Having that much blow by to circumvent the PCV system has me asking more questions.
Like, what's your engine health and history? Are your piston skirts broke off. The 86 had all of them lying in the oil pan on the original engine. Every piston had the skirts broke up clear up to the oil rings.
How low is your compression? Less than 120? Less then 105?
My Saturn had stuck oil rings and burned 1qt every 1000 miles thanks to Saturn engineers deciding not to put oil return holes in the oil ring piston ring LAN. So over the years the oil rings collected dirt and carbon and plugged up the separators. Then heat stuck them fast.
The carbon build up on the pistons and inside the combustion chambers had it pinging all the time. I had upwards of 230psi cranking pressure from all the carbon raising the compression. There was enough to have what is termed "Cold Knock" and that was a mother to get rid of. Piston soaks with a discontinued ring unsticker from GM halved my oil consumption. And swapping heads to one I modified for fuel milage allowed me to scrape the 1/16 Inch of carbon from each piston. But the worse of it was in the combustion chambers. And its still there I never bothered cleaning them since the head in now In A cardboard box. I should take a picture. Its nasty.
Well, tried the above vac advance options with varying results.
First, I disconnected the vac adv and plugged the port and cap. Test drive revealed what felt like a little more power (maybe) but still pinged, maybe a little less but not much. With no vac adv the Jeep wasn't to keen on idling at 800 rpm.
Then, 1/2 turn out of the vac advance and hooked it back up. Fired it up and right away noticed it ran a lot smoother.
Took it for a drive and all was GREAT!
Ripped through first, seemed like it shifted later into second. Ripped pretty hard on second, still no pinging!
I was a happy camper!
Turned around in a parking lot, pulled onto street, hit the accelerator and there it was. Ping was back, in full force... Did this twice- two different test drives.
I tried to get audio of it. Not sure how it came out yet. If it's worth uploading, I will.
Idk, can that vac adv be good when cool then crap out over time?
Did pinpoint my leak, though:
It was bubbling right out of there at high idle. And, let me tell you,goes EVERYWHERE when I drive it! Worse than when my VC gasket went....
Letís talk about this leak for just a minute, not to derail this whole trainÖ.
Itís sudden nature has me thinking. It only started once I put the breather and new (incorrect) PCV valve onÖ.
Before I put a breather on, the open tube (in one of the photos I posted) had always emitted a decent amount of smoke.
Now, I have seen several photos online of 258ís with the PCV valve and breather locations in the reverse locations of mine.
Mine has always been set up with the valve in front and the breather at the rear.
I am wondering if, since the rear location is emitting smoke (gasses), maybe that is supposed to be the PCV VALVE location and the breather (PCV air In) should be in the front?
Or maybe it doesnít matter.
I mean, itís two indistinct holes in the valve cover. And I obviously donít know anything about the PCV system.
Well, out of desperation, I posted my 'pinging/ knocking' issue on an AMC forum.
This was one of the relies I got: Here's the scoop. During the time you turned the vacuum advance set screw (should've been in and not out to lessen the vacuum advance) the motor cooled enough that the CTO disconnected the vacuum to the advance (doesn't operate when cold) As soon as you hit operating temp, the vacuum kicked in and the ping monster returned.
Not sure what year your 258 is, but if you run Autolite 985 plugs stock (look up on any parts site) then you can changed to NGK BKR6EK plugs to cool the chamber down a bit. That's actually a water cooled VW and euro vehicle trick plug because the matching Bosch number caused major ping in US vehicles.
Another trick is to hook the vacuum advance to manifold vacuum instead of ported, then set your timing by ear when warmed up. (the plugs did it for my Eagle and '83 Cherokee with 4.2 as well as my '87 Comanche with 4.0L and disconnected EGR valve)
If your cat is clogged and backing up, the temp of the motor will skyrocket and cause ping as well.
If you have the Motorcraft electronic ignition, there is 2 settings for mechanical advance inside the dist (under the breaker plate) I would at least check to see if one of the springs broke. If you switch the dist, get an HEI converted for Jeep 6 cyl.
So my first thought was "OK, cooler plugs. Doubt that'll do it - too simple."
Then, "Cat's gone" and "Already using manifold vac"
The 2 settings in the distributor sounded promising
But his CTO comment got me to thinking.... Based on my last 2 test drives, where it was fine at first (when relatively 'cool'), then started pinging, maybe it IS temp related. My gauges are the newfangled 'Non-functioning' type...
(Gauges were my NEXT project. Hence the no gas/ no start condition the other day)
You reported pinging without any vacuum advance hooked up. Untill you have zero detonation with mechanical advance only. anything related to vacuum advance is mute.
Your CTO is operating what? You should not be running your vacuum advance through it. You are know where near stock.
In fact I see zero reason for you to be using it. Except for the evap canister if you still have one.
GM has a upper engine cleaner in a spray can that you spray in the intake. Its between 10 and 20 dollars a can. Its what I used along with the piston ring soak to make my detonation manageable Untill I was done working my mpg head.
Detonation is caused by many things. Too much advance, carbon deposits making hotspots, oil burning which has zero octane and actually self ignites like diesel, lean conditions. Bla bla. Even your hot plugs. (Which you went 1 colder with no improvement).
When you watch your timing with a timing light at a steady rpm is it butter smooth or does it jump around?
If you pull the dizzy cap off how many degrees of rotation on the crank does it take for the dizzy rotor to start moving? Like going clockwise Untill it moves and mark the spot then go counter clockwise Untill it moves the other way. That will show how loose your chain is.
Its not looking like a magic pill (or something easy) will solve your problem.
A lot of things could be causing your detonation. From the carbon buildup, to the oil burning, to the higher compression caused by the carbon buildup ( which in in of itself increases blowby on a tired engine)
I don't have anything hooked up to the CTO, if it is still there.
I'll have to look at my pics.
It was just the fact that he mentioned coolant temp stuff, that it 'clicked'.
I didn't think carbon buildup would cause THAT much heat.