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Problem setting timing on my BT7 - maximum distributor rotation reached

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fishyboy

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Hi all,
I tried to set the timing on my BT7 today using my strobe (15 degrees BTDC at 600rpm). The problem is that I can only get up to 8 to 10 degrees by rotating the distributor as far as it will go clockwise and turning A-R knob on the dizzy as far as it will go. I have checked the timing at 3000rpm which is around 20 degrees.

I am at loss. So far I haven't gone back to check the static timing?

Any advice welcome.

Phil
 
fishyboy said:
Hi all,
I tried to set the timing on my BT7 today using my strobe (15 degrees BTDC at 600rpm). The problem is that I can only get up to 8 to 10 degrees by rotating the distributor as far as it will go clockwise and turning A-R knob on the dizzy as far as it will go. I have checked the timing at 3000rpm which is around 20 degrees.

I am at loss. So far I haven't gone back to check the static timing?

Any advice welcome.

Phil
Click to expand...
i believe 15 is only for BJ8's. Look at the AR knob and you should see 4 marks on it with one mark being bolder/larger than the others and that's the one you want lined up with the edge of the vacuum advance part.

If if you can only get 20 degrees advance you might want to check the mechanical and vacuum advance functions. I usually rev the engine to 3k and using a wood block, and with a stable rpm I unplug and plug the vacuum advance connection looking for a increase or drop in timing.

Make sure there's nothing binding the movable distributor plate that moves inside the distributor that moves for your mechanical advance.
 
Thanks Patrick
Pretty sure the 15 degrees BTDC applies to the BT7 (checked out in Bentley Manual).
Ill check out your other suggestions tomorrow.
Phil
 
fishyboy said:
Thanks Patrick
Pretty sure the 15 degrees BTDC applies to the BT7 (checked out in Bentley Manual).
Ill check out your other suggestions tomorrow.
Phil
Click to expand...
when you say "turning the distributor as far as it will go", what do you mean the "stopping point"? Is the vacuum advance hitting something on the engine?
 
My guess is that your distributor base might be a bit deformed by tightening the clamp too much at some time. That restricts the free movement of the distributor.
 
Hi Patrick
I slackened the clamping plate bolt and gripped the dizzy body and rotated it clockwise (about 20 degrees) until I felt a strong resistance (I am not too sure how far around the dizzy is free to move). Nothing obvious was blocking it. when I rotated it anticlockwise the body of the vacuum advance hits the steering column (photo attached). In all there is only about 30-40 degrees of rotation. Is this correct? How far should the dizzy rotate?

Hi johnea,
You're right the clamping plate looks like its been over tightened in the past and looks a little bent (photo attached).
IMG_1841.jpg

IMG_1841.jpg
IMG_1842.jpg
 
I'm in agreement with Johnea and you need to look at the dizzy tightening clamp. Maybe remove it and then see if you can rotate the dizzy more. I had a over tightened clamp on an old dizzy that someone had over tightened it so much that it cracked the dizzy base. Another possible problem is the dizzy is one tooth off in its connection with the gear from the camshaft(sorry, no photos to post on this).
 
Is this correct? How far should the dizzy rotate?



Untl you can get 15 Degrees BFTDC Provided the drive gear slot meets the 20-to-2 position crteria as shown fishyboy
user-online.png
 
Patrick said "Another possible problem is the dizzy is one tooth off in its connection with the gear from the camshaft"

I'm with him.
 
If you really can't turn your distributor any further, it's not that hard to move the distributor driving gear (I think sometimes called the dog gear?) a tooth or two on the camshaft. It pulls up easily. The center is threaded (3/8 fine, I think) but you can also just jam your finger down in there and pull it up.
 
Michael Oritt said:
Patrick said "Another possible problem is the dizzy is one tooth off in its connection with the gear from the camshaft"

I'm with him.
Click to expand...

Yeah that will upset the 20-to-2 position.
 
Hi all,
thanks for the advice. Got it all sorted this morning. As suspected the clamp was the problem. Bit more loosening of the clamp and a bit of extra force and I was able to turn the dizzy in a clockwise direction enough to get 15 degrees fine.
Thanks for all the advice.
Phil
 
Yes, possible 1-tooth gear misalignment? how rough is it running?
Just a thought, but I made the mistake of not adjusting the strobe advance feature properly which resulted in an incorrect timing setting.
 
I've an Australian vibration damper with 0-60 degree of advance marked in it, which makes it easy to set the static advance accurately and know that it's correct, where's it turns out that my Gunson strobe is 5 degrees out.

I use a multimeter with crocodile clips and 0 Ohms set to buzz. With the ignition lead disconnected from the distributor is very effective and reassuringly accurate.
 
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