piston rings (MGB 4cyl engine)

[robert1839]

so this Is for a 1800 4cly original mg engine but maybe some one will know

I have this MG engine that I am rebuilding and when I was putting the rings on I realized that there was still another set of rings that I needed to put on but there was no more groves for the last set. The car came with 2 engines and the pistons from one say mowog so I know there the original set and the ones from the other engine do not say mowog on them so there some sort of aftermarket pistons set witch don't have the last grove and when comparing them there are 5 places for rings on the mowog pistons and there is 4 on the aftermarket set dose this matter if there is only 4 instead of 5

[DiDueColpi]

Doesn't really matter Tristan.
The B engine came with 3, 4 or 5 rings depending upon the series.
What really matters is the wrist pin. The early ones have a pinch bolt on the connecting rod and the later ones do not.
The pinch bolt rods are intended for the 5 ring and 4 ring pistons with a wrist pin diameter of 0.750"
The non pinch bolt rods are divided into  2 groups. Full floating and press fit. The full floating ones will have a bronze bushing in the wrist pin end. These will only accept a piston with a full float wrist pin. The piston will have lock rings and their accompanying grooves in the wristpin bore. The wrist pin will have a diameter of  0.8125". The piston could have 4 or even 3 rings.
The press fit rods won't have a pinch bolt or a bushing. They can accept any 4 or 3 ring piston with the 0.8125" wrist pin. just don't use the retaining clips if they are present.
I don't know which engines you have but they came in 3 and 5 main bearing styles. If you have a choice use the 5 main block as it's stronger.
There should be a plate on the block that says 18G-something. If you can identify that it would help a lot.
Cheers
Fred