How to Fine Tune Timing on a Triumph TR6

I tend to be the kind that would assume that simply setting timing to the factory specification will give optimum performance and economy.  I have learned that octane levels have changed since the 70s, carb settings, engine wear, distributor wear or unique characteristics of a rebuilt distributor, all impact where optimal timing should be set.  If timing is set too retarded, the engine won’t pull enough vacuum, resulting in an overly rich burn.  If timing is too far advanced, the engine will experience pre-detonation and possible valve damage and power loss.

Before you can fine tune timing, some basic fundamentals must be right:

  1. The crank and cam are correctly in sync, chain not overly worn, tensioner in good shape.
  2. Had distributor rebuilt by www.advancedistributor.com including adding the adjusting wheel, specifications at 12-15° before TDC with vacuum disconnected and plugged.
  3. Ignition components are good  – I installed top quality new coil/points/condenser/rotor/cap/wires/plugs from www.advancedistributor.com
  4. Vacuum leaks – I changed all vacuum hoses including the brake booster vacuum line.
  5. Compression is good – 160 on all cylinders
  6. Carbs are in good condition:  Verify no leak in piston diaphragms, healthy air bypass diaphragms.  I had to put new air bypass diaphragms and gaskets in both carbs, screw turned counterclockwise all the way to block off air bypass per Joe Curto.
  7. Decide what gas you will burn most often, and fill the tank.  I decided on Premium.

Steps to Fine Tune Timing

  1. Set valves to .010 with engine cold assuming a stock cam.
  2. Set Dwell to 35° ± 3°
  3. Set timing adjuster wheel on distributor to middle position
  4. Set timing to 15° before TDC with Timing Light, vacuum disconnected and plugged at 900 RPM for a baseline, keep the adjuster bolt loose for further tuning.
  5. Connect vacuum gauge to intake manifold where brake booster vacuum line normally goes.
  6. With engine warmed up and idling, turn the distributor clockwise and counterclockwise until the maximum vacuum is achieved.  For my car with a stock cam this was 21. This will be lower if you have a performance cam.   If the needle jumps a lot, or you have low vacuum, fix those problems first.
  7. Retard the timing (counterclockwise) until the vacuum is 1.5 to 2.0 lower than the maximum.  For my car this would be 19.5.  Tighten Distributor clamp.
  8. Check timing again with the timing light, distributor vacuum hose disconnected and plugged.  Record results.  Reconnect distributor vacuum hose.
  9. Check balance with Unisyn, adjust as needed.
  10. Check air/fuel mixture with Colortune for both carbs:   one cylinder (1-3) for the front carb, one cylinder (4-6) for the rear carb.  Yellow means you are too rich, or timing is still too retarded. Should be yellow on acceleration, blue at any steady speed.  Red means too lean.  Idle may be slightly yellow.  Record results and settings..  Adjust mixture as needed for the front and rear carb (clockwise richer, counter clockwise leaner).  To start, turn all the way clockwise, counting exactly to the quarter turn how many turns in.  Then turn counter clockwise with the engine at about 1500 RPM until it turns blue.  Turn no more than 3 full turns or the needle will fall out of its carrier and you will have to take it apart.  If you turn 3 full turns counter clockwise and you are still rich timing may still be too retarded. Record new settings.
  11. Verify vacuum is still within the range of maximum – 1.5 to 2.0.
    1. If yes, proceed to next step
    2. If no, repeat steps 6-10
  12.  Remove Colortune and Vacuum Gauge.   Test drive.  Car should ping very slightly under light acceleration, not at all under heavy acceleration.  Keep adjusting wheel on distributor until this is the case.
  13. Check air/fuel mixture again with Colortune.  Adjust as needed, record new settings.
  14.  Test drive again if you had to change carb settings.  Car should ping very slightly under light acceleration, not at all under heavy acceleration.  Keep adjusting wheel on distributor until this is the case.
  15. Repeat steps 11-14 until the engine pings very slightly upon acceleration, and the Colortune verifies the mixture is correct, and the vacuum level is maximum – 1.5 to 2.0.
  16. Using the timing light, observe and record the optimal timing for your car.
  17. Set the adjustment wheel on the distributor to the middle of its adjustment range.
  18. Loosen the distributor clamp, and using the timing light set the timing to the optimal timing for your car as recorded in step 16.  Now you can advance and retard equally from the optimum timing setting.
  19. Verify that nothing “slipped” one more time with Colortune that the mixture is correct (blue), with the vacuum gauge (max – 1.5 to 2.0 at idle), and a test drive that pings slighty with mild acceleration, not at all with heavy acceleration.
  20. Record all the appropriate settings:  max vacuum, vacuum when timing is proper, timing, air mixture (turns from fully closed), octane, colortune notes.

How to set valves for a Triumph TR6

1.  Set the valves cold – let it sit overnight.  If hot or warm the metal will have expanded, and the gap smaller than when cold.  If you set the valves warm/hot, when the engine cools off the gap will be larger and the adjustment too loose.

2.  Take records of the following as you go:

  • Mileage
  • Plug color and gap per plug – to monitor over time the mixture per cylinder
  • Pre-adjustment valve clearance per cylinder per valve – if the clearance on a valve keeps getting tighter each time you check it, you may have a valve seat getting pounded down.  This is a great way to monitor a head that has not been rebuilt for unleaded gas.  Erratic readings, going tighter and looser, may indicate rocker arm or tappet wear.
  • Post-Adjustment valve clearance per cylinder per valve (see the “T” and “L” notes below).

3. Wipe around Valve Cover with a rag, remove the Valve Cover with a 1/2 deep socket and speed wrench.  I do this before removing plugs just to prevent any junk from falling into plug holes.

4.  Remove the spark plug wires from the plug side only, being careful to pull them from the boot rather than the wire so as to not pull the wire off from the connector. Leave them in line with the plug you removed.  Remove all the spark plugs with the speed wrench + extension, recording the color (sooty, brown, white) and gap,  to make it easy to turn the engine

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5.  The “Rule of 13” is a slick way to know which valve to adjust on a 6 cylinder engine.  If 1 and 3 are open, 1 + 12 = 13 and 3 + 10 = 13.  Thus 12 and 10 are the valves to adjust. Look at valves to see which pair  seems to be open from the chart below.  A valve is open when the adjuster side of the rocker is up high, and the spring side is down low.  (Note:  someone pointed out that the order of the chart is inverted.  Work your way UP the chart not down.  I will verify this next time I set my valves)

Rule of  Thirteen – Valve Adjustment Order
Open Valves Check and Adjust
1 3 10 12
8 11 2 5
4 6 7 9
10 12 1 3
2 5 8 11
7 9 4 6

6.  Choose the NEXT pair of valves that will open from the chart (a reader tells me the chart is inverted, so NEXT is UP if they are right.  I will check next time I set valves), and put your fingers from your right hand on the adjusters.  I choose the NEXT pair in case the pair that appears open is already starting to close.  Your sense of touch is very sensitive, and you don’t need to watch the valves, you can easily feel when both adjusters rise, and when the one starts to descend. The reason I choose the next pair is so you can be sure they are fully open and am not tempted to turn the engine backwards, which you should never do.  You want to keep the timing chain tight in the direction of the normal rotation of the engine.

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7.  With your right hand fingers on the adjusters, take your left hand, reach down and pull the fan towards you, turning the engine clockwise.  If you have the right pair of valves, they will both start to open after only 30 degrees of rotation (a couple blades worth of rotation).  If only one valve opens, you have the wrong pair,  Keep turning the engine clockwise only just a little bit until one of the valves just barely  starts to close (when the adjuster side starts to go back down).  DO NOT turn the engine backwards if you go too far.  Just go on to the next pair, and adjust the ones you missed on the next full rotation..

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8.  Record the valve clearance of the fully closed pair that pairs with the fully open pair on the chart. So you are not recording the valves you have your fingers on, but the matching pair from the chart.  Use the go/no go method with .008, .010, and .012 feeler gauges.  The largest one that will “go” is the one you record.  I will put a “T” if it is a little tight, an “L” next to the value if a little loose.

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9.  Put a screwdriver that fits snugly in the adjuster, and loosen the nut by about a “flat” with a 1/2 end wrench on the adjuster, keeping the slot from turning with the screwdriver as best you can.  Tighten or loosen the adjuster  as appropriate by about a half of a flat of a nut, and tighten the nut, again holding the screwdriver firmly to keep the adjuster from turning along with the nut.  This takes a little practice, and you may need to eyeball it a little if things get away from you.  The important thing is to watch the adjuster slot, and have it end up a little clockwise or counter clockwise as is appropriate when you are done tightening the nut.  Verify the adjustment with a go/no go test, setting both intake and exhaust to .010.  Record the result for each valve.  If it is a little loose on the .010, but the .012 won’t go, I record this as .010 “L” and move on.  A tiny bit loose is ok, but you don’t want it too tight – “T”.  By recording it as .010 “L”, you can judge if the seat may be wearing if it is .010 “T” next time, or consistently each time you compare.

10.  Put a dollop of Vaseline on each adjuster as you go to keep track of the fact you adjusted it.  (Optional, but helps me keep track).

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11.  Repeat for each pair of valves until you are done.  If you miss a pair, just keep going and do an extra rotation to catch the one/ones you missed.  The “law of 13” method doesn’t require full rotations, and the spark plugs being out makes it easy to turn, so it won’t take you much to get back to that pair of valves.

12.  Double check:  go through the process again, double checking all the valve settings.  This doesn’t take long.  If you have any that fail this test, you need to ask yourself if your valve rocker arms or tappets are worn.  Set the offending valve again, and go through another rotation to see if it still fails.

13.  Put the plugs back, putting a little Anti-Seize on the threads first.  Nothing is worse than stripping a spark plug hole, or breaking off a plug, and the anti-seize will make them come out easily next time.  I put them back in the same cylinders so I can track the mixture in that cylinder by the color consistently.  Use the Speed Wrench plus extension, and tighten to the equivalent of hand tight, and then a slight extra turn, maybe two “hours” or so of a clock face.  Like from 1 O’clock to 3 O’clock.

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14.  Put the wires back on, verifying the firing order as you go.  (No.1 at front) 1,5,3,6,2,4  going counterclockwise.  The wires should be close to the correct plug holes anyway, so just make sure you didn’t get them crossed over.

15.  Put the Valve Cover back on, don’t over tighten it.  I use the same rule of thumb as for the spark plugs, tighten till snug, then a little more, about 2 numbers on the clock face.  (Replace the gasket first if it was leaking).  Be sure to put the emissions hose back.

First Autocross at the 2013 Gathering – Second Place – and Excessive End Float causes Gouged Distributor & Missing

So I hesitated about doing the Autocross at The Gathering.  Last year, one of our club members tore out his trailing arm mount.  I had the rear fixed up – reinforced Differential Mounts, new trailing arm mounts, Goodparts CV joint axles.  I decided to go for it.

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My goals for the Autocross were to not mess up the car, not get lost on the course, and to not embarrass myself too badly.  During the third run, while cornering hard, all of a sudden something didn’t feel right.  I decided not to take a fourth run.  I was pleasantly surprised to place second.  I won’t tell you how many entered.

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So afterwards, the “6” was missing and not running well.  Part way home, I realized what it might be.  I popped the distributor cap, and there was evidence that the end float on the distributor was messed up.  The shaft had risen, causing the rotor to dig an arc across the inside of the cap.  The rotor’s little “tab” inside that keeps it from spinning on the shaft was broken, just barely keeping it pointed in the right direction.

End float causes rotor to gouge cap during Autocross

End float causes rotor to gouge cap during Autocross

I limped home at 45 MPH, keeping the RPMs down to 3,000 or less.   The end float, according to a feeler gauge check, was far too much.  Yesterday I sent the distributor to Jeff at Advanced Distributors for a rebuild.  I asked him about going to an electronic ignition.  He said on his dyno tests, points outperform electronics!   So I’ll go points.  I can always change later.  I did order a Bosch blue coil and Bosch wire set however, per what I have read on the forums, and Jeff’s recommendation.

Replacing the Rubber Support Under the Driver’s Seat

Ever since I have owned the TR6 the drivers seat has been “blown through” meaning the rubber support piece was broken, allowing your rear end to sink down below the seat frame –  it has been rather uncomfortable.  The door latch was stuck (fixed it awhile ago) so the driver side door wouldn’t open.  My guess is the previous owner stepped on the seat to get in and out, and blew out the bottom.   I ordered a replacement from the Roadster Factory 6 months ago, and just got around to putting it in yesterday.  Took me about 45 minutes.

1.  Removed the two bolts in the front of the seat frame, removed the seat.

2.  Removed the old rubber support, as well as a ton of padding the previous owner had stuffed under the seat.  So shredded, no tools needed.

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3.  Installed all but the front two clips by hand or with a screwdriver

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4.  I ended up installing the two clips on the front last.  I had to open them up using visegrips, installed them by stretching/guiding them into the hole in the seat with the screwdriver, then closed them back up with the visegrips.

5.  Here is the final result

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It “sits” a lot better.  Still need to replace the foam at some point.  But I wish I had not put this off so long, it didn’t take long at all, and wasn’t hard to “stretch” it into place, no special tools really needed.

What Damper Oil to Use for Zenith Stromberg or SU

So I have seen a LOT of posts on various forums as to what oil to use in the TR6 Zenith Strombergs, or SUs for that matter.  Moss sells SU carb oil, but kind of pricey.  The important thing is the 20 wt.  After much research decided that I would go with straight 20wt Three in One Oil.  The links that helped me decide were http://www.british-cars.net/triumph-tr6-bbs/carb-dashpot-oil-200405030042384442.htm and http://www.buckeyetriumphs.org/technical/Carbs/CarbsI/CarbsI.htm .   Home Depot sells it 4 Oz for $3 or 8 Oz for $4.29.

One 4 Oz container was more than enough for both carbs, with plenty left over.

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Modifying Big Box Store $7 Siding Removal Tool to Install Weatherstrip Clips

My side window weather-strip on the TR6 is in bad shape.  Got the replacements and clips from TRF, and discovered how hard it is to install those stupid little clips.  Somewhere someone pointed me at modifying a vinyl siding removal tool from Lowes.   I modified it with a Dremel tool cutoff wheel, so the ears on the clip will slide in. Here is the result, and it worked great!   The only extra trick is to put a little grease on it to hold the clip.

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Here it is with the clip inserted below.

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Looks like Lowes doesn’t sell these anymore, but has replaced it with a Kobalt knock off.    To use the tool, I marked where the clips should be inserted by putting some masking tape on the door next to the weatherstrip, marking it with a sharpie.  Then insert the weatherstrip, and then at each point marked with the sharpie, insert the tool/clip, align it, and pull the clip up onto the weatherstrip.

Works great!

Replacing Loud Header/Exhaust System with Stock

Previous owner had put a performance header and exhaust system in the TR6.    At first I thought this was cool, and looked great with the dual chrome pipes coming out the back.

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But I got tired of it being loud.  When I went under an overpass near my house, sounded like a jetliner!  Since I don’t race it, use it to take drives on back roads, and enjoy talking with my wife on those drives, I decided to have Jack McGahey at 42 Dyno Services replace it while doing the other work on the differential mounts.

TR6OldHeader

I decided to replace it with stock stainless steel from Moss.

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Also had the stock manifold blasted and ceramic painted with grey VHT paint at the same time.  A bit quieter now. Glad I decided to do it.  With a tune up, plenty of power still.  My understanding is that the stock exhaust manifold will give me better torque and performance at lower speeds anyway, and I don’t drive this fast (much  :-)).  The dyno showed a slight decrease, but I can’t tell the difference driving it.  Much more of a difference occurred after I had given it a tune up and tuned the carbs too, so hard to know what to attribute to what.