Ignition issues....

[lip277]

Some of you may recall I bought Tony's (velocewest's) car last fall.

All is going well with it (as well as any 40 year old car can go anyway....)
He was chasing an ignition problem that affected driveability...

A general question first then two specific ones....

For a US car MY 1970, was the stock distributor a dual vac advance/retard type? That is what I have installed but all the info I can find shows only the 'regular' vac advance style....
And in the related question - what is the preferred (non-smog/performance) application? My engine has no other mods so - I presume either distributor type would be 'ok' provided it is timed accordingly.

Ok - now to the specific questions for my situation....

#1-
Are replacement vacuum units available?
Seems mine is not holding pressure...

I have a 'spare' distributor (via Tony) that is a vac advance only unit.

The pot on that one seems to hold.
But - I'd like to get that one refurbed before I install it...
A shop in Seattle that is available to me can do this. But - they requested the graph showing what I would want the advance profile to be. They have some info available but if there is 'specific' data for our applications, that is preferred.

#2-
Are these graphs available? I have searched up and down the web but can't find anything. I have found some info for the M10 engines in the 2002 but nothing for the M30 in our cars....

Any info would be appreciated-
Thanks -

 

[lip277]

Some of you may recall I bought Tony's (velocewest's) car last fall.

All is going well with it (as well as any 40 year old car can go anyway....)
He was chasing an ignition problem that affected driveability...

A general question first then two specific ones....

For a US car MY 1970, was the stock distributor a dual vac advance/retard type? That is what I have installed but all the info I can find shows only the 'regular' vac advance style....
And in the related question - what is the preferred (non-smog/performance) application? My engine has no other mods so - I presume either distributor type would be 'ok' provided it is timed accordingly.

Ok - now to the specific questions for my situation....

#1-
Are replacement vacuum units available?
Seems mine is not holding pressure...

I have a 'spare' distributor (via Tony) that is a vac advance only unit.

The pot on that one seems to hold.
But - I'd like to get that one refurbed before I install it...
A shop in Seattle that is available to me can do this. But - they requested the graph showing what I would want the advance profile to be. They have some info available but if there is 'specific' data for our applications, that is preferred.

#2-
Are these graphs available? I have searched up and down the web but can't find anything. I have found some info for the M10 engines in the 2002 but nothing for the M30 in our cars....

Any info would be appreciated-
Thanks -

 

[Ed G]

"Blue" 3 ring binder dealer manuals show both vacuum and centrifugal advance curves.

 

[Ed G]

"Blue" 3 ring binder dealer manuals show both vacuum and centrifugal advance curves.

 

[hans3]

I have a dual advance / retard vacuum distributor in my '70 2800CS--OEM. It would seem to have some type of centrifugal advance mechanism too.

Related question: Anyone know how the small adjusting screw below the vacuum diaphragm is supposed to work? Is it a fine timing adjustment or does it act solely on the retard vacuum linkage?

 

[hans3]

I have a dual advance / retard vacuum distributor in my '70 2800CS--OEM. It would seem to have some type of centrifugal advance mechanism too.

Related question: Anyone know how the small adjusting screw below the vacuum diaphragm is supposed to work? Is it a fine timing adjustment or does it act solely on the retard vacuum linkage?

 

[lip277]

"Blue" 3 ring binder dealer manuals show both vacuum and centrifugal advance curves.

Ahhh...
Doh - Didn't think of that. I'll have to look when I get home.

As to the other -

Any thoughts to what distributor style works better?
Just seeing if there would be merit to going one way over the other.

Thanks-

 

[lip277]

"Blue" 3 ring binder dealer manuals show both vacuum and centrifugal advance curves.

Ahhh...
Doh - Didn't think of that. I'll have to look when I get home.

As to the other -

Any thoughts to what distributor style works better?
Just seeing if there would be merit to going one way over the other.

Thanks-

 

[dp]

I heard Bosch vaccuum module replacements are something like 180 bucks a pop! If you can decide on a dizzy you want, I believe W&N sells certain ones for about 100 euros and you may be able to get what you want/need from them.

This s/b an interesting thread for me as I have just last night started in on research 4-cylinder dizzy's...got a box of them I am digging through and the 02 community has a WEALTH of info on the dofferent types including advance curves and the like. I look forward to seeing if we come up with the same thing here.

 

[dp]

I heard Bosch vaccuum module replacements are something like 180 bucks a pop! If you can decide on a dizzy you want, I believe W&N sells certain ones for about 100 euros and you may be able to get what you want/need from them.

This s/b an interesting thread for me as I have just last night started in on research 4-cylinder dizzy's...got a box of them I am digging through and the 02 community has a WEALTH of info on the dofferent types including advance curves and the like. I look forward to seeing if we come up with the same thing here.

 

[bill]

ignition issues

I had misfire problems with my '74 ( on which the PO removed all the emission mods and replaced the adv/ret distributor with an advance only
distributor) and was able to remove 95% of the problem with a Crane XR 700 electronic ignition...Pertronix is also popular.

 

[bill]

ignition issues

I had misfire problems with my '74 ( on which the PO removed all the emission mods and replaced the adv/ret distributor with an advance only
distributor) and was able to remove 95% of the problem with a Crane XR 700 electronic ignition...Pertronix is also popular.

 

[pamp]

Ignition

When I had similar problems on my car I had three things going on at once.
First was that the coolant block under the intake was plugged and not allowing coolant at temperature to reach the temp. sensor. So the engine ran rich. Second was that the fuel pump relay beneath the brake booster was by-passed by the previous owner. The jumper eventually became loose, causing an intermitant problem, then complete failure. Once these problems were ironed out, it was a simple matter of changing plugs and adjusting the timing. I also found cylinder imbalance as the injectors were mismatched.
Only two injectors were spec. Two were VW. The other two I could not I.D. to any car. Sienna runs like a champ now. The main problem though was the coolant block ( the air by-pass bolts to this as well) A real hassle to pull and I only figured this out by using an I.R thermometer. Good luck to you. My point being that it is possible that your distributor is OK and that the mis- fire is caused by a fuel system problem as was the case on Sienna.

 

[pamp]

Ignition

When I had similar problems on my car I had three things going on at once.
First was that the coolant block under the intake was plugged and not allowing coolant at temperature to reach the temp. sensor. So the engine ran rich. Second was that the fuel pump relay beneath the brake booster was by-passed by the previous owner. The jumper eventually became loose, causing an intermitant problem, then complete failure. Once these problems were ironed out, it was a simple matter of changing plugs and adjusting the timing. I also found cylinder imbalance as the injectors were mismatched.
Only two injectors were spec. Two were VW. The other two I could not I.D. to any car. Sienna runs like a champ now. The main problem though was the coolant block ( the air by-pass bolts to this as well) A real hassle to pull and I only figured this out by using an I.R thermometer. Good luck to you. My point being that it is possible that your distributor is OK and that the mis- fire is caused by a fuel system problem as was the case on Sienna.

 

[gwittman]

My 70 had the dual vacuum advance/retard distributor on it originally. I switched it to the European vacuum advance only distributor. Both had the mechanical advance also. The reason I like the European distributor is it has a higher rpm rev limiter than the US version.

 

[gwittman]

My 70 had the dual vacuum advance/retard distributor on it originally. I switched it to the European vacuum advance only distributor. Both had the mechanical advance also. The reason I like the European distributor is it has a higher rpm rev limiter than the US version.

 

[lip277]

Found the ignition curves (and a bunch of other ignition data) in the blue service manual.

Thanks! I had forgotten how complete these old books are/were.
I have not 'really' looked at it yet though. Just happy to find a good starting point.

As to the other.....

I am still not sure if it is 'better' to go with a vac advance unit or the one that had dual vac advance/retard....

 

[lip277]

Found the ignition curves (and a bunch of other ignition data) in the blue service manual.

Thanks! I had forgotten how complete these old books are/were.
I have not 'really' looked at it yet though. Just happy to find a good starting point.

As to the other.....

I am still not sure if it is 'better' to go with a vac advance unit or the one that had dual vac advance/retard....

 

[hans3]

Update on topic ...

I remembered over the weekend that the (US spec 2800’s) distributor retard vacuum circuit is controlled by a switchover valve that's upstream of the retard vacuum line. The switchover valve is designed to vent to atmosphere under certain conditions, meaning it will prevent vacuum from reaching the distributor’s retard chamber. If one is testing the retard chamber upstream of the switchover valve and the valve is open, then it will appear that the dist. retard chamber is not holding vacuum.

I'm still trying to research under what specific conditions the switchover valve holds vacuum. Shop manual does not address complete performance specs. I know it's controlled both by an electrical circuit (cutoff at ~ 2000 rpm) and the outside temperature. I.e., when cold the switchover valve appears to vent to atmosphere, canceling retard and assisting the engine with startup. If the valve is malfunctioning then it's a wildcard when / if you'll see retard vacuum. An issue here is that if it is malfunctioning then the vacuum advance feature will be impacted, since vacuum advance is fully functional only when retard vacuum is cancelled (a la switchover valve).

 

[hans3]

Update on topic ...

I remembered over the weekend that the (US spec 2800’s) distributor retard vacuum circuit is controlled by a switchover valve that's upstream of the retard vacuum line. The switchover valve is designed to vent to atmosphere under certain conditions, meaning it will prevent vacuum from reaching the distributor’s retard chamber. If one is testing the retard chamber upstream of the switchover valve and the valve is open, then it will appear that the dist. retard chamber is not holding vacuum.

I'm still trying to research under what specific conditions the switchover valve holds vacuum. Shop manual does not address complete performance specs. I know it's controlled both by an electrical circuit (cutoff at ~ 2000 rpm) and the outside temperature. I.e., when cold the switchover valve appears to vent to atmosphere, canceling retard and assisting the engine with startup. If the valve is malfunctioning then it's a wildcard when / if you'll see retard vacuum. An issue here is that if it is malfunctioning then the vacuum advance feature will be impacted, since vacuum advance is fully functional only when retard vacuum is cancelled (a la switchover valve).