E: Engine Liner/muff clearance

[greg brillus]

Barrels are only bored as an assembly never the liner on its own, the liner should not be a tight fit into the case mouth, you should be able to slide the barrel into and out of the cases with hand pressure maybe a light tap with a soft hammer at most. Having said that you also don't want the liners a loose fit or else the rear cylinder oil feed will not be as effective. I do use a torque plate only for the final honing to suit the specified piston clearance...........The barrel/muffs are quite strong and don't tend to distort much, but I have the jig so I use it, and torque the bolts to 30/32 Ft Lb's. This simulates the compressive loads on the barrel when the heads are in place and tightened, remember the head seals on the top of the liner face not the broad alloy face..............Before you do anything further, I would check and make sure that the height of the top hat of the liner is thicker than the depth of the recess in the head.......Otherwise it will not seal.......The difference should Ideally be 2 to 3 thou.......That is the head should measure 0.125" and the liner hat should ideally be 0.128" When all is well, If you sit the head atop the liner/muff assembly, there should be a small gap across the broadface of 2 to 3 thou...............Cheers and good luck................Greg.

 

[Cyborg]

The muff that I'm cutting down will be used to help hold the barrel assembly (muff and liner) in the lathe. The boring bar will get me most of the way and then I just purchased a rigid hone to get to the finished size. I only have a gap of about .0015" between the barrel and head, so need skim off a bit.

 

[greg brillus]

In that instance i have a good sized Linishing plate made of 12 mm glass and woven type emery paper glued to it, great for getting surfaces nice and flat and this works well to remove a thou or two off the head broad face. Good for crankcase halves and all the covers, manifolds, etc.

 

[Cyborg]

I recently salvaged the tempered glass out of a defunct Chinese digital bathroom scale for that purpose. The mating surface on the cylinder head needs to be cleaned up anyway. It was blasted sometime in the distant past with something that was a little too abrasive. I hate when that happens... the head just doesn't look right. I only use bead blasting for corroded steel bits. The head is going to get painted black. I would chuck the head in the lathe, but life is too short at this point for making a jig to hold it.

 

[Vincent Brake]

Do you bore cylinders on a lathe or mill? If so, do you use a torque plate (is that what you mean by pressure plate)? I wouldn't have thought a torque plate would be necessary as the cylinder studs are threaded into the crankcase and not the cylinder, so much less distortion Y/N?

better do all, like as it is on your riding vinnie; its hot, and thers presure on the cast iron liner flange, holding on its turn the muff down.
I always treat Alu like its dried snot, always on the move....
hence distortion.
So if one acts the distortion at honing, the better the roundness, and more over the less conical it becomes.

if you do it all cold, the cylinder is likely to be conical when the liner gives way when hot.
i machine a liner bit more interf fit at the top 10 mm.

but it its just all my little opinion or so.

 

[Cyborg]

Like working on my wood boat! Nothing stays where you put it.

 

[BigEd]

I recently salvaged the tempered glass out of a defunct Chinese digital bathroom scale for that purpose..............

A little heads up regarding plate glass for flattening components. I was loaned a piece of thick plate glass big enough to take a twin crankcase half. Check the glass in several directions with a good straight edge first. (I didn't.) It was not quite flat!
Because the casting is so large you end up with a dip or a high point in the middle depending on which way up you have the piece of glass. If it is too bad you will struggle to get a good joint when you put the halves together. The cases on my "B" cases are so thick and stiff the through bolts struggle to close any gap. I have had a leak that has annoyed me all last year so it is coming to bits any day now for a rebore and I will look to see then if I can find a good jointing compound to seal the gap. I dont want to remove any more material from the crankcase joint faces if I can help it as the end float on the crank assemble will be too small.
What fun we have working with old bits.

 

[david bowen]

On the Vincent brake in 1954 in the test house at night it was recorded that flames were coming out of the head joint so where did they come from the engine was on 12/1 on dope

 

[greg brillus]

Eddy, If your cases are distorted, then a very light skim over them on a mill is the best way. But the main issue to contend with is the cylinder spigot holes close up slightly. The crank and gearbox internals will accommodate some slight changes in overall width. Modern silicon sealants will fill gaps in cases, although it is hard to stop assembly oil from sitting on the joints where you need the sealant to go off without this "Lubricant" getting in the way. I always use "Threebond" sealants and these products give excellent results. Cheers for now...................Greg.

 

[bmetcalf]

Post #11 in https://www.vincentownersclub.co.uk/index.php?threads/to-peterg.5312/#post-35873 has a suggestion. I searched for "silicone" by "riptragle1953" on the Forum and found, surprise, surprise, a number of opinions.