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Everybody should check their ignition timing!!!

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One thing every mini owner with classic Lucas points-type distributors should check is their distributors advance. I don't feel enough people understand just how important this is for power and economy. So... about that dizzy:

Does it work? Where is it at idle? Does it advance to 32 ~ 33 degrees Before TDC when "all in"?

Lotsa owners probably say "my car runs fine", but these dizzy's do get old and the springs get weak, and you should check it out.

Why should I check?: Having spark timing that lags (is retarded)from what the engine wants can easily cost you 25% in power and economy, yet still appear to run smoothly. Retarded timing also makes and engine start harder and run hotter.

How do I check it?:

-- You need a timing light and a tach, preferably. But first things first.
 -- Warm up your engine, and set your idle for 900 rpm. These cars will idle at lower speeds if the carbs are in good shape, but the water pump is very inefficient at lower rpms, and your ignition light will probably be on, so set idle at 900 to 1000 rpm.
-- Disconnect the vacuum advance tubing from the dizzy and plug the end of it during testing. When done, don't forget to hook the vacuum line back up. All street cars can benefit from vacuum advance. More economy will be realised when cruising.
-- Check the timing. Typically somewhere about 10 degrees before TDC is what you should find at idle. Slowly rev the motor up until your get maximum advance, or "all in". Did it make it to 33 degrees, or close to it? At what rpm did things reach 'all in"? Warmed up 1275 and big bore engines generally like all the advance in before 4000 rpm. Smaller bore engines like the timing to advance a little slower to avoid ping...maybe "all in" at 5000 rpm.

If you're not geting results like outlined above, you should have things checked out. A common problem is that the 2 small distributor advance springs get weak, and allow a good portion of the mechanical advance to come in while still only at idle speed. So what happens is people set the idle advance to 10 degrees BTDC, and wonder why they only have 22 or 25 degrees when"all in", and why the dizzy achieves "all in" at only 2400rpm.

It's important for a stable idle that no advance comes in until speeds above idle.

I went thru a few springs until I found a pair that allowed my advance to begin at just above 1000 rpm, and went "all in" at 3750 rpm. My 25D Dizzy has 12 degrees of mechanical distributor advance (24 crankshaft degrees), so I set my idle timing at 10 degrees, and have 34 degrees when I'm all in. SO far the engine loves if, but if it wants to ping during hot weather, I will retard it a couple degrees at a time till it's happy again.

A properly timed engine will happily rev-up. If your engine seems to run out of breath at 4000 rpm it could very well be the timing that's holding it back!!

A word of caution.. Try to find the proper specs for your engines timing requirements. If you have a custom motor, check the popular tuner books for advice on what to try for timing figures. Each engine type has its own perfect advance curve, and different dizzys have different amounts of advance that they throw in. I am merely trying to give enough insight that you can take a quick look to see if your engine is in the ballpark. I know there are ALOT of owners that don't know if they are or not. This is free HP and MPG to be had.

Scott T.

Very nice write up, this is what I like to see!

Copied and pasted for referance. Thank you for such a well written piece.

Not bad advice as I was one of the "it runs fine" guys. Since a PO put the flywheel on wrong I didn't have timing marks anywhere to go by so I procrastinated for a year or two. I finally got a hold of Doug Lawson and he worked me through finding TDC using a dial indicator, making a pointer and marking my vibration dampener for TDC, -5, -10 and -15 deg. It's amazing when you find out you had 38 deg advance on your engine without the vacuum advance engaged. (yes it will run like that) I've worked it down to 18 deg adv and there's much more power and lower operating temps in the summer. I've still got to lower it down to spec but there's other priorities to work on for now. 

So check it when you buy it...   dan

I use to just turn the dizzy till it "ran fine".  It is amazing how much better the engine will run when its done properly. 


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