I recently picked up a '57 Tbird and in going through the engine I found it had cracks in the main webs. I picked up another 312 with a Std bore and unfortunately it also had cracks in the main webs. I then did some research and found this is a common problem with the 312 so think a 292 may be the way at this point my Y-Block knowledge is lacking and I am finding its a steep learning curve so far. I am just looking for a stock rebuild (ie no high performance work) and to that end  my initial questions are-
1. Should I try to get an early or later block? From what I have read, the early blocks have thicker castings around the bore, but the later ones (C1/C2) have stronger main webs.
2. If the early castings have thicker bore castings, what is the max overbore they can handle? Is .060" the max or can they can more. If they can go more, are pistons available for the larger overbore?
3. Is there any problem with using my ECZ-G heads on a 292?
4. Since I have all my 312 innards, should I consider using them on a 292 block? I realize I will need to grind the crank and wonder if it is worth the effort.
5. Are there any other things I should be thinking about as I try to get the Bird back on the road?

TIA for any insight

How bad & how many cracks are there in each block?..  The std bore block may be a 1956 that was pulled by a Dealer years ago.. Many of those blocks were damaged by an incorrect torque spec issued in early 1956, I'm told..  I'll leave most of the overbore questions for the mechanical experts on here, however any large overbore plans should depend on what sonic testing shows.. Imho, boring a street engine to the max, may not be a good idea in the long run.. The ECZ-G heads will work fine on a 292.. Yes if  your 312 cranks are in good reausable shape it would likely be worth while to have the Mains re sized. I think there is a rear seal mod needed also, but I don't have the details.. I'll leave it at that...        


Paul

ive turned down a 312 crank for use in a 292 block its done all the time.you have to turn the rear seal area down .125.same as the mains.

I experienced the cracked 312 blocks years ago. I bored a 292 to a standard 312 and used most of the 312 parts from the cracked motor.

  Vic Correnti

I go with the later model 292 blocks when I have a choice.  Some of those I have bored 0.110” over but only after sonic testing to verify cylinder wall thickness and where the core shift resides.  Beware of the earlier 272 blocks that have already been bored to standard 292 sizes as there’s not much material left in many of those for additional overbores.  As a general rule, all Y blocks handle 0.060” over without a lot of checking.  Beyond that, sonic testing will verify exactly what you have.
 
Keep in mind that most of the Y’s in 1957 had the ‘G’ heads.  This includes the 272 engines.
 
I have done a fair number of 312 cranks for the 292 blocks.  Some were stock 3.44 stroke but many others get offset ground to 3.580-3.610” stroke depending upon the condition of the throws before grinding.  As mentioned, the rear seal journal and rear crankshaft oil slinger must also be reduced in size to fit the 292 blocks.
 
If boring a 292 block 0.050” over and using a stock stroke 312 crankshaft, you will have a ‘new’ 312 cubic inch Y with the advantage of the smaller mains.  If you come across an ECZ 292 block, then you will effectively have a 312 that will be undistinguishable from the outside of the engine from an original 312.  Also keep in mind that starting in late 1961 Ford used the C2AE blocks for both 292 and 312 production.  Those blocks were cast through the end of 1967.
 
Don’t let my post be the final say.  Keep those comments coming.

Lorena, Texas (South of Waco)

All, Thanks for the input and I was not aware of the rear seal area needing rework if I use a turned down 312 crank, so thanks for that info.
PF Arcand, The cracks seemed pretty bad to me. One block had cracks across the screw holes on both sides of 2 and on one side of 4. The other had it across the screw holes on one side of both 2 and 4. I looked to see if there were any repair options but could find anything.

Locally, I know of a 312 that is already .060" over, an EDB 292 that is .040" over and has 2 very rough cylinders that might not take a .060" overbore, and a C2 292 that is already .040" over and #6 cylinder fails a leak down test (holds 40 psi with 100 psi being fed in) and the rings are the culprit. I have no idea if it would accept a .060" overbore. With my limited knowledge, none of these seem like good candidates to start a rebuild with unless I am planning to sleeve ($$$) one.

Ted, I had thought about using an ECZ 292, but since I have had trouble finding any decent 292 blocks so far, I have changed my search criteria significantly.

Another question for the group. If I use the 312 crank in a 292 is it better to resize the crank or the mains? It seems resizing the mains would create the same weakness as the 312 have, but would torquing to the lower 95 ft-lbs mitigate that problem. Also, would tapping the screw holes deeper mitigate it even more?

ther was a co in canada that had a stiching process for cast iron,harmond process. chain lock.
re boring over size I have found blocks from no anti freeze arias usually have erosion issues especially #4 and 8 as water flowed  sharply block to heads . 1 case I had was sleeving these 2 cylinders

 hear the industrial cores wher always a better gamble as users always use some sort ofwatter additive and anti freeze.

Welcome to the site!
1)  Yes, you could have the 292 engine block main bearing bores resized (bored) for the 312 crank.  However, 312 bearings are hard to get, cost more than 292 main bearings, AND you would have to add the notches for the 312 main bearing tangs to seat in the block bearing web and main caps.  The bearing tang orientation is the reverse on the 312 main bearings from that of the 292 main bearings.
2)  IMO resizing the 312 crank's main bearing journals, rear oil slinger, and the rear seal to 292 crank dimensions is the better way to go.  It is important in having the 312 crank mains re-sized to 292 dimensions to have a machine shop that will maintain the radius-es on the edges of the new journal surfaces.  Also, have the crankshaft and entire rotating assembly re-balanced.  The link below will give you the 292 and 312 dimensional information you need.
3)  Use of the 312 crank in a 292 engine block will require use of the 312 ECZ connecting rods or the C1TE connecting rods originally designed for use with the HD 292 truck engines that had a forged steel crankshaft.  FoMoCo used the shorter connecting rods with the 312 crank.  The HD 292 C1TE rods are dimension-ally the same as the 312 ECZ rod, but stronger and heavier in weight.
4)  IMO resizing the 292 engine block main bearing bores to 312 dimension does increase the possibility of the 292 engine block main bearing webbing developing cracks.

5)  In the Spring of the 1959 vehicle model year, FoMoCo revised the production of the 292 and 312 y-block engines.  They increased the length of the main bearing cap bolts they were using.  In doing that, the engine block casting ID was changed from EDB 6015-E to B9AE 6015.  Longer main cap bolts continued to be used until the end of the production of the y-blocks in the 1960s.  See the link below for information from John Mummert's web site regarding using longer bolts for your engine build to avoid the forming of cracks in the engine's main bearing webbing.
http://www.ford-y-block.com/ARPmaininstall.htm

6)  Below is the link to John Mummert's web site with the dimensional information for having a 312 crank machined to 292 dimensions
http://www.ford-y-block.com/crankshaftid.htm

Hope this helps!  

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

Welcome to Y-Blocks Forever.  I started with a Y back in 1962, and came back to them about 15 years ago, and have become a dedicated fan.  The information given is good, and I would like to reinforce a couple of points that may help you with your decision.  If your 312 crankshaft is in good shape, turning the mains down to 292 main journal size and installing it in a 292 block will give a small increase in horsepower due to the smaller journal size.  Off set grinding the rod throws to increase the stroke is a definite plus on increasing the cubic inches without going large overbore sizes.  There are many performance rods available in 2.1, 2.0, journal sizes with lengths up to 6.250" being most common.  That gives a light piston, and good ring package, more cubic inches, and you can find pistons for just about any increment of bore size you need.  Personally I would look for the C2 or newer 292 block and bore it to 3.800, or 3.810 and you will not be disappointed.  Finding a block that has had antifreeze in it its whole life would be a great find since they tend to not be as rusty in the water passages.  Joe-JDC

JDC

I agree with everyone’s assessment of the 312 crank in the 292. Pay close attention to the seal area as many use neoprene/ rubber etc instead of the “rope”. The rope needed a different finish from my experience with other engines.

56 Vic, B'Ville 200 MPH Club Member, So Cal.