ET: Engine (Twin) Torque Plates and Cylinder Honing

[oexing]

I like my liners to have a minimum clearance in the engine case , a few thou but not the least resistance when sinking them in the case. I´d be very worried about any out of round deformation from "grip" in the case, could be the reason for seizures - or excuse for excessive piston clearances.

Vic

 

[Cyborg]

Yes.... an excuse for “extra” cylinder clearance. A subject worth discussion I think. The case can easily distort the liner. Something I’ve though about, but never measured. A while back Vincent made a comment about how easily cylinder liners were distorted with hand pressure. I passed that comment along to Magnetoman who happens to be assembling one of those contraptions from Small Heath. He measured the deflection you could get with hand pressure and it was significant. The discussion was with regards to using torque plates when boring and honing cylinders. His measurements taken after final honing with torque plates still attached and after they were removed indicated that indeed torque plates are a good idea. The BSA cylinder is different in that it has 4 long studs and 4 shorter bolts holding the cylinder head on, but I think the same rule applies to Vincent cylinders.

 

[greg brillus]

I have a torque plate for honing Vincent liners to final size.......Opinions from my engine reconditioning shop are that the Vincent barrels are quite sturdy by comparison to many others.......so I've stopped using it lately. Yes for a performance race engine, but for road engines it's probably a bit of overkill. There are many other things of greater importance to measure and observe when setting up the barrels I feel.

 

[Cyborg]

Up until recently I thought that using torque plates on Vincent cylinders would be pretty much pointless because the studs pass all the way through the muff. Now I’m not so sure. Did the shop actually measure the difference? Next time (assuming there is one) I’ll bore one with torque plates, measure the bore, them measure it again with the torque plates removed.

 

[timetraveller]

I had never head of torque plates so I have looked up what they are and watched a couple of videos to give me some background. I think that I now understand what they are but do not understand how it would work on a Vincent barrel. I assume that one would have to use two, one above and one below the muff with the top one bearing on the top flange of the liner. Education please gentleman.

 

[Pushrod Twin]

I had never head of torque plates so I have looked up what they are and watched a couple of videos to give me some background. I think that I now understand what they are but do not understand how it would work on a Vincent barrel. I assume that one would have to use two, one above and one below the muff with the top one bearing on the top flange of the liner. Education please gentleman.

Correct TT. One each, top & bottom of the muff with pressure on the liner to replicate what happens when the engine is assembled.
I used them when putting iron liners into Guzzi muffs many years ago. Didn't bother measuring the "fitted" vs "non fitted" dimensions, just accepted that the compression of the muff would distort the liner.

 

[Cyborg]

I had never head of torque plates so I have looked up what they are and watched a couple of videos to give me some background. I think that I now understand what they are but do not understand how it would work on a Vincent barrel. I assume that one would have to use two, one above and one below the muff with the top one bearing on the top flange of the liner. Education please gentleman.

You understand correctly. One on top pushing on the flange and one on the bottom... basically replicating the running conditions. Whether or not it’s worth doing on a Vincent road or race engine will remain undecided until I measure one for myself. As mentioned, I wouldn’t have thought it worth investigating because of the stud arrangement. If there were studs (threads) terminating within the muff instead of passing through it, the likelihood of distortion would be much higher. It’s the results that MM got with his BSA that makes me think it is at least worth exploring. Greg’s machinist says no, but what did the before and after measurements actually indicate. Once I/we have a hard number then a decision can be made.

 

[timetraveller]

To read up on this I watched a video of a chap measuring a four cylinder car block with and without the top mounted top plate to represent the cylinder head
He managed to get up to one thou difference but most of the measured changes were less than that.

 

[greg brillus]

Their explanation was that the Vincent muffs are quite strong......the clamping force of 30/32 Ft Lb's is not a huge amount, so the distortion is not that great. You generally only use the Torque plate for the final honing process, not the boring to size. The guy's that build very high performance turbo engines that put out huge horse power actually heat the block up to full operating temperature when they do this as well. I know some of these blokes that build these engines and the details they go to are quite amazing........a lot of these high spec engines run very high toque figures on their cylinder head bolts and this distorts the top of the cylinder block quite a bit I'm told. They run vacuum pumps on the crankcases and many other details all to gain extra power. Some of that technology we can apply to our engines, but it is costly and time consuming.........I wanted to make Titanium valves for my Vin racer but couldn't find anyone who was prepared to do it........the numbers needed are not high enough for them to bother........custom make some from blanks of titanium........very expensive.......you have to weigh up cost verses gain.

 

[Cyborg]

High jacking a high jack. Maybe these folks can help you out.

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MM was using 30 if I recall correctly.... the distortion was significant and right at the top where things are happening. Not so much of a piston clearance thing, but ring sealing? I’m definitely not prepared to wager my left testicle on the results of a Vincent cylinder, but still think it’s worth exploring.

Edit... it may well be that the 4 short studs account for the majority of the distortion in the BSA cylinder. Whatever the case I currently remain surprised how easily the liner is distorted.