Evening all,

Almost finished stripping down my practice engine now so I will be moving onto measuring bores/pistons etc etc soon and have a few questions if I may.

As before I'm a novice here so although these maybe simple questions they are genuinely asked.

1) Piston ring gap - as I understand it you fit the rings one at a time and then slide them into the cylinder with a compressor. I envisaged then putting a feeler gauge in to check the gap not realising that ring gap is tiny - how is this done ?

2) Similarly - how do you measure ring to bore clearance without bending the feeler gauge ?

3) Although I don't have any I would like to get a set of those inner micrometer bore gauge things - but how do you get those "tight" enough to measure bore diameter without scratching the bore when you remove them ?

4) Do you do all the above with or without oiling the surfaces being measured ?

5) When measuring any diameter - is there an easy method for ensuring you are at the widest part ?

6) With a feeler gauge is it meant to drag and if so by how much ?

So hopefully not too many questions there for you all.

Thanks in advance.

Paul

1) Ring gap: Put the ring in to a worn part of the bore and measure the gap between the ends of the ring. The rings are not fitted to the piston to do this.

2) Ring to bore clearance: Not something I've ever heard being measured, there should be no clearance between the ring and bore.

3) Depends what you measure with. Dial bore gauge is sprung loaded as are telescopic plunger guages. Internal calipers should just be a nice drag not tight enough to score.

4) Without

5) Measure at various points, you are looking for the smallest measurement i.e that you are dead square across the bore.

6) Yes it should drag, but not too much.

Any other questions just ask.

Davie

[Edited on 28/10/09 by daviep]

Cheers Davie - I'll see how I get on.

Thanks for your help.

You should also be measuring the ring axial clearance. i.e the gap between the side of the ring and the side of the groove.

Hi Richard

Do you mean fitting the ring and then measuring the gap between the top (horizontal) face of the ring and the ring landing and then the bottom face and ring landing. Does the ring "rest" on its bottom face and therefore have zero clearance ? Do you have to measure top and bottom at the same time - ie. if I put a feeler gauge in the top am I not pushing the ring down the land ?

Or do you mean the diameter of the ring landing and the inner diameter of the ring itself - as far as I can see I'd have to do this without fitting ring so how do I measure inner diameter without expanding the ring ?


thanks
Paul

Good question and Good Answers

Is it not worth making this a sticky post?