391 block

[jholmes217]

There is a guy selling a 391 block and 428 crank near me.  Below is what he has said;

Ford 428 short block.
391 Heavy Duty Block 8G25 date code, C scratch on the back, Webbed block.
STD/STD 1U 428 crankshaft.
Forged STD pistons, part #2287P
C6AE-C rods
C3AE 6059 A front cover

Since my 428 is already bored .060, should I pick this up as a replacement for the future?  What is the difference between a 428 and 391 block?

[mbrunson427]

We're working with darn near the same exact block right now. Its a 428 casting block but was only punched out to a 391 bore size (4.05) from the factory. That allows you to make it a standard bore (4.13) 428. Good block to have on hand. Only special thing you'll need is a distributor bushing, because the truck motors had a slightly larger distributor shaft. 

If you go to look at it, make sure to bring a flashlight with you and you can look down the water jackets and see a 428 cast into the bottom. However, it sounds like the seller knows what he's got.

[thatdarncat]

Not all 391's have the thicker 428 cylinder cores, most are basically the same as a 390. As was posted, you want to look in the bottom of both water jackets to see if there is a cast in "428" one side or both, or do a sonic check. It's probably a good sign that the block has a scratch mark on the back. I searched through many 391's before I found one that had the 428 cores. All the 391 blocks I've seen with 428 cylinders have date codes about middle of production. Keep in mind the cast in "428" doesn't eliminate possible core shift issues. Otherwise the main differences are the previously stated larger distributor pilot hole and an oil return hole tapped in the side of the skirt that can be plugged.

[jholmes217]

Is $1500 a good deal if it does have 428 in the water jackets?

[e philpott]

C scratch on a truck block ??...... seems like someone bored a thick walled 390 out to 428 so that in itself doesn't add value .... would have been better at 4.08 and even thicker wall in my book ..... almost half way to a BBM block that you can beat on all day long

[mbrunson427]

$1500 would be a fair deal for both buyer and seller, i think. For all the parts listed above.

[turbohunter]

That standard 1U crank is getting pretty scarce. Most have been turned.

[jholmes217]

What would be the cubic inches on this with a SCAT stroker kit if I go .030 if it needs it?

[Gregwill16]

Bore x Bore x Stroke x .7854 x 8 = CI

[Barry_R]

I have only seen one "C" scratch truck block - and it had 428 casting cores.

Buy it and run it

A 4.250 stroke deal will be around 462 cubes

[jholmes217]

Thanks Barry.  The stroker kit, and maybe heads, will probably be coming from you.

[plovett]

I have a "C scratch" truck block.  Or at least I think I do.  It has the C scratch and it needed the bushing for the distributor.  It doesn't have "428" cast in the water jacket if I remember correctly.

It was 4.13" when I bought it used and it's at 4.155" now.

For whatever that is worth,

paulie