Shop called today, the 312 block that I planned on rebuilding is cracked at two main bearing bolt holes.   Looking for a good 312 block to rebuild.  The original block has a casting date code of 6 B S.  I know it probably is asking too much but I would like to find a block with 6 B casting code.  If anyone can help me out please let me know.

Randy

We've heard this unfortunate story before. The 312 blocks mains were over tightened at some point. Early 1956 manuals specified a torque that was well above what was needed. Did your shop actually get to the assembly point? 90 to 95 lbs is plenty, no more!

Paul

Randy: If you just can't locate a replacement 312 block, it's possible to convert a 292 to 312 bore etc. However, additional machining is involved to the crankshaft mains & seal area. The specs should be available over at www.ford-y-block.com

Paul

Randy:

Since you are casting date conscious, don't throw away your present block yet.  I have used blocks with cracks in the main bolt holes by drilling and tapping a little deeper and using longer bolts.  If the cracks are on the oil passage side, be careful that you don't drill so deep that the longer bolt blocks the side oil passage.  I have even done this on my drag engine.  Have not experienced any main web failures.  As Paul mentioned, the '56 mains were overtorqued from the factory, so it is possible it has run 50+ years with the cracks.

John - "The Hoosier Hurricane"

Yes john, i agree with you, they are still very usable and retapped as you point out will keep on going.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

I didn't make it over to shop today to look at it but talked to owner, I heard original message wrong, all ten bolt holes have radial cracks starting at threads. Fortunately? I was having it checked for cracks before doing any machining. This is my father's Phase I supecharger car so I wanted to use correct block but, I don't want to risk putting too much into a block that may cause trouble in future, I know my father will want to put his foot into at least once more.  Do you think it will hold up with studs installed deeper if run hard?

Randy

Are the cracks on the same bearing? If only one per bearing you may be able to fix it. I had the same situation. However, the guy doing the rebuild said he could weld the cracks, drill and tap the bolt holes deeper and use studs (ARP) rather than bolts. I have been running the engine for three years now and took two long trips, buzzing along at about 3thou rpm and the motor is running great (knock on wood).

54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

Still haven't seen block,talked to shop again they tell me that some of the holes have multiple cracks. I can't get to shop until Monday, I'll post a picture of worse one once I see it.

Randy

That there is some information... Thanks John

"The Master Cylinder"

Enjoying life at the beach in SOCAL

Randy: With the follow up info you supplied, it sounds like your block is unfortunately toast.. I might be mistaken, but I think you need the correct year casting letters for a start. The chart from www.Ford-y-block.com lists 1957 312 blocks as ECZ- 6015-C. With ECZ marked main caps. However, if equipped with EBU main caps it will be a 292. Also given shipping costs & difficulties,what area are you in?

Paul