82 johnson 140

[tblshur]

seems to me most v-4 johnsons has ring failure on # 4 cylinder anyone have ideas why? is there a way to help prevent it thanks for your responces

 

[racerone]

The failure occurs in # 1 , 2 , 3 and # 4.----Come over and I can show you numerous examples !-----In my opinion it is the design of the piston ring.----Draw a picture of the upper ring in its groove.------Then draw the picture again , adding clearances in a worn cylinder , worn ring , worn piston and worn piston groove.-----The SIDE clearance then increases compared to the lower piston ring.----Motor goes ---BOOM----It will happen to all of these engines.

 

[Faztbullet]

Not to add the carbon build up from improper fuel mixtures,cooling problems, oil and fuel brands as it builds up behind ring increasing ring tension.b Anytime one of theses motors show up at my place for any type of repairs a compression/leakdown is ran before I turn a bolt/nut on it.

 

[tblshur]

Racerone i would love to come over but kentucky is a fur piece from canada i only have saw 2 of these motors but read about a few more after your explanation i understand thanks for your help

 

[tblshur]

Faztbullit i am running a 83 140 that was rebuilt about 6 years ago by a local mechanic with new wiseco pistons and rings use tc3 oil non e fuel . what does a leak down test tell one ? thank you for your help

 

[racerone]

A leak down test measure air leakage out of the cylinder.----You put air pressure in through sparkplug hole.----You determine how much air needs to be added as air leaks out.-----On a 4 stroke air leaks past rings , valves and head gasket.----On a 2 stroke air leaks past rings or head gasket ( if motor has a head gasket )----A useful tool that I do not have.

 

[Faztbullet]

Depends on builders definition of 'rebuilt". Rebuilt is replace and return engine to manufactures' repair specs. Honing ,pistons and rings is a refresh..a patch in my book and is a short lived repair depending block condition. A leakdown test as Racer described is best way to check it can tell you cylinder condition. If leak down is high piston,cylinder,rings have a problem. Compression is not a good test as all it tells you is that cylinder pressure can support combustion unlees PSI is low then you need to inspect.

 

[flyingscott]

I do not believe Wisco pistons have the ring breakage problems. They do not use the same style ring as the OEM piston

 

[racerone]

Correct----WISECO ----Does not have the ring breakage issue.----Rings do not have that wild wedge shape that leads to side clearance issues.----No idea why OMC persisted with that ring design all these years from 73 to 98 model years on the crossflow.