**Need Help Diagnosing Heavy Misfire Lugged Type 4 Engine

[erjones]

Hello,

I purchased a bay window bus that had been parked for about 3 years due to a fuel smell caused by deteriorating fuel lines. I was told the bus had otherwise operated without issue. It is a '72 with a rebuilt 2.0L with Hydraulic Lifters (per invoice motor has about 20k miles on it).

I replaced the fuel lines, and fuel filter, changed the oil and strainer, adjusted the valves to 1.5 turns in after contact, and installed a fuel pressure regulator before attempting to fire up the bus (I believe it is set to 2.5 psi now).

Upon starting the bus runs with a very deep sort of lugging sound and has a heavy misfire. It could technically be driven but it pings and I do not want to run it with this issue. I also hear a loud tap which I assumed to be one of the hydro lifers not pumping up (I havent taken the bus out to run due to the issue). I assumed this was a mixture issue and rebuilt the dual Weber 34ICTs but that didn't seem to help. Plugs are completely black (not oily however). See video.

I then went ahead and threw on my rebuilt dual DRLA 36s but am experiencing the same issue (now some popping out of one of the carbs). Plugs are completely black (not oily however). Coil and plug wires swapped with known set and issue did not resolve.

The engine has good compression on each cylinder (130-140psi cold) as well as good oil pressure (~30psi at idle). Has sort of a "punchy" sound when cranking unlike the type 4 in my other bus if that matters. Distributor is a 009 (yeah, I know) with an old Pertronix ignitor unit installed. Dwell is ~54-55 degrees with the Pertronix.

Please advise as to what may be causing this issue or more tests I can do. Could it be an internal problem, issue witht the Pertronix, fuel components I replaced? Thanks in advance for any help.


Link

[dodger tom]

have you looked for vacuum leaks via a smoke test?
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1978 Champaign Edition 2 Westfalia
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[SGKent]

did you drain the tank and start with fresh fuel?

[erjones]

Hi, Yes tank was pulled (empty and actually quite clean) rinsed out with MEK and a new fuel level sender and in-tank mesh installed before being filled with ethanol free 93 octane.

Regarding vacuum leaks, I have not smoke tested but replaced the intake manifold gaskets (metal) when putting the new manifolds on as well as replaced brake booster vacuums hoses up to the metal hose that runs up the length of the bus. Vacuum port on the left Dell is capped off due to the 009 (no vac advance). When I had the 34 ICTs on I also plugged the vacuum bung on the manifolds to see if isolating the engine from the brake booster would change anything in my driveway but it did not.

[SGKent]

first you need to time it. You may have something going on there. This is what I would do

1) check the plug wires. They run 1-4-3-2. Very easy to get two out of place.
2) do a cylinder balance test to see if all 4 cylinders are running evenly or if one or more are way down on power
3) Use a stethoscope or long rod to listen where the sound is worse. It could be a loose cam gear, a bad bearing, too much end play, a loose flywheel etc..
4) balance the carbs using a unisyn or snail, or something like that. Both carbs have to be synced or they will give you interactions and rough running, especially at lower RPM.
5) Set the timing. I would do this first. Many of us set the timing to 28 to 30 degrees before top dead center at full in at 3500 - 4000 RPM. You'll see it stop advancing. Keep in mind you are leaning over a running engine on some of these things. Long hair, long sleeves, hanging jewelry etc., a hand put in the wrong place can cause severe injury.
6) just to keep the mechanical advance working right, if this is a used and not new distributor, put a four or five drops of oil on the wick under the rotor. It will seep down and keep the mechanical advance lubricated.
7) say it until you never can forget it "I don't need to pull the strainer to change oil on a type 4 engine. I will have to be careful on the strainer bolt. If the strainer gets tightened to more than 9 ft-lbs it will damage the engine, perhaps permanently."
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[Wildthings]

Try setting your valves at ~0.006" and then run the engine. The lifters should pump up very fast this way. After they pump up go back and preload one side of the engine and then run the engine long enough to for that side to self adjust and then shut it off again and preload the other side. Use your own judgement on whether this much running of the engine is detrimental or not.

A thin synthetic oil like a 5w30 or 5w40 will help the lifters pump up and keep the lifters and the rest of the engine nice and clean inside.

[airschooled]

I don’t touch carburetors until all hydraulic lifters are fully inflated and silent. The airflow disruption to a shared manifold/throat can be terrible.

Here’s a corrected video link:

https://vimeo.com/1083342704/9d4deac139

Once your oil is clean and thin enough to fill the lifters, the engine should have some good heat in it and you can time, drive, and tune. It’s just a waste of time while one of your lifters is missing 80* of duration and .100” of lift…..

Robbie
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[erjones]

Thanks for the help so far guys. I went out to do some checks SGKent suggested and it appears that Cylinders 1 and 3 draw notably more air than 2 and 4 (each bank has individual barrel on DRLA but use same airflow adjustment) on my uni-syn. There is also a little bit of white smoke out of the exhaust. I have attached a current video of the engine running with the Dells. Also, after shutoff there seems to be a tapping noise that I don't really notice on my other engine. Not sure if this is a sign of anything.

After running the engine a few times it doesn't seem like the lifter noise goes away. Engine oil is clean (20-50 changed twice). I am reluctant to set to .006 as I am concerned contact here could potentially dislodge the lifter circlip.


Link



Link


https://vimeo.com/1083389856/e14f1cef0b?ts=0&share=copy

[airschooled]

Two more broken links, but the last link has two collapsed lifters as opposed to the single lifter in the first link I saw.

Thick oil makes the lifter problem worse, add some MMO if you don’t want to do another oil change. A 20k Type 4 should not need that thick of an oil unless you’re in the triple digit summer temps already.

Try for a quarter turn preload, but mechanical tricks don’t usually work as well as thin, clean oil.

Robbie
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[SGKent]

[Wildthings]

When you set the lifter with a tiny bit of lash they will typically pump up very quickly, like in one or two minutes the versus 20 minutes they will need if they have preload. Yes there is a slight chance of popping the snap ring out of place, but I have never experience it when trying to get the lifters to pump up.

Finding the exact point of contact can be tricky if the lifters are soft, which they typically are. Just use your fingers to turn the screw and don't put any force against the lift as collapsed lifter will compress very easily and throw you off.

[erjones]

Thanks again for all the advise.

I will switch to 5W-40 today and see if that sorts it out. Lifters are currently set with 1.5 turns of preload. Will look into backing it off if if the change in oil weight doesn't sort it out. Will update.

[airschooled]

Not sure if I saw it mentioned… but heat! Driving the car gently to warm it up makes things go much smoother and faster. Idling in the driveway doesn’t create enough heat to fully warm up a Type 4, especially if you don’t have a thermostat and flaps.
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