360 that I was going to reuse. They have about 1200 miles on them. But I've been reading the Edelbrock cam is weaker than stock.

BREK

First off welcome, and that's a beautiful truck you have! As far as pistons go it could get a bit spendy (to go custom) but contact either JE, Diamond, or ross. Now for the cam I would suggest figuring the rpm range you want to run in,c/r you will have, and what your heads flow and go from there. :sa:

willysworker

So you're saying only custom pistons are available in 10 or 20 over with 9/1 compression? I'm looking at 1000 to 4500 RPM range. RV/ towing power.

rollen dean montoya

welcome aboard =D> :lo1l: :mrgreen: that is one sweet ride! i think fuzz401 would help ya out alot on this. brek is correct in that custom pistons could get pricey. .010 to .020 over is kinda rare. .030 is more common .mc also might know where to go . good luck :t: later, rollen

AMX69PHATTY

If you're only looking for cast pistons, have you tried www.fastengineparts.com ? I believe they show Sealed Power cast pistons for 401 in +.020 as being available for about $200. I think the listing says 8.5:1, but the heads or deck could be milled if ya gotta have 9.0:1, or even offset grind the crank a little maybe.

willysworker

thanks for replies. I'm being to see the light.

82Waggy

willysworker wrote
I have a orig. 401 short block ready to rebuild.

Here is my question? Machine shop says only pistons available for 9/1 comp. are 30 over. I'd like to go 10 or 20 if possible but need a source for these pistons. I'm planning on using stock 401 heads.

Also, what is the best low rpm cam. I have Edelbrock cam, roller timing, intake manifold and carb. on my current 360 that I was going to reuse. They have about 1200 miles on them. But I've been reading the Edelbrock cam is weaker than stock.

About the only off the shelf piston worth a flip is the KB354. It will yield around 9.7:1 with stock 58cc heads, which is a bit high to run on pump gas. It also requires that you bush the rods to accomodate their .9272 pins. The solution with these pistons is to open the heads up to around 63-65cc's (unshrouding the valves will get you close) and zero deck clearance to get compression ratio around 9:1 with a good .045 quench. The advantage with these pistons is a tight bore fit (.0015" - .002") for reduced slap and leakage and a good quench head style (helps reduce detonation and improve fuel burn).

Speed pro pistons will work but have a lousy head style with a shorter compression height - not good quench.

If you want forged pistons you are pretty much stuck with something custom, but these require more cylinder wall clearance (.006" - .012") and must be warmed up before revving to control slap -not really an efficient way to go for a daily driver and can be quite expensive.

For a cam with strong torque across a wide rpm range, look for an LSA of 112 or so. With stock heads there is no need to push over about .450 - .490 lift. In a 401 with around 9:1cr, durations of 258-276 adv seem to work well (about a 600rpm spread between these durations where peak torque is acheived). If compression will be closer to 8.5:1, keep duration shorter to help build cylinder pressure.

Use a good dual plane intake manifold and a 600-700cfm vac secondary carb.

USE A TORQUE PLATE WHEN HONING THE BLOCK!!!!

:!:

PS: Just looked at the pics of your Willy's. Very nice indeed!