Can a guy do this without changing anything else? What would it give me if I did this...a 406? I have an uncle with one and I would like to use this crank if I can. I just don't know what I all have to change in my 390 to use it.

 

390,406,427,and the 428 all use the same lenght of rod so you 390 rods will be fine. I think you have to get either 410 pistons or 428 pistons (can't quite remember) and the only listing I have ever seen for 410 pistons is 10.5:1 comp ratio allthough different heads and head gaskets can change that along with any milling of heads or block. This is confusing because I have heard of 410 pistons being in a 390 from the factory but I think that 410 and 428 pistons have a shorter compression height to compensate for the longer stroke of the 410/428 crank. So I don't think you can use a 360 comp. height piston (same as 390 piston just higher compression height) on a 410 428 cranked engine. One of the gurus will correct me somewhere here I'm sure though. Most 390 blocks will not bore to a 428 size (4.13) and I don't know if you can get any 410 pistons outside of the cast-design. Guys... we need some help here.

 

You end up with a 410 cid and you will need pistons minimum. A 406 is the 4.13" (428) bore with the 3.78" (390) crank.

 

Sounds like too much work for me. I thought I had read somewhere here a while ago that a 428 crank can be dropped into a 390 with out changing any other parts. I don't see the point in completely rebuilding and modifying a good motor like this just to have a 428 crank. I thought it would just be an easy way to get a stump puller out of a 390 without spending $$$$$.
Oh well....back to the drawing board.

 

If you drop the crank in and don't change the pistons you shove the pistons .010 higher in the bore and will have valve interference or have the piston hit the head. Either way, things break with a loud $$$$$$$$$ sound. 410 piston are 4.05" while 428s are 4.13" and both have the same compression height.

 

Considering you get the crank for pretty cheap or for free, it shouldn't have to do more than getting pistons and rings. I think you would be happier with it. Unless you get the counterweight and corresponding flywheel for the 428 crank (which you probably don't have) then you will either need to find one on get some mallory metal added to the crank to convert it back to a simple internal balance engine. All FE harmonic dampers are neutral balanced I believe so just use your 390 balancer if it is in good shape, and whether or not you get the counterweight and flywheel or get it converted to internal balance as an act of insurance I would still have the reciprocating assemble balanced at a reputable machine shop. Maybe e-mail Freightrain or Baddad 457, Scouder, B.B., Rusty70F-100 or the other gurus and ask them. I really think you would be happier with the 428 crank in it even though it is going to cost you a little more.

 

wouldnt it be internally balanced with the 428 crank, unlike the 390?

 

joe the 428 is EXTERNALLY balanced, in other words it takes weight added outside the crank counterweights to balance the rotating assembly. The 390 is INTERNALLY balanced , there are no weights added outside the crank counterweights.:-)

Bear45/70- a lot of truck 390's have very large deck clearances. It is possible the pistons could be as much as .060 to .090" down in the cylinder-some of the reason for the lousy CR from the factory. If they are down in the bore that far, he could reuse his 390 pistons. You would need a balance job no matter what. The 410 is a very good pulling/torque motor that I almost built...except I found a 428 block

 

If that 390 is a truck motor and running the lower compression, it would have the "equvalent" of the 410 piston. You can always add a copper head shim type gasket to get another .020 clearance. Bottom line is, you need to tear the motor down, see what you have and go from there. You can't just put a crank in without going through the steps of a rebuild anyway.... As far as the balancing, get the whole assmembly done. The 428 was balanced on the flywheel or flex plate.

--Mike

 

Thanks guys for setting me straight. I have no idea where I came up with this notion. I think I am just gonna do a basic rebuild with a better cam, 4bbl carb and headers. Call it good and go cruisin'!!!!

 

Mike is right on.

You CAN drop the 428 in a TRUCK 390 with the same rods and pistons. Truck 390's used 410 pistons anyway, so you'll end up with .012" deck clearance. Perfect IMO.

Figure it up this way: 10.17-1.99-6.488-1.680 = .012

You will end up with fairly high compression, so get a good duration cam to go with it. This bleeds off enough compression at low rpms to prevent detonation. I suggest the Crane 344341.

I'd get the whole bottom end internally balanced, then keep the 390 flexplate.