Ring gap, new rings? Or new pistons?

lynall · Oct 16, 2024

I often use an old saying at work, if there is any doubt then there is no doubt, ie if you have to think is it shagged? then the answer is yes.

Years ago they would do what they called top and tail, basically new main and big end shells with new rings, and away you went, not perfect but it worked.

ThomasLRNL · Oct 16, 2024

marjon said:
If you are in this far and it’s out of spec, who knows what it will run like.

But you have wasted the money on a gasket set and your time.

J

I havent reassembled it yet, its all loose parts as of now; so i didnt waste the parts atleast!

steve2286w said:
I could just feel a small ridge and I think that equated to less than 10 thou oversize on mine but I still got a rebore. But if you don’t want to I would measure what you can , completely strip down and check for visible wear , you can always do the minimum , put it back together , pressure test and make a decision then

Yup, seems about 10 thousands indeed.

Some new info:

For starters; i measured wrongly. The gap isnt 1.8mm; its around 1.15. The remarkable thing is that for the entire bore. its 1.15. Give or take .1. So yes, also at the complete bottom of the bore; and also at the complete top ABOVE the wear ridge.

This would shed a new light onto the dilemma what is worn; indicating its the rings. Alongside a thou of the cilinder walls. Any thoughts?

ThomasLRNL · Oct 16, 2024

lynall said:
I often use an old saying at work, if there is any doubt then there is no doubt, ie if you have to think is it shagged? then the answer is yes.

Years ago they would do what they called top and tail, basically new main and big end shells with new rings, and away you went, not perfect but it worked.

i have the tail, just missing the top. I feel like this is where its all going eventually. Just getting new rings and shoving it in. Taking for granted it might run a bit mucky.

steve2286w · Oct 17, 2024

What to the main bearing shells look like , can you post some pics of them, on mine on some the white metal had started to wear off showing the copper , bearings cheap so good one to replace , assume crank bearing surface ok
Turner engineering good for parts also they have some rebuild articles for your engine very useful

freelance · Oct 17, 2024

New shells, oil pump , rings and hone the bores, it will run nicely

steve2286w · Oct 18, 2024

You can check for end float on the oil pump gears and then buy new gears if reqd, but aftermarket pumps will not have the quality of the genuine pump which you will be better off keeping imo

LRO September 1999 - Spring 2001 - 2.25 3MB Petrol - Engine rebuild Pa

Part 1 Part 2 Part 3 Part 4 Part 5 Part 6 Part 7

www.turnerengineering.co.uk

ThomasLRNL · Oct 20, 2024

steve2286w said:
What to the main bearing shells look like , can you post some pics of them, on mine on some the white metal had started to wear off showing the copper , bearings cheap so good one to replace , assume crank bearing surface ok
Turner engineering good for parts also they have some rebuild articles for your engine very useful

Some bearing pics.

freelance said:
New shells, oil pump , rings and hone the bores, it will run nicely

thanks for the input!

steve2286w said:
You can check for end float on the oil pump gears and then buy new gears if reqd, but aftermarket pumps will not have the quality of the genuine pump which you will be better off keeping imo

LRO September 1999 - Spring 2001 - 2.25 3MB Petrol - Engine rebuild Pa

Part 1 Part 2 Part 3 Part 4 Part 5 Part 6 Part 7

www.turnerengineering.co.uk

alr id need to check that for sure, thanks.

As for the rings, i have some A and B pistons in the engine. Am i correct in assuming that if i want a new fresh set of rings, i should buy 4 sets of standard sized rings?

I found this piece of info online about the letter prefix on the pistons:
"
Piston sizing:

"Z" Nominal to minus .0002in
"A" Nominal to plus .0002in
"B" .0002in to .0004in above normal
"C" .0004in to .0006in above normal
"D" .0006in to .0008in above normal
"

Ring gap, new rings? Or new pistons?

lynall

Well-Known Member

ThomasLRNL

Member

ThomasLRNL

Member

steve2286w

Well-Known Member

freelance

Well-Known Member

steve2286w

Well-Known Member

LRO September 1999 - Spring 2001 - 2.25 3MB Petrol - Engine rebuild Pa

ThomasLRNL

Member

LRO September 1999 - Spring 2001 - 2.25 3MB Petrol - Engine rebuild Pa

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