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Triumph TR6 - Advice please-couple of items


I could probably search the archives but I guess I want to see some action on the BBS for the following

I would like a survey of people's opinion on the best grade of oil to put in the Stromberg 175 carb damper. My 69TR6 has been on the road 9 years since rebuild. I started with 20W50 for 7 years and then tried 5W20 for the last 2. I think I prefer the 20W50 but if there is something better I will try that. (the car has been harder to start and smells more of gas with the 5w20)

I have set the timing to stock (4 degrees ATDC). It gives me good mileage- 21-22 mpg(imperial gallon- say 17 mpUSgallon)- and reasonable performance. Any suggestions on where to run to up performance a bit without sacrificing too much mileage?

I have been running stock plugs N-9Y- any suggestions on another?

Thanks for your opinions.
Michael Petryschuk

I think some one it depends on temp and how you drive.
Bet Steve will have the best answer

On the damper oil, it is my opinion (for whatever that may be worth) that the 5W20 has too thin of a base stock to be effective as a damper fluid. I would try and see if you can find a single weight oil in the 10 or 20 range or failing that a 10W-30 or 40 and see how that works for you. Even your own "custom mix" of 10W and 20W or 10W-something and 20W-something could be the answer for you.

On the spark plugs it gets a little trickier and it boils down to who you want to believe. If you look at the Triumph information, all PI cars and carb cars with the CF (73 up) prefix use an N9Y while carb cars with the CC prefix use an N12Y plug which is hotter in the Champion scheme of things. If we look at what champion has to say on the matter, the plug listings are reversed with CF engines using the N12Y and CC engines using the N9Y.

Then we get into what NGK (my preferred brand for these cars) has to say. They list the BP6ES for all TR6 applications. Since the NGK plugs cover a wider heat range than the Champion plugs, these would correspond a Champion heat range of both 9 and 10. Unlike Champion where higher numbers are hotter, with NGK it runs the opposite way so a BP5ES (in line with a Champion heat range of 11 and 12) would be hotter than a BP6ES. Or as the mutant rats from the early Quizno's commercials would have said "toasty."

So which plug to choose? I can't tell you since I haven't seen your plugs, but here are some general guidelines:

1) You want the plugs to run in a temperature range of about 950F to about 1450F or 500C to 800C for the metricated folks out there. Below that low end temp the plugs will not self clean so they get sooty and foul. Above that high end temp, you start blistering the insulator nose and take a chance on taking out pistons. If you are going to err, err to the cold side, you might foul a plug but you won't do anything in the way of permanent damage.

2) There's cool in fuel. If your mixture is rich, it will run cooler and may require a hotter plug. Same thing if you were pulling oil into the cylinder from the valve guides. If your timing is too far retarded, it will run cooler.

3) There's power in lean to a point and beyond that point you start risking preignition, bad things happen then. You can also get preignition if your fuel octane is too low for the compression ratio, if the timing is too far advanced, have a coked up cylinder head or if your engine cooling system has issues.

4) Temperature, humidity and air pressure can also have an impact but as rule that is not much of an issue with a variable venturi carb such as the various SU "Hx" series of the Stromberg "CD" series. If you are running Webers, Dellortos, Mikunis, etc, it's a different story but even then unless you have a reasonably large swing in these factors a properly set up system should be able to handle the normal types of changes seen in a season and/or area.

Bottom line on the plugs is that you have to "read" them and decide where to go. Also note that both companies have revamped their lines so all now carry an "R" in the designation to indicate a resistor plug and they both offer differing tip and electrode configurations along with different electrode and tip materials so the plug number daisy chain is longer. What you choose is up to you and what part(s) of the marketing stuff you want to buy into. The NGK BP6ES for example has morphed into the BPR6ES, BPR6EY, BPR6EGP and BPR6EIX to designate different tip configuration and different tip materials for a spark plug with the same physical dimensions and in the same heat range.

Ignition timing, I am assuming that you are doing the dynamic timing set at idle (800 to 850 rpm) with vacuum lines disconnected. You could advance it some and see how it works, but bear in mind that this will increase the combustion chamber temperature so a cooler plug may be required. If for example you were to advance the dynamic timing by 10 to 6 BTDC, you'll see a temperature increase on the order of 120F to 170F.


Thanks for your input Steve

Another question I meant to ask. I have been running what was advertised as a medium thermostat in the car cooling system. There was a cooler and hotter option. I have been debating on going with the hotter one. Any opinion on that?
Michael Petryschuk

Don't go hotter unless you are running a FI

Unless you are having trouble coming up to proper operating temperature I'm with Don and say don't go hotter. If you are having trouble coming up to operating temperature, I would suggest testing the thermostat first before sticking a hotter one in.

Get about a 3L minimum sauce pan or stock pot and fill most of the way with water and toss in the thermostat. Bring things up to temperature over medium heat (it may take a while) Use a cooking thermometer to monitor water temp, note the thermometer reading when the thermostat opens.

I've seen thermostats stick wide open and not allow the car to come up to temp. I froze my butt off one cold winter night long ago when that happened and couldn't get enough temp to warm up the interior.


Any idea what is operating temperature I should operate at? My temperature gauge is the older style C-H no numbers and it usually runs about 1/3 from the cold side.

it has always been at that point since I rebuilt the car in 2005.

Michael Petryschuk

Point a temp reader at various points and see what the #'s are.
Most carb cars like a cooler number, a point, you still have to get a good operating temp.
Pull the stat and I think they usually say on them what they are.

To get an actual temperature reading you may need to use a substitute gauge and possibly sender unit. The problem on the sender unit is that I don't recall the threading on it. In the back of my mind I want to say that it is a British Standard Pipe Thread Parallel (i.e non-tapered) but that the thread count per inch is different from US standards. I'll have to ponder this one a bit and either see if I have spare buried or just pull one out and measure.

As far as the temperature goes, I like to be in the 195-205F range for water temperature. While that is close to the boiling point of water, we are also dealing with a pressurized system and (typically) a glycol water mix. There were two different pressure caps used on the NA market cars, a 7 psi cap for the early cars and a 13 psi unit for the later ones when the EGR system was incorporated into the emission controls.

In the case of the 7 psi capped system, the boiling point of water would be raised to ~230F and for the 13 psi capped system it would be raised another dozen degrees. Now add in a 50/50 water/glycol coolant mox and you've tossed another dozen degrees of headroom before you reach the boiling point. This means that there is still a reasonable margin of safety with respect to boil over with the 195-205F operating range.

Thanks Steve

I will see what happens and what I get.
Michael Petryschuk

This thread was discussed between 27/04/2014 and 09/05/2014

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