I have a junk block and lots of parts that I don't really care about to play with. I want to experiment with the fasteners and how to get some more clamping load, presuming that the increased torque on the bolts will be beneficial. I'd like to get into building alcohol motors with big compression and cylinder pressures and such.

I stripped a 7/16 main and it made me think. After I installed a helicoil(because it was an easy fix) I noticed that the stud took no damage what so ever. It ripped the threads out of the block like butter. So sometime tomorrow i'm going to take my torque wrench and see if I can actually stretch the stud on a bench, and maybe break it and record what I find.

Then I looked up some different inserts. By far the strongest is the gardsert. it claims something like 8 times the holding power of the original hole. I actually broke a bolt off in a gardsert once at work and tried to drill it out. Long story short, it went to the machine shop. But these are almost too fat to really be useful, there wouldn't be enough base material left in the block because of jackets and cylinder walls etc. But I did come across something called the timesert. Its a very slim profile thread repair that locks into the base material. Its also a thru hole, unlike the helicoil. There are some good promos of it on youtube. And it can be ordered in a long, like up to 1.6". This would transfer the load from the stud, which may only be engaged .500" or something and distribute it throughout the thread engagement of the whole insert. The insert is hardened and I'll try and find a spec for strength and material. Common sense applies, I'd use a CNC to ensure hole concentricity.

So now to my question. I'm still learning engine building. What are the specific benefits and drawbacks of being able to increase the clamping loads of the head bolts and possibly the mains? Has anyone overclamped an aluminum head and warped it and caused it to leak? If you can increase the clapming force in the mains and rods by 30%, after everything had been line honed and reconditioned, would this be a stronger bottom end, spin tighter, handle more power?? Remember I'm thinking about big compression and alcohol, or alcohol and lots of boost. Any input is welcom, Thanks

 

There is one company that I have used with very good success.
"Timesert", a thin body thread insert that locks in with the broaching tool supplied, basically you complete the last thread in the insert with a forming tool which inturn locks the insert into place with the pressure outward in the hole you are repairing.

I have not had one come out yet, but there are Gorilla's out there !
You never know !

LHP
www.haywardperformance.com

 

Ok so timesert worked well for you. Anyone have any ideas about overtorquing the heads or the mains?

 

Time-Sert is the GM and Ford standard thread repair.

 

Over-torquing head/main bolts damages the bolts (stretches them beyond the elastic/yield limit of the bolt material (particular steel alloy) which reduces clamping load and fatigues the bolt).

 

timesert works wonders when repairing a ford head that launch a spark plug

 

I could be wrong, but aren't some head bolts TTY applications? I thought the reason they used TTY was due to the higher clamp loads once the fastener plastically deforms. Of course, a larger fastener could be used, but then you're adding cost and weight.

 

Any Helicoil style repair should be stronger than the original hole tapped into aluminium.
By simple virtue of the new thread tap being larger diameter, and the insert being a harder material than the original alloy.

And factory mains on an LS are not 7/16", they are M10

 

You do not want to increase clamping load. You would want to increase the ability to hold a particular thread true to the tapped hole material at a particular clamped force. This is normally done via increasing the surface area of the forces being dispersed which leads to a clamped load being shared as evenly as possible. In large alcohol BBC compression motors it actually works out to be a 40lb/sq in in the center and 70 on the edge. This helps spread the torque load of big blocks evenly across the gasket and create a better seal. This is the advantage of adding bolts to heads and blocks in order to add clamping sources to better seal gaskets to blocks - preventing the lifting of heads which also blows gaskets.

Increasing the clamping load has no effect and does not solve any problems - if anything it can create more of them simply because heads will not be flush with gasket faces - exasperating problems once materials expand .003-.005; more or less depending on materials used (billet steel, cast iron, aluminum, etc)

There are benefits to using them - but not in the manner of increasing the load itself.