• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

TR4/4A Need timing help - please!

Share this page

Zimmycobra

Zimmycobra

Senior Member
Country flag
Offline
Folks - I need your help. I have been reading articles, posts and manuals all day concerning timing my TR4A. I am now totally confused and am looking for your help.

Here is the situation. My 65/66 TR4A has been running fairly well with a poor and uneven idle. I recently had a coil failure. I did a complete evaluation of the ignition system and made a few interesting discoveries.The Lucas 25D distributor is the original one that was cleaned and reinstalled during the restoration a couple of years ago. I replaced the points and coil when I changed the coil recently. What I had not originally checked was the vacuum system. As the distributor had sat for many years in very hot dry environments, i finally realized that the vacuum system was probably bad. When checked the vacuum advance would not hold vacuum. After a bunch of reading and decision making, I replaced the entire system with a new Pertronix III distributor, Flamethrower III coil, and Pertronix spark plug wires. I even replaced the vacuum tube from the front ZS carb to the distributor in case the tube was plugged. The installation went very smoothly, but the car runs the same way. Before I investigate other issues (such as the carbs) I want to be sure that the ignition system is correct. So now to my questions.

Manual says that the static thing should be 4 degrees BTDC. I have read since the restoration that 8 degrees actually runs better. I statically set the timing to be at what I believe is 8 degrees. (Actually, I just installed the Pertronix distributor at the exact same position as the Lucas was when set to 8 degrees.)

How should I set the timing with the new Pertronix system? I have a dial back timing light as well as a standard light. First thing - I will confirm that the TDC mark on my Moss replacement crank pulley (change over kit to smaller belt. No markings.) is correct. Should I then set my timing light to 8 degrees and set the TDC mark on the pointer? If so, do I do it with the vacuum line attached, detached or detached and plugged? Is this the correct timing to start with? How do I check that the vacuum system is indeed working?

Thanks in advance. I am so confused!!!!!:confused::confused:
 
That flame III coil may give you trouble.
it was not compatible with my flamethrower III ignition on my 3.

i went round & round for months before I swapped the Flamethrower III coil back to a gold coil & solved my problem.
( would run great for 45 minutes, then start missing )
 
Guy:

Thanks. I will keep my eye on it. When I ordered everything, the tech from Pertronix said that it was the one for the Ignitor III that was in the distributor. I hope he was right!
 
Zimmycobra said:
Guy:

Thanks. I will keep my eye on it. When I ordered everything, the tech from Pertronix said that it was the one for the Ignitor III that was in the distributor. I hope he was right!
Click to expand...

That's what they told me also. (Sold the ignitor & coil as a set)

i think you may find other post about problems with the flame III coil.
A tip from a BCF member & a search is what tee'd it up for me.

good luck with that gremlin!
 
Timing a little off will usually cause the idle speed to vary, the car to be low on power, and possibly the car to run hot. However, un less it has run too long and gotten to hot would probably not cause the car to run rough or uneven. That is more likely a carb or ignition issue.
 
Car actually runs very well off idle. It just doesn't hold idle well until it warms up and it also wanders at idle speed. Maybe carb issue but I want to make sure the timing and ignition settings are correct before chasing too many things.
 
Zimmycobra said:
(Actually, I just installed the Pertronix distributor at the exact same position as the Lucas was when set to 8 degrees.)
Click to expand...
If you never made a mistake before, that might have been your first one. The Pertronix isn't exactly the same as the points. The mount fits inside the same general area, but there is no guarantee the physical location can remain exactly the same -and very slight movement can drastically change the timing. The magnets and sensor will probably need aligned differently than the physical location determined by the points. You can use a timing light to verify actual (non-static) timing, but it gets more involved because the mechanical advance comes into play below idle. Another consideration is accurately knowing the engine RPMs. The tach could be way off, and most meters I had wouldn't measure it. -It's important to know the (accurate) engine speed, to know how much the mechanical advance has moved the timing away from the static mark. I posted my approach on 3-7-2014 (if you want to search for it) and it seems to have worked well.

You can check the vacuum advance by using a mity-vac on the line with a timing light and the engine 'locked' to a particular RPM. Or you can look inside the distributor with the engine off and see the advance when you pull vacuum on the unit. -Vacuum shouldn't be an effect at idle.
If I were you, I would start by checking the mechanical advance (for the erratic idle) after making sure the throttle springs are returning the throttle discs the entire way closed when the throttle is released. -And the shafts have not worn oblong holes, etc. If you remove the distributor cap and rotate the rotor a little, the springs on the mechanical advance should return the rotor solidly to the same position all the time. Those two little springs wear out. One should always have tension on it and is responsible for returning the timing to the starting point. Slight changes in timing at low RPMs will have an effect that can change the RPMs as much as throttle changes.
 
Leave it to me to make the waters even muddier!

You wrote "My 65/66 TR4A has been running fairly well with a poor and uneven idle."

Uneven idle, but otherwise running "ok", is often the sign of a vacuum leak.

Just sayin' ....

Tom M.

 
Okay, Folks - here is the latest info and a question. I spoke to Pertronix tech support yesterday and they confirmed to me that the new Pertronix Distributor with the Igniter III module cannot be statically timed. With that in mind, I asked and received the mechanical advance curve that is built into their distributor. I will try to attach it to this post. I hope that information will be helpful to all.

So now here is my question. I now believe that I understand what I need to do to get a fairly good initial timing using a dial back timing light. If I want to use the often suggested 8 degree static timing as recommended, I believe that I need to add the mechanical advance in the distributor for the rpm where I am working to the 8 degrees "static" to get to the degree setting on the timing light. For example, at 900 RPM, the chart shows a mechanical advance of approximately 8 degrees. Adding this to the "static" 8 degrees that I desire, I should set the dial back timing light to 16 degrees and rotate the distributor to place the TDC mark on the pulley back to the pointer. I obviously would have to set the car's RPM to 900 for testing. Am I correct???

Assuming this is correct, this will put the all in advance at about 32 degrees at 3,000 RPM (8 degrees static and 28 degrees mechanical advance). From what I read and understand this is about where we want it. So do I have it right or have I gotten it all wrong as usual?:wink-new:

Pertronix Curve.jpg
 
Zimmycobra said:
So do I have it right or have I gotten it all wrong as usual?
Click to expand...

Yes, grasshopper, I think you've seen the light.
I love the "British Advance Degrees" column -it's actually "cam degrees" (but probably has a funny accent).
I have one of those cheap timing lights with the 'dial an advance' built into it, but after trying several ways to check it's accuracy, decided it wasn't close. So I calculated the distance on the crank for 4 different advance points, used my calipers to mark a piece of tape and transferred colored paint dots onto my crank pulley. Then I could set the different RPMs and check the timing without any 'dialing' of the timing light.
 
Zimmycobra said:
...this will put the all in advance at about 32 degrees at 3,000 RPM (8 degrees static and 28 degrees mechanical advance)...
Click to expand...

Check your math - 36°.

Your approach is, I believe, correct. You would want to use a hand-held tach and not rely on the dash gauge - particularly if you are setting with an RPM as low as 900.

But with that said, I'll add that the advance curve shown looks unusual to me. What I expect to see is a lot more advance as the RPMs rise then a lesser slope at higher RPMs and finally a leveling off of the curve. Typically the curve has a couple of 'knees' in it as the light spring maxes out and as the heavy spring comes into play.

Disclaimer - I am no expert on advance curves.
 
I think once you do all the math and timing light procedure, you'll find that the engine just sounds and feels right when it's idling ..Something you could achieve without all the fuss and muss. Get used to it for the next time you do a tune up.
 
An alternate method for setting timing at idle is to adjust the distributor for maximum RPMs then back the timing off (retard it) enough to drop the RPMs by 100.
 
Geo:

Thanks for the response. My math is okay, it's my typing that sucks! The mechanical advance should have been 24 degrees not 28, making the total 32 degrees as I originally thought. Oh, well.

I agree that the shape of the curve was a bit odd. Not sure what is happening around 2300 when there is a small knee. It is exactly as provided from Pertronix. I will check things out this weekend and report how it goes. I know that the final answer is to see how it drives and adjust from there, but this should at least give me a fairly good starting point. I also agree about the tach reading. I do have a more accurate gauge to use for that as well.

Thanks, Geo.

Corey
 
Okay, here is my update. I readjusted the valve lash. All were good. #1 was a tad loose so I readjusted. Regapped plugs to 0.030" due to Pertronix. Car started and I was able to use the dial back timing light to get the timing set to 16 degrees BTDC at 900 rpm. After test driving the car, it wouldn't hold an idle very well. It would fluctuate between 900 and say 600 or lower. I did check for vacuum leaks around the carbs but found none - either around the throttle shafts or the manifold mountings.

PVC system seems to be working fine and is clear. I'm guessing the next focus should be on the carbs and the floats and the needle valves. Any hints or suggestions are always welcome. Thanks all.

Separate issue - I think that the replacement pulley on my water pump (from the Moss kit to convert to the narrow belt) was not completely straight and square when I installed it and I think it may have worn the bearing shaft unevenly and the water put is making a lot of noise. Thankfully I have a spare new one. I think I will replace it and check out the carbs. Let's see where that takes me? :encouragement:
 
Back
Top