Differences in 318 block.

[hwy2]

I have a 89 block with a crack I cannot have fixed. I also have a good 71 block and rotating assembly. Will this older block work. Its std 3.910 bore. Largest bore size I measured was 3.931 what would be a good oversize .020 over?

 

[AJ/FormS]

3.931, less 3.910 =.021, which is a chitload of wear on a "std" bore.
Was this measured with a dial-bore gauge? If yes, then,
more likely is that the engine is already overbored.
But if no, not by dial-bore gauge, then, no comment.

so to answer your question, as to .020; it would kindof depend on if the bores are straight and/or how badly tapered they are. So then, this needs to be measured with a dial-bore gauge, to confirm.

 

[hwy2]

Yes it was measured using a gauge. In middle of stroke.

 

[AJ/FormS]

You said "a gauge."
You did not say, a dial-bore gauge.

So then, respectfully, I suggest you take it to a machine shop for a second opinion.

 

[Max1196]

Its std 3.910 bore. Largest bore size I measured was 3.931

measured using a gauge. In middle of stroke.

So is it standard or is .020 over? What did it measure 1/2 inch down from the deck surface? This is where the most wear would be.

 

[hwy2]

3:912 after deglaze. I had to go recheck how I was measuring. I am using a inside bore diameter gauge. After deglaze i am reallly now looking at the wear ring at top of stoke. 3.916.

 

[A38Valiant]

In response to the initial question, the later block has the provisions for roller lifters. The older block has no bosses for the "spider" to bolt to. Other than that, there are no real differences in the block. Cranks should interchange. Height of the piston crowns will probably vary some between the two.

 

[Ottmundr]

I have a 89 block with a crack I cannot have fixed. I also have a good 71 block and rotating assembly. Will this older block work. Its std 3.910 bore. Largest bore size I measured was 3.931 what would be a good oversize .020 over?

"Clean up," the '71 block by 0.040" to 3.950.
Get yourself a new 4" crank.
You now have a 392 WEDGE.
Get yourself some of these badges and replace your "V8" badges.

 

[hwy2]

So is it standard or is .020 over? What did it measure 1/2 inch down from the deck surface? This is where the most wear would be.
View attachment 1716238105

3.910

"Clean up," the '71 block by 0.040" to 3.950.
Get yourself a new 4" crank.
You now have a 392 WEDGE.

looked into that. About 2300 on that. Will have to wait on that great suggestion.

 

[hwy2]

So is it standard or is .020 over? What did it measure 1/2 inch down from the deck surface? This is where the most wear would be.
View attachment 1716238105

3.910 is the what I set my digital caliper to. Then use my telescoping gauge 1” down I get 3.910.

 

[hwy2]

3.912 is the largest measurement I can find measuring in the ring that is seen.

 

[junkyardhero]

why not just ask the machine shop?

i mean, they're going to bore it and hone it so they'd know what it'll clean up at.