Ignition timing

[AltaKnight]

I read on a recent post that the timing for a TR6 should be set at about 800 RPM and it should be between 12 and 16 deg BTDC using a timing light.

Mine is at 12 deg BTDC with the vacuum (retard?) connected but shoots over to about 24 deg BTDC when I disconnect it; stays the same whether the hose is plugged or not (the hose does pull a vacuum)

Does this sound right?(BTW it's a 73 stock model with only one distributor "appendage")

 

[TR3driver]

Nope, that's way too fast. With the retard connected and operating, the measured timing should be 4 ATDC. In fact, there should even be a plate under the hood that specifies that number.

The books that say to disconnect the vacuum line are wrong (for US models). With the line disconnected, you should get the "static" timing value, which ISTR is 12 BTDC.

You can experiment with a bit more advance than that if you want, but be careful. Even inaudible knock can eventually damage the engine. Somewhere, I've got a piston missing a few ring lands as a reminder.

 

[Guest]

I agree with Randall that if you have a stock engine and want to stay with vacuum advance, keep it at about 4* ATDC. I do not have a stock engine and have no desire to run a vacuum onto my dizzy therefore I have mine set to run mechanical advance at 8* BTDC. Follow Randall's advice and stay with stock timing.

 

[TR3driver]

Just for clarity, I wasn't suggesting to either keep or remove the vacuum retard. Just wanted to describe how to set the timing if you keepit.

It's my personal opinion that the vacuum retard was at best a misguided emissions control; but I have no argument whatsoever with those that want to keep their cars original.

But my 'new' Stag has vacuum retard; and as soon as I deal with some more important issues (like putting the gearbox back in /bcforum/images/%%GRAEMLIN_URL%%/smile.gif ) I plan to convert it to vacuum advance.

The purpose of the vacuum retard was to reduce HC emissions at idle. But it does so by increasing CO2 emission, which is regarded as much more of a pollutant today than it was 30 years ago.

Vacuum advance will actually reduce CO2 emission at speed, and as a side benefit burn less fuel and reduce heat produced. (Guess which one I'm interested in /bcforum/images/%%GRAEMLIN_URL%%/smile.gif )

Unfortunately, the conversion is not as simple as just changing the vacuum capsule; you also need the correct vacuum port on the carburetor. I'm fortunate enough to have an early Stag carb on hand that has an advance port; but for your TR6 you would likely need to drill & tap the carb body to get the port timing right.

 

[AltaKnight]

Thanks guys, I think I'm going to disconnect/plug that ignition retard device (no pollution control inspections here and it's easy to put it back anyway) and retime it correctly.

 

[RobT]

Are you sure you don't have the vacuum line hooked up to the vacuum advance?

The vacuum advance should be hooked up, but the vacuum is from the intake side of the butterfly, so you only get vacuum on acceleration. The vacuum retard goes to the manifold, but via a valve on the accelerator shaft so it only works at idle.

Rob.

 

[Tim Tucker]

AltaKnight:
I have the same timing values as you do (12/71 TR6). I set my static time to 12 BTDC as the manual suggests. At ~850 idle I also have 12 degrees using a timing light. It also gives me max vacuum. When I disconnect the retard unit, my idle goes way up and the timing goes off scale as well. From the Cape Code Reference Document:

"My Car
·1973 TR6, has vacuum advance on distributor but it’s plugged. RPMs - dashboard tach = 1000, meter tach = 920, vacuum retard disconnected = 1200
·Timing - I pretty much time mine by ear. Vacuum retard connected, 1000 RPM on dash tach, set to 9 BTDC. Disconnected & plugged it advances off the scale."

My car won't run at 4 degrees ATDC...? She runs great where I have her at now... I wish I could explain the reason why my ignition timing is so far from factory spec.

Tim

 

[AltaKnight]

Rob....
My retard unit vacuum hose is via the temperature switch in the upper rad hose then to a connection on the bottom of the rear carb. I'm not sure which side of the throttle plate it's on but there is a high vacuum at 850RPM idle.
It was set up this way when I got the car and seems to be correct.

 

[TR3driver]

My car won't run at 4 degrees ATDC...? She runs great where I have her at now... I wish I could explain the reason why my ignition timing is so far from factory spec.

Have you checked the accuracy of the timing mark on the front pulley ? If memory serves, the TR6 has a rubber element inside the pulley, and they can sometimes shift.

My Dad used to own a Dodge station wagon with the same problem.

Different years had all sorts of different vacuum plumbing. ISTR it was only the TR250 that had the weird valve operated by the throttle linkage, but maybe some very early TR6 did too. My 71 Stag didn't have the valve in the radiator originally, but the radiator has been replaced and there is one there now.

 

[Tim Tucker]

Randall,
It is on my TO DO list. I may check that this weekend now that I have worked through the electrical and various other problems.
Tim

 

[RobT]

Rob....
My retard unit vacuum hose is via the temperature switch in the upper rad hose then to a connection on the bottom of the rear carb. I'm not sure which side of the throttle plate it's on but there is a high vacuum at 850RPM idle.
It was set up this way when I got the car and seems to be correct.

This does sound different to the TR250/Early TR6 set-up. But shouldn't the valve retard, not advance the timing when it opens? If the timing goes from 12 deg BTDC to 24 deg BTDC when you connect the vacuum line, then it is advancing rather than retarding.

Rob.

 

[AltaKnight]

Rob.....
No, the timing goes from 12 deg BTDC to 24 deg BTDC when I disconnect the vacuum hose.

I guess my real concern is that at times of low vacuum ie when the throttle is wide open the timing will presumably be around 24 deg BTDC which seems to be a lot of advance, can't say I've heard any pinging or engine rattle though.

 

[RobT]

Rob.....
No, the timing goes from 12 deg BTDC to 24 deg BTDC when I disconnect the vacuum hose.

My bad - I should have read your original post more carefully.

I usually just set the timing with everything disconnected (advance & retard vacuum) to 12 deg BTDC or thereabouts. Then connect the hoses. 24 deg BTDC is way to far advance. I am suprised you don't get pinging or overheating with that.

Rob.

 

[hkzimmer]

I read on a recent post that the timing for a TR6 should be set at about 800 RPM and it should be between 12 and 16 deg BTDC using a timing light.

Mine is at 12 deg BTDC with the vacuum (retard?) connected but shoots over to about 24 deg BTDC when I disconnect it; stays the same whether the hose is plugged or not (the hose does pull a vacuum)

Does this sound right?(BTW it's a 73 stock model with only one distributor "appendage")

I AM HAVING A SIMILAR PROBLEM WITH THE TIMING BEING TO FAR ADVANCED (BUT THE VEHICLE - '71 TR-6 W/VACUUM RETARD - RUNS FINE). WHAT I FOUND OUT IS THAT I HAVE A LEAK AT THE MANIFOLD GASKET. TRY SPRAYING CARB CLEANER AROUND THIS GASKET AND AT THE CONNECTION WHERE CARBS BOLT TO THE INTAKE MANIFOLD TO DETERMINE IF THERE IS A LEAK. FIX THE LEAKS AND TIMING WILL PROBABLY BE MORE WITHIN SPECIFICATIONS. JUST MY 2 CENTS.

HANS

 

[Brosky]

Just out of curiosity, what brand of ignition wires are you using? Don't think I'm crazy, just tell me. I have a reason for asking.

 

[AltaKnight]

Not sure what brand or type of wires; they're from NAPA, they're a nice blue color and seem fine.

 

[Brosky]

I have Magnecor wires on my car and I cannot get an accurate timing reading on the engine with these on. It's a common problem with racing wires and some others out there.

Try swapping to a different #1 plug wire and check the timing again. You may be surprised. Cheap test even if you have to go to a parts store and buy one.

My initial readings were similar to yours until I did that. I keep a spare stock wire in the trunk for tuning purposes only.

 

[jerrybny]

Ok now I am confused. I have a 73 TR6 with vacuum retard. All the books I have say to disconnect the vacuum retard line and plug it when doing a dynamic timing check. Now to my confusion.

1) When looking from the front of the engine which way is advanced? To the right or to the left of the TDC line. The book says my year should be 10 degrees after TDC. I should add I can no longer see any of the markings other than the solid line, so I will be guessing a little as to where 10ADTC really is.

2)Should the retard vacuum line be disconnected and plugged?

Thanks from a sometime dummy.

 

[TR3driver]

Ok now I am confused. I have a 73 TR6 with vacuum retard. All the books I have say to disconnect the vacuum retard line and plug it when doing a dynamic timing check.

The books are simply wrong. They are referring to disconnecting the vacuum advance line on non-US-spec cars.

1) When looking from the front of the engine which way is advanced? To the right or to the left of the TDC line.

Standing in front of the car looking back towards the engine (which is the opposite of how left and right are usually determined on a car), the pulley mark should be to the left of the pointer for advanced.

The book says my year should be 10 degrees after TDC.

I think you need to read that again. 73 TR6 should be 4 degrees ATDC with the retard connected and operating (not disabled by the TVS).

2)Should the retard vacuum line be disconnected and plugged?

Your choice, really. The retard does little or no harm (beyond a slight increase in fuel consumption at idle); and removing it may cause you problems with getting the idle rpm down where it belongs. The TVS also gives you a little bit of protection against overheating at idle.
If you do disconnect the retard, then you need to use the "static" timing specification when setting the timing, which for a 73 TR6 is 10 BTDC.

I found my 73 Emissions supplement, PM me your email address if you'd like a PDF file of it. At 6.5Mb, it's too large to post here.

 

[jerrybny]

Your right it is 4 degrees ATDC. I timed it with the vacuum retard connected, I am having a little trouble getting the idle down though. It might be a little advanced though cause like I said I can't see the marks on the pulley. I've tried cleaning them and everything. No luck. So I think I will take it for a ride and see how it runs. Will post results later.
My Email addy is jerryny@hotmail.com Thanks