Liner measurement

F

fatmale

New member
Location
London UK
Hi Folks.
I need t ascertain whether I need a rebore. Using too much oil. Compression down on one cylinder also. Head is original save one oversize exhaust valve put in to extend seats life.
Measuring the liners looks difficult on YouTube.
Any recommendations on best tool to get for this or is engineer only way to go? Don?t know one that won?t take potentially years to act. Like to do this assessment work myself but will need a company to rebore if it needs doing. May just need the right new rings but doubt it. I?m based in London these days.
Your thoughts most welcome! I?m not proud by the way...
 
only way to correctly measure cylinder liners is to use a bore gauge made for the job
by saying that though it may be that the liners themselves are not the culprit

how much movement do the top piston rings have in their piston lands ?
if you can move your piston rings up and down in their lands then pistons are junk
they should have no more than 0.003" side movement, or 0.0762mm

have seen engines where the rings had well over 0.50mm of movement and when the ring lands get that worn the rings flutter under load and are ineffective

when was the last time you changed the valve guide seals on the inlet valves ?
they turn brittle with age and exposure to continual heat cycles

 
Hi Red
Thank you so much for your reply. I?ll definately check these measurements piston land gaps. I will also get some new inlet guide seals. I suspect you are correct on both. I will still need to check liner sizes I guess before buying replacement pistons. Might need oversize ones. I?ll probably post my measurements up when I have them. Thanks again! Matt
 
I?ve measured up the piston land gaps and all seem ok except LH piston middle is .004 /0.10mm, RH piston bottom ring is .004/0.10mm. The others are definitely.003 or .002
I?ve not got liners measured yet.


 
Nat Magee said:
I use a telescopic bore guage. You need to measure at different heights.
Click to expand...
+ 1. Measure at different directions (front-rear, left-right), too. The bores will ovalize with time/wear. With respect to compression being down on one cylinder, you might perform a simple leak-down test on the valves by filling the combustion chambers with Kerosene. The Kerosene should not seep beyond the valve seats into the ports.
 
Very simple just using lubricated Cables.

Regarding Bore Measurements.  Redax5 says a Dial Bore - YES but an expensive Gauge. Alternative and just as accurate, if not more accurate, is to push a ring down the bore with a piston to keep the ring level and use feeler gauges to measure the gap.  Manual Stone Honing with a slow 3/8" drill at 45 degree hatch is just as effective as Machine Honing in our small cylinders.
 
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