ISOA Tech Tips - 1997-1998

Last updated December 6, 1998

The articles on this web site are written with the understanding that you have some mechanical and/or electrical knowledge, and that you know and assume the risks and responsibilities involved in working on your own car. If you decide to make a modification to your car based upon one of these articles, you assume total responsibility and risk for those modifications. In no event will ISOA or any of its directors or officers be liable for any direct, indirect, incidental, or consequential damages arising out of your making modifications to your vehicle based upon the contents of an article provided in this web site. It's your car, and it can affect the health and safety of yourself and others - work and drive safely and wisely! To put it bluntly, if you don't know what you're doing under the hood, then you shouldn't be there.

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TR7 / Stag Thermostats

The Triumph TR7 four cylinder and Stag V8 OHC engines use a coolant bypass flow path on cold startup to speed engine warm-up. Coolant flows from the water pump, through the engine and cylinder head to the intake manifold, and back to the suction side of the water pump through a bypass port under the thermostat. The coolant flow heats the manifold and prevents vaporized fuel from condensing on the manifold passages during warm-up. Drivability is improved since "lean stumble" is reduced, and exhaust emissions are cut since the driver (or automatic choke, depending on the model) can open the choke sooner. The OHC engines require the use of a special "reverse poppet valve" thermostat that blocks the bypass port as it opens the large passage to the upper radiator hose upon reaching its normal operating temperature. If a normal thermostat is installed, the bypass port will be left open, allowing the water pump to take suction on heated coolant from the intake manifold in addition to its normal supply of cooled coolant from the lower radiator hose. This will increase the temperature of the coolant pumped into the engine and decrease the flow of coolant through the radiator. This combination of increased water pump discharge temperature and reduced radiator flow rate will decrease the amount of heat that can be rejected to the atmosphere, causing overheating problems in engines that are very susceptible to expensive cylinder head damage if overheated.

Last year, one of the British Motor Heritage parts suppliers in the US published an erroneous part number listing for thermostats in one of its seasonal special publications. The listing stated that the thermostats normally used in the OHV 2.0/2.5L six cylinder engines used in the GT6, 2000, TR250 & TR6 and the OHV four cylinder engines used in Spitfires were also suitable for use in the TR7 and TR8. While these thermostats will work on the TR8 and will fit into the TR7 thermostat housing, they will cause overheating problems when used in the TR7 and Stag OHC engines. The OEM Unipart part numbers for the OHC thermostats are GTS 101 (82C) and GTS 108 (88C). If your thermostat has failed and the Unipart thermostats are unavailable at your local autoparts store, you can use the Robertshaw 412-180 or Stant 35398 (BT 339 180) thermostats, rated at 180F/82C.

tstat.jpg - 12kB - picture of Unipart, Robertshaw, and normal thermostats.

This picture shows the Unipart GTS 101 (left), Robertshaw 412-180 (center), and for comparison, a "normal" thermostat (right) as used in most other Triumph engines except for the TR2, TR3, and TR4.

The Stant and Robertshaw thermostats are used in a wide variety of cars and trucks and should be available in autoparts stores nationwide. They will require a slight modification (see below) to vent air from behind the thermostat as the cooling system is filled.

The TR7 thermostat is mounted horizontally, so the vent hole position isn’t critical. The Stag thermostat is mounted vertically, so you must make sure that the vent hole and "jiggle pin" is toward the top of the thermostat (12 o’clock position). This is necessary to prevent air from collecting behind the thermostat, which may prevent you from completely filling the cooling system. The Robertshaw and Stant thermostats do not have the vent hole or jiggle pin. You’ll need to drill a 1/8" hole in the stationary face of these thermostats to prevent an air pocket from forming in the cooling system. If you have a jiggle pin in your old thermostat, carefully bend the tabs to remove it. Install the jiggle pin in the new thermostat so that it will seal for flow toward the radiator.

I experienced overheating problems in my Stag last year due to the use of a "normal" thermostat that had no provision to block the bypass port. The cooling system temperature would appear normal (1/4 to 1/2 scale) for the first 20-25 miles of 65mph driving, rising to the 3/4 position within one or two miles, followed by full hot indication and boilover within the next mile. If you’re experiencing these symptoms in an OHC engine, check your thermostat to see if it closes the bypass port at normal operating temperature. After replacing my thermostat, I found that the temperature indication dropped from 1/2 scale to just above the 1/4 mark in normal driving and the boilover problems disappeared.

Tim Buja 7/14/97

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Repairing TR6 Spin-On oil filter adapter leaks

Last fall, I changed the oil and filter on my 1972 TR6, which has been equipped with TRF's spin-on oil filter adapter since 1991. In order to remove the filter, I had to rotate the adapter and filter slightly around the axis of the bolt that retains the adapter to the engine block. Upon startup, I noticed a slight oil leak from around the copper sealing washer that seals that bolt to the spin-on adapter. In a week's worth of driving, I lost about a half quart of oil. No amount of fiddling with the sealing washer (including installation of a new one of similar design) would seal the leak. I finally called The Roadster Factory to see if they had a solution for the leak since they did not list this seal in their catalog. They suggested I order a new sealing washer, which is a thicker steel washer with a rubber insert, p/n TRFEL403/WASHER. This part lists for $0.71, and is not shown in any of their catalogs or price lists, including the dBase version available on their web site. I installed this part and successfully repaired the oil leak.

Tim Buja 7/15/97

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Converting your Triumph from Positive to Negative Ground

There comes a point in the life of a purist when the convenience of maintenance and accesory management takes over. There will always be a continued debate over the physics of electron flow, electron hole theory and various other aspects involving the direction of subatomic particles in your early Triumph. (I knew a Electrical Engineering degree would come in handy some day.) The fact of the matter is that switching from a positive ground system to a negative ground system is easy and should be considered as a short winter project.

Two big reasons to consider this a "to do" project are:

  1. Easy addition of reliability enhancements such as electronic ignition, electric fuel pump etc.
  2. The ability to add a decent radio/CD/tape deck to your car without going through a major exercise in isolating the audio device from the car chassis.

If you must keep the illusion that the car remains a positive ground, then keep the Red battery cable hooked up to the negative ground terminal of the battery. Just don't let anybody "jump" start your car.

The steps to complete the project are as follows:

  1. Disconnect the battery cables and remove the battery
  2. If you have a original radio, remove it. Hopefully you are not replacing it with one of those 8 track units.
  3. If you have a ammeter, you'll need to reverse the wires connected to it unless you want to remember that when the needle goes negative you are charging and when it goes positive you are discharging. Reversing the leads is much easier.
  4. Diodes Schmiodes. Some distributors may have a diode across the points rather than a condensor, reverse the connections to the diode. Also some electric fuel pumps (if you have one) may have a diode going across them as well. If unsure, there may need to be further discussions needed about your electrics. (How about a electrics clinic?)
  5. Flip flop the wires going to the ignition coil. Leave the big fat one in the middle alone. So you'll be connecting the (-) side of the coil to the wire going to the distributor and the (+) side of the coil to the wire going to the ignition switch.
  6. Flip flop the wires going to the heater fan motor. If you don't, the fan motor will rotate backwards. If it's a centrifugal (squirrel cage) fan, you'll only have around 40% flow into the car. If it's an axial (bladed) fan, it will suck air out of the car instead of blowing air in. Either way, you'll be colder than you want to be. (It is not necessary to change the leads at the starter motor. The starter uses a series-wound motor that will always rotate the correct way with either polarity.) Some Triumph owners have installed an auxiliary electric radiator fan. If your car has one, you'll need to flip flop these leads. If you don't, this fan will attempt to blow air in the opposite direction of the engine driven fan. This will cause an overheating problem.
  7. Replace the battery. This time you'll be rotating it 180 degrees so that the negative battery terminal is connecting to the cable strap that attaches directly to the body/chassis.
  8. Disconnect the two leads to the generator. Temporarily connect one end of a length of wire to the positive terminal of the battery. Touch the other end of the wire to the F terminal on the generator (the one the smaller lead is connected to, the wire is brown with a green stripe) several times briefly. You'll get a few sparks and thats ok unless you have a natural gas leak happening. This repolarizes the field windings so you get the proper output.
  9. Reconnect the two leads to the generator.

That's it! All you need to do now is call Tim or Joe to help fix the other electricals (just kiddin'). Everything electrical on the car will/should work like normal. I promptly installed a Pioneer SuperTuner Tape deck plus 4 speakers in the car (present from Kathy). Jimi Hendrix, Cream and the Yardbirds never sounded so good. (A 60's vintage car should have 60's vintage tunes, right?) Better than the AM with the 2" speaker. So I'm not concours material, but I at least DRIVE my car.

This is the first in a series of Snic-Braaapp articles that will cover updating and converting the charging system, as well as other electrics of your Triumph. Converting to negative ground needs to be the first step. Let's do our part to stamp out consistently unreliable components in these wonderful machines.

Joe Pawlak 12/13/97

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I have Seen the Light!

For seven years, I've lived with a right turn signal which flashed very slowly or not at all. I just couldn't figure out what the problem was. One day I asked Tool Man Buja if he would test the wires, etc. sometime to see if he could help. Within one second, he said "Relamp the car." I said "Say what?" "Change the turn signal bulbs", he answered. I said "Why, they all work." He responded something about higher filament resistance as bulbs grow older and that I should try it. I did it, and the right turn signals flash perfectly now. I wouldn't have thought of that solution in a million years. (Of course, I only changed the bulbs on the right side of the car. No sense wasting money on the left side since they flash fine.) Once again, I'm glad I'm in ISOA. Thanks, Tim.

Jack "Spuds" Billimack 8/24/98

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TR6 Intake/Exhaust Manifold Gasket

The Triumph TR6 has two correct manifold gaskets available for all nine years of production. On the correct head/manifold matchup, each works very well. On the wrong head/manifold matchup however...... it sucks!!! Now I mention this because even the most talented Triumph "mechanic" has been known to overlook this most obvious error in a rush to prepare, for say... a national convention for instance.

If you happen to have maybe a 1969 TR6 and attempt to mount a later style manifold gasket on the head, you would obviously see that the gasket overlaps and closes off each of the ports, intake and exhaust. It really makes a BIG difference, and is really a pain to fix and I would think almost impossible detect without disassembly. So remember, no matter where you order your parts, no matter who says its the right gasket, always be aware of this and be sure to check before bolting up the manifolds.

Note: All names have been withheld to protect the guilty.

* - Six Tips are a collection of little known and, at times, obvious tricks of the trade, with most tips specifically suited to the TRiumph TR6 sportscar. Some may be "correct", useful information and some could possibly be dangerous. So as with any new found "technique", one should be leery of trying any of these on your own car.

Jeff "Stalker" Rust

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TR4 Straight Axle Hub Removal

There may come a time when it is necessary to separate a hub from a rear axle on your TR3 or TR4. Perhaps, to change the, studs from shorter to longer since all the manuals say it's a no-no to run solid wheels on the short studs made for the wire wheel adapter piece. Perhaps a broken stud needs replacing. Finding myself with the wrong short studs and one broken on each side, my time had come.

Luckily our Elwood Manteno knows Mr. Joe Alexander in Cedar Falls, Iowa, a very knowledgable TR, guy, who provided the "heat and quench" method which follows. He said first remove the axle, then back off the large castellated nut past the threaded end of the axle. Next, heat the spiral threaded part of the axle end to cherry red. Next, quench in a bucket of water. Then drop onto a "forgiving" surface, and presto, Houston we have separation. Joe said he does NOT use a hydraulic press to accomplish this; it's far to easy to get carried away, bend the wheel disk, and end up with trash instead of a hub.

I called Peter M., err.. Billy Pyle, to see if he was interested in undertaking this with me, especially since the extent of my pyrotechics amounts to a broken propane torch. Bill said: "What day, what time?"

Before going to the Itasca Garage, I pulled the axles - a simple process:

  • Remove the wheel.
  • Bend back locking plates to get at the attachment bolts.
  • Remove bolts.
  • Withdraw hub/axle assembly.

Friday night. We put axle one into Bill's press with the ram on the big nut, at about two-thirds pressure, just for a little additional persuasion. Bill hands me the torch with a small tip and I heat away. Specks of red appear. Quench. Reheat in the press for more red specks. Drop on railroad tie. Nothing. Bill says "More flame" and puts on a bigger tip. I heat away again until more and more red specks. Quench, reheat, drop, nothing. Bill's not too comfortable with the "drop" part.

Bill changes to the BF diameter hoses, and the cutting tip. Serious more flame. Well, there's red specks, and then there's cherry red. We got that puppy glowing, keeping the flame as far away from the bearing as possible. Quench. Reheat. Bill bangs on the ram with a claw hammer as we reheat in the press.

Requench. Reheat and bang on the ram. "More hammer", says Bill and gives a whack with the two pound sledge and presto - separation. This took about twenty minutes.

With the benefit of our experience, axle two took about five minutes. Biggest torch tip, cherry red, quench, bang the ram with the big hammer. Done. No damage to any bearings, (which need repacking, as the torch does turn the grease to liquid), no broken parts, and something new learned! Reassembly is the reversal of removal. Reattach bolts, bend over locking tabs, torque big nut to 110-120 lb-ft. (Do this in two or three steps.) No need to be intimidated by this job!

Mike Blonder

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Repair, Adjustment and General Maintenance of the Zenith-Stromberg 175CD Metering Needle

[Ed. note: If you'd like to see the original article complete with several photos, use this link to download a 608kB .pdf file.]

There isn’t a whole lot of readily available or detailed information on pulling the metering needles apart on your later model Stromberg 175 CD carbs. Maybe I didn’t look hard enough for the information. Since I needed to do some maintenance in this area, I figured I’d snap some pictures and give everyone a write-up on the process. This is not all encompassing, but it’s enough that you learn something and may be able to fix without any major headaches.

Before we get into the repair procedures, a few reasons why you want to goof with the things in the first place.

  1. You find yourself constantly topping off the damper oil.
  2. You can’t seem to be able to adjust the mixture.
  3. If you can adjust, it’s hard to turn the hex wrench inside the carb tool.
  4. Good excuse to pull them and inspect the rubber diaphragms.

Reason/Problem 1: At the bottom of the slide tube there is a adjusting screw. The head of the screw is what the hex wrench of the carb adjusting tool mates with. This allows you to bring the mixture metering needle up (turning clockwise) to richen the mixture or to bring the needle down (anticlockwise) to lean it out. There is a rubber o-ring that fits around this adjusting screw and after a bunch of years, is just plain worn out. This allows slight amounts of oil to pass by the metering needle and eventually lower the dampening oil level causing other problems. These are not 2 cycle engines so we don’t really need a fuel and oil mix.

Reason/Problem 2: There may have been a time when the mixture needed to be adjusted. In some cases Problem #3 allowed the hex wrench to round out the hex opening of the screw. The adjusting screw is made out of brass that had a hardness coefficient between silly putty and 2 year old gum stuck to the bottom of the table. With that rounded out, you were pretty much stuck with the needle where it sat.

Reason/Problem 3: This usually results in Problem 2. Couple of things I noticed cause this. There is a small itsy bitsy roll pin through the side of the metering needle assembly. On one of my carbs, it was sticking out ever so slightly that it would bind in the damper tube, impeding movement for the adjustment. Another area was the damper tube area in which the needle assembly sat was fairly contaminated. Still another was the retaining screw in the air valve being slightly long, pushing against the needle assembly adding to the resistance of movement. Finally, the o-ring on the adjusting screw and the threads of that screw where it goes into the metering needle assembly needed some attention.

Reason/Problem 4: The rubber diaphragms are critical in regulating the vacuum in these carbs. It has nothing to do with the mechanicals of the needle, but they do crack and cause problems. It is a good idea to inspect them prior to placing your parts order.

Repair and Renewing
With the air valve out of the carb body, remove the diaphragm to prevent it from getting damaged. Use the hex wrench from your adjusting tool and turn anti-clockwise to back out the metering needle to its farthest point. Remove the retaining screw on the side of the air valve and the needle assembly should be able to be pulled out. You may have to give it a half turn but it should come out.

If the adjusting screw is stripped, the assembly extraction is a bit trickier. You will need a very small punch and a small manually operated inertially driven impact generator, something like a tack hammer. Turn the air valve over and carefully secure it in a vise. If you warp this thing, forget about the next steps since you’ll have to get a new one. You will see a small notch at the bottom of the needle assembly where the retaining screw floats in. This slot will give you some leverage as it is the only way I can see that would give you a chance of rotating the thing out. I’m sure there is a special tool, but geez who would have that? Using the small punch and hammer, angle the punch and gently tap on the edge of the notch so you can rotate it anti-clockwise and wind it out of the tube. Lots of baby steps here and be gentle! You will probably knicker up the edge a bit, but that can be dressed up and it is fortunately in a non critical area.

With the needle assembly out, you can check the itsy bitsy roll pin and clean any corrosion on the assembly and in that same area on the tube. Using a larger punch or dowel rod, you can now push/punch the adjusting screw and retaining washer back out the top of the tube. At this time you’ll be replacing the o-ring on the adjusting screw or screw if needed. It is a good idea to get a new retaining washer as they are cheap. Place the new screw back down the tube. Make sure the hex hole faces up. This will rest on a shoulder at the bottom of the damper tube. The retaining washer is concave. It's tricky, but place the washer down in the tube making sure the cave of the concave screw faces up. Push this down until it hits the adjusting screw. Turn it over and you’re ready for the needle assembly.

With everything clean including any edges you may have induced during extraction, the needle assembly should slide nicely into the bottom of the tube. Rotate it around, line up the notch and put the retaining screw back in. Using the hex wrench, turn clockwise to bring the bottom of the needle assembly flush with the bottom of the air valve. This gives you a basepoint for the mixture adjustment. Nine times out of ten, that’s usually where it ends up staying. Turns nice now, doesn’t it? Before total reassembly, check the notches at the top of the damper tube where the adjusting tool attaches. Sometimes with a hard adjusting needle assembly, the notch develops a burr which is enough to cause binding with the dashpot cover. Take the cover and slide it up and down on the tube to check it out. That’s it, put the diaphragm back on and put back in the carb body. Top off the damper oil and perform any final mixture adjustments. Other notable checks involve your adjusting hex wrench. Make sure the edges are square and clean. If needed, grind away the worn area. Then take off for a nice ride, you’ve accomplished something.

Next month, I have a article on the whole theory of ops on how the air valve works and some discussion on damper oils.

Joe "Stagmeister" Pawlak

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TR6 Clutch Master Cylinder Rebuild

Every ten years or so a certain amount of attention must be given to the hydraulic system. Even the best silicone fluid gets roeggy after awhile. (see sidebar below). I say "ten years" because at twelve the whole mess goes to s***.

A couple of weeks ago my six decided some bonding was in order for the two of us so it puked its clutch master cylinder. Even though I did the silicone implant thing years ago, the six very neatly took out all clutch operation without spilling a drop of fluid.

Upon disassembly of the master I found the main spring was broken into four pieces! One of the sharp ends had worked it's way under a seal and into this article. Thank god it waited until AFTER the twenty-five hundred mile journey east to TRials '98.

What I had forgotten over the past twelve years was how really easy it is to rebuild the clutch hydraulics on a six. Two half inch bolts, a cotter pin and a half inch fitting and you're walking away with the master.

Needle nose the snap clip at the end, shove an air compressor hose in the out hole and blow out the guts. The rest is reassembly.

Rebuild kits have great pictures for when you get lost and all the parts you'll need are included ............... except the main spring.

One thing to note is that no matter how bad a clutch master may look, even with a broken casing and a torn cap put on with visegrips, the main spring can still be in perfect shape. I'd like to take this time thank the member that gave me that bucket of trashed clutch parts at the swap meet last year.

And now for a short NAPA commercial. Somewhere in my travels I happened to pick up the "One-Man Brake Bleeder" NAPA part #700-1147. Being an embarrassed owner of the K-Tel "In the Shell Egg Scrambler", a "Four Level Food Dehydrator" and other assorted late night television tools I would like to distinguish this one as a tool that really works! Being void of a wife or any otherwise useless offsprings has it's disadvantages in times of engine removal and clutch/brake bleeding.

This "One-Man" is no more than a one-way valve within a rubber hose with a spring around it. You push it on a bleeder nipple backed out one turn and pump the pedal until it's hard. That's it. No begging, no new shoes, no big food bills, no nose ring trauma, just pump.

Sidebar:
While there are conflicting opinions on the advantages and disadvantages of silicone brake fluid, everyone is in agreement that "regular" brake fluid will destroy every seal in your Triumph hydraulic system. Use only Castrol DOT 4 and then only if you truly believe that you, unlike the original manufacturer and every mechanic on earth, can repair a Triumph hydraulic item so it will never leak all over your new (or original) paint job.

Me? I use Silicone brake fluid ..... "IT DOESN'T EAT PAINT". I don't care if it's made from baby seals and whale oil and it contributes to enlarging the ozone hole. I repeat, it doesn't eat paint.

1 - Six Tips are a collection of little known and, at times, obvious "tricks of the trade" with most tips specifically suited to the Triumph TR6 Sportscar. Some may be "correct", useful information and some could possibly be dangerous. So as with any new found "technique" one should be leery of trying any of these on your own car.

Jeff "Stalker" Rust

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