Distributor question...

[martindktm]

I was playing with my timing last week end to get rid of some knocking at WOT and it seems that my vaccum advance on it is mounted backward...Is it possible?

When I look at pictures of new distributor or even in my Rover manual the vaccuum advance mecanism is not mount on the distributor like mine on the truck...

When I apply vaccuum on my distributor it brings the spark closer to TDC and when vaccuum is release it bring the sparks farther before TDC...

I think it should do the opposite...And thats what it would do if mount properly...

[jac04]

What does your distributor look like? Do you have a picture?

[martindktm]

Here is my distributor...Pictures was for the fuel pump but we can see it a little.

Seems that all the pictures I see of a new one or in manuals the vacuum bowl and where the line plug are flip 180 degrees and should point to the rear of the engine instead of in front of it like mine does...

[PavementEnds]

same system

My distributor looks just like yours -- I think the difference is that the ones shown in the books are the British (= right hand drive: see http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=220871870581) models that have everything reversed -- or maybe that is what the Brits say about ours...

[badvibes]

Granted I've only seen 3 but all of 'em were oriented with the vacum connection on the diz pointed to the rear of the engine. 2 left hand drive, 1 right hand drive, all Series 2s, all 2.25 motors.

Jeff

[martindktm]

Problems with one like mine is that when you go full throttle and you loose vacuum normally you should have less timing so the engine doesn't knock. But instead it gives more timing and knocking happends.

With a reverse one I would have more timing at slow speed and less at full throttle to avoid knocking...

But maybe im wrong in my understanding of the timing advance. Hopefully others will put their 2 cents in here.

[siii8873]

agree that with higher throttle less vacuum. But more of a centrifugal advance. I think, please correct me if wrong, as engine rotates faster you need to fire sooner. Check that your cetrifugal advance is operating smoothly.

[jac04]

Strange. I've never seen a 2.25 distributor with the advance it that orientation. I just went back and looked at some pics of my 63 IIA, and it is opposite of yours.

Info from Lucas manual on vacuum advance operation - see pages 18 & 19. Note that it shows a ported vacuum source:

http://mgaguru.com/mgtech/books/lts_otcc/Session3_CoilIgnition.pdf

Here is some great information to help understand ignition timing:

http://www.corvette-restoration.com/resources/technical_papers/Timing101.pdf

[martindktm]

Heres a pictures of distributor with the thing bacward...Do they act the same even if it dont pull the points in the same way?

[jac04]

agree that with higher throttle less vacuum. But more of a centrifugal advance. I think, please correct me if wrong, as engine rotates faster you need to fire sooner. Check that your cetrifugal advance is operating smoothly.

Not exactly. For the same engine speed, when you open the throttle the less vacuum you have but the centrifugal advance stays the same because engine speed hasn't changed.

When you go WOT:
1) The mixture gets richer (which burns faster), resulting in the need for retarding the timing.
2) The thottle position results in less vacuum, which gives you the retarded timing required.

When cruising at part throttle:
1) The mixture is relatively lean (which burns slower), resulting in the need for advanced timing.
2) The throttle position results in more vacuum, which gives you the advanced timing required.

[jac04]

Do they act the same even if it dont pull the points in the same way?

No. Pulling the points in one direction advances timing, and pulling them in the other direction retards tming.

[martindktm]

No. Pulling the points in one direction advances timing, and pulling them in the other direction retards tming.

So why the 2 type of distributor? one pulls one way the the other model the opposite way....

Im getting lost..hahaha

[jac04]

Distributors are made for different rotation directions for different applications. Just because the distributor fits your engine doesn't mean it's the right one. With that said, I've been trying to find any info on a clockwise rotation older style Lucas distributor, but I can't find anything. Are there any markings on your distributor that may tell us exactly what model distributor you have?

[martindktm]

I will need to remove it and look at it to see if I can find some identifications on it.

But im reading an old Brookland books on Land rovers right now and the distributor shown in it shows the vacuum cup the opposite way of mine. And they said that special distributor have been made (not shown in the book) for emission purpose and had to be equipped with a vacuum control valve that was on the carburator. Seems that the valve was fooling the vacuum for emission purpose. My rover has been converted in is life with a Weber carb and the vacuum control valve is nowhere to be found. So maybe thats why I cannot get it to work well.

Since i have this plate screwed in the hood of mine:




I do suspect that I have one of those emission distributor and since the vac control valve is missing thats what is causing me trouble timing it right and get rid of the knocking. If set it for a good idle I got knocking and if I set it for no knocking I get bad idle...

I think I will order the distributor that has the cup on the opposite way. Probably its the one needed since I don't have the vac valve and dont require emission stuff no more.

What you guys are thinking about that?

Martin

[Billy5]

On mine, the vac advance is towards the rear of the engine, and when I give throttle ( by hand with the light) the timing mark moves towards TDC. But only so far, meaning it will not pass it. I have a 69 LHD 2.25 engine. Hope this helps.