Vacuum hose to what?

[Roadstir]

Hi,

The reason I am writing is that while replacing my spark plug wires I moved a vacuum line for better access and it appeared to have broken. However, upon closer inspection I noticed that it was previously broken, but a soft rubber sleeve was used to rejoin them. There are no clamps to guarantee a tight fit- they are just pushed together into the sleeve. (see attached picture) Can anyone tell me what this line is? It connects into the dome-topped aluminum cylinder referenced on the left side of the picture. The cylinder also appears to have some sort of adjusting nut on top. Is it alright to just reconnect the two lines by pushing them back into the sleeve? Or should a better method be used?

Thanks for your help.

David


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[Tom]

David,

It looks like the original brown colored vacuum line from the intake manifold to the two way valve (dome topped aluminum cylinder) is broken.  This controls the retard to the distributor.  Your car should be revving pretty high at idle without this connected.  Suggest you replace the line with a new one from the dealer (only comes in white) as it is probably quite brittle.  In the interim, you can patch it the way the other break was patched-with a rubber hose.  No clamp required.

Best,

Tom

[n/a]

Thanks, Tom.

Next question is:  When I recently purchased this car I noticed it had been converted to a Crane XR3000 Electronic ignition system.  Would that negate the need for this vacuum retard?  When I separated the two pieces of hose there was no appreciable change in the idle speed.  Could the two-way valve be bad?

Also, not sure if related, but even though I use Amoco premium fuel, I still get a bit of knock under full power.

Thanks for the advice!

David

[Tom]

David,

The electronic ignition does not eliminate the need for that vacuum line.  If you notice no change, then something else is not functioning properly in the emissions control circuit such that your two way valve is not functioning.  Many of the emissions controls have been disabled over time as they are difficult to maintain and frequently don't work right.  The problem is you can not optimize performance easily without the system, unless you start switching out distributors, coils, etc.  This system regulates retard which must go away at high speeds.  If the retard is not shut off via the 2 way valve, you will not have adequate ignition advance at the distributor at higher speeds.

It may be that your RPM relay is not working or another relay is not working.  It could be your 212 degree switch is not working, which I believe effects emissions control.  There are a few posts here and other places that go into great detail on the emissions control circuit and I would suggest you research this further if you want to optimize performance.  The Big Blue Book has pretty good details on how to diagnose relay issues in this circuit.

Hope this helps,

Tom