I have had this engine for about 4 months I am not sure what it is the guy said it was rebuilt and that it is a 350. I do not know if it is bored or not or what I should do with it.

 

What is it you're asking?

 

You identify a block by its casting number, which is on top of the bell housing flange behind the driver's side head.

Looks to me like yours is a 3970010. Pretty common 350 block casting, probably the most common in fact. Was used from 69 to about 80. Nothing special one way or another.

Plus, using my finely calibrated eyeball micrometer, it looks to me like about the right distance between cylinders for a 350. Too little for a 305, at least; and it's positively not a 400. The pictures are too fuzzy for me to tell if it's been bored, but I'd expect it has, since those don't look like stock pistons. So it's probably AT LEAST .030" over. Measure the bore with a steel ruler; it's 4.000" stock, .030" over is just under 4-1/32", .040" is a little than that, .060" over is just under 4-1/16". A micrometer would of course be even better.

 

A) check the casting number, and match up to the description at www.mortec.com

B) measure the bores. If its ~4" its a 350, if its ~3.75 its a 305.

 

The cylinder walls look to me like it's been re-ringed, not re-built.

 

The block has so many different numbers I just wrote a couple things down..

The cylinder measures 4.1inches
A couple of things it says on the block

^F3412
GM56

010

also on the cylinder it says 080

The bronze things say EPC41B (1 5/8)

3952302 24

 

for the casting number it says

38GM
3970010

 

Gee, I guess I'm not as blind as I thought I might be.

4.1" is WAY too big for it to actually be that. But it definitely sounds like it's been bored, probably .060". As one would expect, looking at those cheeeep cast "rebuilder" pistons.... those guys don't measure crap, they just go as far as it will go and if it's not enough, throw it away. I see VERY VERY few "rebuilder" 350s like that one these days, that are not already .060" out. Used up.

Yours does not appear to be runnable at its current bore, judging by the wear. I can tell you for certain, I would not run that block, at its current bore size; and if it's already .060" over, it will go no farther. Time to throw that block away and get another. No biggie though, you can pick up a roller-able one (87-95 TBI truck) for $100 or so. Pocket change in the overall scheme of rebuilding a motor. The money is not in the core (the big junk thing you're rebuilding); it's in the machine work. Don't try to salvage that one, don't spend even 1¢ on it; trash it and move on.

Just like the "rebuilders".

 

what is tat number on the piston? I think it says .060 which means it's been bored over that far. I can tell by the new freeze plugs it's rebuilt. Stick some heads on that sucker and run it.

 

says 080 on the piston

 

Holy s**t.... the guy who built that engine was either stupid or brave

 

I have personally seen a 305 taken .120 over with no ill effects. It was basically a 350.

 

A .120" overbore on a 350 would be 3.856", still well short of the 4" bore of a 350, more like a 325. I wouldn't expect that engine to live long under any abuse.

 

Right....

"a" motor that went .120" (wonder where the pistons for that came from? ) doesn't begin to make up for the PILES of cores headed to the furnace I've seen, that had already hit water at .060"....

Certainly, it's not something I'd want to bet my money on, even if I'd seen ONE.

But, however all that may be, the 080 may or may not be the actual size... I can't say that such a size is even available. Maybe it is, I don't know. But if so, and if this was a cat, it would be on its 8.8th life or thereabouts. Not many more opportunities for mistake recovery left.

 

how can I find out for sure?

 

Measure it with a telescope gauge, and a micrometer. Or, a bore gauge.

 

haha 080 over is nuts.. even is you do get it running every time you beat on it a little bit you would have to turn the damn thing off do to heating issues..

that block is worthless..

 

The amount of overbore doesn't have much to do with heat.

 

I would infer that bringing the cylinder wall closer to the water jacket would improve cooling, as the heat does not have to travel through as much mass before it can be carried away by the water. What do you think...?

 

So if it is not bored all my 305 parts SHOULD fit on it?

 

All your 305 parts will fit on it regardless of whether it's bored or not, except for the parts that actually make it a 305.

 

mines bored 060 over and i got a new fan and 160 stat because it was heating up so fast..

maybe it was my motor.. but i asked a few people and they said the fact that there was less metal it would heat up a hell of a lot faster..

once the stat opens its not too bad but a stock fan has trouple keeping the temp down.. or maybe its just me

 

The cylinder wall thickness should be at least .180" after boring, preferably more like .200", and from the factory it'll typically be thicker yet. Boring reduces the thickness by half the amount of the overbore, so a typical .030" overbore will take off .015" of material, or less than 1/64" of an inch. It's a tiny amount of material, and on the outside the cylinder is still surrounded by the same huge mass of water, so you'd never notice a difference in temperature from boring alone.

 

Agreed. If it was running hot after a rebuild, something is wrong. Simply boring the block - all else being equal - should not make the engine run any hotter than before.

 

I might drop it from somewhere high I want to see how durable this thing is haha