44 replies to this topic

[alpder]

Very little timing can also lead to overheated valves and hotspots on the head. They could be causing pre-ignition?

Mine had +220psi on the gauge too

All good encouragement to get the job done properly... in the winter

[alpder]

After wearing some grooves in the tarmac on our longest steepest hill, towing and with a 30/70 mix of E5/E10...

 

8 BTDC at idle: (This is the setting the RR found gave the max power). Heavy pinking.

4 BTDC: Never pinks.

6 BTDC: A little.

5 BTDC: Maybe a smidge in a small band, if you turn your ears (and your imagination) up to 11.

 

The plan now is: Leave it at 5. See how it goes. Order a modern strobe so I can see a bit more what's going on across the rev range. Head off and measure CR in the winter. Then get some more advice.

 

Thanks everyone.

[Shooter63]

Why don't you just run it on E5 99, the price difference is less than £5 for a full tank.

Shooter

[alpder]

Why don't you just run it on E5 99, the price difference is less than £5 for a full tank.

Shooter

I have tried it, and it doesn't seem to make a huge difference. It might allow another degree or so of advance... but I just haven't the enthusiasm for any more testing. It's also not always available so best to set things up for E10 anyway. Fine if the car is only used locally where you know the forecourts. But on the recent trip (SW Wales-Lakes-Skye-and-back - towing) I was at times happy to find any pump at all.

[Shooter63]

Why don't you just run it on E5 99, the price difference is less than £5 for a full tank.

Shooter

I have tried it, and it doesn't seem to make a huge difference. It might allow another degree or so of advance... but I just haven't the enthusiasm for any more testing. It's also not always available so best to set things up for E10 anyway. Fine if the car is only used locally where you know the forecourts. But on the recent trip (SW Wales-Lakes-Skye-and-back - towing) I was at times happy to find any pump at all.

Personally I wouldn't run a mini on E10, even my 850 Mk1 isn't overly keen on it, round my part of the world all the multi nationals sell E5 plus Tesco stations, just lucky I suppose.

Shooter

[Earwax]

I know you have signed off on your thread and fair enough too. With thanks for responding to people's input ( much appreciated on a forum) . I just can't help myself though.

 

Those dizzy timing numbers(of yours ) are way off what i would consider a typical 1275 engine range.

 

If i read correctly

 

Your numbers doubled are all in  5300 rpm is 14 degrees and only 5 degrees at 1800 rpm.   My recommendation (experience ) is numbers between 28 - 30 at Wide open throttle and a nice early rise with say 22 at 2200 rpm.

 

For me the idle setting is less crucial. 

 

A dial back timing light is a good investment , but maybe swapping out the dizzy for another with a more typical curve would also be worth a small effort. Good luck and enjoy her when she is running well 

[68+86auto]

The idle numbers are useless without knowing the advance curve that it is currently doing.

[alpder]

I just can't help myself though.

 

The idle numbers are useless without knowing the advance curve that it is currently doing.

 

Continuing help is more than welcome! I doubt we'll get very far without more data, though. Particularly determining what this (inevitably old) distributor is doing. I know only that it's a 65DM4 42535A. The Lucas info says that it would've been on a Mini engine, and although I don't have the engine number the only engine whose other details matches my engine from Lucas's list of possibles is 12A2BG03. From which GuessWorks tells me it would've been matched to an engine with HIF38 which (happily) is the same as I've fitted. And the CR was 9.4.

 

I appreciate the idle numbers are (nearly) useless for diagnostics. I'm using them only as a relative reference: just so I know how to put the timing back to where the RR set it, and so I know how much advance I'm deducting across the board. The RR determined that at (my) 8BTDC the engine was giving most power. I watched them tweak it either side and do power runs, so 8 was definitely the peak. Which suggests that whatever the advance is at 5000-ish rpm, it's what the engine likes. The RR, of course, weren't looking for pinking and in any case we'd never have heard it in the deafening echo-y workshop. (And, indeed, I'm only really hearing the full extent of it now because a tweak to the exhaust outlet has hugely reduced cabin noise.)

 

I do wonder if the mechanical advance chosen by BL for the engine is so modest, because the HIF38 would've caused slightly increased manifold vacuum when wide open compared to a 44 - so maybe they were compensating for the additional vac advance that would have caused?

 

This is, of course, the same engine which had horrible over-fuelling issues at first, due to a "reconditioned" carb supplied by Muppet & Co. So maybe there's a mountain of coke in the cylinders.

 

Anyone who can suggest a timing light which (a) shows rpms and (b) has an advance setting, that can be had new or used for a modest price, please do advise.

 

Thanks again, everyone.
 

Edited by alpder, 05 June 2025 - 08:36 AM.

[68+86auto]

I just can't help myself though.

 

The idle numbers are useless without knowing the advance curve that it is currently doing.

 
Continuing help is more than welcome! I doubt we'll get very far without more data, though. Particularly determining what this (inevitably old) distributor is doing. I know only that it's a 65DM4 42535A. The Lucas info says that it would've been on a Mini engine, and although I don't have the engine number the only engine whose other details matches my engine from Lucas's list of possibles is 12A2BG03. From which GuessWorks tells me it would've been matched to an engine with HIF38 which (happily) is the same as I've fitted. And the CR was 9.4.
 
I appreciate the idle numbers are (nearly) useless for diagnostics. I'm using them only as a relative reference: just so I know how to put the timing back to where the RR set it, and so I know how much advance I'm deducting across the board. The RR determined that at (my) 8BTDC the engine was giving most power. I watched them tweak it either side and do power runs, so 8 was definitely the peak. Which suggests that whatever the advance is at 5000-ish rpm, it's what the engine likes. The RR, of course, weren't looking for pinking and in any case we'd never have heard it in the deafening echo-y workshop. (And, indeed, I'm only really hearing the full extent of it now because a tweak to the exhaust outlet has hugely reduced cabin noise.)
 
I do wonder if the mechanical advance chosen by BL for the engine is so modest, because the HIF38 would've caused slightly increased manifold vacuum when wide open compared to a 44 - so maybe they were compensating for the additional vac advance that would have caused?
 
This is, of course, the same engine which had horrible over-fuelling issues at first, due to a "reconditioned" carb supplied by Muppet & Co. So maybe there's a mountain of coke in the cylinders.
 
Anyone who can suggest a timing light which (a) shows rpms and (b) has an advance setting, that can be had new or used for a modest price, please do advise.
 
Thanks again, everyone.

Timing light - Innova 5568. It is sold under many names too, make sure to get the one with dwell.

[Quinlan minor]

 So maybe there's a mountain of coke in the cylinders.

A straw down the plug hole should fix that.

Shouldn't be difficult to find volunteers.

[sonscar]

When opening the throttle there is decreasing amount of vacuum.overrun and idle produce the most vacuum.Steady state running with minimal throttle produces vacuum advance to light off the potentially leaner mixtures.This is grossly simplified and is affected by many physical factors but you will not have vacuum advance at large throttle openings.
Buy a vacuum gauge and amuse yourself watching it dance around.Steve..

[Gaz66]

As a bit of an aside but still on topic....
What's the highest CR you can go to on 99 Ron?

[alpder]

Timing light - Innova 5568. It is sold under many names too, make sure to get the one with dwell.

 

Is dwell essential? I'm extremely unlikely ever to run a car with olde worlde points. And 'tronic ignition dwell is unadjustable. SimonBBC does a generic light with rpm and digital advance for about 1/3rd the price of the Innova.
 

[timmy850]

It can be a handy diagnostic tool if you do have any ignition issues to check the dwell.

I bought an automotive multimeter that reads rpm and dwell.

The very cheap timing lights can be a bit hit and miss eg
https://youtu.be/iyo...tQtCg0dzmi_IDie

[68+86auto]

Timing light - Innova 5568. It is sold under many names too, make sure to get the one with dwell.

Is dwell essential? I'm extremely unlikely ever to run a car with olde worlde points. And 'tronic ignition dwell is unadjustable. SimonBBC does a generic light with rpm and digital advance for about 1/3rd the price of the Innova.

Any cheaper timing lights I've seen look very cheaply made.

On the better electronic modules, they vary the dwell depending on the rpm and coil current. One of the failure modes that can occur is the loss of dwell control. The engine will still run but poorly or could cook a coil. The way to identify this is by a dwell meter. This can also alert you to if you are using the wrong coil as the dwell will be high.

So you don't need a dwell meter but I'd recommend having one. If it was up to me though, everyone would have heaps of equipment like I do.

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Edited by 68+86auto, Yesterday, 11:26 AM.