teardown pics of my bearings & crank... (56k warn)

General engine questions/issues that aren't specific to the other categories
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By ee8
- Mon Oct 01, 2007 6:22 pm #24836
teal_dx wrote:I bought new bearings from them and put them in myself through the bottom w/ the motor in the car. Easier than I thought and a good learning experience! :thumb:


ok, but do you know what caused the damage to your previous bearings?
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By teal_dx
- Mon Oct 01, 2007 7:15 pm #24847 I've gone through everything in my head again and again and the only possibility that I could come up with is timing being off (advanced)

The builder thought fuel was in the oil but that did not happen. running a P28 w/ stock maps.

I broke it in properly...
cranked it w/o fuel & spark to get oil in all the journals.
started it for the first time, let it idle for 10 min then changed the oil & filter.
gradually gave it more RPM as it got more miles.

with no sound deadening, I was able to hear the slight rod knock and stop driving it before any damage hapened. I'll be listening carefuly again.
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By ee8
- Mon Oct 01, 2007 8:06 pm #24851 so if I understand everything you say, the bearings got worn out because of too much advanced timing which caused detonation?

so det killed your bearings?

regarding your bearings I find that very hard to believe. looks like heat indeed but more from too little oil pressure on the bearings or wrong size bearings.
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By teal_dx
- Mon Oct 01, 2007 8:56 pm #24864 like I said, I thought of everything and that is the only possibility I could come up with.

maybe the force against the piston caused my pre-detonation due to advanced timing was enough over time to wear the bottom rod bearing. With forged rods & pistons, the bearing was the softest metal between the combustion chamber & crank. So I'm guessing (and thankful) that the bearing took the beating and that's why the bottom one had much more wear than the top one.

the engine was never low on oil, had dirty oil, and never had low oil pressure.

The builder measured all the clearances, and showed me what he had written down when I went back to show him the bearings. I guess if it starts making oise again, I'll know for sure...
Just glad to be driving a hatch again :)
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By teal_dx
- Fri Oct 05, 2007 1:02 am #25333 I have been had my timing slightly retarded since I started driving my hatch again this week, just in case it had anything to do with the rod bearings wearing out. Now it looks like the timing was not a factor. I had marked the position of the distributor at 16° BTDC.
I thought that I may have moved the advancement dial on the end of the gun and maybe that cause the timing to be more than 16° advanced. But I checked everything out again tonight and advanced 16° puts the dizzy at the exact same place it was before. So there goes my theory on that.

Anyone know what the tolerance/clearance for bearings are on these motors? I'd like to compare them to the builder's...
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By ChicagoMike
- Fri Oct 05, 2007 3:34 am #25350 main bearing clearance
No. 1,5 journals: 0.018-0.036mm (0.0007-0.0014in)
No. 2,3,4 journals: 0.024-0.042mm (0.0009-0.0017in)
service limit 0.05mm (0.002in)

connecting rod bearing clearance

0.020-0.038mm (0.0008-0.0015in)
service limit 0.05mm (0.002in)
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