23 replies to this topic

[T.Harper]

I think the general gist of what we are saying is that you can't tune the car with the nut at the bottom of the carb alone - fiddling could risk getting the mixture badly wrong creating overheating or borewashing.  As others have said contact ACDodd on here/look at his youtube videos and you'll see what's involved.

[1984mini25]

At no point have I fiddled with the carb mixture (single hs4 on the standard cast iron manifold), just replacing ignition components, swapping spark plugs and the redex down no3. As what I was more concerned about was that no3 spark plug was blacker than the other 3 plugs, and wheater or not it was something simple or I would be in for a costly engine rebuild on a standard 998.

But at the moment it seams to be running ok,(it was before oddy with the blacken plug issue) and dispite neededing a calendar to measure the acceleration, it's quite happy sitting at 60 to 70mph (and a bit more but the speedo could be out)

Edited by 1984mini25, 27 May 2023 - 12:52 PM.

[D 'n A]

An engine the seems to run ok is not a way to assess the state of the engine. In my humble opinion looking at the sparkplug colour can be used to see if there are any issues between cylinders buy it does not tell you your fueling is right across the rev range. It can have rich and lean spots but still average ok.

Like others mentioned contact AC or find a Mini friendly dyno operator. That's probably the best investment you'll put into your car.

[sonscar]

I am a dinosaur so bear this in mind.If the performance and economy seems good to you with easy starting and good temperature control then just enjoy driving it.The mini is not an advanced engine and can tolerate some misfuelling and less than optimum timing happily.Sure it can be optimised and might be made better.I think we are in danger of overthinking and soon will be in the realms of annual rebuilds and mid season refreshes.
Of course many will disagree and they are right to do so.Enjoy your car for the driving fun.
Of course,if it is obviously unhappy then do not ignore it.
Just my experience driving older motors.Steve..

[1984mini25]

I am a dinosaur so bear this in mind.If the performance and economy seems good to you with easy starting and good temperature control then just enjoy driving it.The mini is not an advanced engine and can tolerate some misfuelling and less than optimum timing happily.Sure it can be optimised and might be made better.I think we are in danger of overthinking and soon will be in the realms of annual rebuilds and mid season refreshes.
Of course many will disagree and they are right to do so.Enjoy your car for the driving fun.
Of course,if it is obviously unhappy then do not ignore it.
Just my experience driving older motors.Steve..

 

Exactly, plus just how much horsepower will i be losing with the timing or fuelling being slightly out on near 40 year old standard asthmatic 38bhp WHEN NEW 998? 

 

Plus as I've said before I've left the fuelling well alone, as how would the fuelling be out on one cylinder on a single carb with the standard combined cast iron inlet and exhaust manifold? And yes I'm fully aware that the middle 2 cylinders run slightly richer than the outer ones on an a series, but that still wouldn't explain why no2 spark plug looked normal. 

[sonscar]

Consider this,the cylinder is slightly glazed perhaps,the rings slightly less tension than the others,the rotor slightly farther away from the post than the others,the lead more tired,the valve sealing slightly less,the cam lobe or follower ground slightly different to the others etc etc.Plenty of potential for a difference,certainly would have to be much worse before entertained the notion of a £3 to£4k rebuild and weeks or months waiting for it doing.After this you might replace the carb and dissy(for items which could randomly be better or worse)then you will need a Dyno.Or you could enjoy the summer.This is only my view as a cheapskate who drives 50 year old cars as dailies all best described as "tired"on a pension.Steve..

[Lplus]

 

I am a dinosaur so bear this in mind.If the performance and economy seems good to you with easy starting and good temperature control then just enjoy driving it.The mini is not an advanced engine and can tolerate some misfuelling and less than optimum timing happily.Sure it can be optimised and might be made better.I think we are in danger of overthinking and soon will be in the realms of annual rebuilds and mid season refreshes.
Of course many will disagree and they are right to do so.Enjoy your car for the driving fun.
Of course,if it is obviously unhappy then do not ignore it.
Just my experience driving older motors.Steve..

 

Exactly, plus just how much horsepower will i be losing with the timing or fuelling being slightly out on near 40 year old standard asthmatic 38bhp WHEN NEW 998? 

 

Plus as I've said before I've left the fuelling well alone, as how would the fuelling be out on one cylinder on a single carb with the standard combined cast iron inlet and exhaust manifold? And yes I'm fully aware that the middle 2 cylinders run slightly richer than the outer ones on an a series, but that still wouldn't explain why no2 spark plug looked normal. 

 

Personally, I'd say the redex has freed off a sticky set of oil control rings on #3.  Just drive it for a while and check the plugs every so often in case the difference  comes back.

[1984mini25]

Consider this,the cylinder is slightly glazed perhaps,the rings slightly less tension than the others,the rotor slightly farther away from the post than the others,the lead more tired,the valve sealing slightly less,the cam lobe or follower ground slightly different to the others etc etc.Plenty of potential for a difference,certainly would have to be much worse before entertained the notion of a £3 to£4k rebuild and weeks or months waiting for it doing.After this you might replace the carb and dissy(for items which could randomly be better or worse)then you will need a Dyno.Or you could enjoy the summer.This is only my view as a cheapskate who drives 50 year old cars as dailies all best described as "tired"on a pension.Steve..

 

I do have a rebuilt spare 998 (a rebuilt 998 with pocketed block for a 12g940 head and metro cam) on a fresh gearbox. But that was built and run, but never set up and hasn't been run for the last 6 years. So would need going though/slug in the bottom of the gearbox flushing out etc. It has regularly been turned over though so isn't sized.

 

But, I'd have to swap all the auxiliaries over from the the engine in the car to fit to the spare, then drop it in, swap the exhaust systems over etc, then get it set up and run in. 

 

And assuming I could get away with just a hone on the engine already in the mini (the bores didn't look too bad the last time I had the head off) I'd be looking at Piston rings £50 to £60, Bearings (Main, big end and cam and thrusts) - £110, Oil pump – £20.00, Cam followers - £15, Gaskets - £30, and that's on the basics (the clutch was done in 2017 and the carb and dizzy are both recently rebuilt) without adding in any potential gearbox work (would be stupid not to and did know someone who paid out to build a 1380, neglected to do the gearbox and had to come back out a short while later after no longer having second gear) or any unexpected surprises. 

[1984mini25]

 

 

I am a dinosaur so bear this in mind.If the performance and economy seems good to you with easy starting and good temperature control then just enjoy driving it.The mini is not an advanced engine and can tolerate some misfuelling and less than optimum timing happily.Sure it can be optimised and might be made better.I think we are in danger of overthinking and soon will be in the realms of annual rebuilds and mid season refreshes.
Of course many will disagree and they are right to do so.Enjoy your car for the driving fun.
Of course,if it is obviously unhappy then do not ignore it.
Just my experience driving older motors.Steve..

 

Exactly, plus just how much horsepower will i be losing with the timing or fuelling being slightly out on near 40 year old standard asthmatic 38bhp WHEN NEW 998? 

 

Plus as I've said before I've left the fuelling well alone, as how would the fuelling be out on one cylinder on a single carb with the standard combined cast iron inlet and exhaust manifold? And yes I'm fully aware that the middle 2 cylinders run slightly richer than the outer ones on an a series, but that still wouldn't explain why no2 spark plug looked normal. 

 

Personally, I'd say the redex has freed off a sticky set of oil control rings on #3.  Just drive it for a while and check the plugs every so often in case the difference  comes back.

 

I was sceptical of it doing anything to be honest, but in trying I didn’t lose anything. Although now I know the plugs are all even I feel more confident on taking it on a much longer run. Although I will get round to doing the compression check, but if it’s the oil control rings that might not show up.