Hello, 
I am new to this forum, and to the Y-Block. Interesting engine. I'm freshening a 312 Interceptor marine engine from an 1964 wooden ski boat. I've read about the main bolts being shorter in the 312, and about bottom tapping for longer bolts. This engine makes 215  h.p, about all the transmission can handle, so it won't be a hipo build. Are the longer bolts necessary for my needs? What fasteners would you suggest? Thanks in advance. 

I won't comment about whether or not you should tap the main bolts further, I'll leave that to the engine gurus here, but will issue this caution;  Some 1956 factory car manuals contain a serious error on the maximum torque specs. The 1957 manual says a maximum of "105 lbs".  Do not exceed that figure!      


Paul

Welcome to the site.

The main bearing caps for 292s are smaller than the main bearing caps for 312 engines.  292 main bearing caps have the letters EBU showing between the main cap bolts.  312 main bearing caps have the letters ECZ between the main cap bolts.

John Mummert indicates that In the Spring of 1959, FoMoCo began using longer bolts for both 292 and 312 main bearing caps.  It is believed that the change in fastener lengths resulted from Ford and Ford Authorized Re-Manufacturers reporting some cracks being found in engine block main bearing webbing saddles.

Longer main bearing cap bolts were used by Ford in y-block engines with the following casting IDs (found above the engine oil filter adjacent to the external engine oil pump) per John Mummert's website:
B9AE 6015-F
C1AE 6015-R
C2AE 6015-C
B7ME 6015

Click the following Internet link for information on John Mummert's website pertaining to FoMoCo engine block identification information.
http://www.ford-y-block.com/Block%20identification.htm

IF your engine block has any of the above casting IDs, you can probably use ARP maincap bolts or studs without any of the additional drilling or tapping required to install the longer fasteners on earlier production y-block engine blocks.

Click the following Internet link for information on John Mummert's website pertaining to ARP fastener installation.  John sells both ARP main cap bolts and studs that will fit the 292 or the 312 main caps.  Again, the length of the fasteners is different for the two different cap sizes.
http://www.ford-y-block.com/ARPmaininstall.htm

Hope this helps. 


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Thanks for the reply. Yes, I've actually read that 92 lbs. is a good value for the 312, as opposed to the initial 125. 

Yes, great help, Thanks for the info. Yes, it is C2AE casting with correct caps. Will go with the Mummert-supplied ARP bolts.

MourningWood,
Be sure to read John's stud installation notes on oil passage possible interferences. My observation is the C2AE blocks -292 truck ( I have never seen the holy grail marine block you apparently have) have what appears to be slightly relocated oil passages likely made possible by the revised cores and molds done in 1963; regardless # 4 main is where I most often see intrusion into the oil passage regardless of the block. I built a tool which uses a center drill brazed into a close fitted piloting thin wall tube to make an easier job of removing and or marking the interference.  I have used studs on both older 312 and 292 builds, in my opinion a good reliability move.  Good luck! 
WLJ1943