Used main caps

[ninjapumkin]

Hi guys

It has been a while as everything has been put on hold a few years back.
But back on the horse again.

So, my original 64 block was cracked.

I purchased a 66 bare block with main caps and a 67 bare block with out.

Today i found out the 66 block is cracked beyond repair.

So the issue is, can i use the main caps from the 66 block for the 67?
My mechanic says its not worth it. Issue being that main caps are matched to blocks.
True? If this is so, why can i buy new caps?
Trying to build a streetable engine. Nothing really more.

 

[Photon440]

No difference between using the 66 main caps or new ones, they can both be brought to the same tolerances with line boring.

 

[ninjapumkin]

No difference between using the 66 main caps or new ones, they can both be brought to the same tolerances with line boring.

Thank you.
Trying a budget build. As everyone.
Line boring is costly as my mechanic has told me.
if its close......can i get away with it? Or am i hooped? Hahaha It was a $20 investment on the 67 block.

 

[sdconcepts]

we sell brand new billet aluminum main caps for $339.00 all usa made from usa materials. it costs a lot of money to build an engine. the stock main caps are prone to cracking after about 500 hp. if you're not going to replace them at least magnaflux them and make sure they aren't cracked. the aluminum we use is stronger than the cast iron in the caps and acts a little bit like a shock absorber when clamped down. add some arp studs for $89.00 and then have it line bored. line boring should be about $150.00 in most areas.

 

[Cranky]

Align boring is usually something that's done to true up a block IF it needs it but most shops don't want to bother checking them and will just throw the block up on the machine. Years ago, I had a block that needed caps and I had 3 sets of extra ones and actually found a set that fit perfectly. Close enough doesn't get it. Stick them on and then measure them two ways across the split line...IE 10 to 4 and the 2 to 8 position like a clock or if you can hook your fingernail on the split line, it's not even good. If that measurement is good, then check 12 and 6. A couple tenths of a thousandths difference (.0002) would be about my limit with the parting lines but you also want the 12 and 6 to be the same. You want them as round as possible. It's not a problem for a good machinist to do an align bore job. Sounds to me like your guy is not comfortable doing it. You will also want to make sure the thrust bearing face fit is flush or not too far off. The thrust cap can be adjusted back and forth but your main bolts will not let them move much at all. Just got to check closely.

 

[ninjapumkin]

Thank you for your help.
Have not heard yet how well they will work.

sdconcepts. Went to the site and do not see them on there?