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Discussion Starter · #41 ·
Hi rockers were removed so both valves closed -you can feel it tapping the head i just need to find out why !
this happed while it was ticking over. It went from silent to sounding like a ball bearing in a can with in like 10 secs but the noise is the piston tapping as it gets toTDC
I have all the replacement parts on the shelf -crank -Conrods - pistons. I just need to know what changed in a perfectly running engine for the piston to start tapping !
over the weekend I will use a DTI gauge and measure the lift of each piston
 

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If the valve is bent then it won't seat properly and the piston will still be hitting the valve, it depends what the tolerances are.
You would have heard it in the exhaust, but not so much in the intake.
Ay any rate it will be interesting to see what the problem is.
 

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If the rod bearings are not shot, and I think you mentioned they were fine, then it is likely the piston has broken at the top ring groove. I have come across the same situation where a piston has cracked at the top ring groove but not all the way around so the part of it no longer attached will bend up and hit the head.
 

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Not arguing with you Jim, but that's not supposed to happen to a RR piston, I would expect that of my crumby TR7 when I had it, and that car was abused.
Maybe that happens with boutique engineering, the quality control isn't there because things are made in such small batches.
A friend of mine wasn't impressed with Eggy Machine shop pistons, one of them totally let go later on.
 

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Not arguing with you Jim, but that's not supposed to happen to a RR piston,
IMHO it depends of engine load. Bentleys, driven with turbo compressor have a lot more heat loads than non-turbo. It is why they could have head gaskets and, possible, pistons problems.

EDIT: ah! It is model Eight without turbo... :?
 
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