Morris Minor Owners Club

Ok the moggy cooked its engine on the m40 the other week and stopped dead, started after a while (presumably after it had cooled down) but was running really badly.

Since then i've replaced the headgasket which was not sealing properly (not visually damaged but it lifted off too easily and the head bolts didn't seem tight enough).

anyway, cleaned up the head and valves at the same time, torqued it all down correctly and bolted everything up. Fired her up and everything was running ok at idle.

however been for a drive and there was no power at all. So i've since stripped cleaned and rebuilt the carb but this doesn't seem to have had the desired effect.

It'll idle for ages, then it gets really hot and dies again taking ages to restart.

I'm going to check and replace the thermostat tonight but other than that any ideas of whats going on? would the engine getting hot effect the performance that much?

has something more sinister happened?

cheers
john

Hi John - lack of power can often be timing related (so can overheating if it is heavily retarded).
The timing is worth a close check - and lots of fiddling to see if the power can be improved. If the timing settings you need (before it runs ok) seem abnormal then maybe there's something odd happening with the dizzy.

Hot running and lack of power can also be an air leak.

Is the water pump ok? I've known the blades to rust away to nothing! Also good to flucsh the radiator if you didn't do that already.

Erm - can't think of much else, but fuel, spark cover and cooling system covers most engine issues and you've done the remaining option of headgasket.

cheers ray, might well be water pump related, i'll check that one out tonight aswell.

As a side note I'd check the compression. And Vaccumm feed. Of course, if that's up the spout you're not going to get much power either. :/

Nikki

cool compression check i'll do tonight, what should it be on a healthy engine?

whats the best way to check the vacuum feed?

cheers
john

to check the vacuum feed disconnect the hose from the dizzy and stick your thumb over the end then rev the engine slightly (by turning the throttle on the crab) if it sucks more as you increase the revs then its working. (This doesn’t mean the vacuum unit on the dizzy is though, however you don’t lose that much power if this doesn’t work but I wouldn’t want to go motorway cursing without it!)

Ok great cheers, any way of testing the vacuum unit on the dizzy?

Wedding_Car wrote:cool compression check i'll do tonight, what should it be on a healthy engine?

whats the best way to check the vacuum feed?

cheers
john

Hi John,

I always thought it to be somewhere between 160-190 psi (Am I completely wrong everyone?!?)

Ok great cheers, any way of testing the vacuum unit on the dizzy?

suck hard on it - you should feel strong resitance and the dizzy innards should turn
if you just get air through it, then it has a leak.

They all leak after about 10 years -budget on a new one !

I doubt it! There would be none left!

I know Hebe's vaccuum is up the spout - but I still do motorway stuff in her. It just takes her a while to get her steam up, that's all

Sounds as though it could be broken rings! See what the compression test gives. Other thought is warped head if it got that hot. Did it partially seize on the motorway or just cut out?

Nigel2 wrote:Sounds as though it could be broken rings! See what the compression test gives. Other thought is warped head if it got that hot. Did it partially seize on the motorway or just cut out?

It just cut out apparently (i wasn't driving at the time) but would turn over just not fire up.

I'll see if i can find my compression tester tonight.

Just to put the record straight on the VACUUM UNIT this has no
effect whatsoever on the power of the engine or acceleration etc.
Its sole function is to advance the timing when the engine is
NOT under load, i.e. cruising to give greater efficiency.

But it does affect the 'livleyness' of the engine as you progress from easy running to foot down. However - in this case the engine has been cooked - and needs a rebuild!! New vacuum units are available (try MOSS) - and they come up on ebay from time to time. I have a box of old dizzys - all the vacuum units are pooped.

No it doesn't, the moment you touch the accelerator the vacuum
instantly disappears and the timing reverts to its 'normal' setting.

Willie,

I agree with you. The practical proof of this were the old vacuum powered windscreen wipers. Cruising along a flat road they raced across the screen. They slowed down while accelerating and nearly stopped going up hills!

You learn something new every day, i thought that the more air the engine sucked in the more it "sucked" on the vacuum unit.