7 replies to this topic

[MrBounce]

In the New Year I will be looking at building the engine up for my Midas project and have a question surrounding the pistons & rings. I bought the pistons & rings as a set from Mini Spares - these ones: http://www.minispare...ck to catalogue and I can't remember if the rings were already fitted to the pistons at the time of purchase. The machinist fitted the pistons to the rods and also did the rebore, as well as balancing the crank, pistons and flywheel assembly. At the time I did not know about gapping rings so we never had the conversation about whether he did it. I can't contact him until the New Year.

 

My simple question is this: How do I gap the rings? I have done a quick search & can't find much out.

[minimadles]

Take a piston ring fit it in the bore square it up measure the gap with feeler blades if it's been rebored nice and accurate the rings should fall nicely in spec do all rings and keep each set together with the cylinder they are going in

[MrBounce]

And what should the gap be?

[grumpy dad]

12 to 14 thou is right

the way to get the ring square 

is to put the ring in the bore

and push down using the crown of the piston

push down about a inch

[MrBounce]

Awesome. Many thanks guys

[Guess-Works.com]

12 to 14 thou is right

the way to get the ring square 

is to put the ring in the bore

and push down using the crown of the piston

push down about a inch

 

I believe the accepted standard / rule of thumb is 0.0035" per inch of bore for the minimum ring gap, and then a maximum of 0.006" per inch...

 

Working on the principle that you're fitting std size 21253's then ring gap should be between 0.010" and 0.016", however allowing for the fact that the rings need to bed in, and you want the engine to last more than 30 minutes, I would aim for somewhere between 10 and 13 thou. 

 

As a personal rule, If I drop a new ring down a std bore and it measures more than 13 thou, it's on the rebore pile, and even at 13 it'll be remeasured after a hone and probably will still end up on the rebore pile.

[Guess-Works.com]

 

My simple question is this: How do I gap the rings? I have done a quick search & can't find much out.

 

Didn't look that hard ;)

 

http://www.theminifo...n-ring-end-gap/

[MrBounce]

Oops! Probably because I didn't use that particular search perameter by using "gapping" instead!

 

The block has just been bored to +020" so I will amend the figures to suit