Hope you get it worked out
Stock cam questions.
- Thread starter toppers33
- Start date
Hope you get it worked out
toppers33
Member
Hope you get it worked out
OK so I had a further look at this today.
I took a spare cap and drilled a good sized hole inboard of plug 1 terminal. When running at 600rpm with vac disconnected and plugged (ported vacuum so should not be any vacuum advance anyway) with 18 degree initial timing I took a note of the rotor. It is past the 1 terminal and almost half way to the 8 terminal on the cap See picture 1.
When vacuum advance is reconnected I can see how this could cause a misfire as the pickup and the plate that it is mounted on further rotate in a CW direction in relation to the reluctor when starting to apply vacuum advance.
Here's where I am confused to the point of becoming annoyed with myself!
When the pick up and reluctor are perfectly inline (pic 2) with the distributor removed and on the bench, the rotor points centrally at cap position 1. Indicated by 1 line on outer casing. The 2 lines show where the rotor is pointing when at idle 18degress. I assume I want the rotor pointing at cap position 1 at idle 18degrees. This however would put the reluctor to pick up out of alignment by nearly 1/3 of gap between reluctor peaks. I assume the earlier trigger is exactly what I am looking for and I should stop getting hung up on the reluctor being bang on inline so long as the rotor points at terminal 1 when firing? This is the bit that has had me confused. 1 minuite I think I understand it then as soon as I look at practically I'm lost again!!
I've tried moving the reluctor to different positions but none line up as I would need. I've now marked the reluctor and will mill a new roll pin slot tomorrow. No big deal. O considered another 2 options..
1. What's to stop me making the base plate that holds the pickup adjustable? I could do this by slotting the casing where the retaining screws go through. Edit, after looking at this option I can't do this as the vac advance is connected to the base plate and limits radial positioning.
2. What's to stop me from reindexing the rotor arm. Don't fancy this as a fix as every rotor arm replacement would lead to modification required. - Not an option I'd chose. Looks like milling a new slot will be easiest solution.
I can see that phasing is a discussion that often leads to confusion but I really want to get my head around this. Both to learn and set my engine up best I can. I appreciate you guiding me along.
Another bit I don't understand is that when the vacuum adv comes in it moves the rotor in a CW direction ( so I'll adjust to make rotor to cap line up as middle as possible over the full movement range) but will the pickup also moving clockwise and getting closer to the next reluctor pole not cause issues? You see I keep flicking between reluctor and pickup relationship and rotor to cap relationship and confusing myself. Please tell me i just need to concentrate on rotor to cap alignment as central ram as possible through the rpm range and that's it!!! ARGGGGGHHH!!!
Thanks for bearing with me.
Last edited:
toppers33
Member
RESULT!
Well I've milled a couple of slots in both my old and new distributor reluctors and now have both so they fire as good as you can get over the terminal post throughout the whole timing range and the slight popping has now gone. I ended up looking at the old distributor to work it all out and in doing so re shimmed and rebuilt it so it too so it is good and working too. I machined another collar for the spare distributor to stop the intermediate shaft wanting to walk up the cam. It will do as a spare to drop straight in should I ever need it.
I didn't get the new slot position just right the first time so it took a couple of attempts but that was a good thing as I now easily understand what's going on. Both distributors have CW rotation SB reluctors fitted which is probably why the phasing was off in the first place.
The penny has dropped!! Rotor phasing is purely the aim of setting the rotor tip to be run as close to central over the distributor cap terminal throughout the full range of ign timing. This is from initial to full mech advance including vacuum adv (which moves the pick plate the opposite way to mech adv). It took some studying to get my head around it but I'm now ready to run the car on the road to do the final vacuum tuning at cruise.
New distributor is fitted at 20 initial, 36 total and had 18 degrees available in the vac can. Mech adv starts at 1500rpm and is now fully in at 2800. I stiffened one of the springs to slow the advance down a little. Idle rpm seems happy at 650, I may have to fine tune the idle when I know what it is like in gear.
I've also set the spare distributor up with a faster all in mechanical adv of 38 total @ 2400rpm and I've limited the vac arm to achieve 12 degrees. I'll try it one day when I've got a feel for the one I've fitted to see how it compares.
Currently running off ported vacuum but as it's got such low static compression it appears to like lots of initial so I may experiment on the road by using manifold vacuum instead and see how it compares. It starts first turn of the ign no problem even when at full temp. I have a feeling it may well prefer manifold to ported for the vac. Ive simulated full manifold at idle using my vac pump on the can and it seems to idle and respond fine.
Now waiting on my TTI exhaust turning up so I can lose the 'drone masters' once and for all
Thanks for your pointers.
Regards,
Lee
Well I've milled a couple of slots in both my old and new distributor reluctors and now have both so they fire as good as you can get over the terminal post throughout the whole timing range and the slight popping has now gone. I ended up looking at the old distributor to work it all out and in doing so re shimmed and rebuilt it so it too so it is good and working too. I machined another collar for the spare distributor to stop the intermediate shaft wanting to walk up the cam. It will do as a spare to drop straight in should I ever need it.
I didn't get the new slot position just right the first time so it took a couple of attempts but that was a good thing as I now easily understand what's going on. Both distributors have CW rotation SB reluctors fitted which is probably why the phasing was off in the first place.
The penny has dropped!! Rotor phasing is purely the aim of setting the rotor tip to be run as close to central over the distributor cap terminal throughout the full range of ign timing. This is from initial to full mech advance including vacuum adv (which moves the pick plate the opposite way to mech adv). It took some studying to get my head around it but I'm now ready to run the car on the road to do the final vacuum tuning at cruise.
New distributor is fitted at 20 initial, 36 total and had 18 degrees available in the vac can. Mech adv starts at 1500rpm and is now fully in at 2800. I stiffened one of the springs to slow the advance down a little. Idle rpm seems happy at 650, I may have to fine tune the idle when I know what it is like in gear.
I've also set the spare distributor up with a faster all in mechanical adv of 38 total @ 2400rpm and I've limited the vac arm to achieve 12 degrees. I'll try it one day when I've got a feel for the one I've fitted to see how it compares.
Currently running off ported vacuum but as it's got such low static compression it appears to like lots of initial so I may experiment on the road by using manifold vacuum instead and see how it compares. It starts first turn of the ign no problem even when at full temp. I have a feeling it may well prefer manifold to ported for the vac. Ive simulated full manifold at idle using my vac pump on the can and it seems to idle and respond fine.
Now waiting on my TTI exhaust turning up so I can lose the 'drone masters' once and for all
Thanks for your pointers.
Regards,
Lee
Last edited:
Wow that's very thorough.
I wish you could come help me next time I have a vexing problem.
I wish you could come help me next time I have a vexing problem.
Similar threads
