Wanted: camshaft 67-0334 67-334 New

[limeyrob]

So do you have a good explanation of the noise? Pistons, cam, followers or valves?  It does rather sound as if the pistons are touching the valves so they could be bent now. Put some Plasticine on the piston and turn it over very slowly and see what clearance you have.  Rather than change the cam it may be better to change the pistons. There's little to be gained by upping the compression with the pistons then reducing it again with a compression plate.  The pistons should stop flush with the top pf the cylinder.

[JulianS]

I think that because the A7/A10 cam followers are set at an angle rather than vertical the use of a compression plate between crankcase and cylinder results is a change in the geometry between follower and cam.

The below is a cross section view taken from a 1952 BSA patent and shows that the centreline of the cam core passes through centre line of the follower. Raise the cylinder with a compression plate and the follower sits lower in its tunnel and moves its centre line to the rear and out of line with the cam core centre line? Is this enough to cause the noise?

The other thing is to make sure that the follower full movement not held off the base circle of the cam by the position of the retainers.

[chaterlea25]

Hi All
Be aware that a batch of cams were made and advertised as 344  but are actually long stroke 695's
I would agree that fitting a compression plate will cause problems,
Along with the followers that may hit on the retaining pins making a larger unseen gap between cam and followers,  raising the cylinder vertically will also alter the valve timing to some degree
More importantly making up the 2mm on the tappet adjustment  will alter the angle of the pushrod/ rocker. This could result in the pushrods touching the cylinder or head 

I would think that 8.25:1 pistons and a 356 cam would result in a very pleasant engine

John

[trevinoz]

I have a 356 cam and 7.25:1 pistons in my "55 Flash and the motor is very quiet running.

[CheeserBeezer]

I have a 356 cam and 7.25:1 pistons in my "55 Flash and the motor is very quiet running.

Yes, of all the various options, I find that the iron head, 356 / 7.25:1 option is best for everyday running. Not fast, but adequate for main roads and country lanes. A nice, comfortable, lazy ride.

[Black Sheep]

"Yes, of all the various options, I find that the iron head, 356 / 7.25:1 option is best for everyday running. Not fast, but adequate for main roads and country lanes. A nice, comfortable, lazy ride."

But still capable of a god turn of speed should you so care.

[limeyrob]

I too would not fit a compression plate, but that still leaves the problem of the noise. Could the 8:25 pistons be coming up too high in the bore, ie wrong pistons?

[Rien]

there is a new one on ebay and a decent second hand one ,

Thanks Berger. I can't the new one on Ebay, only used. Can you send me the link?

[Rien]

I think that because the A7/A10 cam followers are set at an angle rather than vertical the use of a compression plate between crankcase and cylinder results is a change in the geometry between follower and cam.

The below is a cross section view taken from a 1952 BSA patent and shows that the centreline of the cam core passes through centre line of the follower. Raise the cylinder with a compression plate and the follower sits lower in its tunnel and moves its centre line to the rear and out of line with the cam core centre line? Is this enough to cause the noise?

The other thing is to make sure that the follower full movement not held off the base circle of the cam by the position of the retainers.

Thanks JulianS for your clearly explanation. Never seen the drawing before. To reduce the compression a bit I'm thinking of - instead of the compression plate under the cilinder - to place a solid copper head gasket of 2.0mm. Now there is a solid copper of 1.0mm.

[Rien]

Hi All
Be aware that a batch of cams were made and advertised as 344  but are actually long stroke 695's
I would agree that fitting a compression plate will cause problems,
Along with the followers that may hit on the retaining pins making a larger unseen gap between cam and followers,  raising the cylinder vertically will also alter the valve timing to some degree
More importantly making up the 2mm on the tappet adjustment  will alter the angle of the pushrod/ rocker. This could result in the pushrods touching the cylinder or head 

I would think that 8.25:1 pistons and a 356 cam would result in a very pleasant engine

John

Thanks John. I've made longer pushrods (from old A10's) plus 2.5mm 0.1" alsoo because of a ticker solid copper head gasked of 1.0mm 0.04"

[Rien]

I too would not fit a compression plate, but that still leaves the problem of the noise. Could the 8:25 pistons be coming up too high in the bore, ie wrong pistons?

Thanks Limeyrob. After 10.000km you can see on the head of the pistons a bit of coal so I don't think they hit the valves or the head.

[Rocket Racer]

very late to the party, the cam followers only have limited travel so its very likely the sound is the cam hitting the follower as the follower cannot drop far enough. get that compression plate out and put some nice flat top IMD pistons in it.
Decompression plates only suitable for the pre unit singles not the twins

[Rien]

Thanks RR. We've checked the cam followers and they came onto the camshaft.

Update: so now I have a camshaft 0334 and I've made a solid copper head gasked of 2.0mm installed. The noise is over!  Thanks everyone for the comments.

[chaterlea25]

Hi Rien,
It could well be that the compression plate is the cause of the noises 
Reground followers add to the equation

I think it's likely that the followers are bottoming out on their locating pegs and not reaching the camshaft base circle

John

[Rien]

Hi Rien,
It could well be that the compression plate is the cause of the noises 
Reground followers add to the equation

I think it's likely that the followers are bottoming out on their locating pegs and not reaching the camshaft base circle

John

Hi John, indeed the followers are  regrounded. More I think the cause of the noise was the 'character' of de camshaft 0356.