WolfMann

Another update,
stethoscope came in, got to poke around with that today, noise is most noticeable at top of head/bottom of valve cover, dampens out towards middle of timing cover. Picks up some at bottom near oil pump. To be honest, this is a whole new way of listening to an engine (for me). So It may take a few tries to really refine it. The smog pump is loud but it's with an "air" noise like the cold air intake/air filter housing. Alternator was surprisingly quiet. Fuel pump and distributor were noisy but seeing as how there so close, I think the harmonics are carrying. Water and oil pump both seemed consistent. Again I'm going to poke around more to try and refine, but this still seems like chain noise.
I also checked valve clearance (.008 and .012 with warm engine) and took a peak at chain while cover was off, it felt like it still had tension (wouldn't lift off cam sprocket with engine still warm) and the guides were still in place from last time I checked.

Moving forward, I've ordered a new oil filter with anti drain back valve, and a digital oil pressure gauge. My plan is to install the gauge and get a sense of where things are at, then drop/clean sump and change oil/filter. I'll see if that makes a difference in pressure/noise and take it from there.

Thommo Thompson

thats a good idea to check the oil pressure for a while. also, dont get hung up on my distributor suggestion from the noise u heard in it. the sparks in the rotor cap do actually make a lot of noise through a stethoscope.
it ia possible that ur camshaft sprocket or crankshaft sprocket are loose and rattling around. that would also make the dizzy timing jump around.

WolfMann

Hey guys, here's an update:

Spent the last week waiting on oil pressure gauge and sender adapter in mail. Replaced heater core hoses while waiting but that unfortunately did not clear up the issue.
​​​​ Trucks been running noisy most of that time. Parts showed up the other day so today I made it down to town to pick them up.

Sure enough I got to town and the truck was running quiet. No rattle noise, no noise anywhere. Ran my errands, picked up mail, made my way back. When I hit the dirt road the oil light started to flicker, I locked the hubs, and noticed the engine was still quiet, no rattle. Got back in and drove off, oil light turned off immediately upon acceleration.
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​Made it home and set to work installing pressure gauge, got it in pretty smoothly. The temp had dropped and the truck cooled down while this was happening. When I finished and started the truck it went through the fast idle process. These are the numbers I got from the gauge during warm up, shortly after, and after a drive around the property. Truck ran quiet the whole time.

61-63 psi during warm up/fast idle.
22 psi at warm idle, right after fast idle.
60-64 psi at 3000 rpm
30-40 psi between 1500 and 2000 rpm
16-17 psi at idle during drive
​​​​After a quick drive oil light starts to flicker the gauge reads 15 psi.
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So keep in mind those numbers are not from a true cold start, the trucks been running most of the day, but I'm curious about the oil light flickering at 15 psi, that seems high when the fsm minimum is 4 psi.
I thought that was closer to when the light turns on, can anyone confirm? It's possible the gauge is off, but I'm not sure.

On a side note, I got the stethoscope out while the engine was running quiet. The most noticeable difference in noise was the top of the head/distributor/fuel pump area I described earlier in this thread.

Moving forward, Im gonna check the numbers again tomorrow and see how they compare. Planning on an oil change. Picked up some 10w40 and a new filter. Still planning on dropping the oil pan and cleaning/checking things out. Will update again soon. Thanks guys.
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Thommo Thompson

ok so it sounds like the oil pressure light isssue is related to the pressure switch and is seperate from ur rattling issue. dont u love those bumsteers?
when u revv the engine, it is probably giving the faulty switch enough pressure to turn the light back off. however,
remember that the switch earths the light so if the wire is earthing (shorting) elswhere this will turn the light on, so be sure to check all the wiring before replacing the switch.
it is still possible that when idling, the engine is vibrating enough to make a short in a wire worse. ive seen that on my jeep.

WolfMann

Fiddled with truck today, numbers from gauge were a little higher during cold start but everything was in the same ballpark. Noticed oil light flickering at 20 psi, on at 15. Took oil switch out and cleaned it up, put it back in tight. Oil light did not turn back on after that but I'll be keeping an eye on it.

Truck is still running quiet, I think the problem was with the chain tensioner, it seems like it wouldn't build enough pressure to keep chain from rattling unless I took it on a long drive. Maybe it was getting stuck somehow? The timing was steady when I checked today too.

The plan is the same as a week ago, going to drop oil pan, check oil pickup, I'd like to check the bearings (picked up some plastigage, figure while I'm there right?) I've just been waiting on rain to clear up some, hopefully in next couple days.

WolfMann

So yesterday I dropped oil pan and cleaned it out, there was a good amount of gasket material, left the bearings alone as I figured they're not the problem and I shouldn't make them one. Added new filter and some 10w40. Took the truck for a long drive afterwards, there was no timing chain rattle, I think whatever was causing the tensioner to stick got cleared out. The oil warning light on dash has not turned on once since I cleaned the switch in the block. I suspect that was the problem (bad ground) and not low oil pressure. Going to keep an eye on everything for awhile, but I think it's mostly figured out. Thank you everyone for your help with working this out.