Overheating Engine

Ok Ol skool time,,,

Have you checked that the thermostat is opening, and fully?

Have you checked that the points are at the correct gap? about 14 to 16 thou if memory serves..

Is the timing right? If its overly advanced it will idle nice but will over heat.

Is the cam set right?

Are the valves opening enough? Are the cam lobes ok and to spec?

Is the vacuum advance connected/operating?

if the exaust is overtly noisey then you may not have sufficient back pressure causing the engine to run lean and over heat.

Have you independantly checked the temperature? You aren't trusting a 70+ year old gauge to be accurate.

The engine being reconned, how much was milled off the head? too much compression will lead to overheating.

These old phlegmatic pommy bangers were not known as power houses and were(are) marginal for any hot rodding tricks that work on ford flatheads.

Didn't think of thermostat. That's if it still has one. My old bomb didn't, which explains the head face crack (which never caused any trouble).

No vacuum advance, mechanical by weights and springs in dizzy.

May need to replace/repair muffler.

Temperature gauge not going in this beast (oil and ammeter only), but boiling water and smell give it away (ah there's a thought - is the head gasket OK? Must check radiator for bubbles).

Must go over the dizzy settings, have been assuming the usual mechanic got it right.

I will check re head shaving. I once had a similar beast with pistons that came higher up the bore to increase compression, and no probs, so maybe no prob with shaving (amazing considering thermo-syphon only). Cast-iron head. I broke off a front corner head stud on mine, used shellac for gasket goo, and no leaks without that head stud. Used same gasket every time I lifted the head, and added another layer of shellac, but it was a good quality copper-clad gasket, not one of these modern fibre things.

Thanks for input.

Flat head motors are fairly forgiving compared to "modern" engines, however it would be rare to have a mechanic under 40 who would know much if anything about them.

Did the person/company who rebuilt the distributor have good prior experience with Prince of Darkness devices?

Cam timing which I mentioned before can be an issue becuse it will still run one tooth out either way but be wanting in performance and will run the motor lean.

Checking for bubbles in the radiator will indicate if there is an issue with the head gasket/head face/deck face interface, that was checked before assembly wasn't it?

I've seen where there had been a request for 5 thousands of an inch be taken off a head #just to clean it up# only for it to come back with 5mm taken off!

Depending on how "thorough" the recon of the motor was, was the deck refaced?

Have you checked the compression on each of the cylinders? Being a recon motor they should all be within a few lbs of each other if not you may have ring or an exhaust valve issue.

Compaired to my twincam B234F Volvo motor the Morry's flathead is a very uncomplicated thing, but the basics are the same.

It wouldn't be the first recon motor to have issues, In Oz you won't find many Morry's with the old sidevave motors in them. Most have been replaced with Datsun #Nissan# 1200's from 120Y's /Sunny's

Oops that's the Minor, not the Morris 8 that you have. Dare say that not many of those around Oz either..

Wilipedia tells me that they have a 918cc motor rated at 23 1/2 HP.

Black sooty exhaust and spark plugs highly suggests its running way too rich or the fuel is not all that compatible with the old style low compression engine or you have severe ignition system issues.

Stumble above a specific RPM or load point suggests weak or intermittent spark either caused by incorrectly set points, timing, or weak/faulty coil or condenser, reversed coil polarity, or a combination of two or more of these issues.

After that I would suspect cam timing.

I agree with the sooty exhaust completely, far too rich. Any petrol will be OK as long as the valves have been rebuilt with proper hardened ones and seats for lead free petrol, or an additive is used instead.....

Assuming that the water ways in the block has been properly cleaned of all deposits from water like calcium. If it uses a siphon method to circulate the water, the passages must be fully free.....with an engine that old, its possible that the block is heavily coated.

I have used coffee machine cleaning chemicals to de-calcify blocks, never had a problem, just run the engine up to temperature, switch off, leave for 2 hours, run it up to temperature again and do this over a week, whenever you think about it - clean as a whistle. I have even driven with it but some chemicals will foam in pumped engines, when driving and that stuff is caustic......

I am sure someone here will find a reason NOT to do it! Wait up.......but I have never had problems.....just rinse and run the motor several times to make sure it is all removed and use a quality modern antifreeze, correctly dosed, to keep it clean.

If all the hoses are new (I would hope so!), then they should not be a problem, but old hoses sometimes lose the inner lining.....

Wrong timing is a strong possibility as well, over advanced timing will cause over heating. It can even damage the engine, even though pinking may not even be apparent.....

Check to see that the water passages in the block are not clogged with mineral deposits.

Poor circulation and poor conduction of heat from block into coolant can result of passages are blocked with insulating crud.

Being as I am unfamiliar with that engine I would just offered two generic suggestions. Some engines of that era circulate water by thermal convection, if so my suggestions are useless.

If the engine utilizes a water pump, checked the lower radiator hoses, there should be a spring to keep the hose open. If this spring is missing or rusted out the hose will collapse as engine RPM increases.

Also check the water pump impeller, I actually had an engine that the impeller had completely rusted away. Interestingly enough it would run hot initially and then begin coolIng by thermal circulation.

In addition to checking for bubbles in the radiator tank you might want to test for the presence of exhaust gases in the radiator - there is an affordable test kit available for this - which indicates a failed head gasket, cracked block, or cracked head allowing hot exhaust gases to enter the water jacket.

Check the correct thermostat is fitted and functioning correctly. The thermostat is a by-pass type, not like a conventional through feed type, system and has to be fitted and closes the by-pass as the engine heats up to running temperature before closing the by-pass then forcing the coolant to go through the radiator. If the thermostat is not functioning or removed or modified, as some people do in the hotter climates of the world with through-feed thermostats, the engine will do nothing but overheat. The purpose of the system utilized is to combat frozen engine & radiator coolant so the engine is warmed up to running temperature and then the radiant heat and hot water melts the frozen or nearly frozen semi-solid/solid coolant in the radiator core until everything is stabilized temperature wise. The thermostat then operates by opening or closing the by-pass to the divert the coolant to the radiator.

Hope this has not been overlooked in your checklist.

Have you checked the water pump? On the 1000, it was part of the cooling fan assembly, so that, if you took the fan belt off, there were about 4 bolts holding the assembly onto the engine block. I had a similar problem on a Ford and found that all the vanes on the impeller had corroded off, hence a lack of cooling. Before the engine gets hot, take the radiator cap off and rev the engine gently. You should see the water circulating, if my memory serves me correctly. If it is, then the problem is elsewhere. If not, then you might need to take the pump off and have a look.

Good luck

Thermo-syphon system, no water pump.

check for rust buildup inside the cylinder block and cylinder head water passages. "insufficient heat transfer"

#5

Try using NO coolant. My pre-war vehicles overheat with coolant. There are additives you can add to the water to protect the radiator from rusting. But there is something in the coolant that causes the cars to overheat.

Probably, we need a little more information. Have you checked to make sure that the thermostat was installed right side up? Have you checked for circulation through the heater core?

About the black spark plugs: You have an SU side draft carburetor and there is a gadget made to check for proper air flow at idle. You can adjust the richness of the carburetor. When properly adjusted for peak lean your spark plugs should be light grey. There is probably some old coot in the UK that still knows how to work on the Minors but he is probably afraid of computers.

If its an SU, they are easy to set up, especially a single one.

There is a pin at the base of the piston/cylinder, which when pushed and held up, lifts the piston a little. If the mixture is too lean (also if the timing is wrong) the engine will either cut out or run slow and rough.

If its correct, the engine will speed up for a few seconds and then return to the idle speed still while holding the pin up.

If the mixture is too rich, the motor will speed up and stay at that raised RPM as long as the pin is held up.

To alter the mixture, there is an adjustable jet at the bottom of the carb, screw it out/down to make richer and screw it in/up to lean the mixture.

Stromberg carbs have the same method and actually work in a similar fashion....but diaphragm instead of a piston.....

Engine must be warm, choke off.....do make sure that the choke is working correctly. Also needle needs to be of the correct type and correctly adjusted....see the Hayes manual first!!!

Make sure that the dashpot is full, I used engine oil for mine....and that the float chamber is level with the ground.

For twin carb engines, its slightly more complicated but still easy when you know how....Here in Germany, when you can adjust SUs or Strombergs, you get to be known as some sort of God.......why I really do not know!!!

I hope this helps.

The SU carby is the old version. There is no spring or dashpot with brush, it relies on a heavy brass and steel piston and a puddle of oil on top of the piston shaft. There is no lift pin, have to remove the air cleaner and insert a screwdriver in the throat to lift the piston. How things have improved.

Thanks for the test procedure, never knew about it, even after 50 years, but another older mate confirmed what you said.

In your position I would look for a 50's-60's SU carb with a 1.25" throat, maybe off an old mini or any of the small cars from British Leyland of the time, it should fit the manifold....or be easily modified to do that.

All problems solved....

The 1.5" carb will be too big for that engine, make sure you get the small one.....

Phaddy, there are some insightful and informed suggestions here so far.

This overheat condition... is this a constant chronic condition, or mostly when idling, sitting in one place for tuning/tinkering?

Occurs when driving normally. The driver is sober, conservative, and doesn't thrash cars the way I used to.

I once installed the sprocket on the end of the cam shaft 'wrong side first' (different than your vehicle). It ended up making the cam timing about half a tooth off. The car seemed to run fine but overheat after about 20 min. Flopped the gear over and no more problems.

A lot of good suggestions so far. I missed the fact that it's thermal circulation in my original post so that eliminates any water pump problem. One problem I ran into when I rebuild the engine for my avatar was it to ran on the warm side, I also had a new radiator. It was not as severe problem you just had to keep your eye on the temperature gauge at low speeds. I tried just about everything I could think of to correct the situation with no results.

I had it in the body shop a few years, later when it was returned the heating problem was much worse. The resolution to the problem was to pressure washed through the radiator,of course being extremely careful not to cause any damage. Not only did this correct the new problem but also the original problem of running warm it now runs on the thermostat even in extreme conditions.

The darlin' old thing is probably not being fed right.

I've had overheating in old engines simply by using the inappropriate petrol( gasoline)

Check her minimum requirements. RON 93? 95? 98?

My old Benz will ONLY drink 98. Fuel Co specs say different tho'. Benz say 97 minimum.

How long does it take to reach overheat, from cold, and at what % load?

With respect to all the preceding. the heat load needs to get into the coolant and then be transported to the surrounding air by the radiator, as well as directly to the air from block/head/sump surfaces as well as the exhaust.

NOTE here; had a mate, years ago decide that he didn't like the look of his mat black radiator and had it chrome plated. LOL LOL LOL LOL

IS the radiator in good nick and nicely blacked so's it will actually ransfer the heat load into the air stream?

Is the exhaust restriced so you need to get the pedal 'down' to make her perform.

Those old girls didn't like to perform near their their maximum load for too long.

What's the ambient air temp? They won't perform their best in the tropics either.

Now obvious why.

There has to be something REALLY wrong with a SU carby to give you problems.

One can HEAR when they run lean. Did someone change the needle?

Interested to hear what you solution is when you get there.

Cheers.

Stu.

Being an old pommy flathead with 5.8:1 compression it would of run on what was then known as "Standard" fuel. Standard fuel in Pomgolia back then was around Ron 85, and didn't have any tetraethyl (lead) added to it so in theory it should run just dandy on what we (in Oz) know as unleaded.

I had an ol 62 Finny Merc, which by virtue of it having been set up for Oz conditions back then ran on our "standard" fuel which was Ron 89 so running it on 91 Unleaded was no biggy.

Curiously MB had a range of "tunes" for the 220 depending on the country the car was destined for. Any where from 6.5:1 to 9:1 compression was available upon request.

The OP is posting for an associate, but from what I've read, its a recent resto with a freshen up job on the motor. Now how thorough was the rebuild? I'd suggest there may have been a couple of corners cut to save a farthing or two.. Which is now coming back to bite them....

Fair Comment.

Cheers

Could you expand a little on a possible motor rebuild fault.

I am not sure exactly how long ago the job was done. I think it was about 18 months.

The idle is OK and the oil pressure is OK. I would expect an idle or oil pressure problem if bearings faulty, but it could be more subtle than that. However I used to run my old Morris on SAE 50 oil with 15 lb oil pressure and it went for years without any problems, except for the rattles on hard throttle and overrun. However I did have one later car (Riley 2.5), which let me know very quickly there was a problem. Found bearing metal on the shaft and blocked oil hole, which increased the friction.

Gudgeon or piston rings? Compression OK. Would have expected overheating early while motor was tight and high ring to wall pressure.