Main Cap Bolts-Length Issue


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By Jack Groat - 4 Years Ago
I just discovered my new ARP main cap bolts are too long.  As it turns out, I must have a block earlier than mid 59.  After that, Ford deepened the main cap bolt depth.
I was told go to your friendly machine shop and have them deepen the main cap threads.  I just got off the phone with them and they said they have never heard of this operation and are reluctant to go forward with the process.

I can certainly use the existing bolts or find new of the same length.  I was told the existing bolts are really too short for a high performance engine.  The ARP bolts are only available in the longer length.  I could try and find another machine shop familiar with the operation.

My engine will have 10:1 compression, a performance cam, and 3-2bbl carbs.  I may, if given the opportunity see my quarter mile time or run it on a chassis dyno.  Otherwise the engine will not see much severe action.

OK guys.  Need your advice and opinions.

 
By Cliff - 4 Years Ago
It's an easy job to drill and tap the main holes deeper, you can do it with a hand drill if your careful, use the main cap as a guide, it is about a 1 hour job for all bolts, when your done look down the oil galley and make sure the bolts do not block the oil galley.
By DryLakesRacer - 4 Years Ago
I Have ground off threads of Grade 8 bolts/studs for my GMC head. I have also used additional hardened washers under the cap screw head.
Curious, why didn’t you go with ARP studs? I order them by length from them for my racing GMC’s along with nuts and washers. I never tell them the engine because they have no listing for it so I do it by size. If they give me the part number sometimes I look it up at Summit or Competition Products and the have them at a lower costs. Good luck.
By charliemccraney - 4 Years Ago
Studs may not be required and they require clearancing of the rear main seal retainer, which I wouldn't recommend unless they are really needed for the build of the engine.
By 55blacktie - 4 Years Ago
If your machine shop is reluctant to do the work, I wouldn't attempt it. Find a machinist who knows these engines and has done it. Send an email to Ted.
By paul2748 - 4 Years Ago
I would ask Ted if you really need the longer bolts for the engine you have (actually need the additional length for high performance use)
By Jack Groat - 4 Years Ago

If Ted says to do it, I'm gonna do it!!

I talked to my machine shop again and they asked me if the block will set flat upside down on a milling table;  It will.. in which case it should be an easy fix.  They told me to bring the caps and bolts and they will check the line bore before it leaves the shop.

FYI..  I have read the "Rebuild your Y-block" cover to cover and lots of comments and questions on this website and I never heard of this issue.  When I called John Mummert he said it was fully explained in the documentation he sent me.  As it turned out, setting right next to the recently opened bag of main cap bolts was a folded sheet explaining the whole situation.  Hopefully, by posting this I can save someone else from getting blind sided by the same issue.
By paul2748 - 4 Years Ago
What did John say to do?
By Jack Groat - 4 Years Ago
When you asked, "What did John say?"  I assume you meant what was written on the sheet of paper with the bolts.

First he listed the block casting numbers that did or did not need the bolt holes deepened.  Then directions on how deep to drill, the drill size and a warning...  do not attempt to do this by hand...

By paul2748 - 4 Years Ago
Thanks
By NoShortcuts - 4 Years Ago
Paul.  IF you click the link below you'll view the complete information sheet that John Mummert includes for guiding those installing the longer ARP bolts or studs that are recommended.
http://www.ford-y-block.com/ARPmaininstall.htm

Looking back, production of the FoMoCo y-block began in the U.S. for the 1954 model year.  For the engineers to decide in Spring of 1959 model year to increase the length of main cap bolts in the 292 and 312 ('59 & '60 Merc application!) engines was significant.  Imagine how many 239, 256, 272, 292 and 312 y-block engine blocks had been made between 1954 and mid-1959 for the various Ford car, Ford pick-up truck, Thunderbird, Mercury, Edsel, Ford heavy duty truck, and various industrial and farm related applications.  WoW!

A number of y-block engines being re-manufactured by FoMoCo or by Ford Authorized Re-manufacturers had to be found with some pattern of cracking' in the main bearing block webbing area,  Extending the length of the main bearing cap bolts was a solution.  Seemingly simple enough, but not without expense for FoMoCo to implement.  Necessary OR wise to-do for heavy duty applications like big, heavily loaded trucks OR for those actively exercising their engines capability with acceleration, elevated rpms, or load pulling ability. 

For those of us putting together anything more than a grocery-getter, if you're going through a pre B9AE engine block with main cap line honing, block squaring, cylinder boring, zero decking for pistons, rotating assembly balancing and the like, installing longer main cap bolts is something GooD to do.  Studs are a little more effort to do, but . . .    Smile           .