Fitting head to Dunstall cylinders

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madass140

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the Dunstall cylinders are about 9/16" thicker where the 3 x 3/8" head studs pass thru. simple enough I thought I'll just make 3 longer head studs.
ooops, obviously not so simple, now with longer studs its not possible to fit the head with the pushrods. the longer studs prevent the head being lowered coz the pushrods foul before the studs have a chance to enter their respective holes.
I could possible shorten the studs by about 1/4" and also removing the 4 rocker arms may help a bit.
anyone had this dilemma?
 
madass140 said:
the longer studs prevent the head being lowered coz the pushrods foul before the studs have a chance to enter their respective holes.

Not having tried it, have no magic answers.

The pushrods foul what though.
Can they be gathered together with elastic bands/string (undo the string later), or the cardboard comb method
 
well the push rods foul on the pushrod tunnel on the cylinders at the top. this cant be relieved anymore as the 2 x 5/16" tapped holes are already breaking thru into the pushrod tunnel at the bottom of their thread, probably coz these 2 holes have been helicoiled.
the standard cylinder thickness for the 3 studs is 1" , Dunstall is about 1-9/16".
its not possible easily to reduce this back to 1" as the nut face is not a machined face, bit hard to get in there to machine.
 
Put the studs by themselves into there respective holes in the cylinder first, fit the head/pushrods and support it on wooden blocks, screw the studs into the head (you may have to make some stud boxes to help in this operation as it will be a fiddly job)
Regards
Peter
 
Peter I had considered that, when I machined the studs this morning I made them a very firm fit on the threads. I would have to make the threads not so much interference otherwise I wont be able to tighten them which will be a headache anyway as there is not much room to get a spanner on the nut as it is, but yes I may have to go that way
 
Gidday Don.
Hope u r good.
mate, I have a suggestion.

Not having seen a Dunstall, this will depend on how much meat there is is to play with.

Therefore this may work, or there may not be enough meat.

the rear stud.

From what I gather, the length from rear washer spot face to top of cylinder length needs to be reduced by 9/16th.

This is where there may not be enough meat.

To machine this u only need a drill machine, suitable dia round bar incorpating a pilot, and a piece of round tool steel to be ground as a spot facer operating in the Up direction. There is only one way to machine the spot face.

Though much care and very gentle feed would be needed not to pull out the Morse taper. A mill with hand feed to a quill would probably be ideal. Reverse spot facing mate.

Which leaves the 2 front ones.

Same principle mate. Upside down spot facing with the bar doubling as a pilot. piloted guidance is essential..

As an old Evans Deakin man, you will be right on top of this.

If the full 9/16th cant be achieved, then may be this.

Depends by how much things are long. If you only need 1/8th or 3/16th to get things to fit, and meat permits, just shorten by that amount.
This would be a permanent operation and careful examination of how much meat there is on the cylinder would be recommended before taking metal off.

There are plenty of cutting tools for taking off metal. the add on tool is called a welder.
Edit. Just re-read your second post.
if the nut face is not machined, thats pretty poor engineering. However, if there is room for a nut and spanner, there should be enough room.
the bar would be the hole diameter to act as a pilot and drilled to mount a single point UP tool ground from round tool steel. easily made.. Fiddly maybe, but only needs to be done once.

Hope this may help. Best wishes bradley
 
Thanks Bradley I had thought about the reverse spot facing with a 3/8" + small boring bar. I just fitted the cylinders and really didnt want to pull them off.
I just now recut the threads on the studs so that they are now are a normal fit, I'll make a couple of small hex (probably 7/16") nuts to lock together and tighten as previously suggested. So its gonna be a case of drop the loose studs in the cylinders , drop the head on and screw the studs in. Just have to remember not to try and pull the head off without removing the studs.
well its about beeraclock, a ride off to the pub to test my new helmet cam.
 
I find a similar problem with the Maney barrels, which are basically a high quality copy of the Dunstall type. The front studs just clear if I push the pushrods as far into the head as possible, put the head in place, then screw in the rear stud to the head before finally lowering the head into place. This is the only way mine will go together without reverse spot facing the barrels.
 
It's been a few years since I put a Dunstall engine together, but I've done it several times, and don't recall having the problem you are experiencing. I've sold off most of the Dunstall stuff I had around, including all the fasteners, so I can't measure a stud for you. I'd suggest shortening the studs as much as possible and trying again. I do recall that you have to get the pushrods up past the rockers into the head, not resting on the rocker end balls. That might only be for the two longer pushrods, I'm a little fuzzy on remembering the details.

Here's a picture of the fastener kit I took a while back. You might be able to visually compare the stud lengths with yours.

Fitting head to Dunstall cylinders


Another solution, used on the Robertson alloy cylinders I imported and sold a couple decades back, is to use a stepped stud that is 3/8" at the head end and body, and 5/16" at the nut end. That gives a little more clearance between the stud and the hole in the cylinder at the beginning of the installation.

Ken
 
So how did Dunstall do it?

1) fit the head to the barrels with barrels off the cases, insert pushrods from the bottom of the tunnel, then lower the whole assembly onto the cases?

2) use flexible pushrods? :D

3) use 9/16 shorter pushrods? :D

Good luck finding a solution

Slick
 
as suggested , I'm dropping the studs in the cylinders, plonk the head on and then screw the studs back up, I reckon thats the best way and the head gasket wont get damaged by the studs if the studs are fitted normally, the studs I made are probably longer than the Dunstall studs, I'm using the long hex nuts.
 
gidday Don
just another crazy thought.

if you have a post 70 frame, can either both or just the front ISO bolts be removed after supporting the engine and cradle. this might allow lowering or pivoting the assembly just enough to get the job done.

A 70 or earlier frame, the cradle would probably touch the crosstube and restrict pivoting or lowering.
just a thought bubble. bradley
 
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