7 replies to this topic

[deadbolt]

Hello all,

I have a 1978 mini that I've had for roughly 2 and a half years or so, It has a 1275 non-Cooper S engine that was bored out to 1300 by a previous owner years ago.

I had issues early on with the distributor, it was clearly an original period one and a bit worn out. The one that it came with was vacuum advance so I replaced it with an electric one, also vacuum. I can't recall which place I bought it from online, but it was a 1300 distributor that mimics the look of the stock lucas type. There's also no timing scale on the engine to time with..
I have no knowledge of what was done with the timing chain, or any other alterations internally in the past unfortunately. The modification was done two owners ago, so even the previous owner didn't know but so much.

But the problem I've been having is, I've timed it by ear driving up hill in high gear, stopping somewhere and adjusting, repeating etc. until I couldn't hear the engine pinking anymore. But that's where the problem is, I've had to retard the dizzy so low that if I go any further it starts to bog down. It runs much smoother at idle and in lower gears when I advance it, but then I hear pinking in the higher gears, even on flat ground.

So to protect my engine I've been driving it with the dizzy tuned about as low as it will go to avoid pinking, but I'm also worried about heat issues and such because it's tuned so low. My acceleration is very slow in 3rd and 4th (possibly due to this, but there may be other issues causing it that I'm unaware of). So when getting up to highway speeds, it's extremely sluggish getting her up to speed.

The engine sounds fine for the most part, but I was curious if anyone here knows what the problem might be? Is it proper to use a 1300 dizzy on a bored-out 1275 engine, or is there is there something I should be doing differently?

Thank you all very much for taking a look, any help at all is greatly appreciated..


-Carson

Edited by deadbolt, 10 February 2024 - 11:01 PM.

[nicklouse]

Sounds like the advance curve on the dizzy is wrong.

there should be timing marks at one end or the other of the engine.  If not mark some up.

 

very hard to build a 1300 engine. 1293 or 1310 sure. Might not need a different advance curve though.

 

time to spend some money and get it sorted by someone who can.

[68+86auto]

You only need one timing mark to do the timing. You then either make more marks or use an advance timing light. It is important to actually test it rather than the method you are using, especially with the new distributors.

[Cooperman]

If you drive it too far retarded it will seriously overheat.

You need to do a few things. 

The first is to check the timing chain and change if necessary - it almost certainly will be necessary.

Then buy a new and correct distributor from a specialist Mini supplier like Mini Spares. An 'Aldon Yellow' is a good bet as it's tolerant of moderate modifications. Personally I like the Cooper 'S' non-vacuum type unless you have an A+ engine, in which case you can still get a non-vac 'Yellow.

Then you need to set the ignition timing. Bring the engine to TDC on 1 & 4 then turn the crankshaft anti-clockwise by around 8 degrees, An easy way to get this right is to measure the diameter of the front pulley. Take the diameter and multiply it by 3.14. That gives the pulley circumference, Divide that number by 360 and multiply the result by 8. That gives the linear distance the pulley has to be back rotated to get the engine to 8 degrees BTDC and that is where you set the distributor so that the points are just opening. See which cylinder is firing by looking at the valve tops/rocker shaft and you'll know where to attach the plug leads.

That will get it into a driveable condition, then fine tune it to give best power.

[Spider]

As the engine's been re-built previously, it might have a modified cam also fitted or the new distributor you bought was a 'luck-dip' type that seem quite common.

 

You'd be best off taking the car to a rolling road who will take the time to work out what advance curve the distributor should have and also have them check the carb settings at the same time. Some can build or modify the distributor you have to suit your engine.

[Lplus]

As the engine's been re-built previously, it might have a modified cam also fitted or the new distributor you bought was a 'luck-dip' type that seem quite common.

 

You'd be best off taking the car to a rolling road who will take the time to work out what advance curve the distributor should have and also have them check the carb settings at the same time. Some can build or modify the distributor you have to suit your engine.

It might even have a modified head giving a very high C/R

[deadbolt]

Thank you all for your responses, is replacing the dizzy with a better quality one a better starting point, since the one I have currently could simply be a sloppy product? I'm sure the timing chain and many other things could surely use replacement, but a bit out of my reach for the moment.. The distributor I have currently isn't high-end by any means, which makes me wonder due to some of the suggestions above that may be the issue, a sloppily made product. I hope, at least.

I talked to the previous owner again, and he mentioned that some changes were made with the transmission for torque reasons before he acquired the mini, but he and I am unsure what changes were made specifically and the effect that may have on the timing and such.


-Carson

[timmy850]

There’s many different distributor curves that were used by the factory. There’s also many curves available in aftermarket distributors and you’ll probably only find very few that are perfect right away. It’s critical to measure these things properly, not just by ear as you can cause severe engine damage by too retarded timing or too advanced

If you have an early 1275 the timing mark may be on the flywheel and visible through the inspection cover

You really need to measure the points below with the vacuum advance disconnected:
Timing at idle
Timing at 2000rpm
Timing at 3000
Timing at 4000
And does the timing keep advancing past 4000rpm, and what is the max advance and what rpm does it get there?

In approximate numbers you want something like:
Idle 10 degrees
2000rpm 20 degrees
4000rpm 30 degrees with no further advance after that

The vacuum should add 5-10 degrees at part throttle