Leak Down Test (Don't Laugh!!)

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Fast Eddie said:
Of course, if you want a really sweet running 850 AND you gotta buy new pistons and rods to do so, you could do a lot worse than check out JS web site, an 850 with his lightweight pistons and longer steel rods is very sweet indeed.

That’s what my current 850 motor has in it. Here’s some pics:


View attachment 3938 View attachment 3939 View attachment 3940
Click to expand...

O'Dear God, stop, stop, stop :)

I've already priced up the JS stuff, no question about the quality of the parts!

One question about this IF I got the JS standard pistons & rods, do you need, as opposed to want!, to get the cam kit also or is this another option?

REALLY nice setup on your engine, coated pistons in all!! Really like your board for holding the pistons in place:)
 
I suspect I can supply 880 bore pistons with the larger pins.
Do you want to send me your barrels and wrist pins for fitting?
 
Fast Eddie said:
It would be daft to sleeve down your barrels to 850. Much better of buying another set of 850 barrels. You’re highly unlikely to find some that don’t need a rebore though, not that that’s any real issue.

I wonder if you could run those big pin Ford pistons successfully in a Maney barrel?
Click to expand...

I would not attempt to sleeve down the 920 barrels I have, I'd use a used set or purchase new, depending on the cost differential!
 
click, I think somebody already suggested this, but for now why not accept "Grumpy knob's" kind offer of his good 920 pistons. Give them to your trusted man, and see if boring to the correct clearance will remove the scores in the barrel. (if it's a tad over it might smoke, but it won't seize) Rebuild it as a 920, and in parallel start collecting the bits for an 850 motor.

Cheers,

cliffa.
 
If you can send jim your barrels for re lining/880 pistons to take the big small end pin I'd bite his hand off and I'd be boxing the barrels up ready for shipping right now.
You will end up with a more reliable motor with a little more punch than stock,plus a little bit more reliability than the 920
 
I rang the mate & he brought around another bottle of whiskey :)

Leak Down Test (Don't Laugh!!)
 
I have 2 comments after following your saga.

1) IF Jim offered to help you, You are indeed a lucky man, because you get more than just "the work done right", you also get someone who knows the best, AND WORST options, which is not something you get from good machinists who aren't familiar with nortons. (add to that, he'll make it so you can use your existing connecting rods with the 13/16th" wrist pin) Don't hesitate,... and go buy a lottery ticket or two because this IS your lucky day...

2) In case of any doubts refer back to comment #1
 
Last edited:
LH piston 355 grams
RH piston 354 grams (this is the worse piston and the cylinder that was smoking)
 
o0norton0o said:
I have 2 comments after following your saga.

1) IF Jim offered to help you, You are indeed a lucky man, because you get more than just "the work done right", you also get someone who knows the best, AND WORST options, which is not something you get from good machinists who aren't familiar with nortons. (add to that, he'll make it so you can use your existing connecting rods with the 13/16th" wrist pin) Don't hesitate,... and go buy a lottery ticket or two because this IS your lucky day...

2) In case of any doubts refer back to comment #1
Click to expand...

Totally agree:)
 
splatt said:
A waste of time trying to measure those, the pistons will have collapsed, wouldn't be surprised if the liners have distorted off the barrel in the middle.
Click to expand...

Well if the pistons have "collapsed" and you are measuring 0.004" to 0.005" clearance (with a paper thin feeler gauge - done all the time), what does that say?

Never heard of a liner distorting off the barrel, after all the liner is a hoop in compressive stress (press fit). Not saying it cannot happen, just trying to understand how.

I think comnoz's concern with the liner is if someone is trying to bore out an apparently already thin liner 0.020".

Trying to clean up the liner with a hone was worth a look based on click's assessment of the grooves and getting replacement pistons of the same diameter as long as the bore clearances (after honing) were good. No commitment on purchasing pistons until attempting to clean up the bores and measuring. In light of comnoz's offer, I would go with comnoz's offer and move on.
 
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