Back to the extra block studs

[Ian Williams]

Perhaps Geoff is wanting Unified threads simply because of the ready availability of high grade fasteners in these threads, I can not believe the actual thread type has any advantage. BSF and Whit threads are extremely good, and from my own personal experience it is frustrating as hell to work on an engine which has a mixture of non standard threads and spanner sizes.

[Charles P]

Quick summary of my thinking here:

Firstly a lot of the examples of extra block studs are from coil engines or even coil engines with the later "rear facing" starter motor. Both these engines are easier to put extra studs in. In the case of all coil engines the dynamo mounts aren't in such an awkward place (and there's the cam locking bolt). With the later motors you don't have the starter motor mounting to consider, only the the tin flywheel cover. It's much harder with a roadgoing mag engine!

Secondly the bulkhead/block clearance is tight on a road car. Design in more clearance than I did.

Thirdly any extra stud has to have some meat to tap into. The rear camshaft bearing is the one sensible point at the rear. The front cam bearing is useful in the front. Also if you put brackets on the block they must clamp to the crankcase perfectly. This means mounting them and machining them flat with the base of the block. If you use a long stud you'd need the widest foot to preload against to avoid pulling up the metal around the thread.

Finally it worth noting that some cars do run very well without extra studs - Jeremy Flann's blown Super Sports is very quick on 8 studs.

Charles

Ps. Geoff's stud thread changes were for material purposes. Finding high strength BSF/BSW fasteners is very hard and something of a lucky dip.

[Dave Wortley]

I think I have mentioned this before. Ian Bennett has a Pigsty blown engine with some extra block crankcase holding down arrangement. I can't remember the details except it involved a fabricated bracket at the front. May not be relevant to a mag engine.
Cheers,
Dave.

[Ruairidh Dunford]

I have a rearward facing starter in place of the bacon slicer type on my mag engine - this is a direct fit and just requires a starter button.

Using one may give you more room. Mine is fitted because I find it gentler on the fasteners.

[Charles P]

I have a rearward facing starter in place of the bacon slicer type on my mag engine - this is a direct fit and just requires a starter button.

Using one may give you more room.  Mine is fitted because I find it gentler on the fasteners.

I have the same, for similar reasons. 
However if you look at the picture near the top of this thread you'll see how the stud encroaches on the starter motor casting's mounting area. And of course, the starter castings aren't exactly strong before you start grinding bits off!

Charles

[Ruairidh Dunford]

I cannot locate it just now but somewhere in the sheds is a homemade brace for this type of starter (see sketch below) - I wonder if making similar with a tin cover might allow you to be more creative with the shape and get what you need?

   

[Zetomagneto]

Quick summary of my thinking here:

Firstly a lot of the examples of extra block studs are from coil engines or even coil engines with the later "rear facing" starter motor. Both these engines are easier to put extra studs in. In the case of all coil engines the dynamo mounts aren't in such an awkward place (and there's the cam locking bolt). With the later motors you don't have the starter motor mounting to consider, only the the tin flywheel cover. It's much harder with a roadgoing mag engine!

Secondly the bulkhead/block clearance is tight on a road car. Design in more clearance than I did.

Thirdly any extra stud has to have some meat to tap into. The rear camshaft bearing is the one sensible point at the rear. The front cam bearing is useful in the front. Also if you put brackets on the block they must clamp to the crankcase perfectly. This means mounting them and machining them flat with the base of the block. If you use a long stud you'd need the widest foot to preload against to avoid pulling up the metal around the thread.

Finally it worth noting that some cars do run very well without extra studs - Jeremy Flann's blown Super Sports is very quick on 8 studs.

Charles

Ps. Geoff's stud thread changes were for material purposes. Finding high strength BSF/BSW fasteners is very hard and something of a lucky dip.

Charles, are you wanting to run a dynamo, obviously easier to fit an additional front stud without a dynamo, but your Bolt/stud will need to go through the timing gear cover And into the front cam bush

[Zetomagneto]

Quick summary of my thinking here:

Firstly a lot of the examples of extra block studs are from coil engines or even coil engines with the later "rear facing" starter motor. Both these engines are easier to put extra studs in. In the case of all coil engines the dynamo mounts aren't in such an awkward place (and there's the cam locking bolt). With the later motors you don't have the starter motor mounting to consider, only the the tin flywheel cover. It's much harder with a roadgoing mag engine!

Secondly the bulkhead/block clearance is tight on a road car. Design in more clearance than I did.

Thirdly any extra stud has to have some meat to tap into. The rear camshaft bearing is the one sensible point at the rear. The front cam bearing is useful in the front. Also if you put brackets on the block they must clamp to the crankcase perfectly. This means mounting them and machining them flat with the base of the block. If you use a long stud you'd need the widest foot to preload against to avoid pulling up the metal around the thread.

Finally it worth noting that some cars do run very well without extra studs - Jeremy Flann's blown Super Sports is very quick on 8 studs.

Charles

Ps. Geoff's stud thread changes were for material purposes. Finding high strength BSF/BSW fasteners is very hard and something of a lucky dip.

Charles, are you wanting to run a dynamo, obviously easier to fit an additional front stud without a dynamo, but your Bolt/stud will need to go through the timing gear cover And into the front cam bush

[Greig Smith]

  Additional hold down block.JPG (Size: 110.69 KB / Downloads: 392)
  Additional hold down block front.JPG (Size: 50.73 KB / Downloads: 390)
  Additional hold down block rear 1.JPG (Size: 120.71 KB / Downloads: 392)
  Additional hold down block rear 2.JPG (Size: 106.67 KB / Downloads: 391)
  Additional hold down block rear top.JPG (Size: 121.86 KB / Downloads: 393) 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

[Colin Reed]

Hi All,
On the old forum there was a post about crossover intakes for SU carbs and somebody had posted a photo of one of Frank Hernandez cars showing this setup but it also showed the rear clamp down arrangement that he had used which is very well Engineered  but I have not been able to find on the old site,
Perhaps Alan Might be able to help on this one.
Regards to all
Colin