Before taking engine apart try to stop vibration in steering wheel with ignition adjustments.Remove vacuum advance hose,retard or advance timing and put stock coil on in place of the blaster. Reduces voltage lesser chance of cross fire. My stock slant at 1500 rpm with lights on high beam heater fan on high,{this loads the alternator puts small load on engine}. will begin to shake as the timing is advanced too much.

I've already played with/tested timing, valve adj, coil, vacuum, etc., but thank you for sharing your interesting discovery.

brian

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I pulled the engine and broke it down.

There was some wear on the cam, rod and main bearings, but it didn't look terrible:

http://s785.photobucket.com/user/67dart ... .html?o=25

http://s785.photobucket.com/user/67dart ... sort=3&o=2

...until I got to the last (rear) main bearing:

http://s785.photobucket.com/user/67dart ... ort=3&o=12

http://s785.photobucket.com/user/67dart ... ort=3&o=11

http://s785.photobucket.com/user/67dart ... sort=3&o=9

Here you can see the bearing material squashed out on the edge of the bearing: http://s785.photobucket.com/user/67dart ... sort=3&o=8

There is a line of bearing material adhered to the crank journal. http://s785.photobucket.com/user/67dart ... sort=3&o=2

Everything else looked pretty good, rings were in good shape, the cylinder walls were glazed but not torn up or anything. Rods looked good, no damage to the pistons that I could see, wrist pins were freely moving but tight tolerance, no play whatsoever. You can see some signs of the detonation issue if you look at #6 cylinder wall, see the double dark areas (presumably where the piston slapped).

http://s785.photobucket.com/user/67dart ... sort=3&o=6

Question: would a main bearing this torn up cause a vibration in the engine? Seems like it was running good except for that vibration (and I could hear that strange whine, this must have been the bearing drag on the crank).

Brian

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No, that is only a symptom...something caused the bearing to get torn up. .I'm guessing it was detonation that ...wounded something in the #6 spot..

Is that the #6 piston pictured? the second ring looks to my untrained eye, to be twisted (when installed in the bore) as it is not uniformly shiny, other than close to where the ends meet..

If you were to check the ring lands of the top two rings of each piston with a feeler gage, what size gap do you get?

I did a check on a few pistons, #1 ring to landing tolerance was 0.005" or less, #6 was 0.010" on one ring, less on the other one. #3 had one ring with a 0.013" gap. They don't appear twisted to me, the edges look straight (there is a carbon film on only the top 1/2 of the second rings side, so maybe...). What should the gap be?

Brian

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From what I have just read the ring land should be .001-002 larger than the piston ring..... (that sounds pretty tight to me)

and the lower edge must be flat and square.... too much space will allow the ring to twist, or not seal properly.. (your machine shop would be able to say very quickly if the pistons have been damaged.. )

also I wonder if the scuffing that is happening in #6 is due to a bent rod?? That is a total wild A$$ guess, and wondering out loud.. I guess I am saying:if it were me, I would want to check the rods to make sure they are still serviceable. No idea how one does that at home...?

All that being said, there are many here on the forum that have MUCH more experience than i do...

.010" side play on the rings?? You mean you can fit a .010" feeler gauge between the ring land on the piston and the piston ring with the ring pushed in flush? That's nasty,but I doubt it's the actual case, check your measurement. Seriously,I see a total rebuild of this thing. What I see from the pics is...
1/ Deck block,you can see where it's been leaking like a sieve between the cylinders
2/ Those bores are a mess,may hone up,but they are scored from running it with all the metal in there,plus the discolouration looks like corrosion in the pics. The rings are scored,remember you had low comp and oil breathing?
3/ what was your bearing clearances? They look pretty tight,even the ones you think are good.
4/ Were the main caps in the right position? That rear main is a mess.
5/ Crank,regrind it and get it crack checked after its gone thru all this. Buy .020" bearings first,measure ID,then get crank ground to suit to obtain correct clearance.
6/ Main tunnel dimensions and alignment must be checked and possibly line honed. Are the caps in the correct position and are they the correct ones for the block...ie did they get mixed up.
7/ Rods need to be checked for bearing bore size and twist,probably need close and hone.
8/ Pistons probably have small particles of ferrous metal impregnated into the skirts,may need replacing,may be OK...moot point if bores don't hone out OK.
So did you check the valve timing when you stripped it? What were the bearing clearances? I'd also take a good look at the trans pump bearing after all this.
Why don't you just buy a good used and proven runner and fit it for now and save yourself a lot of time and frustration.

I agree, I think the block needs to be checked, very likely the main bores need align honed. Also, the crank definitely needs to be checked.

It was leaking between the cylinders due to the lean condition, the head gasket had eroded through between #3 and #4. But, I had changed the head gasket and fattened up the AFR and that was resolved. There was no head gasket leakage after that.

The cylinders will need honing, they are glazed, but I don't think that situation is all bad.

Connecting rods and pistons? Maybe...

I had high compression (on static check) and oil breathing...strange? Yes. New cam and lifters, absolutely. i was getting bearing material and magnetic "fuzz", the (new) double roller timing chain was stretched way more than I thought possible. That said, after the head gasket and fattening up the AFR, I saw no metal at all in the oil.

No doubt the internals need a redo, they were stressed considerably during the detonation issue.

The head and deck are true, and the head was recently redone, so it seems to me having the crank and main bores assessed is what's needed. Once that those are checked out and/or corrected, then cylinders honed and new rings/pistons and possibly rods.

No use to buy a used runner for now, I'm committed to fixing this issue and I have a block that is either good or can be repaired.

I had an engine vibration. There is a chance that the crank is fine but, due to the main bearing being crushed due to detonation, there was sufficient clearance between the journal and the crushed bearing that the crankshaft could develop a harmonic that otherwise would be unavailable to it. That is, it might be the case that I can simply install new main bearings and be done. I doubt it, though. The main bores and the crank need to be checked. As for the rods and pistons (rings), the jury is still out...though my clearance measurements suggest that at least pistons and rings are in order.

Brian

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No mix up there, correct bearings and correct caps, all in order...this is damage due to a detonation (lean AFR) issue...shows you what havoc it can wreak inside an engine...

b

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Im sorry but I can't really keep up with the whole thing here... You had cylinders with low comp,some high..now they were all high. You had Pistons with .010" ring clearance now they are ok...you can see where the gaskets leaked,how many friggin gaskets did you change and your saying the deck is ok with obvious black marks all over the deck. Your saying the rear main got killed with detonation,but Pistons ,rods and big ends all go by passed? The main stopped making metal when you change the mixture? Your thoughts are all over the place... The thing is a total f...k up. Time you regroup or you'll never get it right. Do you even know what bearing clearances,valve timing you had?....good luck .

Steve,

Sorry if this sounds all over the place, it has been a roller coaster for me as well. It is more clear in retrospect, with the benefit of hindsight I believe this is what happened.

This all started with a lean condition and detonatoin (I thought that I had an exhaust manifold leak tick). The engine was otherwise smooth. What I didn't realize was that the head gasket was eroding through, particularly between #3 and #4 cylinders. When it finally burned through in that spot, the engine was shaking hard as you might imagine. That and the detonation issue did a lot of damage, including the main bearing and stretching the timing chain.

The Reader's Digest version is that I replaced the head gasket, fattened up the AFR, went to colder plug, adjusted the timing and valve lash (I thought it might be a sticky valve at one point, so I tried a different head (I did see the varied compression numbers with that head)). I took a detour to repairs to the drive line as I had tore up motor and tranny mounts and tail shaft bushing (I was getting some vibration from my tranny being cockeyed from when the head gasket blew and the engine was shaking badly). After those steps, I was seeing no more metal in the oil, so I believe I fixed the detonation issue, but I still had this engine vibration that I couldn't explain. So, after more testing and convinced that it wasn't the peripherals, I tore her down and found a stretched chain and this destroyed main bearing. I'm assuming the vibration was from that, perhaps my main bore is warped and/or my crank is wobbly from the detonation issue. I'll need to have them checked. The engine ran fine other than the vibration issue (the rear seal was leaking badly, but upon inspection it was in good shape, this makes be believe it was indeed a vibration at the rear main area).

This was a fairly recent rebuild (had about 6000 miles on it), the head and deck had been resurfaced. I don't think the new head gasket was leaking, I ran a compression test right before I tore it down and all cylinders were at 180 psi (this is the head rebuilt and installed as part of engine rebuild). Granted, I did not run a leak down test, that would have been more thorough, but I don't have a leak down tester (yet). When I pulled the head this time there were no indications that the head gasket was leaking (I had used a graphite gasket with copper spray and it was adhered strongly to both the head and deck surfaces (the gasket literally tore apart, leaving graphite stuck to both surfaces and the metal core came free from both sides).

I didn't say the piston ring gaps were OK. i simply measured them and asked what was normal, clearly mine are not. I definitely had crank case pressure at higher rpms.

I don't know about the rods (yet).

My point about not getting another engine, is that I'd prefer to work with this one if it can be repaired. I'm starting with a core issue and working my way outward. First thing to do is check the main bores and crank, given the damage seen.

Brian

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You saw the rear main bearing damage. I took the crank and block to the shop, the guy said the crank was bent 0.006". Not exactly sure if he meant the rear main journal was off or out of round by that much or the crank was off center axis by that much, he wasn't clear after his first statement, but he did say that he fixed the crank and on balancing it was "perfect" in the rear and 0.5 gram variance in the front, but within acceptable parameters and well balanced. The block is prepped, he took 0.002" off deck and rehoned the cylinders; he said the main bearing bores did not need align honing, they were dead on specs.

I'll report back after its rebuilt and broken in. Might be some weeks before I get to that point, other things on my plate.

Brian

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