Stripped main cap threads


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By cos - 4 Years Ago
Hi Fellas   Trying to save this std bore 312. Bought this and 4 or 5 others in early 80s. Was looking for a std bore 312 for my 56 TB. Most of them were freeze broke. Finally found one with wrist pin gouge that I used. I saved this one, has a dent in deck (web area) where push rod go thru, 4 missing caps and number 2 main threads stripped. I check for cracks when I took it out of hot tank. Any body have opinion for thread fix or just let it go. Bill  Oregonhttp://forums.y-blocksforever.com/uploads/images/3d137836-b236-40e3-950a-fe73.jpg
By Vic Correnti - 4 Years Ago
I would think a helicoil would work. I believe they are stronger because the tap size is bigger for the helicoil.
By Ted - 4 Years Ago
Like Vic, my vote goes towards using a Helicoil for the thread repair.  The inserts are available in a variety of lengths so go longer than standard for a Ford Y main bolt thread repair.
 
https://www.albanycountyfasteners.com/Coil-Threaded-Insert-Stainless-Steel-7-16-14-p/11310000.htm
 
When replacing the main caps, try to replace all five with a matching five from another block.  If align honing, using five matching caps as a set will be easier to fit them to the different block.  If align boring, it will be easier to use mismatched caps in a block. Having a large selection of main caps will make it easier to find a set that comes closer to fitting a given block.  I like to keep the main caps from junked blocks bundled together as sets just for these occasions.
By Cliff - 4 Years Ago
Tyme sert will do the job
By 2721955meteor - 4 Years Ago
[quote]cos (5/23/2021)
Hi Fellas   Trying to save this std bore 312. Bought this and 4 or 5 others in early 80s. Was looking for a std bore 312 for my 56 TB. Most of them were freeze broke. Finally found one with wrist pin gouge that I used. I saved this one, has a dent in deck (web area) where push rod go thru, 4 missing caps and number 2 main threads stripped. I check for cracks when I took it out of hot tank. Any body have opinion for thread fix or just let it go. Bill  Oregonuote]
looks like there is a helacoil  in there.
By cos - 4 Years Ago
Hi Guys  Thanks for advice. My first thought was a insert of some type. My main cocern was oversizing boring bolt hole for 1/2 inch insert would weaken the block where cap seats. Ted, did you suggest using a 7/16 insert and bolt? Thanks
By Ted - 4 Years Ago
cos (5/24/2021)
Hi Guys  Thanks for advice. My first thought was a insert of some type. My main concern was oversizing boring bolt hole for 1/2 inch insert would weaken the block where cap seats. Ted, did you suggest using a 7/16 insert and bolt? Thanks

Keep it original; ½ -13 thread size for the Helicoil insert.  The Helicoil inserts are available in different lengths so use longer when possible just for additional thread retention.  Because this is a 312 and not a 292, I’ll suggest using a Helicoil insert rather than a Tyme insert as less material will be removed from the block in which to install the insert.  The amount of material at the edge of the main bolt hole on a 312 is marginal so minimizing the amount of material removed for a thread repair is recommended.
 
The Tyme insert will require an 11/16” drilled hole before tapping to the required ¾-16 outer thread size.  The Helicoil requires a much smaller 17/32” drilled hole before tapping the hole with the supplied Helicoil tap.