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Triumph TR6 - Grey smoke, white smoke?

Here are the facts, any help pointing to a diagnosis would be appreciated.

'76 TR6 unkown mileage, probably around 100,000 miles. Cylinder head was reportedly rebuilt back about 15,000 miles ago.

When starting, I get white/grey smoke on choke which disappears at 800 rpm idle. Starting warm engine, slight touch to throttle, again I get a puff of smoke. No smoke while driving.

Compression shows 120-130 across the board.

Choke never really works as well as I'd like it to, I kinda expect the motor to spin at 1100-1200 on full choke and slowly reduce to 800 rpm. Fact is, choke gets it going, but sluggish. Idle improves closer to 800.

Also have rough idle at stop lights. Immediate stop I have probably 900 rpm and after 20s it starts to settle to 800, maybe less, but never even close to a stall. Motor pulls smooth to 5+ G on acceleration.

I've read somewhere that white smoke (maybe grey?) could be related to carbs. Rough idle sounds like vacuum leak. Should I continue to investigate rings & valves or look at a carb rebuild? It's been done previously and if you've read my posts, you know the PDO has used incorrect o-rings etc. Who know's what else he did??
Mati Holland

Mati,

White smoke usually means coolant is getting in the cylinders. Probably a very small leak since it burns off right away. Perhaps head gasket, maybe head warpage, and hopefully not a crack. For starters why don't you try retorquing the head. Some stop leak might put off the problem for a while if retorquing doesn't work.

Doug
Doug Campbell

Sounds like carbs that need rebuilding and perhaps worn valve guides.

Tim
Tim Brand

My first guess was valve guides, but if the history is correct, they were done fairly recently. Compression is also good. Would a leak test show anything when compression appears ok?

I also don't think head gasket because compression is normal, and with a cold motor, if I push in the choke, smoke disappears, but if I pull it out again, it smokes again. Not really a burn-off situation.

As you said Tim, I may have two problems but both are $$ so I'd like to narrow it down a little if possible. Perhaps since the carbs "likey" need a rebuild, I start there and see what happens.

P.S. - smoke descrition is like buying white paint. Nevada white, arctic white, moon white, pearl white? Is it grey or is it white? It's a thin puff, not a heavy cloud. I should ask my wife what color it is?!
Mati Holland

Mati,

Pull all your plugs and check coloring. That may help with which car/cylinder is acting up.
Rebuilding the carbs is actually pretty easy to do yourself which will save $$. Let me know if you need help.
Do you have any receipts from the PO re. the rebuild? It'd be nice to know what was actually done and replaced.
You could do a pressurized radiator test to assure you don't have H2O leaking in.

Valve guide wear is aggravated by worn rockers. The problem with valve guide wear is that it accelerates valve seat wear. Unfortunately the only way to check it is to grab a valve stem and feel the play - very difficult with an assembled engine. A leak down test would tell you if there was some valve seat erosion.

I'd do the carbs first and see what happens. Don't worry about the guides just yet.

good luck
Tim

Tim Brand

It just sounds like it's running a little too rich when you choke it.
Tom

So I leaned out the carbs a 1/2 turn which I also suspected might help a little. I increased the idle to 900 rpm which gives me a much nice idle, and here's the final question, on a day like to day where it's 21C outside (75F?) how many notches on the choke to most people need? I pulled it out just one and it started just fine and I didn't get any smoke.
Mati Holland

Hi Mati,
I just drove my car tonight...15C and I used the choke to start and pushed it back in after 300' of road and the car ran great, I probably didn't even need to use it at all as it only sat for 2.5 hrs.
I use a cable tie to adjust the idle screw head up against the choke cam on both carbs and the choke works great in all temps.
Cheers
Charlie
Charlie Ballard

Charlie
QUOTE "I use a cable tie to adjust the idle screw head up against the choke cam on both carbs and the choke works great in all temps."
Please explain.
I forgot to show you the quick-adjust at the TR6 BBS-BBQ. Just get one...you will not regret. Do not forget, no tax from Fred at Bronte. But, if Fred brings one specifically for you, you pay tax.

Mati, I need to pull my choke out all the way to start then immediately in 1/2 way till she warms up. I have "popping" during idle and deceleration ..carbs where rebuilt. Probably have an issue with the bypass valve. I hate the darn little things.
Rick C

If you choke a goose...will it honk?
The darn birds are starting to flock up my way...a bad sign. Look out Jim! They will soon be flying over head:)
Rick Crawford

Mati, my smoke continues and it coughs a light white between shifting...I will live with it and if it gets worse I will rebuild one out of the two engines I have. It could be many reasons. Rings, heads...who knows. Just a good reason to lift it out and re bore.
Let me know what you discover.

Ps,I never have to use my choke to start....why??
marcello

My smoke on starting is somehow directly related to the choke (ie rich mixture). As I push my choke in, the smoke disappears. I've tried starting with just one notch and it takes an extra spin to start but I avoid the smoke. Oddly my smoke is not black (except right at the tip of the exhaust - just a hint). Also on occasion, it coughs a puff on a warm engine, but not always. If i spin the motor and then depress the accelerator I can avoid the smoke. Press accelerator and then spin the motor, puff of smoke. Again, seems directly related to excess fuel. Hence, thinking about carb rebuild despite the odd symptoms.
Mati Holland

I'm sorry if this is barking up the wrong tree, as I have SU H6 carbs on 4 cylinder older cars. Could it just be a choke linkage adjustment? My theory is that only one choke is activating, or at least activating before the other. In other words, half the engine is running on a different mixture than the other. The number of clicks you need to pull the knob out is dependent on the way it's adjusted, too. One person's adjustment may have more slack in the cable (more clicks) than another's. So I suppose that's not the best way to judge how far to pull it.

Unless it's real cold out, you shouldn't need full choke, but you should need some, in my opinion. (The book starting procedure for my car says "pull the choke right out", and push the accelerator down a little). If you never need to choke it when it's cool, I think you're running rich all the time. In my experience, this will produce a burbling, loping idle and an unburned hydrocarbon smell (black or gray smoke). I'm not saying to just turn the mixture adjusting screws to solve this, running at high speed with a lean mixture will break stuff. The chokes should be the first suspect. After you are satisfied they are working as they should, adjust the mixture by the book. Then if you think you can hone it in a little better, OK.
Tom

Rick,
I used the cable tie as a spacer to adjust the nut up to the choke cam..
Charlie
Charlie Ballard

Hmmm...carb adjustment? Could it be that simple for me Mati? Here I am looking at a rebuild and it could be the carbs.
Marcello

Grey White smoke is usually a somewhat rich mixture on a cold running engine that only goes short runs.

If you look at your exhaust system. Its all down hill for moisture and condensation. If you add exhaust heat to water plus a rich mixture you get grey white.

Nope thats no guarrantee thats the problem cause I can't see it? But if your running the standard muffler. You know that big monster at the back or dew collector? With the pipes collecting moisture from dew as well.

Start the car blow condensation back to the muffler. Look at the design? Where does it go? It won't go up that nice dual pipe arc. Nope sits in the muffler and waits for nice hot air to come and turn it into steam. With the Canadian conditions this summer if your already running rich or otherwise known as cold you will have that smoke.

Old cars don't have catalytics that turn up the temp. TR6 muffler is far from the engine with the pipes in the airstream. Muffler does not get hot enough to steam off the water unless run for quite awhile.

One of my toys runs grey/white on one pipe for a bit AM due to the performance carb over rich at idle and exhaust routing. I have a low spot in pipe because of a frame part. About 1/10th the size of that muffler?

Grey white is not a panic smoke guys. Concern yourselves with the plug read. And rich.

Carbs rich due to compensation for vacuum leaks are likely?

My opinion

Bill
Bill Brayford

This thread was discussed between 28/08/2004 and 08/09/2004

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