Piston clearance in bore

[Altijdgriep]

I've been busy changing the cilinderhead gasket and noted that the pistons wobble a bit in the cilinder.

If i push the piston from one side to another i can hear it slap against the cilinder, is that normal? I can still see boring grooves in the cilinder so that should be ok.

Also, the top from the cilinder is slightly wider than the rest, why is that?

Thanks in advance!

[79 Zagato Spider]

Ummmm, if your pistons wobble back and forth in your cylinders, that usually means your rings are totally shot. Did you do a compression test ever on it, before you took the head off? If you put it all back together, do a compression test. You might find that your rings are warn.

[Altijdgriep]

No i havent done a pressure test, I had oil in my coolant and coolant in my oil so it looked like a no-brainer so I took the head off.

I did take off the oil filler cap while still running and didnt notice any pressure so i thought piston rings would be ok, but when i was cleaning the tops of my pistons i noticed this clearance very clearly. I've done several head gaskets before on other brands but never noticed a thing like this before so I'm kind of worried,

I did have black smoke before but i thought that was caused by my valve seals wich were totally wasted.

Is it worth to waste a head gasket on this to measure compression or should i get the pistons out to look at wear and the rings? I cant imagine good rings would take out this clearance and since my cylinders look perfect it must be the pistons, but then again I can't imagine they have heavy wear since my Cylinders look so good.

Some further advise would be greatly appriciated.

[ncundy]

I'm not a Beta man (Fulvia myself) but I think if you are concerned then a compression test is a good first stage. If that throws up concerns then measure the bores with a bore gauge. They should be parallel and the same diameter all the way down, or as far as you can measure. It is not unusual to get wear near the top of the cylinder at the position of the top ring at TDC, usually you can see this by way of a dark ring on the cylinder face. If this is severe (>0.2mm) then you are probably looking at a re-bore (dimensions will be in the book).

If a measurement of the bores comes out OK (you'll need to get the Beta dimensions) and you are still concerned then really you need to take a piston out and measure it against the book and also put the rings back in without the piston to check the gap (again against the book). If the bores are ok but the gap too big then new rings are probably in order. You also want to check the ring slots in the piston. They should be square and of consistent depth and width - again you should find the dimensions in the book.

But before you get too concerned, if the engine feels OK and a compression test gives good and consistent results you've probably got nothing to worry about.

Hope you sort it
Neil

[DJ]

How much actual movement are we talking about?

[Altijdgriep]

I have tried to make some pictures from it but the clearance is too small to show anything. I have indeed a black ring on the cylinder face so it might be a re-bore.

I'll put stuff togheter again today and then do a compression test to see how things are. Doing that before i took things apart wouldn't be very usefull anyway with a leaking headgasket so no time lost :)

I'll keep in touch, thanks for the advise.