• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

TR2/3/3A TR3 Timing

Share this page

RedTR3

RedTR3

Jedi Trainee
Offline
Hi all, I have a really basic question concerning timing the TR3. When I put a timing light on, the mark (hole in the pulley) shows about an inch to the left of the pointer. Is this retarded or advanced?

(I know from reading other posts that the timing light is not an accurate way to time this engine but I am trying to get a "ballpark" idea of where I am.)
 
If the hole is to the left of the pointer (as viewed from the front of the car) then that is advance... i.e., the engine rotates clockwise as viewed from the front.
 
Since you cant possible know for sure what a crazy PO may have done with the crank pully(5 ways to get it wrong) you should first check it staticly... If he didnt muck it up use the light as directed. If he did, you will have to time by ear.This is as much art as science...
If you are starting for the first time,come up to TDC #1 and make sure that the rotor is pointed at #1 plug(ignore the mark,verify by piston/valves)
MD(mad dog)
 
Another suggestion: Find TDC#1 with rotor pointed at #1 and both valves closed (as stated by Mad Dog) to verify the accuracy of the timing mark; if accurate, use the timing light to set the total advace to 28 degrees at 4000 RPM (I use 30 on my modified engine, but most sources, including TRF, say 28) If it pinks, back off a degree or two. You now have the best running advance instead of the best idle advance, which IMHO is preferred.
 
Thanks JFS, that sounds like a good approach. Now, how do I know when I am at 28 degrees, since the pulley has no calibrations? (My timing light is over 20 years old, it is not one of the ones where the advance can be set).
 
You got me there, Red; my light lets me turn a dial to read the advance. I think I remember seeing a scale where you can measure off the degrees for a TR3, but I don't remember where I saw it. Without a variable timing light you might have to use the static method along with Don's good ear.
 
When I first started tuning my car I went nuts with the timing light and tach/dwell meter only to read the Bently manual and do it exactly the way Don is. The car runs great.
 
You've probably done this but did you dial the advance back to zero on your dizzy prior to the reading? For a ball park figure use the two degree increments on the dizzy to figure the advance reetive to the pointer and extrapolate.
 
Long before there were timing lights, cars had a lever stick on the steering column (much like a lever arm for the directional signals) and the driver could advance or retard the timing as he was driving. I wonder why they dropped the idea ?
 
[ QUOTE ]
Thanks JFS, that sounds like a good approach. Now, how do I know when I am at 28 degrees, since the pulley has no calibrations? (My timing light is over 20 years old, it is not one of the ones where the advance can be set).

[/ QUOTE ]
It's quite easy to put additional timing marks on the pulley.

Measure the diameter of the pulley & multiply by 3.14. This gives the distance around the pulley (circumference).

Divide this distance around the pulley by 360 degrees.
This gives you the spacing distance around the pulley that represents each degree.

Mark the degrees that you wish to read on the outside of the pulley with a narrow paint stripe.


For example:
The pulley is 6 inches diameter

6 inches times 3.14 = 18.84 inches.

18.84 inches divided by 360 degrees = .052 inches per degree.

If you wanted to mark 28 degrees BTDC
Multiply .052" per degree X 28 degrees = 1.47 inches, round up to 1.5 inches.

Mark 1.5 inches CW from the TDC mark (as viewed from the front)
This would be a 28 degree timing mark.

Just put your actual pulley diameter & desired degrees into the numbers.
D
 
You can go thru all the math, timing lights, dwell angles you like... but in the end you will drive the car and it will tell you when you get it right.

Like Don, I just set it static (I use a test beeper but one can get close enough by ear) then drive and tweak to get it right for my engine (vernier adjustment makes roadside adjustments very easy).

I keep a 3x5 card in the door pocket with notes on initial setting and subsequent adjustments so I can remember where I am.
 
Don, they stopped using the levers because they are making the cars idiot proof. Can you imagine someone today, getting into their Toyota and actually knowing wether they should retard or advance the spark? /ubbthreads/images/graemlins/confused.gif
Back in the lever days people knew more about the cars and the inner workings, course you know all that anyway.
Tinkerman
 
[ QUOTE ]
Another suggestion: use the timing light to set the total advace to 28 degrees at 4000 RPM (I use 30 on my modified engine, but most sources, including TRF, say 28) If it pinks, back off a degree or two. You now have the best running advance instead of the best idle advance, which IMHO is preferred.

[/ QUOTE ]

I pretty much agree.

[ QUOTE ]
You can go thru all the math, timing lights, dwell angles you like... but in the end you will drive the car and it will tell you when you get it right.

[/ QUOTE ]
Geo,
You may get away with this method on an old, low compression engine, with conservative cam timing.

On higher compression engines, & especially with more radical cam timing, you can easily get into high rpm detonation that likely won't be heard. It can result in severe damage. You won't know or hear it until too late.

With such an engine, it becomes very important to not exceed a given maximum timing advance at higher rpm. This might be 28 - 34 degrees or such, depending on compression ratio, fuel octane, cam characteristics, etc. There is no way to verify this high rpm timing limit by setting static timing, idle timing, or setting it by feel or sound. You must set with maximum static plus centrifugal advance fully in at the higher rpm & let the idle timing fall where it may.

A few degrees under advance will reduce power very little. A few degrees over advance can create a disaster.
D
 
[ QUOTE ]
Don, they stopped using the levers because they are making the cars idiot proof...

[/ QUOTE ]

And, I think, on early cars with a handcrank start one would retard the timing with that column mounted lever to make starting easier and backfiring (and breaking your arm) less likely.
 
[ QUOTE ]
...You may get away with this method on an old, low compression engine, with conservative cam timing...

[/ QUOTE ]

Good point, and that pretty much describes my engine.
 
Back
Top