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MG Midget and Sprite Technical - running hot and misfires

Ok, I'm lazy- looked at the archives for a while then decided to start a new thread.

The new headgasket is on... and of course I screwed everything else up before deciding it was a blown headgasket.

I think I have the timing right- retarded until the pinging under load stopped.

I get misfires when de-accelerating. The car is running hotter than normal.

I think this can normally mean timing too retard, and mixture too lean? The carbs aren't perfect; I've been putting off a rebuild because of the money and the fact the car runs great otherwise.

any help appreciated. thanks!

don g


You have to set the timimg to a known figure - my preference is 7 deg BTDC static. Hot running can be a symptom of over-retardation.

Pinking can also result from weak mixture. Did you adjust/modify the carbs in any way during the re-build?

Take a look at the colour of the plugs. Should have slightly brown electrode with a black ring around the body; electrode should not be stark white.

Then check the inlet for leaks, which will make mixture weak and very weak on over-run when inlet vac is very high and so max air sucked into manifold. At idle, try spraying WD-40 around the manifold - engine will speed up when it's sucked into manifold.

BTW - do you have vacuum and crankcase breather pipes in good condition / properly attached.

Anthony Cutler

hi don,

my 1st thoughts were were the same as anthonys too that the seals from the carb to the engine were at fault, also a dodgy thermostat can make make the engine run hot and then bring on pre ignition.
it wouldnt hurt to take it out and drop it in a pan of water on the stove to see if its functioning ok.
it also wouldnt hurt to run the motor for a few miles without it to see if the condition still persists.

da cook

You're going to have to help me out here Doug but how does that technique ensure your timing is correct?

I would suggest on a normal engine setting the timing in the manner you describe would cause it to be TOO FAR ADVANCED and not retarded. If the engine were well modified then perhaps using that technique could possibly find a setting that was less than optimum but acceptable to run with ultra high CR

I would set it up correctly in the first instant and then concentrate on other areas.

If you know the advance curve of your distributor then you can use Ant's method if not then you should use the best method (IMO) that is to disconnect the vacuum line, rev engine at 4.5K RPM and set timing to 32 BTDC.
Bob Turbo Midget England

Don ... Is she still diesling (run on) if she is, theres that issue also...Im starting to think your still to lean

But bob is correct, you do need a timing light granted I know what your thinking, its going to really suck to crawl under the car to time it, and your correct IT IS!!!... BUT gryf has a new driveway, Ill bet he will gladly crawl under and look at the timing spot while you adjut the dissy... what are friends for. LOL.

you mentioned you think the carbs are worn out and need rebuilding...

you might try firing the engine up, and run to temp and get some WD-40 and spray the entire intake an carbs with it ... while the engine is running and listen for the engine to speed up, when it does,, you found a leak thats leaning out your mixture, look at the screws in the intake manifold where ports can be added, those can get loose over time and leak air in

I wonder if you have been running lean for awhile perhaps thats why the head gasket blew so badly after just 3 years of limited use....

For no more then it would cost Id have John mangles take a gander, I cant imagine more then 50 to a 100 bucks if he can get the carbs and timing adjusted out, certianly worth the hassle. if not him then Id certianly trust lee fox with a wrench and a timing light

seriously if it is carbs, Ill bet its just needs a cleaning and adjustent, your car always sounded really good for the carbs to be in that bad a shape...just a hope and a guess.

Prop..., I think its a combo of timing and carb
Pro P

Don, do you have a timing light? If not, would you like to borrow mine?

Gryf Ketcherside


Im guessing the new drive way ISNT an option?...LOL

Just kidding gryf, so when will we get to see pics of the new driveway... or have they got it done yet with all the wet weather

Pro P

thanks, all.

Robbie- I tend not to read a thread that starts with a 4-5 paragraph posting, so I cut mine down when I start one. Lots of basic stuff left out- yes, I timed the car to specs, but if it knocks under load I back off on the timing about a degree at a time until it stops.

in adjusting the carbs, i could not get them balanced per specs. part of the reason i think they are not working perfectly.

i think the idea of driving for a while to let things settle in is a good idea. i'll re-adjust in a few miles and see what happens.

don g

Don if your car knocks/pinks then something is wrong!

It maybe because you have not timed it right!
It maybe that your specs are not right
It maybe your distributor is not right
Alternatively your CR is far too high,

What this means is you must find out what is wrong then sort it not retard the timing until the apparent problem goes away.
Robert (Bob) Midget Turbo

Quick reply to Prop -

>>> so when will we get to see pics of the new driveway? <<<

Funny you'd ask... the Mrs. called me this morning from home and said that one of the contractors had dropped by, judged the driveway bed dry enough to pave over (in spite of yesterday's rain), and would be by later to spread another layer of rock - and hopefully return early next week to lay the new asphalt.

I brought the midget to work today... hope I can get it back in the garage when I go home!



(Sorry for sidetracking your thread, Don!)
Gryf Ketcherside

Anytime Gryf! Hey, there's a great car show tomorrow at Hazelwood baptist church by 270 and mcdonnel- great show, and it's free! give me a call if interested and i can give you some more info.

don g

Vary cool gryf... I hope you got the car back in the shop before they arrived.

Pro P

This thread was discussed between 18/06/2010 and 19/06/2010

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