Rough Running Patrol

[Slackd]

All, I need your input. Please.

My ‘69 was running ok until it wasn’t. Runs ok at 1400 rpm and higher, runs very rough at idle up to 1400.

To date I have:
-installed new spark plugs (correct gap)
-installed new plug wires
-installed new coil (12v)
-installed new distributor cap and rotor
-had Rochester B carb rebuilt
-installed carb isolator
-checked/adjusted timing

I have not played with points or condenser.

It seems as if not all cylinders are firing at idle. If I pull wires off of 1, then 2, then 3, I don’t see expected rpm drop but I do on cylinders 4, 5 and 6.

Thoughts?

Thanks
Dave

[plateaucal]

The rpm drop test is a classic. Good place to start.

I would look for vacuum leak through intake manifold or possibly carb gaskets. If you get the rpm drop test spray with non-chlorinated carb cleaner or certain other flammable substance should make sense. Look for rpm changes when you spray along the carb base and along the intake to head connections.

Of course check your dwell and peek inside the distributor cap to look for carbon tracking.

Probably a bunch of other stuff you can check so just count backwards from 3- 2 - 1 and River and Esteban will be checking in.

[L60Boerne]

I second Plateaucal first thought. My never ran smooth till the vacuum line to the air filter housing was connected and working properly and 3 mechanics never even considered it important.
Patrolling and rolling,
L60Boerne

[RiverPatrol]

This seems to be a recurring theme with your Patrol. Did you ever check the vacuum advance and vacuum lines as suggested previously? Did you try spraying WD-40 around the base of the carb while it's running to see if the idle changed at all? Sounds like you definitely need to check the points since that hasn't been done. And are you making sure to warm the engine up well first? These engines don't like to run cold.

[Slackd]

Thanks all. River, yes I checked the one vacuum hose from distributor to carb. RPMs drop when disconnected. Yes, I tried the WD40 test, did not observe any RPM change. Yes, Patrol is always in warmed up condition when trying to sort through these many issues.

I appreciate all of the feedback. Apologies for continuing to post on same issues but don’t know where else to turn to for help.

Next step will be to remove air cleaner and carb and inspect intake/exhaust manifold and to do a deep dive into points.

Dave

[Flaggoni]

Random thoughts… check points to see if they still are opening enough. Perhaps the rubbing block on the distributor lobes has worn: Do you have one of those old fashioned dwell meters?
Is it possible that a couple of plug wires are swapped? If close in firing order, it may seem ok at higher RPMs.
To verify a lean condition, apply partial choke. (without allowing the fast idle cam to actuate) if a warm engine speeds up that means it was running lean. There could still be a restricted idle fuel passage in the rebuilt carb. The fuel level in the carb if set too low will also cause poor (lean) idle.
I realize you may have already thought of all these possibilities, but thought I’d toss a couple your way anyway,
Mild Bill

[Slackd]

Thanks again for all the help. Much appreciated.

I’ll post a couple of photos to go along with a few more questions.

My air cleaner has two unused open taps, one on the housing and one underneath the top cover. Should these connect? L60, you said you connect air cleaner to vacuum, where is the vacuum connection? I only have one vacuum hose, connecting distributor to Rochester B carb.

River, when I planning to install carb isolator I understood that I needed to carve out slot to match up with carb base hole. My carb has two holes so I carved two slots. Is this correct?

Thanks again. Beers on me if we ever meet up.

Dave

[L60Boerne]

Dave,
I am no expert and I direct you back to all the others. I am, by far, the weakest link, but I have experienced that of which I speak. Your picture of the inlet on the air filter housing is the same one I am referring to and it should connect to the distributor as you said. Also, the isolation spacer you pictured plays a role too. How? I have no clue, but it does.

Then switched plug wires can produce your problem too.
I worked through every conceivable fix until the spacer and vacuum line solved my problem on several Patrols. It is now one of the first things I look to get sorted when starting a refurbishment…..as evidenced by RiverPatrols Punkin most recently.

Patrolling and rolling in the snow,
L60Boerne

[RiverPatrol]

Does your Patrol have the water protect distributor (distributor caps held on by 3 screws) or does it have the non-water protect (distributor cap held on with clips)? If it has the water-protect then there are 2 more vacuum fittings on the distributor that need to go to the fittings on the air cleaner.

The vacuum advance on the distributor needs to be checked. In the absence of a vacuum pump the easiest way is to suck on the fitting that the vacuum line connects to. If the lever on the other ends moves, it's good. If the lever doesn't move, it's bad. Also ensure that the breaker plate - the plate inside the distributor that the points are mounted on - rotates relatively freely.

Points are critical. Check them first.

Yes, the carb insulator is correct. Usually the stock Rochester B carbs only have one hole but that should still be fine.

Yes, double check that the plug wires are routed correctly.

[Slackd]

Thanks River. I believe this Patrol originally had the water protect distributor but now has the non water protect. I have the one vacuum tube running from distributor to carb. If I unplug, RPMs drop. I will do the vacuum suck test. I have ordered a set of points and will replace once they arrive (my first foray into points…).

I’m all about 1-5-3-6-2-4, so confident in correct firing order.

Spark plug Q: how critical is it to use NGK BPR6ES plugs. I have ordered additional NGK plugs but currently running AutoLite.

Thanks again.
Dave