GB is not OK!

[Greybeard]

I'm going to stop for a while and get some tea, and then take the dog for a walk. Maybe I'll think of some obvious reason for this problem that I've overlooked.

[a10 gf]

I have another copper head gasket, so I could try fitting two to increase clearance. I also have a new composite head gasket that, at least before tightening down, is thicker. I think I have another cylinder base gasket so doubling them up might help.

...maybe better to find and fix the cause than treat the symptoms ?

[Greybeard]

I've been studying the BSA parts list. Here is a possible explanation of the problem. Pushrod lengths: The Plunger A10 uses part No's 67-360 and 67-362. The Star Twin and Shooting Star uses part No's 67-979 & 67-977. I've fitted a camshaft intended for the Star Twin & Shooting Star. The cam I have now has higher lift, so maybe the pushrods I have are too long. Anyone?

[Greybeard]

I have another copper head gasket, so I could try fitting two to increase clearance. I also have a new composite head gasket that, at least before tightening down, is thicker. I think I have another cylinder base gasket so doubling them up might help.

...maybe better to find and fix the cause than treat the symptoms ?

You are right of course. I've promised the organisers that I'll try to get to the Norfolk BSAOC camp, but it looks like I may not be able to sort out the problem before the weekend.

[RoyC]

The cam I have now has higher lift, so maybe the pushrods I have are too long. Anyone?

That makes sense GB.
When I put a high lift cam in my Trans-Am, I had to fit shorter push rods.

[chaterlea25]

Hi GB,
My 2 cents worth,
If you can get slack in the tappet adjusters then I dont think the problem is too serious,
Loosen the tappets right off and see will the engine turn over?
If not next  loosen the rockerbox and raise it up 1/4 in, then check if the engine turns
If the pushrods have not sat into the followers or rockers properly then the engine will jam as it is turned
I do not know why but the pushrods seem to like NOT sitting into their proper places

John

[berger]

agree with charterlea25 I once had one sitting on the very edge of a rocker cup and didn't know about it until I heard a twang when I was pulling the rocker box down, this was in the seventies and when I stripped the engine a couple of years later I found a bent push rod which explained what had happened

[Greybeard]

Hi GB,
My 2 cents worth,
If you can get slack in the tappet adjusters then I dont think the problem is too serious,
Loosen the tappets right off and see will the engine turn over?
If not next  loosen the rockerbox and raise it up 1/4 in, then check if the engine turns
If the pushrods have not sat into the followers or rockers properly then the engine will jam as it is turned
I do not know why but the pushrods seem to like NOT sitting into their proper places

John

Mmm, yes, that seems possible. With my bright torch I could see that the rocker caps were all located. I'll refit the head and rocker box and make sure the push-rods are in the cam followers properly. Fingers crossed that is the problem.

[berger]

greybeard I drop oil into the cam follower cups and put pushrods in then lift them out and feel the suction its a good way to find they are in

[Greybeard]

Right, I've had my tea and done my duty by the dog. I now feel quite hopeful that John, (chaterlea25) has the answer.

I'm going back out to the shed, (at 20:30). I may be gone some time!

[RoyC]

I don't know how much higher your cam is lifting, but I had to change valve springs as well because they were getting coil bound.

[chaterlea25]

Hi GB,
Roy has a point, did you replace the valve springs?
There have been some badly made ones on the market lately
II had a similar issue wit a B33 a few years ago, I had fitted goldie scrambles cams, but one spring had an extra 2/3 turn of wire even though overall length of the spring was correct

John

[morris]

I've been studying the BSA parts list. Here is a possible explanation of the problem. Pushrod lengths: The Plunger A10 uses part No's 67-360 and 67-362. The Star Twin and Shooting Star uses part No's 67-979 & 67-977. I've fitted a camshaft intended for the Star Twin & Shooting Star. The cam I have now has higher lift, so maybe the pushrods I have are too long. Anyone?

    I don’t see how the length of the pushrods or cam followers have any influence on the valve lift. If the followers or rods are too long or too short you’ll run out of adjustment on the tappet adjusters that’s all. If you can obtain your 8 or 10 thou play when the valves are closed and they are to far open when fully open it can only be the cam lifting them to high.
Another possibility is that your pistons don’t have the cutout for the valves.

I don't know how much higher your cam is lifting, but I had to change valve springs as well because they were getting coil bound.

Or that may also be possible.

[RogerSB]

Hi GB, very sorry to read you’ve hit a snag.

I did wonder about valve clearance & springs in one of my earlier posts if using camshaft 356. (edit: reply no 50).

According to my parts list camshaft 356 was used for 1960-62 A10 s/a as well as A7SS, A10RR, it's pt no 67-0356 and the pushrod are 67-0360 inlet & 67-0362 exhaust (so are just renumbered 1954-59 A10 Plunger nos 67-360 & 67-362). Same pt nos also for 1958-59 A10s. So they're the same parts from 1954 right through to 1962 for A10s.

Tappets & springs are also the same from 1954 to 1962 for all std A10s.

Not sure but I have it in my head (from many moons ago) pushrods lengths for A10s are 8 1/2” and 9 1/2”. A7s being shorter. I'm sure someone will be able to confirm that - or not?

[edboy]

i would double check your valve timing before you do anything else. valves should not touch pistons whatever the cam. maybe your camshaft is bad pattern.