Angle of the dangle // on valve geometry

[Rgs-Bill]

Pete, or Avatar name Billybream suggested we all kick this one around a bit, to see what the general consensus of opinions could come up with.  I explained to him that I was using the hardened valve stem end buttons, on the end of all four valves.  Now if you add that distance to the new rocker box gaskets, made of copper, or as some have mentioned here, double rocker box gaskets from gasket material, (home made gaskets much thicker than factory), would not the combinations in these forms, change the geometry of the rocker arms, where they contact the end of the valve buttons ?  Now could there be a possibility of that forcing the valve stem front to back, or side to side, and create more rapid wear on the inside of the valve guide, causing a replacement situation sooner, rather than later.  My rocker adjusters do have a small bit of radius face to them, could that be enough to compensate for the added thickness of things ? All of you guys out there put your thinking caps on, and come up with a tangible answer please .
      Thanks Much
        RGS-BILL

[bsa-bill]

Hi Bill - Bill here

I'm thinking that no matter what you do the lift on the cam remains much the same so the arc the rocker tappet moves through remains the same but will be scribed very very slightly more to the fore or aft only because the length of the tappet will have altered a thread or two.
Consider that BSA made a few different cams for A's without thinking there was a need to alter the valve geometry and also normal wear and tear will have some effect.
IMHO the increased wear is negligible compared with all the other things going on in there, unless your thinking of using A10 valves in the swivels on the pilot jet of a Saturn V

[muskrat]

 The geometry is altered by any change in valve length (caps), head refacing, thicker or thinner gaskets, push rod length etc.
At 1/2 lift the tappet should be central and in line with the valve stem. Lifting or lowering the rocker box (thicker or thinner gaskets) will move the contact point in or out of the stem center line. Push rod length or head/barrel refacing will alter the angle of the tappet in relation to the valve stem. Any variation will cause quicker wear.
Clear as mud.
Cheers

[bsa-bill]

Any variation will cause quicker wear.

yep granted Musky but I would be inclined to think the amount of wear would not warrant whatever amount of work needed to eliminate it, how long would it take for this extra wear to have any effect on an engine, and how much time and money would it take to eliminate it against the cost of a set of Valve guides

Of course it's not beyond some members here to come up with an OHC A10 (or has it already been done)

[muskrat]

 Copy of PM sent to RGS-Bill.
"G'day Bill. I'd have to agree, unless you ride like I do (rocket to anywhere) you won't notice much difference. Life span of valves and guides might go from 50000 miles to 40000 miles. If you can adjust something easily to get it right I would.
 I do mine out of habit (ex racer). Alloy push rods made to length, varying gasket thicknesses etc."
In saying that and going back to the original ? altering gasket thickness and valve stem length doubles the err.
Cheers

[Greybeard]

Of course it's not beyond some members here to come up with an OHC A10 (or has it already been done)

Like this?

[kiwipom]

hi guys, yes i don`t think there is much of an A10 in there,cheers

[muskrat]

I want one .

[bsa-bill]

I thought I'd read/seen/heard of this just couldn't recall - just Knew if I mentioned it here it would come to light
Well done Graybeard

[kiwipom]

Hi guys, came across this on the net:- Google it to see all the other interesting BSA information.
`Roland Pike Unpublished memoirs of his BSA years, 1952-1957`
 “The single overhead camshaft A7”
In 1952 they were working on a single overhead camshaft 500 twin. It was a handsome engine with alloy head and barrel, fine pitch finning, exhaust pipe held to the head by nuts. The single overhead cam was driven by bevel gears and a shaft running up what would normally be the push rod tunnel, the valves were operated by rockers. Arthur Bridgewood was working on it in great secrecy in a little shop at the end of the test shop; he had to put up with the noise and fumes of engines being tested. At this point in time it gave the same power as the A7 push rod engine and broke crankshafts with equal regularity. The camshaft was lubricated by the rocker feed which was completely inadequate and of course it wore out cams and nd rockers. Doug Hele suggested using a single wide cam as they did on some Ariels. This cured the rapid wear but the performance suffered due to the geometry of the rockers to cams, one rocker being a trailing rocker, the other a leading one this giving different opening diagram for each valve. I personally felt that the engine could have been made to go if I had been given more freedom as I had with the Gold Star and MC4. One problem was excessive oil consumption due to an accumulation of oil in the rocker box which ran down the valve guides. This we cured by using a C11 oil scavenger pump to pump surplus oil direct to the tank. The feed side of the little oil pump was used to squirt oil through 1/16th holes on to the cam lobes; this cured the rocker and cam wear. At this point we needed a stronger crankshaft and a different design of cams to
take advantage of the overhead cam arrangement. By this time Mr Hopwood had lost interest in the engine and said he did not think it would ever be any good, so scrap it. I think that’s what finally happened to it.

[Topdad]

Thanks for an interesting post Kiwi,  yet another piece of evidence of bad management /use of talent and resources coupled to lack of forward thinking and disinterest in there customers future requirements . Sums up my thoughts of bsa management from my dealings when working for a bsa dealership.
On the other hand what a project and what it could have lead to ,sound familiar ?? BobH.

[bsa-bill]

On the other hand what a project and what it could have lead to

Possibly the Bandit and the Fury albeit much in the future from 52

[kiwipom]

hi guys,yes looks like bsa were ahead of the game, if they had just stuck with it,cheers

[Greybeard]

Don't forget that Ariel made 600cc and 1000cc OHC square-fours before WW2.

I think that the BSA and other parallel twin push-rod engines aready provided excellent power to weight in a reliable and simple unit. This is amply proved by the many examples still on the road.