Bosch Distributor insufficient total advance ... please help

[fizeus]

I have a problem with my distributor: It's a Bosch (0231169008) on a stock 2.4T from 1973.

The distributor has been overhauled from a rebuilder and he told me it's OK and do not needs to be rebuilt because side-to-side and axial plays are in specs. He also tryed to twist the rotor and told that weights are free to move. Vacuum pod seems ok and it can keep depression with no problems.
Anyway the dizzy has been soaked into degreaser and lubed with fresh engine oil.


The problem persist. Timing is still unstable because at idle it jumps +/- 2-4 degrees.
Also total advance seems reduced and the dizzy really cannot arrive to 32 degrees at 6000 RPM when I set timing at 5 BTDC at 950 RPMs (vacuum connected).
I only get 22-25 degrees at 6000 when I set 5 BTDC at 950 RPM

Now timing instability makes me think that this behaviour is a symptom of tired springs, but if springs were tired I would expect to see a faster advance (that I don't read with the timing light which report a gradual advance).


Searching at the forum I see i'm not the only one having this problem
Distributor rebuilt, won't advance...?

Can experienced users give help ?

[wayne robson]

For memory you say at 6000revs, but i may be wrong, on 73 T
ex Us max is only 5600, so you should not expect to time at 6000.
the hesitation may be over revs at that .
i think the E and S may go over 6000 Perhaps you expect to much
for what you have,regards.

[30westrob]

I have a friend with a 73T, MFI with the same issue. I have gone through the distributor and every thing works as advertised, yet in the car we can not get the total advance we should. I will be following with great interest. Rob

[Trackrash]

Originally Posted by wayne robson

For memory you say at 6000revs, but i may be wrong, on 73 T
ex Us max is only 5600, so you should not expect to time at 6000.
the hesitation may be over revs at that .
i think the E and S may go over 6000 Perhaps you expect to much
for what you have,regards.

According to owner's manual the maximum (rev limited) rpm is 6500 for a 2,4l T motor.

5600 is the rpm where the maximum horsepower occurs.

[Flat6pac]

i would disconnect the vacuum and plug it
Set the timing BTDC up to ten degrees and see how it runs
The vacuum is for emissions control of the era.
Bruce

[Goth]

Your diagnosis is mostly correct. Just slightly tighten or move in the end hoops on the springs until the timing at idle is stable and mechanical advance starts just off idle. Then reset initial timing. This should give you back the travel needed for full mechanical advance.

[Trackrash]

The book says to adjust at idle then to disconnect the vacuum line and check at 6000RPM.

[Goth]

You may also find the engine temp at highway speed now runs a bit cooler.

[john walker's workshop]

If you want 32 degrees total, then set it there and live with wherever it idles at. Probably just needs a few more degrees advance at idle to get to 32. If you want steady timing at idle etc, go crank fire ignition. Distributors tend to be slightly inaccurate..

[fizeus]

Ok...
Thank you all for suggestions... I'll order a set of new springs for my distributor and i'll see if problem goes away or not.

I was also wondering if those distributors have a way to limit maximum total advance...

I also noted that this distributor has a small iron ball on the outer sliding plate; it's kept in place by an holder... Can anyone explain its functioning?

[tobluforu]

On my 72 max timing occurs at 5000, no need to rev it to 6000. You can test though to see if it changes. Forget the timing at idle, what only matters is max. How are your points, make sure they are spot on before you time.

[faapgar]

The starting point has to be that the point gap or dwell angle is correct.Usually the springs get softer over time.38-40 degrees of dwell.Fred

[fizeus]

Points, caps, rotor are brand new.
Also dwell has been checked and it's 37.7 degrees (by specs it should be 38° +/- 3).

[75 911s]

Just one more thing to check, but I recently had my 184 distributor reconditioned. When it came back, the copper ground wire that attaches the advance plate to the housing was frayed (same as the way I sent it) and barely hanging on by a strand. (FWIW the dizzy tested fine, and the person who refurbished it offered to fix the frayed wire at no additional cost)

I can't leave it be, because after researching it, I found that if disconnected it could leave me stranded. Your issues don't sound like problems caused by this braided copper ground wire, but I believe it is on 73-75 dizzys so it's something worth checking. If the ground is not good, the plate has to ground via the shaft I think - which is an iffy at best connection.

[T77911S]

clean up all the metal to metal grounds IN the distributor and where the distributor contacts the engine block.

[fizeus]

Originally Posted by T77911S

clean up all the metal to metal grounds IN the distributor and where the distributor contacts the engine block.

Can I ask you why ?
Supposing it's a grounding problem - I doubt it- how ground can affect total advance ?

[Walter_Middie]

Timing is still unstable because at idle it jumps +/- 2-4 degrees.

On my distributor, the ends of the advance springs were held on small posts. From the factory, these posts had plastic sleeves over them to hold the ends of the springs tight. After many years, these plastic sleeves got brittle and broke leaving the ends of the advance springs bouncing around on the posts at idle. This could cause your jumping idle when the springs are not under tension - like at idle.

I simply put some small plastic tubing over the posts to hold the spring ends tight.

[frosty2]

Are you sure the timing is not set at 5 deg ATDC with the vacuum hose connected
Rather than BTDC

[911pcars]

The mechanical advance mechanism on many cars begins well below the idle RPM. In order to eliminate the effects of the advance mechanism, suggest determining static or dead-timing. It can be confusing, but begin here with this incomplete description.

https://www.youtube.com/watch?v=DeNN-LzJh2I

As Mr Walker suggests, check total timing and adjust to spec. As follows:
With a timing light connected, loosen the hold-down nut slightly, rev the engine to 5000 rpm, then rotate the distributor so the TDC mark aligns at the specified total crank advance setting (e.g. 32º). Lock the distributor in place.

All else is superfluous unless a PO had modified the distributor with lighter springs and modified the weight travel. A street-based engine does not want excessive ignition timing as it might affect cranking speed as well as invite low-speed detonation under load. However, check the timing with the engine at normal idle speed as a reference point.

Sherwood