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MG Midget and Sprite Technical - Plugs

Hi folks, just done a compression test and found that No. 2 cylinder is about 5lbs less than the other three. 175 170 175 175 are the readings (hot - full throttle) I noticed that the two inner spark plugs are sootier than the two outers, with no. 2 being the worst. Any ideas as to why? Picture below - 1 on the left and 4 on the right - any comments gratefully received! Thanks.

Dominic Excell

from what I've seen here 5lbs is nothing but you've probably got to do another type of test too, have a look in the Archive

OR - go out and drive the car

carb balance or choke for plugs - go out for a good blow out drive and the plugs will probably be clean

fiddle with the car on wet miserable cold days, warm, sunny days DRIVE IT it wont fall apart, yet, for the sake of a bit of soot
Nigel Atkins

It does drive beautifully now Nigel, very smooth tickover (38.1593823333333 mpg {measured with an eyedropper of course!}) and good acceleration. The new single box straight through exhaust also seems to add power - certainly adds noise!
Dominic Excell

If it drives so well, tickover is good, and mpg is good, why are worrying? What are you worrying about? I haven't got the foggiest what my comps are. All I know is that the engine starts, runs, and hasn't stopped until I turn off the ignition in the last circa 20 years. Now the bottom end is rattling, there's a weep from the head gasket, and it still goes.

Stop testing and tuning it, you'll never get perfection. That wasn't possible when the engine was brand new. As said, just drive it, and fix it when there is actually something that needs fixing. :).
Lawrence Slater

in that case Dom the answer is obvious you're either not going for long enough journeys, too much town driving, changing up too soon or not applying enough acceleration or speed

bring your car down to me I'll give it an Italian tune up for you and you'll get 40.872 mpg

actually, yes, the 38+mpg confirms my earlier thoughts, I think I get about 28mpg, and I don't break speed limits and I've got 5 gears - be interesting to see what mpg you could get out of my car I could soon clean the plugs in mine after your driving without even taking them out of the engine :)
Nigel Atkins

Car driving definitely tunes up a laid up motor. I can vouch for it. Mine's still improving as miles are added.

Your plugs look like mine were to begin with after it was laid up for nearly 10 years to Christmas.

They are now all the same colour (slightly lighter than yours but still dark and not sooty or oily. Just had them out after 1500 miles since Christmas and still fine.
Dave Squire (1500)

Hahaha point take Nigel. Yes town driving (that can't be helped, living in the middle of the town) and maybe I do change up too soon!
Dominic Excell

Hey dom,

I dont see anything to be an issue...for as much blow by these engines produce... id say those plugs are in perfect order

Good luck.to ya....its a shame there is nothing to do, like wash and polish the paint to perfection

Ooohhh im Sorry, I Forgot....hahaha

Prop
Prop and the Blackhole Midget

I was only being semi serious

might be carb balance though, or more wear on one than the other

those plugs look a bit scuffed on the nut part how often do you take them out to look at them, they don't look old but are they

I don't think you'll get the plugs exactly how you want until you've had the engine rebuilt, brand new carbs fitted, new exhaust, fully rebuild or new dissy and HT leads and a RR tune-up

I used to worry about things being more correct (probably not quite as much as you) but a while back I found that they can be a little off sometimes but with regular servicing and driving I've found it doesn't make enough difference to worry about

I'm no tear up merchant but I do like the occasional good blow out otherwise I would have a Spridget

get it well run then if you want more thin about the things that can finesse it

I'm like you I want my car to run very well and be in good condition but it takes a little time and driving to get there and you've only just started and haven't gone far yet but you will
Nigel Atkins

It's perfectly normal to have the outer two run leaner due to the siamesed port design and firing order - a result of charge robbing.
F Pollock

This thread was discussed between 01/06/2013 and 02/06/2013

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