hchris

Sounds high up to me, possibly piston/gudgen pin ? If the noise decreases when you pull a plug wire that's indicative of lightening the load on a particular piston and subsequent noise reduction, also it might account for the now you hear it, now you dont symptom due to the piston/pin moving around. Certainly doesn't sound like bearings or crank issues, perhaps you could start investigating by dropping the oil, put a stocking or something over the catch pan and see if there are any metal bits floating around.

Steady 18" Vac at idle is good, below 15" means wear and tear making an impact. Compression around the 80 - 100psi is desirable but anything above 60 means there's life left in it, so long as all readings are within 10 - 15% of each other.

One of the 70 Series, 72/ 77 Chryslers ?

There's only one fuse in this era mounted, on the ammeter as you've found. At some point a fusible cutout was introduced on the lighting switch, it's function was to break the circuitry if a short occurred and then reset. Might be a good place to start.

Optional windscreen screen/bug protector ??

Same as most every other engine, around the 180 mark is good.

Yes and yes; doable but difficult with the manifold (s) in the way. You may well find better access by taking the wheel off on the manifold side and seeing if there's a removable inner guard panel, many vehicles of this period were fitted like this for that reason. Obviously safe jacking and supporting the car is paramount!!

If it's a fluid switch cnrack a brake line/nipple, if the light goes out you've got pressure trapped in the system.

This style of joint is completely different to what we now know as a U joint, so short answer is no. However I have seen later era (50s) Mopar tailshaft conversions adapted without too much work.

I'm a little confused, you say backfire out the exhaust? technically a backfire is through the carbs; afterfire is through the exhaust. Afterfire is pretty rare and is more likely to be a timing issue, wouldn't entirely discount carbs but more inclined to look at timing particularly when you mention cam,coil and distributor; assuming these have been newly installed ?

Looking at your photo I'm sort of amazed that whoever did the conversion didn't aim to get the threaded portion of the plugs to sit at the same depth of the originals, I'm guessing that the 45s is at least 1/8" or more longer than the 10mm plug; wondering how far above the piston the electrode sits ? As to the plugs themselves, the 45s is going to run much colder having almost twice the ceramic insulation of the original, but I'm assuming, it's been running ok with them for some time, would be interesting if you could find some plugs of similar size to the originals in 14 mm (i.e. electrode depth and insulation) and see if they made a difference in performance. Re plug location, as Dusty explained their positioning in the combustion area is critical for design performance, engine designers go to a lot of trouble in positioning valves, plugs etc to achieve the best performances. Although it's probably not worth it now, a better solution to going upsize with the plugs would have been a screw in adaptor to accommodate the 10 mm plugs in the 14 mm hole.

What Brian said; beyond that I'm a great advocate of tuning with a vacuum guage. If you can find a port in the manifold to hook up a vacuum guage it's so much easier to get timing/mixture etc. sorted, bearing in mind fuel properties have changed so much since these cars were built.

Correct - having said that, with fuel injection and engine management systems plus the ability to lean out the mixture in cruise they`re not too bad.

And the thing about (light) aircraft engines in the main, is that max rpm is generally around 2700 - 2800 and for cruise 2300 - 2500. Typical Cessna/Piper run 160 - 180hp, so overall they are pretty low stressed engines, the design emphasis is really on big bore, big torque and low revs, not forgetting that a boxer configuration makes it easier to cowl and streamline. Different story when you get into turbocharged and higher output engines, using 98/100 octane low lead.

Correct, distributor vac is drawn above the throttle.

If you have an accessible vac port hookup a vac guage and see how it's behaving, great diagnostic tool.

Have you tried another battery or used jumper leads to another battery ?

She's a keeper then !

Plenty of home made cheap and effetive centralising tools out there, do a search.

Have you centralised the shoes ? Chrysler/Dodge/Plymouth brakes require that you get the shoes concentric in the drum before anything else, it's complicated if you don't have the right tool, plenty written up about it.

There are some people who shouldn't be allowed near cars..😥

During the casting process an open ended passage is formed, there's more than one of these within most carbs, so these plugs are used to close off the internal passages for fuel and airways to function. Where there's a need access these passages in service for cleaning etc you will find a removable/replaceable aluminium plug, and of course at the other end of the passages are jets or vacuum ports as required.

When vaccum is drawing fuel into the upper housing of the tank you will feel the feed pipe go cool/cold, then warm up when the flow stops; the temperature changes are not drastic but you can feel the difference with your hand. The other indicator, if you listen carefully at idle, is the change in engine revs as the vac cuts in and out in time with the fuel being drawn into the tank. Beyond these indications there's not much else other than opening up the tank after the engine has been running.

Yep, that would be an access panel to the fuel cap. There would have been an extension pipe from the standard filler opening in the beaver panel, the extension would pass up through the bottom of the aftermarket trunk.

Re the heat shield, generally it's an add on piece of folded sheet metal to cover the pump and shield it from the heat radiated by the exhaust manifold. It's held in place by utilising nearby bolts or studs.