Cam gap - what's happening ?

[1975-S1C]

Guys, I need help please.

Made good progress yesterday, or at least I thought I did.
Got the top end on, all seemed to be fine. Checked the cam clearances I've end up with and they all are around .12 to .15mm with the exception of 1 which was about .08mm. No problem I thought as I had a shim 1 size smaller. Popped that in, the gaps increased to about .25mm ! Thinking I must be going mad, I went back the other way and put a larger shim in than original, now we were at .30mm. Madness
So I put the original back in that was giving me .08mm, now it gives about .6mm.
What the hell have I done.

Mucho depressed. After a whole day grafting yesterday and making good progress it all seems to have turned to crap

Any suggestions on what the problem might be before I end up having to tear it back down again ?
Cheers

[z1bman]

is the shim bucket a tight fit ? does it turn freely in the head ?

[1975-S1C]

I can spin it with my finger if that's an indication ?

[z1bman]

what size shim was in there originally & what size shim did you replace it with ?

[1975-S1C]

Can also move it up and down with a little screwdriver till the shim touches the cam so I'd say it's fairly free in there

[1975-S1C]

Originally a 255, gap was about .08mm so replaced with a 250 expecting to get about .13mm but all of a sudden it was about .25. Large shims making no difference. Original shim back in there now and the gap is about .6mm

[z1bman]

are the threads on the cam cap bolts stretched ? did you use a torque wrench

[1975-S1C]

Yeh I used a torque wrench and only torqued to the proper amount

[z1bman]

is the valve timing ok

[1975-S1C]

It is the first time I've done this, so but I'm pretty sure I've followed everything correctly.
With the 1-4 timing T Mark aligned numbers 1 and 4 are at tdc and the cam pointing horizontally.
That would be a major problem if I screwed that up though I guess.

Can't see why it's just this one valve that's playing up. It all seemed fine when I assembled it.

[kev edwards]

is your first shim going into the bucket properly and not a tight fit?

[1975-S1C]

Yes, seems to be Kev. I've tried 3 or 4 different ones in there anyways, but in any case I'd imagine that would make the gap smaller rather than larger.

The weird thing is, it was only .08mm at first with the 255 shim. A 250 shim should have given me .13mm which would have been spot on where I wanted to be. But as I tried different larger shims the gap seemed not to reduce. Put the original back and the gap was now .6mm ! What the !

I'm also starting to think maybe it is something to do with the cam caps / shells maybe like z1bman was saying. I did torque them down to the correct setting though. The other thing is that the next valve along I.e. On the other side of the same cam cap doesn't seem to have a problem.

I'm confused as hell

[pluto]

Have you measured the shim with a micrometer or are you going by the number on it? Things arent allways what they claim to be. Just a thought.

[1975-S1C]

Yeh, measured them just to ensure I wasn't going mad, but something's not right somewhere because I went somehow from a .08mm gap to about .6 mm.

I guess the next step is going to be to have to start tripping it back down again. I'm thinking remove the cam caps on the inlet side and see if I can see anything going on there.

Is it ok to leave the exhaust cam bolted in place and just remove the top idler and inlet cam ? Or must I remove both cams ?
Cheers

[z1bman]

personally i would change the bolts in the cam caps & start again


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