3.9 strip down , a few questions

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Mc Tool
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3.9 strip down , a few questions

Post by Mc Tool » Sat Jan 11, 2020 5:45 am

I bought a 3.9 serp motor supposed ,( yeah ,I know :roll: )to have been serviced by a reputable firm and only have 120,000 km. Everything was fine till I got the heads off and then I find pistons fitted backwards , some at least are
IMG_20200111_174239.jpg
IMG_20200111_174524.jpg
[attachment=0]IMG_20200111_174531.jpg[
Do these pistons get chucked in any old how or are some of these in back to front?
These two pistons are side by side ......one surely had to be arse about face ?
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IMG_20200111_174531.jpg


I wish I was young again , Id be heaps smarter than the first time

Mc Tool
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Re: 3.9 strip down , a few questions

Post by Mc Tool » Sat Jan 11, 2020 5:53 am

This piston looks like a bit of (exhaust ,) valve contact , and the bearing shell looks a bit suss ( only one. I have removed so far )
IMG_20200111_174851.jpg
IMG_20200111_174655.jpg
I wish I was young again , Id be heaps smarter than the first time

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Rossco
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Re: 3.9 strip down , a few questions

Post by Rossco » Sat Jan 11, 2020 2:51 pm

Putting pistons in facing backwards is usually the result of someone failing to remember that Rover rods have dimples on them which for each pair of pistons have to face each other. So they fit all the pistons onto the rods the same way. Result is 50% of the pistons are on the wrong way. Not the worst thing that can happen.

Valve contact is most likely someone over-revving it, unless its got some monster cam in there.

Mc Tool
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Re: 3.9 strip down , a few questions

Post by Mc Tool » Sat Jan 11, 2020 5:29 pm

Yeah your right . If I were to turn one piston out of every pair round 1/2 a turn they would all line up ......actually I bet every 2nd rod is in back to front. Supposed to be an unmolested motor but unless rover stick their sumps on with roofing silicon and no gasket someone's been in there and put all the dimples facing the same way upon reassembly. I can't see someone removing pistons from rods and then refitting them (wrong way round ) , poop of a job, all that pressing. Anyhow I bought it as a rebuilder so it's about right :D
I wish I was young again , Id be heaps smarter than the first time

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