Taking apart a rusty 391

[Leny Mason]

It has been sitting out side for a long time, the oil pan almost full of ice two days in my shop and still ice in the pan, to my surprise it turned over the two barrel carb had a rag that had rotted away, every thing looked nice in side some rust in two cylinders but not bad, we are trying to make a 428 out of it, unbelievable how nice it is inside. Leny Mason

[machoneman]

Lucky, I say! Buy a lottery ticket today....LOL!

[blykins]

Leny, don't make a 428 out of it...

You're better off keeping it with the standard bore or a slight over bore.  I've ruined several blocks that way....they sonic'd good, but it was a different story once you start boring them. 

I'd rather have a 410 with a stable cylinder wall than a thin 428. 

[BattlestarGalactic]

With a 4.25 crank, you can make good power with any bore. 

[CaptCobrajet]

Look in the water jacket...... it may have 428 cast in the floor, right near the center expansion plug.  If it does, your good.  If not, stay with the 390 overbores.  Often they only have it in one side, but both cores are "428".  Not many 391s have the 428 core, but some do.......

[Leny Mason]

It say's 428 in it so is it Ok to bore or like Bret said stay 410. Leny Mason

[CaptCobrajet]

If it says "428" you can tell it that it's a 428 and it won't know the difference.  I've seen many of those go 4.190 for drag racing.  4.130 would be just fine.

[MeanGene]

2 barrel carb? More likely a 361

[Leny Mason]

Hi, we didn't measure the stroke but it is a standard bore for a 391, it was supposed to be a 391 I can look to see what the stroke is on a 361 but the pistons came to the top of the hole. Leny Mason

[country63sedan]

They both use the same bore, just like the 360/390. I've been told all 391's were 4 barrels. Fwiw, I own a 4bbl 391, a 2bbl 361 and a 2bbl 330.  Good find on the 428 cores though, none of mine have 'em.  Later, Travis

[Leny Mason]

This one has had some work on it so they may of changed the intake ? but the pistons went to the top of the hole. Leny Mason

[FirstEliminator]

2 or 4 barrel carb isn't a sure way to tell. I have a 330 powered truck that originally had a 4v and a 391 that was originally 2v.    Measure is the sure way.

[MeanGene]

I did not say sure way to tell- I said more likely. There were also some kinda rare variations, 359, 389, different "Duty" levels etc. Still more likely to be a 361 than a 391, but could be 330, 359, 389, or intake changed