14 replies to this topic

[steeley]

I have stripped down the engine to give it the once over and check everything before i rebuild it i am going to fit new piston rings how do i know which ones i need it is a 998 from a 85 mini i have attached pics

i got a set from a mate but they are a four ring set not 3 ring also i am sure i read somewhere that if i fit new rings to old pistons there should be a step in the top ring to stop it smashing when it get to top of stroke and hits the ridge from the old ring 

 

as help would be appreiciated

 

steeley

 

 

Attached Files

•  IMG_1237.JPG   52.35K   16 downloads
•  IMG_1238.JPG   31.97K   7 downloads
•  IMG_1240.JPG   52.24K   13 downloads
•  IMG_1242.JPG   57.35K   12 downloads

[Gr4h4m]

Have the machine shop confirmed that you don't need a rebore? No point buying rings if you need Pistons

[Spider]

If there is any step in the bore you are not only wasting your time, but good money too.

[steeley]

thanks

 

machine shop says bores are ok and the slight ridge at the very top of the stroke is quite norrmal

 

when i put  rings in the bore that i got from my mate the clearance between ring ends is 10thou which is ok according to spec

 

are the pistons in the pics std or uprated?

[sledgehammer]

is that a crack on the skirt ?

 

or just my eyes ?

 

 

 piscrack.JPG   97.78K   24 downloads

 

[Fast Ivan]

It does look like it's a crack

[steeley]

Just a lump in the forging Ithanks I've now checked them all
Anyone know what piston rings I need ?

Top of piston is marked front G8
20528 K29
And inside AE 75311A and am413 on one side
And hepolite 20528 and a 5 in a circle on the other

[Stevie W]

Hi Steeley,

That piston looks a tad rusty around the gudgeon pin circlip. Has the engine been stored with either
the head off outside in the rain or has water got into the cylinders at all?

If the machine shop state that it's ok to reuse the pistons, with just new rings fitted, I'd personally want to strip the gudgeon pins out of the pistons and off of the con rods and give everything a darn good clean before reassembling with fresh engine oil & new circlips.

You don't want any rust particles running around in your engine. The secret to a good thorough engine build is to have everything meticulously clean before reassembly!!

Cheers, Steve.

Edited by Stevie W, 20 September 2015 - 03:30 PM.

[sledgehammer]

+1 on circlips , they sometimes get annealed thru the heat cycles

 

& go weak

 

they can make a mess of the bore 

 

IIRC Teflon bungs aren't much better

Edited by sledgehammer, 20 September 2015 - 03:47 PM.

[steeley]

thanks for advice havent started rebuild yet just collecting parts i will need plenty of advice but stuck on ring type any idea of a supplier who could help

[sledgehammer]

http://www.fjpayne.com/

 

they are in oxfordshire but could probably post

 

they found some rings for me

 

Tel: 01865 882299 

 

http://www.fjpayne.com/contact

[steeley]

Thanks I will try them

[eean]

Try Geoff at Autosprint in Birmingham, top bloke, really helpful, I honed my bores after speaking to him and he supplied new Cooper S pistons and first oversize rings to fit, motor has been brilliant since

Edited by eean, 20 September 2015 - 05:48 PM.

[ACDodd]

Before you part with any cash measure the ring side groove clearance. Google it for a demo. If you can fit a 0.004" or bigger feeler in the pistons are scrap.
You can't just re ring an engine. The parts need to be suitable for re-use. Old Pistons usually fail this test.

Ac

[steeley]

.002 side clearance already checked