Svo what? A4, R302, New Boss 302 block? Svo has been dead for decades. A4 is a 4 bolt main block, with basically stock cylinder thickness. It's nearly a stock block with 4 bolt mains. After 4.060 it's worn out. R302 is completely different, more akin to a dart, but can run hot at 4.125 bore.

 

I'll get the casting numbers. It's supposedly and older SVO block that came before the Boss. The guy is an old drag racer and has raced with this engine for many years in possibly Super Stock class?

 

Svo is the division from the 80s and 90s. It's highly likely it's an A4 or an R302.

 

It is a 4 bolt main block. Waiting on pics.

 

Ya it's just a screenshot. Here is an r302 block, notice the bottom of the cylinders are not extended like the a4 or a stock block.

 

I ran an A4 for 7 years and a Dart Iron Eagle for 6 so I know both well. A4 is a Good block that does have more meat in places than a stock block and has 4 bolt mains on 2, 3 and 4. They don’t crack like stock blocks do.

It is a conventional design in that the cylinders are water jacketed and not siamese. Because of this, A4 does provide better cooling than siamese blocks like R302 and Dart, but because of water jackets, A4 blocks cannot be safely bored beyond .060 and I, myself would not go that far.

When I ran the A4, I did so with a 3.25” stroke; first with stock 4” bore (327) and then with 4.030 (331). Power ranged from 575 to 725 RW in supercharged applications. Never had any issues and know people that ran them over 1,000RW.
Only reason I switched to Iron Eagle is I wanted 4.125 to unshroud the valves and make more power and have some overbore space.

Edit. Let me add that if this block is an A4 and already at .070 don’t go there.

 

I ran an R block on the steet with no running hot issues. Always heard those concerns floating aorund the forums, but I had zero issues, ran just as cool as a stocker with the right supporting rad and fan.

 

If you read; Woody stated that they ran hot at 4.125 bore. Nobody stated that these blocks ran hot in general.

 

If you read; Woody stated that they ran hot at 4.125 bore. Nobody stated that these blocks ran hot in general.

Not referring to anything Woody stated, only that back when these blocks hit the streets, it was generally a concern for anyone looking at one because of the design.

 

Here is the casting number and a look at the A4. Note that 1 and 5 main caps are not only 2 bolt but are cast.

 

Thanks. I think the two bolt caps are nodular.

 

All 5 mains caps on the A4 and R302 are nodular. They just machine 2-3-4 smooth.

 

It's in fact a m-6010-boss302 block at .070 over. Ford specs are all over the place as far as the beginning rough bore and the bore limit.

 

Ok so that's easy. It started life at 3.990. It's probably an older one from the beginning where it has the small steam holes drilled between the cylinders. You can see these on the deck. Fast forward and they stopped drilling those steam holes on the 4.125 blocks because I believe those holes may become a liability on large bores such as like 4.185 and up. 4.185 was the answer they always gave for max bore size.