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E: Engine Valve Timing


Bill Thomas

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VOC Member
I think one of the books tell us the breather goes the wrong way ?,
Not bothered me too much as I don't use the standard one.
I don't think you need marks doing it my way, If you have trouble on the road,
It's TDC with the valves rocking on the wrong stroke, On either cylinder.
The halftime pinion keyways don't make much difference, It's only a way of giving you half a tooth ish.
Another way of checking the timings right is to look at where the brass bit on the mag' pickup is on the firing stroke.
 
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ClassicBiker

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VOC Member
David,
Yes, you have posted that before, but I can't remember whether it was on this or the old forum. Anyway now that you've posted it, it brings to mind something I read either here or on the old forum, and it raises a couple of questions. I remember reading that with regards to the twin drawing above, that the slot in the rear camshaft is in line with a line drawn from the crankshaft center through the rear camshaft center. While at the same time the front camshaft slot in perpendicular and down ward to a line drawn through the two camshaft centers. If this is the case I would think it would be easy enough to make a jig with a pin to fit the in oil quill hole in the end of the crankshaft and holes to fit over the camshaft spindles and pins to align the camshafts. If it were a plate it would need a large hole for the large idler to fit through, but if it were "V" shaped that might be avoided. If the former is true has anyone attempted to make the latter?
Steven
 

oexing

Well Known and Active Website User
VOC Member
Would you really rely on any slots, marks, dots on unknown parts with unknown history ? I did have dots on these genuine Andrews cams but would not care to dig into scetches and procedures for setting up the timing gear from books. I only trust in my measurements of equal overlap at the valve ends as shown above. So I really KNOW about the actual timing and not rely on somebody having pressed up the gears on the cams to specs and marks, slots, dots and what not.
Also, my marks on each cam tooth which align with the chisel mark on the engine case at equal lift can be checked any time I like for self assurance. Just find TDC for one pot at overlap and the corresponding alignment must be allright. All slots, dots etc. are void when you turn the crank a few revolutions as the idler gear has different numbers of teeth. So you can only start from very first step to check anything.

Vic
 

vibrac

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VOC Member
I agree with oexing dont trust the slots use them in the first instance to do a rough set up but then refine. After all if you are putting new cams in chain wheels you may not have a jig to align the parts up and in any case using the 4 degree method a wheel is a wheel and any old marks dont matter
 

timetraveller

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VOC Member
Posting #2 above. If you do not know the cam profiles then what are you timing for? I remember one set of cams that were so extreme that I had to time them with the lift half way down the stroke as the valves were hitting the pistons near TDC. By all means use short cuts once you know what you are dealing with.
 

ericg

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VOC Member
I agree with oexing dont trust the slots use them in the first instance to do a rough set up but then refine. After all if you are putting new cams in chain wheels you may not have a jig to align the parts up and in any case using the 4 degree method a wheel is a wheel and any old marks dont matter
Tim, does this means that one can press a cam in its pinion in any position and end up with no problem when using the 4 deg method? I have a brand new TP 105 cam in one hand and a new cam wheel in my other hand for my Comet project.
 

ClassicBiker

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VOC Member
As I said I timed mine by the 4*BTDC method.
But others on here have timed their cams to the timing marks on the pinions, using the slots, and then aligned the all the timing marks and called it good. I would suspect for expediency in manufacturing the machines originally, the cams were aligned to the marks on the pinions. Which in turn were align to the marks on the large idler. With the crank in position the and all the marks aligned the half time pinion was the last one to be placed once the assembler determined which key way lined up best with the slot in the crankshaft itself.
These machines were a mass produced item. So methods were devised to make assembly as quick a process as possible.

In these threads the relationship between the dots and slots are outlined.
So I would be willing to bet that the slots are datums for the manufacturing of the standard cams and that you could time the cams from them.
 

SteveO

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VOC Member
Turning my engine over and observing the valve movements it is quite obvious that the painted marks represent TDC (or 4 degrees BTDC) on the compression stroke on the back pot. I suspect whoever built the engine timed it then blobbed the paint on wherever. They may well have used the 4 degree method. As far as I can tell, the slots and cam are aligned properly. I have no idea what the provenance of the cams is. I have been loaned the Elgers collection of half-time pinions to use one to replace the one with the busted tooth, although Ray did say it would probably be OK.
 

Marcus Bowden

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VOC Member
Prof Neville Higgins didn't like the 7/16" spindles so ground his cams out to take 1/2" Torrington bearings (crowded roller). On the other hand good oil pressure & oil light bushes work fine for me and my MK2 cams have done over 300k miles.
 

SteveO

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VOC Member
Prof Neville Higgins didn't like the 7/16" spindles so ground his cams out to take 1/2" Torrington bearings (crowded roller). On the other hand good oil pressure & oil light bushes work fine for me and my MK2 cams have done over 300k miles.
Marcus, I agree the crowded rollers are overkill. They are in the rockers too which is a poor use as the rockers only move a few degrees. But they are what I have so I have to use them. The whole engine displays serious attempts to get it to rev, hardly necessary on the road for such a torquey engine, but I suspect it has been set up for racing. Ray Elger has told me it is well on the way to being as "hot" as his is.
 

oexing

Well Known and Active Website User
VOC Member
7/16 " shafts would not be to my liking but I was lucky with the new Andrews cams which had an i.d. of 5/8" , a tad below 16 mm. And yes, I like crowded needle bearings in various places when lubrication or very high loads are a factor. For crowded roller bearings you have to stick to certain sizes to get 0.10 mm gap, 4 thou, between last and first roller to prevent the lot from rolling scewed. In this case one pair of sizes for 1.5mm needles was 16.09 mm in the camshaft and logically 13.09 shafts - plus half a thou running clearance. So with a bit of lapping operation of camshaft bores and home made case hardened shafts this should be allright for life. Lubrication into the cams will be increased for sure with two start oil pump. Made crowded needle rockers too, don´t really like alu for bearing material. Needles not in the rocker of course, too narrow for that, but pressed in pin in rocker and needles in alu holders with a thin outer steel race made from gutted drawn needle bearing cups.

Vic
P1070238.JPG

P1040843.JPG
 

Pushrod Twin

Well Known and Active Website User
VOC Member
Nice work Oexing. I wasnt sure about the wisdom of the rockes initially, but on second thought, it cant be bad in view of the sketchy oiling in that area.

Prof Higgins dislike of 7/16 spindles is well founded, I believe. Read our NewZ editor Alice's account of wandering around Europe & finding he had 1 roller bearing cam shaft, which collapsed in fine style.
 

SteveO

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VOC Member
Interesting. Those rockers look pretty similar to mine, but mine are obviously a lot older. I suppose you can make case for roller bearings throughout the Vincent engine, the oil pressure is pretty low and the flow isn't great from the speed of the pump. I still think the rockers are overkill, but I suppose people use taper rollers in steering heads all the time which likewise have limited movement. Can I just take this opportunity to thank you all for your input. I am now much wiser than I was at the start of this post and have actually learned quite a lot about basic four stroke operation that I had never considered before. I said when I embarked on this rebuild that it would be a steep learning curve but even then I underestimated it!
 

Bill Thomas

Well Known and Active Website User
VOC Member
For me the taper Rollers are a good mod for the standard front forks,
As one who has tried to dismount !! via "over the handle bars", It seems to steady the front a bit.
Plus with an Hydraulic steering Damper = Much better.
Say Hello to Ray for me, He does not know me but we have spoke a few times,
A Sprinting Hero of mine !.
Cheers Bill.
 

A_HRD

Well Known and Active Website User
VOC Member
I am certain that I posted these before. I keep one for the twin and another for the single as a reminder.
David, Yes, I've seen these online from you before. However, unless I've failed to engage the old brain properly this morning, surely there is something wrong with the Breather nomenclature on the 500cc diagram - top left. That "B" on the breather must surely be just ENTERING space B on the Large Idler (not LEAVING it!)??
Peter B
 

davidd

Well Known and Active Website User
VOC Member
Excellent catch Peter! I thought the revised Richardsons had been heavily vetted. Of course, every other gear turns in the same direction. So, the breather will turn the same direction as the half-time pinion. I will have to fix the copies hanging in Pat's shop.

Before building a cam indexing tool we used to push the gear in anywhere and time it without reference to the marks, using only the timing of the cam. Although I used the timed breather on the Flash, I timined it by blowing through the outlet and moving the gear until it was timed correctly.

I can see using the marks in a factory setting and a repair setting, but I think we are so far from that time that checking all the data is the best. The downside is that it requires more tools, but that is something to which most have become happily resigned.

David
 

Mikeant

Website User
VOC Member
I have been following this interesting thread. Mine is a 48 Rapide engine in a Wideline frame. Effectively laid up not quite finished in 1977. At the time I bought new cams from the Thresher down at Lymm. Later I head that there was a batch of cams about that were not properly hardened. I got mine tested; they were too soft so they were nitrided and retested so should now be good. I got out the dial gauge and the degree disc and checked with the following results. No 1 Inlet opens 50BTDC max lift 0.319" closes 92ABDC. lift at TDC is 0.083" and at BDC 0.190". No 2 Inlet opens 49BTDC max lift 0.325" closes 85ABDC. lift at TDC is 0.110" and 0.200" at BDC.
No 1 exhaust opens 76BBDC max lift 0.318" closes 45ATDC has lift 0.174"at BDC and 0.091" at TDC. I could not get the gauge on the valve stem of No 2 exhaust due to the proximity of the frame so put it onto the tappit screw head instead and obtained No 2 exhaust opens 66BBDC max lift 0.292" closes 21ATDC, lift 0.168" at BDC and 0.062" at TDC. I am surmising that if the rocker arm has equal lengths either side of the pivot the lifts should be the same as measured at the valve but the timing should still be correct whichever.
Now these cams are not standard as the lift is too much. The inlets are about the same and not too far away from the book numbers, No2 exhaust looks to have less lift that No 1 exhaust but that might be down to the rocker arm. Oh and I checked with the valves on full lift to see how much more I could lever things and the results were not a lot so I clearly have some work to do here. I look forward to the experts' opinions.
 

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