GB is not OK!

[muskrat]

G'day fellas.
Just got up and read the reply's since my last post.
The A10 iron head and the A7 iron head and A7SS alloy head have the same collet and collar set up different to the SR so valves and collet/collars can not be mixed. Aside from the cam profile the timing of the cam is controlled by the keyway and is placed in the same position on all shafts.
I agree with John, the collets are too proud of the collars and too much valve tip protruding. The collar may well be hitting the top of the valve guide. This is the same as before but the slightly higher lift of the 356 may be causing the lockup. After market valves, collets etc often show inconsistencies to genuine. Collets "should" come in pairs and mixing them can create problems.
 I had this once when fitting a wild cam in my A7SS racer. I cut 1/8" off the top and all was good, no coil binding and no valve and piston kissing.
The cam does have end float and is held in position by the cork and inner cover. Without these the cam can move outwards enough for two lobes to contact the same lifter (had that happen when experimenting with the breather) also causing lockup.
In my last rebuild (dropped valve) I used SR valves and collets in the 54 A7SS head but had to remachine the taper in the collars and use the iron head springs, the SR springs became coil bound..
So in saying all that you need to check collar to guide clearance. If the lockup is happening when the valve is nearly fully open John has found the problem. If this is the case lop 0.06" off the top of the guides.
Cheers
Ps: Trev got in 1st

[duTch]

 

..... If this is the case lop 0.06" off the top of the guides. ......

 I can see your point regarding colllets, but can't see that will fix any coil binding, whereas machining the collet groove further up to the tip will do both, and it seems to be (more-or-less) agreed there's enough material to do that

[berger]

o yes those coils seem way to close , just had a look at the picky [after all this time] and compared it to one off the net, with the bigger cam she will be coil bound , the bounder

[muskrat]

GB has already taken 60 thou off the length of the springs to get over that problem.
Cheers

[berger]

mmmmm seems very close on those coils something is very wrong as we know, maybe as dutch says and what I did on mine might help. machine the top of the valves where the collets fit to lift the top collar and face off underneath the bottom collar more

[KiwiGF]

Here some pics of parts lying around. A small fin a10 head with bottom collars, and springs I think are from a later head but fit the collars ok.

I bought a basket case with several head and spring sets, but bought new springs and these were left over, but I’m fairly sure they are a10, apologies if not 

The outer springs are 1” I.d. And the longest is 1.96”. Wire dia 0.147”.

The spring compresses to 0.875” before binding, in the vice.

Edit: the spring lying crosswise to the others is slightly smaller I.d and made with thicker wire, it could easily be made to fit the head but binds at 1”l long.

[muskrat]

Gone back again and found I missed this "The symptoms are: turning the engine over by rotating the back wheel, (in 4th gear); engine goes almost full circle but comes to a stop when a rocker is fully down.". Indicates collar hitting top of guide. I also agree the coils of the spring are too close. What is the free length of those springs? Lengths are as Roger quoted 1.53" and 1.87".

Wow, on page 16  . See GB we do luv'ya.
Cheers

[kiwipom]

hi guys, GB, this is probably the silliest observation yet but i see a gap at the bottom of the spring and retainer, i know some of these retainers need to be fitted a certain way, is it possible that the retainers are up the wrong way, this is probably way of of the problem, so good luck with the answer you will find it in the end, cheers

[trevinoz]

GB, I fitted a valve and springs to head to compare with yours.
Kiwi, the bottom cup can only be fitted one way as it has recesses for the springs on the top side. There is a shoulder on the bottom to keep it clear of the head.

[RoyC]

It is noticeable that GB's collets are not seated as well as Trevinoz.
If the collets are hitting the top of the guides, could you not file a little off the top of the guides or modify the collets.
If there is coil bind, when the top retainer is allowed to come to the top of the collets that will give a 1/16" more spring clearance.

[muskrat]

Good onya Trev, saved me taking a few pics  .
Just took the covers off the plunger to check a few things. Although it's an SS the valve train is the same as A10GF. At TDC with both valves rocking I can push them down at least another 1mm. At full lift I can get a mm feeler between the coils easily and push the valve at least a mm till it hits the guide. This is with a 357 cam and low comp 7.5:1 pistons.
So it may be a combination of wrong valve springs, dubious valves (too much stem above the collets), collets not seating far enough in the collar and compounded by a higher lift cam. As mentioned the previous cam and follower wear would be attributed to these faults as well.
Oh the joy of working with so called pattern parts.
The way I see it the only way to get back on the road would be as mentioned earlier to machine the valve stem to lift the collets and collar higher say 2 or 3mm.
Cheers

PS: just measured a few old valves. From top of groove (where collets sit) to tip of stem inlet 0.305", exhaust 0.320"

[RogerSB]

Up early and trying to think out of the box (dangerous) and this may be another red herring but in 1958 the base flange of the A10 cylinder block was increased by 1/8" to make it 1/2". Did this make the whole block higher or did they shave off that 1/8" from elsewhere to make it the same overall height as it was before?
If it did end up 1/8" higher overall then everything above it was 1/8" higher and other parts would have changed to compensate.
According to the parts lists I see A10 piston and con rod pt nos changed from 1954-57 con rods 67-1203/4, pistons 67-423 to 1958-62 con rods 67-1205/6, pistons 67-1416.
Is it possible that could be causing the problem if using the later 356 camshaft with the smaller block and also it's original pt no valves?

[muskrat]

G'day Roger.
I think we're all overthinking this. The flange thickness was added to the top of the flange so all the valve train stayed the same. Even a 357 can be used in a thin flange motor without any changes. The rods were changed to large journal hence the part numbers, and higher comp pistons.
Cheers

[RogerSB]

Thanks Musky , I thought it may be a red herring but I got it into my head about 4am and I felt I had to put it forward

[duTch]

 GB - not important now, but for the record, I think grinding the Springs shorter was a little preemptive and not such a good idea- but good at the time ...mainly due to potential loss of spring preload, which may or not be regained by cam lift, but maybe not where it's needed at 'rest'....this can if need be alleviated if necessary with shims later on I guess...  ....