Back to the extra block studs

[Greig Smith]

  Additional hold down block.JPG (Size: 110.69 KB / Downloads: 394)
  Additional hold down block front.JPG (Size: 50.73 KB / Downloads: 392)
  Additional hold down block rear 1.JPG (Size: 120.71 KB / Downloads: 394)
  Additional hold down block rear 2.JPG (Size: 106.67 KB / Downloads: 393)
  Additional hold down block rear top.JPG (Size: 121.86 KB / Downloads: 395) Hi Charles et al

A little late to this party, I too was curious about additional studs on the old forum and looked at a variety of options before settling on this one. The new bolts are metric because we are a metric country and imperial HT is not readily available

We bought a length of aluminium bar stock and measured carefully to suit the front cam bearing locating screw - The cam bearing hole in the block was tapped to 8mm and a HT cap screw was modified to replace the square head one. The cap screws into the block are 6mm. The top cap screw at the back is 8mm as that was the closest to the original 5/8ths bolts which originally held the block down (now 10mm HT bolts from underneath but that is a post for another time).

The aluminium bar was then drilled & countersunk on the side to clear the timing cover / generator / dizzy mount.

The block was cleaned and checked for flatness, then the aluminium bar pieces bolted into position and tightened down. Once done we drilled a short way into the block through the new aluminium bar. Removing this let us finish the drilling using the protrusion of the new 6mm bolts as a guide for the drill depth. These were then tapped to 6mm threads - at no time did any of these 4 new holes actually penetrate the valve chest, they are small blind holes so there is no risk of oil leaking there. We then fitted the black & torqued all the bolts into place with Lockite. We fitted a piece of Vellumoid between the new lump and the crank case, like the block to crank case gasket + a wipe of sealer.... we were in 2 minds about this, but in the end went with it.

The idea isn't to try clamp the whole block, just to provide another pair of hold down bolts at the outer ends of the valve chest which we felt were the weak spot in the mix. I looked at a few other options, one of which was a chunk of angle iron and the other that Pigsty head clamp and long stud before coming up with this as an alternative.

Time will tell if we were right in our thinking.... 

Cheers
Greig

Sunny South Africa