390 block bored .080 over would hard block help?

[67xr7cat]

Was looking at an early 70's 390 block that was bored to standard 428 size as the owner bought into the myth that it was same as a 428 service block because it has external ribs and passed the drill bit test.

So block had a lot of machine work done and cracked a cylinder.  Clearly I'd never start with a 390 block to make a 428, but can get it cheap and was wondering if a sleeve and a 1/2 fill of hard block would work for a basically street deal. Thanks, Steve

[My427stang]

Sonic check and if good might only need a sleeve, but usually a whole bank has similar thin spots

[plovett]

Hard Blok is not magic.  It won't fix a bad block.  I like Hard Blok and have it in my 428, but as said sonic test it and then decide based on that.

JMO,

paulie

[Yellow Truck]

Bored .080 over and cracked a cylinder? Is it safe to say it has never been assembled and run? In other words, it wasn't run and cracked the cylinder. This might suggest only one was bad (of course that assumes it was run for a long time and beaten up enough really test it).

Assuming it has never been assembled and run, in theory there is value to "all the machining" that was done, but I'd be asking if all the machine work that was done was done well. Any shop that knows the FE would have pushed back on an ask to bore it .080 over. I think you will find you are chasing a rainbow.

Scrap value of a 185 lb hunk of iron is about $138, scrap yards don't pay extra for machine work.

[67xr7cat]

had a 4.25" stroker kit in it. Ran 20 minutes on the dyno and split a cylinder.  Are too many question marks on this one to bother.  My thought about the hard block is support the cylinder wall better, but as said without a sonic test is a roll of the dice. Now if was a drag race only running on alcohol think I'd roll the dice and fill the block to within an inch of the deck. Was just wondering if anyone actually did the 1/2 fill on a deal like this and if it worked or failed.

Anyway guy has this up on the Dallas CL.  Is selling the stroker kit for $1,450 which if you have a std bore 428 may be a good deal.  I don't and a set of pistons make it not worth it. Thanks, Steve

[Barry_R]

1/2 fill will help support a marginal cylinder.
Still need a sonic - probably wishing they had started out with one...
Putting boost on a marginal deal was...."brave"...

[Rory428]

Block filler should be installed and cured before the machine work is done. This is because as the filler sets up it can push things around some, so cylinders that were round before the pour, may not be round after the filler has set up. I had a similar situation several years ago with one of the 428s I ran in my Fairmont. It was a early "A" scratch 428, that had been bored .030" over, and ran for years in a truck. Since the cylinders looked good, and were straight, we just honed it and used the pistons from my other 428 that had cracked the main webbing. It ran quite well for a bit, but then split a cylinder wall. We installed one sleeve, and filled the water jackets with Hard Block. there was some shadowing in a few cylinder walls, but figured I had nothing to lose, so ran it . Again, it ran well, but in short order, it split another cylinder wall, even though the split occurred in an area surrounded by the Hard Block. ended up on the scrap heat after that.