390 pistons in a 401?

[gschuld]

I have a 401 block freshly bored at .030 and I have a set of NOS Badger B888(cast flat top with double eyebrow valve reliefs -14cc) .030 (68-69)390 pistons that I've had around for a while. Soooo...since I intend for this motor to be a torque motor maxing out at about 5500rpm and I have no interest in nitrous, I like the piston design as it has a very healthy quench area. Realizing that the 390 piston's compression height is .050 taller than a standard 401 piston, would it be reasonable to use the pistons as is leaving them .050 out of the hole and using a thicker head gasket to give me the ideal piston to head clearance? I know copper gaskets are available in fairly thick material. I would much rather buy or trade with someone who has a set of 401 B888s(.030 or .040) but that might not be very easy. This motor is more of a budget build so I have to ask.

Any thoughts on the Badger B888 pistons in general?

Thanks in advance...

George

[jeepsr4ever]

Do you know what year 390 they were for? 390's had two distinct deck heights. 68-89 were different than 1970 and so they used different length rods for that one changover in 70'. Not that the rod makes any difference but you may actually be under deck if it was an early piston.

[gschuld]

My pistons have been checked, they are 68-69 pistons with the 1.56 compression height rather than the 401s 1.51. Which leaves me with a .050 "taller" piston compared with the standard 401 pistons.

George

[jeepsr4ever]

Thats tall! You would need almost a .100" gasket to make it work. I think SEC can make them but I thing they list them but its hard to say if they are off the shelf.

[AMX69PHATTY]

Could '68-9 390 rods be used since they're .068 shorter ?

'70 & up 390 & 401 are 5.858 and '68-9 390 are 5.790.

:-|

[JERSEYJOE]

i bought a 401 once from a guy that said it was " rebuilt " and ran well until it blew up. I bought it for a great price . When I took it apart it had same pistons you described ,the 888's . Most of the pistons had destroyed top ring lands, from the detonation. I guess the compression ratio was somewhere North of 11 to 1 even witht he 58 cc heads. At least i was able to save the block which is std, and the crank which is .010 and .010.

[JERSEYJOE]

I might be interested in the psitons if you are going to sell them. I have a 390 waiting...

[gschuld]

AMX69PHATTY,

Interesting idea! I have several sets of 401 rods but no (68-69)390 rods currently (other than the rods IN my other 390). Acquiring the 390 rod's won't be too hard. I suppose the big question would be whether the 390 rods shorter length cause clearance problems with a 401 crank. I assume that AMC made the 401 rods longer for a reason (predumably clearance reasons). Has anyone done such a parts mixing?

The other obvious answer would be to have the tops of the 390 pistons milled down .045 or so to get me in the 0 deck range for the 401. I wonder what a machine shop would charge me for that operation? :-|

George

[Ghinmi]

Couldn't you have your rods shortened? I know you lose a little bit of length when you have the big ends redone. Why couldn't they take .050 off your 401 rods? I'm not an expert so check around before you have this done.

Greg

[Dusty]

just throwing it out there but with all the machine work ect and special gaskets wouldnt it be cheaper to call up summit and spend the $400 for some speed pros or $430 for some KB's? you could probably sell the ones you have for $250-300. i am all for trying to use what you have but by the time you either machine the pistons and or source out shorter rods ect or go with a thicker more expensive gasket, it might be easier to contemplate the easier options :idea: