GB is not OK!

[Bsareg]

Surely if valves, push rods, followers etc are longer, it would only make a difference if there were no tappet clearance. As there is clearance isn't the problem elswhere?  Or am I missing something ?

Tappet clearance is set when the follower is on the flat area, not when the cam is lifting the follower/tappet/valve.

Thats what I mean. If the valve is hitting the piston but you have clearance when on the base circle, surely all thats left is either coil bound or cam lift.

[RoyC]

Hi GB,
I think I can see what the problem is??
First though, what shape groove is on the valve stems?
semicircular or a parallel reduced portion?
From your photos there appears to be too much valve stem protruding up from the valve caps
also the collets are not sitting far enough down into the caps
I had a thought earlier that maybe the top collar/collets were hitting the tops of the guides
I came across an A10 head where the components were mixed up and Super rocket valves and collets were fitted to
iron head valve caps, they do not fit correctly
The collets themselves maybe too thick??

If you take a valve cap and collets and assemble them off the engine will the collets hold the cap solidly without "rock"
The taper should hold the cap from falling

I am wondering now if this problem existed and contributed to wearing the reprofiled cam ????

John

I see what you mean, if the caps are being held down by the collets, that could cause coil bind.
It has not yet been confirmed that the valves are hitting the pistons.

[RogerSB]

I guess if that cam requires different timing there must be a camshaft pinion to go with it. I'll check the parts book.

Looked at my parts list and they have the same pt nos 1954 - 1962, cam 67-337/67-0337, idler 67-335/67-0335, crank 67-339/67-0339.

[berger]

sorry to jump in without reading all the posts,,, greybeard have you got the timed breather and cork washer and inner timing cover on... if you havn't the cam is wandering as I learnt and jamming two valves together hope this helps, ps I have not been to the pub

[Greybeard]

sorry to jump in without reading all the posts,,, greybeard have you got the timed breather and cork washer and inner timing cover on... if you havn't the cam is wandering as I learnt and jamming two valves together hope this helps, ps I have not been to the pub

Hmm, interesting. I had the inner timing cover off when I first noticed this problem but It's been off today while I've been testing. I don't get this though: The cam has a flange on the inside and the pinion fixed on the outside so cannot really wander, (as long as there is not a huge amount of endfloat).

[RogerSB]

After checking the pinions I compared all the pt nos for 1954 - 1957 A10 s/a and plunger valve gear with 1960 - 1962 s/a models valve gear. All use the same pt nos except for valves.
1954-57 A10: exhaust 67-324, inlet 67-323
1960-62 A10: exhaust 67-0743, inlet 67-0742

In addition the A7SS and A10SR, which also use the 356 camshaft, have even different pt nos again for the valves.

That's the only difference I could find between the valve gear. What the actual difference is in the valves I don't know - but there must be a difference.

[berger]

mmm tricky one this you could do with someone helping and 4 eyes are better to make two brains work, I do know when dry building my spare shooter engine with 357 cam to get none binding springs[ long story modified head with SR inlets standard exhausts ] I was turning the engine without everything in situ and eventually found the cam was riding two followers at a certain point and jamming two valve heads together , it took me ages to find out by using a good torch down plughole. it could also be it wasn't meant to have a 356cam like my shooter wasn't meant to have 357 without lots of things to put right to make it work, even srm knew when I told them what I was doing that they had to supply me with ground down bottom valve spring holders so I didn't get coil bind on the innlets and I had to take out some from where the collets fit on the exhausts to raise the spring height and stop those binding , some people had to remove metal from the cam trough when fitting a 357 I was lucky I didn't but I had a 4 day MARE trying to get valve gear satisfactory.

[RoyC]

After checking the pinions I compared all the pt nos for 1954 - 1957 A10 s/a and plunger valve gear with 1960 - 1962 s/a models valve gear. All use the same pt nos except for valves.
1954-57 A10: exhaust 67-324, inlet 67-323
1960-62 A10: exhaust 67-0743, inlet 67-0742

In addition the A7SS and A10SR, which also use the 356 camshaft, have even different pt nos again for the valves.

That's the only difference I could find between the valve gear. What the actual difference is in the valves I don't know - but there must be a difference.

Are there any part numbers on valves ?

[duTch]

 

That's the only difference I could find between the valve gear. What the actual difference is in the valves I don't know - but there must be a difference.

   My bit;  Reply 192 
 

I know the springs and collars & collets/keepers are different for SR, and apart from head size, I'm not sure if the valves *may* have slightly longer stems also....big can ' worms there     

 Without being a camshaft expert, I suggest the opening closing time difference is only due to fatter profiles at those points, and the fatter duration at TDC may vary a bit, but I'm running a 357 (with Ally head), and it works fine for me with 7.25:1pistons

 GB, if the springs *are* binding, you may have missed my suggestion;

 Reply 189;
 

I wonder if you could make/machine the top-cap/collet grooves a bit closer to the valve tip, would depend on how much is there to play with...?
Modify message     

 chaterlea-Johns idea sounds familiar and worth a look....

 **   bergers' idea got me thinking that before I finally put my barrels on properly,( because I gouged a cam-bush- yep with the key), I left the lifters out and had a look down the tunnel to ensure that the cam is running central and all the lobes are running true to each own lifter- no clipping, but as you didn't change bushes it should be fine 

  ** berger got in while I was writing...but same-ish story.....  then Roy

[KiwiGF]

I agree with the earlier comment the valve stems seem to be sticking out of the top collet a long way (which may cause coils to bind, and the jamming issue), has anyone got a pic of their head/valves handy, for comparison?

When I said earlier the valve stems could be too short, the same effect could be caused by the collet recess in the stem too far down the stem, or for that matter incorrect collets or spring retainers (or all 3!).

[KiwiGF]

Here is a random pic of a plunger head (allegedly) taken of the net, I’ve no idea of its history, but it might shed light on the matter, or confuse things further!

Certainly the gaps in the coils seems larger, but there is a fair bit of stem above the top collar....

[duTch]

 
 

...... the same effect could be caused by the collet recess in the stem too far down the stem,..................

^^ that agrees with my comment above (#218) & in reply #189, (also in bergers comment)

[edboy]

 have a good 334 camshaft and thought i would never use that as the lobes have hardly any lift on them. but it reads like greybeards top end has  been set up for that particular camshaft. do you have a photo of your old camshaft ?

[Greybeard]

have a good 334 camshaft and thought i would never use that as the lobes have hardly any lift on them. but it reads like greybeards top end has  been set up for that particular camshaft. do you have a photo of your old camshaft ?

The one I've taken out had been re-profiled. It's knackered so no point in a picture of it. I have the camshaft I took out six years ago which is a lot better than the reconned one. I'll take pictures next time I'm in the shed.

[trevinoz]

GB, I would think that the camshaft is not the problem, I have fitted a 356 in my '55 Flash with flat top pistons and no problems whatever.
I would look very carefully at the valves and springs, the springs look very heavy without much clearance between the coils as fitted.
I think that the camshaft wear can be attributed to these springs, I wore out a cam many years ago with the wrong springs fitted.
Also, as John pointed out, there seems to be excessive valve stem above the top cap. Maybe an idea to remove the valves and springs and compare them to originals if possible.
Just my two-bob's worth.