TR2/3/3A TR3 Smoking Rich?

I have gradually come to the conclsuion that my TR3 is running a little rich. It is getting less than optimum gas mileage (somewhere in the high teens), the spark plugs have a black buildup, there is a bit of smoke (very little) evident from the engine compartment but does not seem to be coming from the exhaust pipe, and at low rpms (like when you switch up to the next gear) it misses a bit until it gets warmed up or I drive at higher RPM's to "blow out" the carbs.

Does it sound like I have concluded the right thing? Is it running a little rich? I am one step shy of totally ignorant when it comes to working on these things, but since I would like to avoid the cost and hassle of having a mechanic do everything, it seems like this would be something I could adjust myself. How do I make the necessary adjustments and how do I know I have done it right?

Thanks for your help.

Bryan,
In your profile you stated that your father owned the car for 37 years. Who did his mechanic work all those years? If it is someone close by, you might hang out at his shop for pointers. If that is not an option, and you really are not that adroit at mechanic work, get some books, especially specific to your car. You really need to get the best shop manuals you can, the Service Instruction Manual would be good for starters. I knew how to turn the ignition on when I started. Just dove in by reading, making mistakes and trial and error. There are many here on the forum that have forgotten more than I will ever know about these babies. You got to start somewhere, start by reading. Good luck.

Oh, and specific to your answer, someone here will step up to the plate. I have a TR6 and am in the process of tearing down a TR3 engine, to the last bolt. Talk about learning the hard way.




Bill

Bryan,

Get a good TR3 manual, I have both a Bently and a Kenneth Ball manual and find them both to be invaluable. To explain how to tune and sync. the SU carbs in this format would be very lengthy. I would suggest first that you make sure the choke is fully coming off. Check that the connecting rod between the two carbs when fully choke off forward (toward radiator) is pushing the jet assemblys for both carbs fully up against the mixture adjusting nut at the base of each carb. Also check that the air filters are not plugged up causing an air restriction. If all that checks out OK then you will have to tune the carbs which will require a good tech manual.
Harry

Harry -

Good info, and welcome to the Forum!

Bryan -

Here's a link to a great site for SU tuning:

https://www.mgcars.org.uk/cgi-bin/gen5?runprog=mgoc&p=emg/basic4.html

And another:

https://www.gowerlee.dircon.co.uk/Tips.htm#mixture

Let us know what you discover.

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What color is the smoke?

Hi Bryan,

There are a number of other things that could be the problem, or contributing to it. Besides the other excellent suggestions you've already got (which primarily point to the carbs and very correctly recommend you get hold of a good service manual), a good, old-fashioned mechanic might help you diagnose problems. Even if you do the work yourself, it's often helpful to have some help finding the problem when you are unfamiliar with this sort of work. Most shops are happy to do this for about a 1 hour labor charge. And, many mechanics actually appreciate people who want to learn about and work on their own cars. Now, a lot of young, modern-trained mechanics might not be able to find their way around an old-style engine compartment (where do I hook up the computer?) so I'd suggest you look for an "experienced" shop! They can run a few tests and really help narrow down the possibilities.

Yes, it certainly could be that the carbs are out of adjustment. (A good shop's exhaust gas analyzer can quickly help identify that.) But there are a variety of other possibilities that come to mind as well and can be checked out pretty easily.

For one, I'd want to run a compression and/or leak-down test on the engine to get some idea of the condition of things inside. You mention smoke in the engine compartment, and that might indicate blow-by coming out of the crankcase vent. Blow-by might be evidence of carbon build-up on piston rings or worn rings and cylinders. It could also be a vent hole plugged up or something simple like that. Or, it might be some oil getting past worn valve guides and into the cylinder, where it burns and produces the smoke, as well as carboning things up and fouling plugs. A leak-down test can help identify the problem, if there is one.

There's also a possibility the valves are receding gradually due to using unleaded gas, which is mostly a matter of re-adjustment until the recession gets pretty extreme. (Note: The TR 4-cylinder head is actually relatively resistant to this problem, more than many people give it credit for. It holds up pretty well with unleaded gas unless it's driven hard and fast. So, don't panic if it's never been converted to an "unleaded". Eventually it will need exhaust valve seats, different valve guides and stainless steel valves installed. But, that job can often be put off for a long, long time and many miles.)

There could also be an ignition system fault such as old wiring or slight mis-timing or worn points, rotor and cap on the dizzy. Or, it might be as simple as old spark plugs, excessive plug gap or the wrong type of spark plugs being used.

Back to the fuel supply, a less-than fully functional (i.e., worn) fuel pump can cause some backfiring or missing, similar to what you describe. Also, the needle valves and floats in the carbs need to be working properly and the carbs themselves need to be in synch.

Overall, it's a good idea to make sure everything else is working right *before* starting to adjust and fuss with the carbs. They are usually about the last thing on the tune-up list... after the ignition system, fuel supply, internal engine condition, valve adjustment, etc. are all checked out, corrected and adjusted as necessary.

Doug's question about the color of the smoke is an important one, too.

Finally, how long have you been driving the car? I ask because some roughness and valve noise is really pretty typical with these old engines, when cold at startup. Folks who haven't driven vintage cars like this, who's only real experience is with cars made since, say, the 80s, might find some of the typical noises, smells and smoke of older cars a little disconcerting, although it might not be a problem at all! The real proof is how the engine runs once it's fully warmed up.

Hope this helps!

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[ QUOTE ]
The real proof is how the engine runs once it's fully warmed up.
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Wow, Alan, that's some great stuff, and I do have a very good experienced mechanic that would be happy to look at it and even teach me a little along the way. I thought I would see if anything obvious jumped out.

In the end,the car does run fine when warm, it just seems to be missing when cold, and it was not doing that when I first got the car from my Dad. Even now, it is really not that bad, and it goes away quickly. Since I have to have the OD looked at, I will also have the mechanic check out this issue as well.

Thanks everyone for your advice.