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By aussiebill - 16 Years Ago
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Thought I would point out what to look for with these 312 blocks mainly, with cracks on 2 main webs. regards aussiebill.
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By Nick Brann - 16 Years Ago
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Hi Aussiebill and all, Can't tell from the photos which side of the block has the cracks. If it is the passenger side, then there is an easy fix. Pardon me if I am telling you stuff you already know. When I first tore down my '57 312, two of the main bearing cap bolts were a good two inches longer than the rest. Someone had drilled and tapped the block deeper for the longer bolts. I didn't see any cracks in the main bearing web area, but I kept the longer bolts anyway. Also at the rear main cap, one of the bolts was too long and one of the shorter bolts had been used at another main cap. Luckily no damage was done. Also there was an article several years ago about repairing a 312 block with the cracked main bearing webs in Y-Block Magazine, can't tell you offhand which issue. Have fun, Nick Brann - K.C., MO
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By aussiebill - 16 Years Ago
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Thanks nick, i welcome your interest, i am going to drill the holes deeper, then retap them and use screw in studs so the extra threaded length should lock the web together for added strength. Should be ok for grocery getter. Best regards, aussie bill.
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By Hoosier Hurricane - 16 Years Ago
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Bill: Be careful drilling and tapping the holes deeper on the left (oil filter) side of the engine. Don't drill so deep that the studs block the main oil passage. Nick, I'm the one who wrote that article in YBM, but don't know what issue. If someone needs to know, I can look it up.
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By Don Woodruff - 16 Years Ago
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Locally I have been able to find people to weld or braze (as the situation demands) heads and blocks. Perhaps you can locate some one with that talent near you. Don W.
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By Ted - 16 Years Ago
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I trust the 312 blocks are not being repaired like this one. 
This one went went to the scrap pile after the engine was brought to me to correct but only after the customer had spent a ton of money on it trying to save it at another shop. In this case, a 292 block bored 0.050” over and using the original 312 crankshaft and rods had the engine running like new again.
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By Nick Brann - 16 Years Ago
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Hi Guys, First I want to thank Hoosier John for the excellent article about cracked main caps, thought you were the author but I wasn't sure. And thanks to Ted for the advice about connecting rod side clearance when I was assembling my 312, and many other tips. It's a good thing the guy didn't bring the brazed up block to me instead of Ted, I would have tried to use it. Talk about spending a lot of money, when I disassembled my engine a few years ago, I looked down at the bottom end and noticed that one of the cylinders had been sleeved. Then I looked a little closer and found that all 8 had been sleeved! Someone spent a bunch of money to save that block. The sleeves are all bored .040" oversize to boot. I had everything balanced, plus ARP rod bolts installed, and then assembled it myself. Basically with all new parts, cam bearings, etc. That was 12,000 miles ago and I'm happy with it. But I'd be afraid to build an all out race engine using this block because of all the sleeves, seems like it would weaken the block. Have fun, Nick Brann - K.C., MO
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By aussiebill - 16 Years Ago
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Ted, its sure not a pretty sight! With that rebuild you mention, i assume you ground the 312 mains down to fit that 292 block. Its been hard here over the years as the old machine shop guys like yourselves are gone and so are the smaller ones that understand, so getting unusual machining done is a chore, But i,ve just caught up with old friend who is still crank grinding and is going to machine my 312 crank down to 292 journal size to fit my C1 block to replace the cracked one i pictured. At least it will be stronger in the tunnels. Best regards aussiebill.
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By Glen Henderson - 16 Years Ago
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I have seen two blocks over the years with all eight cyl's sleeved, both were Fred Jones rebuilds with Fomoco pistons. Both were std bore. I think this was common practice with Fred Jones, they must have had a stock of std pistons. I still have one of the blocks and would not worry about using it again. The cyl's are very clean with miminal wear.
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