Broke down. Weird symptoms - help needed please

[Nine One One]

You really need to try and run through the basics first, and then update the thread once you have done so.

I am not sure what your mechanical knowledge is so please excuse anything which sounds like somebody trying to teach you to suck eggs.

Firstly, it all started on a run into London (from Kent I assume) so was fairly warmed up when it happened, which is when most issues arise.

When a car is warm, things expand, heat can cause vaporisation of fuel, electrical contacts to come apart, or break down…………etc.etc…………There is no reason the fan should not be working. If the fan belt is on, WITH THE ENGINE AND IGNITION OFF, turn the pulley by hand, and just feel behind the back of the fan housing where the alternator/dynamo goes into it. You will feel the fan blades behind turning. Or whilst the car is running, take off one of the paper hoses for the heating system, on the front of the fan housing, either side of it, if it is a Euro model, and you will feel the air being pushed out.

1) Check the points gap, the heel wears on the cam lobe and can close your points up.
Check that all your HT leads are good. Get a decent pair of rubber/plastic handled pliers and remove each lead, one at a time, and see if the engine note changes, you should hear it. Put the lead back on the plug, and go onto the next one. The leads can break down with heat, until eventually they just fail. Likewise the coil. If it is an old type and oil filled, over a period of time the oil degrades, if it does overheat, because say the spark plug gap is too big, the coil has to work harder to provide the voltage to bridge the gap. So check your spark plugs. Also check your timing. This can be done statically without the car running or ignition on.........see item 5) below which shows you TDC and the marks on the distributor housing and number 1 cylinder. Sometimes the clamp bolt on the distributor can come loose and move the timing so check that is roughly where the video shows you

2) Check you have sufficient fuel going through to each carburettor…………..if mechanical, get a feed from the fuel pump, get some one to crank over the engine, whilst you see what comes out into a large jam jar, or similar container. If electrical just get them to turn the ignition on, and see that fuel is coming through.
You could also have sludge, grime, rust in your petrol tank, which has now decided of its own accord to dislodge itself, either restricting flow, and/or blocking your fuel line with it, and it turn making its way to the carburettors. Again not sure what model 356 you have..........may be a piece of wood to check the fuel level, or a sender unit. If electrical, undo the screws, carefully take out the unit slightly, and shine a torch inside the tank, to see if it is clean?

3) Check your fuel lines, are they showing any signs of aging, especially if yours runs behind the fan housing via a ’T’ piece. Ethanol in fuel breaks down rubber hoses, and you could have some crap that has worked its way into the carburettor and blocked a jet.
You haven’t said what carburettors you are running, but although it sounds daunting, there are enough tutorials on the internet, with clear and precise instructions how to dismantle them. This is not as daunting as it sounds, as most of us started doing our own cars long before the internet, and had to use books, but now somebody will give you a stage by stage tutorial on the internet…………..any jets you take out to clean, just record how many turns it is to screw them fully in, then when rebuilding it, just screw them back in fully, and unscrew by the amount you recorded. Others are just screwed tight in their corresponding holes…………you will see which ones are which. Check things like the float levels……..blow into the fuel take off, and raise the float manually to see if you can still keep blowing. Get yourself a few cans of brake cleaner/carb cleaner. Remember if you take the carburettors off, to put some paper down the inlet manifolds to stop you dropping anything else down them, and REMEMBER to take it out before you put them back.

The soot you are seeing inside the carburettor is unburnt fuel igniting in the venturi (the big hole the carburettor delivers fuel into the manifold) The float could be stuck open meaning there is a constant flow into the carburettor constantly via an overflow via the jets.Or the valves may not be fully closing resulting in combustion gases being thrown back?

4) Check your spark plugs, they are normally a good indication of what is happening inside your engine, compare them against charts you view on the internet. https://www.tuningmatters.com/how-tos/b ... r-setting/


5) Check the valve clearances WHEN THE ENGINE IS COLD …………quite easy to do, just take your time and be methodical, and check the clearance for your model/engine. I think the rule of thumb was .006” for all valves, with cylinder number 3 exhaust valve set at .007” for 356 engines as some had different clearances for inlet and exhaust, dependant on what cylinders/push rods the car was equipped with.
Over a period of time, as the valves wear in the head, they can fully close up, with no clearance left on the tappets. This means the valves may not fully close properly, especially when the engine warms up, and metal expands, meaning that there is a loss of compression and incomplete combustion, in turn leading to higher temperatures in your engine
There is a simple guide on the internet, which refers to a VW engine, but the principle is the same…….
https://www.youtube.com/@MaineMachinist

[sladey]

Brilliant post

[Disco]

You really need to try and run through the basics first, and then update the thread once you have done so.

I am not sure what your mechanical knowledge is so please excuse anything which sounds like somebody trying to teach you to suck eggs.

Firstly, it all started on a run into London (from Kent I assume) so was fairly warmed up when it happened, which is when most issues arise.

When a car is warm, things expand, heat can cause vaporisation of fuel, electrical contacts to come apart, or break down…………etc.etc…………There is no reason the fan should not be working. If the fan belt is on, WITH THE ENGINE AND IGNITION OFF, turn the pulley by hand, and just feel behind the back of the fan housing where the alternator/dynamo goes into it. You will feel the fan blades behind turning. Or whilst the car is running, take off one of the paper hoses for the heating system, on the front of the fan housing, either side of it, if it is a Euro model, and you will feel the air being pushed out.

1) Check the points gap, the heel wears on the cam lobe and can close your points up.
Check that all your HT leads are good. Get a decent pair of rubber/plastic handled pliers and remove each lead, one at a time, and see if the engine note changes, you should hear it. Put the lead back on the plug, and go onto the next one. The leads can break down with heat, until eventually they just fail. Likewise the coil. If it is an old type and oil filled, over a period of time the oil degrades, if it does overheat, because say the spark plug gap is too big, the coil has to work harder to provide the voltage to bridge the gap. So check your spark plugs. Also check your timing. This can be done statically without the car running or ignition on.........see item 5) below which shows you TDC and the marks on the distributor housing and number 1 cylinder. Sometimes the clamp bolt on the distributor can come loose and move the timing so check that is roughly where the video shows you

2) Check you have sufficient fuel going through to each carburettor…………..if mechanical, get a feed from the fuel pump, get some one to crank over the engine, whilst you see what comes out into a large jam jar, or similar container. If electrical just get them to turn the ignition on, and see that fuel is coming through.
You could also have sludge, grime, rust in your petrol tank, which has now decided of its own accord to dislodge itself, either restricting flow, and/or blocking your fuel line with it, and it turn making its way to the carburettors. Again not sure what model 356 you have..........may be a piece of wood to check the fuel level, or a sender unit. If electrical, undo the screws, carefully take out the unit slightly, and shine a torch inside the tank, to see if it is clean?

3) Check your fuel lines, are they showing any signs of aging, especially if yours runs behind the fan housing via a ’T’ piece. Ethanol in fuel breaks down rubber hoses, and you could have some crap that has worked its way into the carburettor and blocked a jet.
You haven’t said what carburettors you are running, but although it sounds daunting, there are enough tutorials on the internet, with clear and precise instructions how to dismantle them. This is not as daunting as it sounds, as most of us started doing our own cars long before the internet, and had to use books, but now somebody will give you a stage by stage tutorial on the internet…………..any jets you take out to clean, just record how many turns it is to screw them fully in, then when rebuilding it, just screw them back in fully, and unscrew by the amount you recorded. Others are just screwed tight in their corresponding holes…………you will see which ones are which. Check things like the float levels……..blow into the fuel take off, and raise the float manually to see if you can still keep blowing. Get yourself a few cans of brake cleaner/carb cleaner. Remember if you take the carburettors off, to put some paper down the inlet manifolds to stop you dropping anything else down them, and REMEMBER to take it out before you put them back.

The soot you are seeing inside the carburettor is unburnt fuel igniting in the venturi (the big hole the carburettor delivers fuel into the manifold) The float could be stuck open meaning there is a constant flow into the carburettor constantly via an overflow via the jets.Or the valves may not be fully closing resulting in combustion gases being thrown back?

4) Check your spark plugs, they are normally a good indication of what is happening inside your engine, compare them against charts you view on the internet. https://www.tuningmatters.com/how-tos/b ... r-setting/


5) Check the valve clearances WHEN THE ENGINE IS COLD …………quite easy to do, just take your time and be methodical, and check the clearance for your model/engine. I think the rule of thumb was .006” for all valves, with cylinder number 3 exhaust valve set at .007” for 356 engines as some had different clearances for inlet and exhaust, dependant on what cylinders/push rods the car was equipped with.
Over a period of time, as the valves wear in the head, they can fully close up, with no clearance left on the tappets. This means the valves may not fully close properly, especially when the engine warms up, and metal expands, meaning that there is a loss of compression and incomplete combustion, in turn leading to higher temperatures in your engine
There is a simple guide on the internet, which refers to a VW engine, but the principle is the same…….
https://www.youtube.com/@MaineMachinist

Thank you for this. I am a complete novice, so this is super helpful. I really appreciate the time you and others have taken to detail out possible solutions !

Joe

[Nine One One]

You are welcome.
Have a look at some of the videos on Heidi and Franny, doing work on their 356, and they explain things quite simply. They cover a Zenith Carb strip down and rebuild, as well as setting the valve clearance, setting the timing, how to service the car.......all quite informative.

https://www.youtube.com/@HeidiandFranny ... sche%20356

[Nine One One]

Just to give you an idea of how easily carburettors can cause all sorts of issues, here is a picture of another DDK members car, with rough running, all caused by a tiny piece of metal blocking one of the jets..............

So the bad running was persisting, annoyingly.
Its not what you want when you've spent considerable time rebuilding it.
Working through things to narrow it down, I had checked the fuel as I had suspected the garage I bought the last tank full from.  But after checking to see if it had water in it proved that wasn't the problem.
I read up on similar problems on the 356 registry and deduced it was either my adjustment of the valves,  although I am always very careful with that,  or a blocked Idle jet, which it might be considering the rusty spots that appeared on the engine over the winter.
As it was fathers day, I tidied up the garage and tossed a coined, what to check first,  the valves or the carbs.
Carbs won, and when I took the first carb off and then the first Idle jet out, this is what I found.....

Removed it, checked all the others, just to be sure, and put it back together. 
After a test run,  I can confirm, a slither of metal in an Idle jet will cause constant popping back up through the carbs.
Where it came from is a mystery, and I'm glad it didn't make it into a cylinder.

Just glad I can think about using it again now.
Thanks for listening.
Karl

[neilbardsley]

I see you are not far from me. I'm in SE London during the week. If helpful, I could come out some evening and bring my service tools so we can do the valves, points, timing and carb mix/mix etc. that way you know you have a good base and can start to change bits like the condenser etc.

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[roy mawbey]

Some really good helpful advice made I would mention one more thing, that caught me out and took me some time to sort with a similar problem to yours. You no doubt checked the main and idle jets under the square cover but have you checked the accelerator pump jets too? These squirt the fuel into the venturi's and you can see that happening if you take an air cleaner off and look over the top of the carb and depress the throttle. The jets are behind the top of carb body on the outside behind the two brass injector rods. I had my engine only running on 2 cylinders the other two partial or not at all. Unscrew the two jets and clean them.
I had immediate success all 4 cylinders back to normal and chrome exhaust stubs clear of soot. It worth a try only a minutes to do !

Roy

[RobFrost]

If the carbs are getting hot, try a thick gasket between the carbs and the head.

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[Disco]

I see you are not far from me. I'm in SE London during the week. If helpful, I could come out some evening and bring my service tools so we can do the valves, points, timing and carb mix/mix etc. that way you know you have a good base and can start to change bits like the condenser etc.

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Thank you Neil for your very gracious offer. Sorry I haven't been in touch until now - I've been out of the country. In the end, with all the faffing about and time away from being able to use the car, I sent it in to repair - Carrera Performance in Horsham quickly identified the problem and also fixed the additional problem that I had caused, by faffing with the carb mix. the car is up and running again. interestingly still popping a little in the down shift, maybe that's just the age of the engine, or maybe its just because the car could do with a proper service. either way, I drove it back to home, a little nervous but it made it.

I'll take some advice, buy a book, watch some of the franny you tube clips and see if, next time something like this happens, I can fix the car on the road side. - a new set of points and a new condenser is all that it was in the end...

thanks once again @everyone - for all for your help and guidance - its just a fountain of knowledge and generosity.

disco

[Nine One One]

So what was wrong with it in the end?

[Lightweight_911]

.

- a new set of points and a new condenser is all that it was in the end...

disco

[neilbardsley]

Here is a guide from the master. Jack has been working on 356s since the 60/70s. There is a good chance he has tuned more 356s then anyone alive.

https://share.google/rpzdwaZubi2bKdJEQ

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