High RPM misses

[PareosWC]

Guys, I have a WC52 230 motor that sat idle for years, and here's the symptoms:

1. Starts and idles perfectly
2. Drives well under 20mph, but under load, will start 'snapping' and backfiring through the carb
3. Vacuum gauge at idle reads steady at 18
4. Dry compression readings are that 2 cylinders are way below even 70psi
5. Wet compression testing has not been confirmed yet; that's next.
6. Oil pressure sits at 50psi
7. I haven't changed the plugs, wires, rotor, points, or cap

I was thinking sticky valves that cause the backfiring through the carb, but I'm not well versed at what I'm looking at here. May I get your input? I do focus on one valve that seems to look non lubricated?

https://www.youtube.com/watch?v=WIU0DTTA76Q

[krisinwa.st.]

Sounds like timing to me , although the points could be pitted , obviously you
should check the cap rotor wires ect. , One way I check for a good blue spark
at the plug is a little tool that has a clip on one end a plastic window with two
points about a 1/4 inch apart inside the window and a post on the the other end
for the plug wire boot / connector , connect it to a spark plug ,start the motor
and observe the spark , It should be a bright / strong blue color , as opposed
to a weak yellow , this procedure helps to give you a idea of a good or bad wire
plus the points as well . Just my two cents .

[PareosWC]

Kris- another item I looked for was any intake/exhaust leak. HAMB stated that a carb backfire could be caused by a lean condition as well. I am running the motor without a filter on the carb; perhaps that's allowing too much air, too quickly...

[krisinwa.st.]

I'm not a trained mechanic , learned mostly from the school of hard knocks,
so I'm sure that a intake leak could be the problem , one thing that I would
try is to bump the timing one way or the other and then test drive , repeat ,
repeat , and if it runs better check with a timing light and see were your at .
I've never had backfire when running without a air cleaner , I would run it with
the oil bath just in case you get a stack fire . Better safe than sorry ...

[tankdriver]

Are the 2 low cylinders next to each other? If so, it could be a bad head gasket.

[PareosWC]

Tank, wouldn't I get a lot of white smoke in the exhaust, and a lower coolant level? I'll keep that in mind, though.

*Note*- the Carter carb is a YF 2100s- intended for a 50's Chevy 235. Would this possibly cause incompatibility issues?

[gyknot]

You may not get white smoke depending on where it blew the gasket between the two cylinders. If it didn't get into a water jacket part there would be no smoke or coolant issues.
I once bought an old dodge that idled great but would stumble and backfire something fierce if you tried to pull any rpm's out of it. Turned out the guy who put the points in, only hooked up the little brass contact strip instead of the steel spring as well. The brass contact strip allowed enough tension to run at idle but couldn't hold tension as it rev'd up which caused all of the problems. Once I put the spring strip in place all was well.
Just an idea...
George

[tankdriver]

Tank, wouldn't I get a lot of white smoke in the exhaust, and a lower coolant level? I'll keep that in mind, though.

*Note*- the Carter carb is a YF 2100s- intended for a 50's Chevy 235. Would this possibly cause incompatibility issues?

Not necessarily. If it is blown between 2 cylinder at the center, narrow area, that will not get to the water jacket area.

Look at this head gasket, any of the circled area I added could have a leak, and not have any water leaks, or white smoke.

[Andersun]

Easiest thing to try first is to replace the condenser.

[krisinwa.st.]

Hey guys , what about centrifugal advance ? , maybe rusty , or bad or broken springs

[JBizal]

The most commonly over looked part in any restoration is one's distributor. Typically, if you have a miss at speed and not at idle it is an indication that the bushings in the distributor are worn. People simply do not rebuild and or inspect their distributors. Take the cap off and grab the rotor. Push the rotor to the side. If you have worn bushings the shaft will move and open the points. At speed, the shaft runs in an ellipse rather than a true circle causing the points to float and create a miss.
John

[PareosWC]

4. Dry compression readings are that 2 cylinders are way below even 70psi
5. Wet compression testing has not been confirmed yet; that's next.

All cylinders are slightly above or below 90psi, except #6.

#6 dry was 40psi, and #6 wet was about 43psi.

Time to get into the TM and ensure that the valves are adjusted as they should. (3) of the (12) tappets are tough to turn by hand, but they do move.

I'll address the dizzy components as well

[krisinwa.st.]

Did you figure out the high rpm miss ? am curious as to what the problem was

[PareosWC]

Kris- to ensure that I'm not wasting my time and you guys' energy, I needed to start back at the basics. And what I mean is this:

I had a plug wire that's tip came from a lawnmower
The carb not only was not 'correct' for that WC, but I had not rebuilt it, or even opened it fully up to check jets and that the accelerator pump was working
The #6 exhaust valve is stuck- I really need to pull the head and get a solid eyes on examination of the pistons and valves.
Either the fuel pump or the carb was allowing fuel into the crankcase.

So spending time on the WC is great, but allotting money towards the issues she has is taking me just a bit more time. Once I have pulled the head(new head gasket), rebuilt the Carter ETw1(rebuild kit), freed the stuck valve/piston rings, and have checked vacuum, dwell, and compression, I will report back