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Triumph TR6 - when to leave well enough alone
|Thanks for all the previous advice, that buckeye web site is excellent. |
Well, here I am new to TR6. Getting familiar with it, have some experience with MGs. I have had the carbs off cleaned up replaced few rings, gaskets, diaphrams... all looked ok just figure replace em while I had them apart. This is all due to being incapable of setting the mixture to a rich setting.
So went over the normal tune up steps, valves, igition settings, timing, carb balance, fuel filter...
By some miracle the engine started right up. I have read previous posts on timing settings, wow what a diference from book settings why? Anyway ended up setting by book to 4ATDC 850 rpm with advance disconnected. Now piston lift still seems too lean, plugs look ok not too white. The darn motor seems to run fine to spite me : ) Not so much burble with ATDC setting instead of the 16BTDC that a lot seem to use?
Now it seems to run fine do I just leave it alone, what do you think? What may I have missed? It is correct to set time with advance disconnected? not plugged? Guess i should be thankful I have a car that puts up with my ham fisted tinkering. : )
|Ian: I have about the same indications on my '72 which I've had for a year now. Set my timing according to the book, rebuilt the carbs, switched to electronic ignition and did all the wires, cap, etc. It seems to very run well but can't really get it to go rich on the rear carb. No hesitation, plugs look good, but I don't have anything to compare it to. One thing I did was re-adjust the float level to give a little more gas in the fuel bowl of the lean carb. The only strange thing is that my carb syncro tool shows pretty low air flow at idle on both carbs. I don't know if this is normal.|
Anyway, I decided to leave well enough alone for now on the motor, plenty more things to mess with.
Mine has what appears to be low air flow too. Reach about the first line on the sychro tool with middle adjustment about as much as possible without choking off the air. Didn't think about adjusting the float level, it is set at book value 16-17mm. Anyone else change the float level?
|Ian: FYI I'm getting EXACTLY the same air flow reading at max adjustment on the tool as you are. I always thought it was a problem - now I think it might be normal.|
still tinkering with settings,after a short period with Bently book values started to get vey short diesel after turn off. What are main causes of dieseling? Also no amount of bypass valve ajustments prove to support any noticiable to engine.
That is an awfully old TR6 u have. Must be worth lots of money. Below was right off the NET with the search word "dieseling"...amazing this WWW!!
"The most common cause of that is the failure of the anti dieseling mechanism, sometimes an "anti dieseling solenoid", found on most late model carbureted cars. What is happening is that the throttle is remaining partially open when the engine is shut down, which gives the hot engine sufficient fuel to run without a spark from the spark plugs. Most hot engines have sufficient carbon build-up that remains glowing red hot and acts as an igniter for the fuel. The solution is to make sure that the throttle closes completely when you turn off the ignition switch. Check the throttle stop and make sure that the fast idle on the choke or the "bottom stop" isn't what is stopping the throttle from closing. It must be the anti-dieseling mechanism and that mechanism must be functional. "
So forget the solenoid as we do not have them on early TRs and look at the throttle linkage and the throttle stop.
P.S. The BPValve also has me baffled as no change also.
|Ian and Rick C. Your BPV must be defective somehow (wrong gasket orientation or hardened diaphram for example). Tweaking (screwing CW to unseat the diaphram) a properly functioning BPV will result in an increase in engine rpm off idle due to additional air leaning the mixture. I suggest you remove the offending BPV and take it apart and renew as necessary. ALthough I wouldn't do this to my car, you can further disable the BPV by simply blanking off the BPV ports with some gasket material.|
Have had the BPV off as I did your suggestion and removed the plug so as to have access to the adjusting screw. Looked clean inside and I guess the gasket is on correct way...have a second (spare) intake manifold with carbs and removed one from it and gasket is same way so mine must be also. The diaphram with the metal ring looks ok but how would one tell if it is hardened. It will move in its frame so there is some movement to it. Maybe I need to get the carbs set correctly using my new colourtune then attack the BPV....EH?
|Rick C. The diaphram in my BPV was very old and wasn't made of rubber (some sort of impregnated fabric). It did not flex at all! Have you verified (using the carb spray test) that the throttle shaft bushings are still intact? You may be sucking air already, making the BPV appear useless. How many turns CCW from full rich are your needles set now?|
|I have the same symptoms as Rick C. Last year I completely rebuilt both carbs, new shafts, seals, diaphrams, etc. My plugs look "normal" (tan) but doing the "lift the piston test" as described in the book, I always get a reduction in RPM indicating lean mix, especially the rear carb, but it's adjusted full rich. I havn't been able to find any vacuum leaks (tested with carb spray, changed all hoses and gaskets anyway). Car runs well with no hesitation, but it just seams that I should be able to adjust to a rich setting. Does anyone have any advice?|
|I'm still trying to get a handle of my "lean" TR.|
Have checked my BPV valves all appear normal. Now if the car was allready running lean the normal BPV test wouldn't result in an increase? as you would would be leaning out an already lean mixture?
Dan I am in a similiar situation as you, seems there are a few of us out there baffled by the piston lift test. Both my carbs are set full rich, can't find any leaks either. Thinking maybe I'll try different needles or gross jets just cause I can : )
|I always read what you have to say about your TR6's and I have learnt considerably. The TR6 sounds really complex compared to my TR3A.|
I have mentioned before that with the twin SU carbs on my 3A, I use a simple length of garden hose to tune them by listening to the "hiss".
As for richness, with my air filters on and the engine running for a bit so that it's up to temperature, I raise the little side plunger on the side of each carb, one after the other, to hear the engine idle speed change when lifting the inner piston with the plunger.
I consider that the rich/lean adjustment is correct if the engine speed slowly increases (say from 700 rpm to 1100 rpm) then I listen to it slowly fall again. If the engine speed drops (say down to 300 rpm) while still holding one of the the piston lifters up, but the engine doesn't stall, then I assume the rich/idle mixture is set correctly for that carb. Then I repeat the test for the other carb.
If I make an adjustment, like I had to when I was driving in Colorado, at VTR last August, I had to lean out the mixture because there is less oxygen at 10,000 feet, the carbs need less gas to keep the air/fuel ratio at, or close to, 14:1 (14 parts by weight of air to 1 part by weight of gas). After a good run, say 30 miles, I pull the plugs and check the colour of the plugs to make sure the ratio is correct.
And that's the way I've done it for years.
Maybe this can help you with your TR6 adjustments.
Don Elliott, Original Owner, 1958 TR3A
|Ian & Rick C: I discovered that I have a small vacuum leak from the brake servo unit. This is the only hose I didn't replace on the thing because it looks good. It also appears that the gasket on the plastic connector/valve at the servo is not tight. Just by fiddling with these I was able to increase carb air flow a little and the reaction with piston lift. I need to get some new parts here and try to isolate this leak. The hose connects to the intake manifold just above the rear carb, likely why I had more problems with that one. I will keep you informed as to progress.|
|I just checked my hose to the brake servo and the servo unit. The servo unit is not fully sealed up. This is causing all the problems it appears. I started a new thread on this - anyone with experience with rebiuld or replace or operation of these please comment. As far as I can tell there should be absolutely no vacuum loss from this unit.|
|Dan-The article on servo rebuilding on the Buckeye website recommends a vendor(Partco ph: (513)-471-7000) that will rebuilding the servo, including a new diaphragm, for $85 plus shipping. Also, the car can be driven with the servo disconnected, but will require more pedal pressure.|
This thread was discussed between 20/05/2002 and 25/05/2002
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