Post valve grind discoveries 1933 10/4

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GaryCullen
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Joined: Wed Nov 20, 2019 1:34 am

Post valve grind discoveries 1933 10/4

Post by GaryCullen » Sat Jan 09, 2021 8:40 pm

As promised this is a new thread, hopefully not as long as the last one.
After the valve grind I wasn’t happy with the compression measurements on cylinders 3 and 4.
Decided to extract #4 while the car was still up on its stands.
I have discovered I have 4 x ring pistons and the bottom oil scraper was broken. Fortunately it hadn’t damaged the bore.
Put the top compression ring back in the bore and the gap is huge. Didn’t even bother trying to measure it. 1/8 inch at least.
Should be from 6 to 8 thou according to my Austin manual.
Pulled out the remaining pistons and two more broken oil scraper rings but this time the ones above the gudgeon on pins.
Compression rings same as for #4.
So all runs are badly worn.
Each piston is stamped STD and the bores measure an average of 2.4998 in three places up and down and at 90 degrees.
Known miles for the car is only 5,687 since 1973. Previous history is lost as the Speedo was service then and zeroed. Considering the bore measurements I think I have a low mileage vehicle.
So plan is to buy a set of standard rings with new big end tab washers, de-glaze the bore and rebuild the engine.
Plan is also to use some running in oil while the rings bed in.
Any other advice grateful received.
Our local VAR has rings for these engines manufactured in NZ.

Kind regards
Gary
Auckland VAR

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