My Willys 3A and 3B Community
TECH FAQ SECTIONS => Engine compartment => Topic started by: PercyUK on April 16, 2021, 06:10:25 AM
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I thought you might be interested in this.
My 1953 CJ3A was ticking over like a sewing machine but had an annoying misfire once underway and an unidentified tick.
In every other respect it seemed fine with great oil pressure but it did smoke a bit.
I did a compression test and got, from front to rear, 125,125,110 and 105.
Ah, a possible problem i thought.
Did a leak down test and found that cylinders 3 and 4 were losing 80 to 90% of their pressure which you could clearly hear entering the block.
Long story short is that despite running and driving I had two completely knackered pistons with clear evidence of massive ring loss which could not have been doing much with most of the pressure created during combustion escaping into the block and passed the poor valve fit.
I also found a broken valve spring.
How it was running, first turn of the key everytime, I have no idea.
The bores were undamaged and within tolerance but the head had been changed to an m38 one I assume because the original had been destroyed.
I don't want to pull the engine so am replacing all the pistons, lapping valves etc and then see what happens.
Given that it was running "fine" before the strip down I am expecting to see a noticeable improvement.
Updates to follow!
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Man, I really hate it when my pistons get knackered. 😉
BW
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Or threaded nuts!!!
It was effectively running on two so I am hoping for some real improvement.
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Late Update,
having lightly honed the bores I replaced two valves and a number of guides and then lapped the valves in testing them with a vacuum cleaner as I went.
I also fitted new valve springs and, as the head was off I got it skimmed and thoroughly cleaned it.
I am happy to report that I now have a smooth and non smoking engine which is far more enjoyable to use.
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Great de-knackering story!
Sounds like you made some good choices on additional work to ensure smooth running!