258 Engine rebuild ... Oil fouling Cyl #1 - JeepForum.com
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post #1 of 6 Old 08-02-2021, 04:15 PM Thread Starter
jimsahm
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258 Engine rebuild ... Oil fouling Cyl #1

I rebuilt my 258 from an '89 YJ. All seemed to go well...engine started fine (GM TBI Mod)...did proper 2k rpm for 20 minutes... Then ran gently through the farm country here...up and down hills...engine braking going downhill...no jack rabbit starts...etc... Cylinders 2-6 are 100% fine. Cylinder #1 is apparently oil fouling. Worse at idle and than with throttle...blows blue smoke (oil burning smell)... It has only about 90 or so miles on it now...Plug from #1 oil fouled...shiny, oily...Plugs 2-6 are all light tan--normal...By 50 miles, plug #1 fouled to a no spark condition.

I bore-scoped the cylinder walls and compared #1 to #2... about the same...still cross-hatched and seemingly ok...some vertical scratches...nothing deeper than honing marks. Noticed oil puddle on #1 piston at about 50 miles...Apparently will burn off on running...

No blue smoke while running at road speed. Stop for a light and there is a blue smoke at throttle application.

EDIT: Compression test shows 149-150psi across all cylinders.

I am thinking the following:

1. Oil rings not seated yet and this cylinder is taking longer for some reason.

2. Oil rings defective or installed wrong.

3. Compression rings installed wrong.

4. Thought it was maybe valve seals....replaced and zero difference.

Anyone have some advice? Thinking of pulling out cylinder #1, re-hone, re-ring....and try again... OR preferably someone tell me that the rings are just not seated yet....

Ideas??

Thanks,
Jim

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post #2 of 6 Old 08-03-2021, 12:02 PM
fishadventure
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Oil drip on piston: rings can’t drip

No smoke running: positive pressure
Smoke at idle: high vacuum

Good compression. Probs not rings

Valve guide worn is my first thought

Someone remind me or correct me: is cylinder #1 the one that needs a head bolt sealed with RTV? Or am I confused?

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #3 of 6 Old 08-03-2021, 08:49 PM
Azhunter1
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Yes cylinder 1 drive side bolt number 11 needs to be coated with sealant. Valve guides is my thought too or a worn valve.
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post #4 of 6 Old 08-04-2021, 05:37 AM
fishadventure
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Well I think you know what to explore.
Good (dry) compression gives an indication that the short block is probs ok. The head bolt, gasket, or valve/valve guide is all that’s left for your exact fresh rebuild symptom imho

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #5 of 6 Old 08-04-2021, 08:16 PM
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Isnt the #11 head bolt coated because of how close it is to the water jacket?
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post #6 of 6 Old 08-05-2021, 04:21 AM
fishadventure
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Quote:
Originally Posted by Azhunter1 View Post
Isnt the #11 head bolt coated because of how close it is to the water jacket?
Yes, and- I may be wrong- but I think it’s running through antifreeze in the middle and crankcase on the bottom?
I actually can’t remember, just that there’s a cruddly one
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[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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