artemyk

A little bit of summarized background:
My 1993 Pickup overheated about 1.5 weeks ago, it has ~180k. I noticed coolant in the oil. Compression testing (not done very reliably/well, long story) showed that cylinder 2 could barely get up to ~100 psi, the others were around 125-135. I suspected the head gasket. I talked to Ted at Engnbldr and he said its likely to be the piston rings. He suggested bad rings would show up as pistons that are dirty in the middle and clean/oily on the outside, suggesting oil is seeping up and cleaning them. Also scoring on the cylinder walls.

Today I finally got the head off.
First off, when I was undoing the head bolts, there was a distinct smell that resembled tar/railroad. I suspect this is burnt oil (also some of the head bolt holes had oil in them, which may have burnt up when the engine overheated). Is this unusual/bad?
Second, I found a FelPro head gasket! So somebody has pulled the head before (that explains why there was anti-seize on many of the studs / bolts, and made (e.g.) removing the exhaust manifold fairly easy). BTW, I did not take pictures of the gasket, but it looked in great shape. I inspected the fire rings fairly closely and saw no cracks / damage.
Third, ​I should add that the timing chain guide on the driver's side is broken and I can see fairly significant tracks in the timing chain cover. I have not pulled the timing chain cover yet but I would not be surprised if there is a hole there.

I took the head to a machine shop to be check out. The owner took one look and said that my valves look like they got real hot. He specifically pointed out that the cylinder 2 exhaust valve looks like its starting to burn up.

I'm going to post some pictures below. Given my untrained eye and info from the machine shop, I would guess that the pistons are fine, but that the valves are bad. The coolant in the oil could be from the timing chain cover, or maybe because the head is warped. Any of this would be good news since I have the head pulled and as you know it is not extremely expensive to get a rebuilt head. Unlike pulling the engine, rebuilding the block etc etc.

If any of you can take a look and tell me what you think of my diagnosis, I would appreciate it immensely.

This is what the pistons / cylinders look like (from front to back)









As (I hope) can be seen, the cylinder walls in cylinder 2 and 3 are not scored, they even still have faint crosshatching (not sure if that can be seen). You can't see cylinder walls for 1 and 4 but I rotated the crank a bit and I can tell you they also look good. None of the pistons seem to have clean / oily outsides.

This is what the valves look like, again from cylinder 1 (front) to 4 (back). For cylinder 2, I highlighted the darkened areas on the exhaust valve that was pointed out as damage.














BTW, one thing that I noticed is that there is a ring of "gunk" at the top of the cylinder walls. However, based on other pix I've seen on the Internet, it think this might be normal. In my case, this gunk was at the same level in all four cylinders.



Anyhow, thanks and any advice super welcome!

4RunnerFreak12

Better gunk there then a ridge! That's where the piston reaches tdc

mine smelled to very nasty burnt oil smell so would assume that's normal as I never overheated my engine.

Also- Run your finger nail over the lines on the cylinder walls those vertical lines are scoring although doesn't look bad but if u can feel them with your finger nail not so good.

You most likely talked to Tod (Teds son) I'm pretty sure he runs the place now awesome guy to talk too he has a VAST wealth of knowledge and is more than happy to share it! Not to mention awesome heads and cams.

Great progress!

edit: your lucky! Your compression loss was in cylinder 2 which is were burnt valve was. Get the valve job and put it back together with STEEL RAIL timing set and all the stuff you already got and you should be good to go for long time!

The BEST advice I can give you is make a card board Template of the t cover and put the bolts in the right spot they MUST go in the correct location and they are all different. This was MY mistake!! I pinned the chain tensioner and melted my #2 piston see https://www.yotatech.com/forums/f116...arnage-296318/

artemyk

Not sure who I actually talked to at engbldr. They were incredibly knowledgable but also scared me somewhat with the piston damage prognosis. Now with this info I'm starting to feel hopeful after an emotional rollercoaster .

Trying to figure out whether to get this head milled + valve job (I got quoted ~$250) or buy a rebuilt head (I found somebody an hour away offering one for $170 + core). Since the head gasket wasn't OEM, I'm wondering if the head has already been milled and if the former is even possible.

If anything the pictures overstate the vertical lines, I will do the fingernail test but from what I remember the surfaces are really very smooth.

Thanks for the tip re the timing cover. A bunch of the bolts are out and some are labelled some are not :-/ Will be extra careful putting it back together.

4RunnerFreak12

Pic referenced from 4crawler
Credit 4crawler

This diagram helped me a ton. THANK YOU 4crawler!!

If that head for 170 has a decent warranty and when u go pick it up you don't get a bad vibe from shop, might as well get it, that's much better that 250 (or more if any issues)

osv

burnt valves could have come from the valves being out of adjustment... the only real cooling that the end of the valve gets is when it's resting on the valve seat in the head, which is why regular valve adjustments are so important.

when the valve is so far out of adjustment that it doesn't hit the seat, or hits the seat for a very brief time, it can run so hot that at some point parts of it will crumble off... prior to that it can build up crud around the seat area, so it can't make a clean match against the seat even if you try adjusting it.

i would just get a new head from ted.

4RunnerFreak12

X2 Brand new casting that's thicker in critical areas so even their stock one is better than stock plus could have them put a bigger cam in to suit ur needs