Distributor (Lucas 43 D) clamp - anyone had one of these lose it's grip? Fail to clamp the distributor? ANS: Yes

[anthony1956]

Covering the bases here. Probably my error when retightening it, but I do seem to keep finding the timing has changed. 

Nothing surprises me any more with this car being (nearly) 40 years old.

Anthony

Edited 20 hours ago by anthony1956

[OldAndrewE]

One like this I presume Anthony

They can stretch such that the clamp gap closes up before the distributor is gripped.  When you have it tight can you move the distributor by hand?

[Miker7]

How much is it losing timing?

If you can turn the distributor by hand, how much does it move? If its only a little bit do you have a spring washer under the bolt head that goes into the block?

[anthony1956]

@oldandrewe Yes exactly one of those. Yes it is looking a bit out of shapish. However, not closing up where it shouldn't. 

and @MIKER7 No can't turn it by hand, checked that, in fact always check that. It lost about 6 degrees, or 2/3 of a cam tooth. "A" tooth defined as one tooth AND one gap on the sprocket. Given a cam degree is half a crank degree that'll be 12 degrees on the cam I guess. 

I THINK what's going on is that I am not tightening it enough so that when driving it gradually loses its grip just a bit at a time. I did it up much tighter today and it hasn't budged. Also previously I was having to put a lot of force on to the dizzy to turn it to get enough advance. So I Moved all the HT leads one-to-the-left. I.e one contact clockwise given the rotor goes anti-clockwise, which retards the dizzy by 45 degrees, and then I can advance it to get my 6 degrees nice and easily. This has worked today so whether the fact it was forced top far and slipped back or was not tight enough or both is as maybe was. 

I picked up the 45 degree trick for a 2006 post of chevy owners, which I find remarkable. 

All the above is subject to my timing should be 6 degrees BTDC no 1 compression stroke. I am not at all certain the numbers I mention above stack up in the context given cam degrees are half crank degrees. 

If you could sort me out in that regard I could stop worrying about it 🙂

My cam sprocket has 40 teeth so 360/40 = 9 degrees, but do I then want 2/3 of a tooth (defined as above) or if this is only half, then 4/3 of a tooth i.e. 1 1/3 teeth? We do not have any crank markers that are capable of use. 

edit @OldAndrewE the one I found had two holes for bolts..

Have to admit I am very wary of replacing it as it looks like one has to lift the dizzy out completely and knowing me I would put it back a tooth different

https://www.holden.co.uk/p/distributor_clamp

Anthony

Edited 22 hours ago by anthony1956

[anthony1956]

I am clearly wrong about doubling the timing, but it's doing my head in:

[anthony1956]

a bit bent but still working

[Miker7]

Cams spin at half engine crank speed, as does the distributor - 360 degrees of distributor/cam shaft is 720 degrees of crank. Is this what you mean about doubling?

[anthony1956]

2 hours ago, Miker7 said:

Cams spin at half engine crank speed, as does the distributor - 360 degrees of distributor/cam shaft is 720 degrees of crank. Is this what you mean about doubling?

yes, I see you illustrated doubling.

Holdens want £6 to deliver their £20 item. Not willing to be ripped off like that.

Edited 18 hours ago by anthony1956

[anthony1956]

So I did it tighter and today, for the first time, I got her started at the first attempt. It wasn't easy, but she started. I checked the timing and it has not changed from yesterday.