(Dis) Advantage? FT vs FE block?

[tpiini]

My friend with the stack of 390's just dropped a heavy-truck FT 391 engine off. Best as I can tell from limited reading, these were cast with thicker main webs, resulting in a heavier-weight foundation. I'm not sure if this is something that is desirable, or if it's just more weight to lug around.
Would I be wise to keep my original plans of building on a 390 FE block, or use the FT block?

Thanks, experts.

Tom

[LwCwb]

If you go with the FT, you will need to get a distributor bushing or else the distributer will be really sloppy in the block, either that or use the stock truck distributor.

[blykins]

The FT blocks were meatier and thicker in the mains...What weight that is added wouldn't be noticeable between that block and a regular 390 block when driving the car around. They're both freakin heavy.

Like Mike says, you will have to a distributor bushing because of the distributor bore sizes that vary.

Also, I think the crank is significant to an FT engine....I think the snouts have a bigger OD....so you will have to either have it turned down to the regular 1-3/8" diameter....or make sure you reuse the FT timing cover (probably cast iron....yuck), harmonic balancer, and crank pulley. The FT's were also externally balanced.

I'd definitely reuse the crank and just have it turned down so you can use regular FE parts....harmonic balancer, front cover, etc. Unless someone's swapped it out, it should be a forged steel piece.

[FFR428]

It's expensive to turn the snout on the FT crank. The block would be a good foundation and weighs no more than a CJ block or any other HD or HP block. G.

[BrianPaul]

The mighty 391 truck blocks designated with a numbering sequence like D3TE, D4TE, etc. denotes that it is an FT engine and the number is the year it was produced. I made one into a 428. These engines were made to be rebuilt many times and therefore have very thick cylinder walls. Get yours sonic checked and see what you can do. Mine took an 0.080 over bore, to 4.13", with plenty left to spare.

[tpiini]

Hmmm...

I'm thinking that I'll leave the 390's piled up and go to work on the FT block instead. 428 is sounding nice.

[FFR428]

Not all 391's can accept a .080 overbore. You need to check the cyl wallcores. Knock out the freeze plugs and see if the shank from a 13/64" drill bit fits snugly between the wall cores. If it does it's worth the sonic for the 4.13 overbore. If a 17/64" drill bit fits snugly between the wall cores it has the std 390 wall cores and will be hard pressed to go .080. I've seen them both ways. Even if the 428 bore is not doable it's a nice HD block for a build. G.

[Enginetime]

I've done two 390 to 428 builds. The best 390 blocks are a 66 to 67 date code auto blocks. We found that 3 out of five can be bored to 4.13 (428 standard bore) with plenty of meat to spare. Truck blocks did not pass sonic test as well. The webs may be thicker but the walls were not as thick as the C7 date code auto blocks. Go for the 390 to 428 build up. Far better perfomance, and not that much more $$$.
Mark