Re-Ring? Guru input needed

[Girvin]

The other day my timing belt snapped. I'm already prepared to replace/rebuild the poor cylinder head,had only 4k on it, as well as the new timing parts. Since I will obviously have the head off, would it be recommended/acceptable to replace the piston rings while I'm at it? Normally I wouldn't even think about just a basic ring replacement. However, the motor has 30k on a full rebuild.

My reasoning to a possible ring replacement is just prior, weeks, to the timing belt problem I was starting to burn small amounts off oil (not timing belt related) and did a compression test which yielded in the late 130's across the holes. I didn't get a chance to do a leakdown before the belt went but I was having some blow by problems( more than normal amounts of oil coming from the valve breather). Another reason is because I would like to check to make sure none of the piston heads were damaged causing the top ring to fail.

If I was to do a ring replacement, block is currently .20 overbore, what steps should be taken to minimize failure of reseating the new rings? I plan on having the bores re honed and possibly leaving the rod bearings while replacing the rod bolts. Sound reasonable?


Keep in mind....this is IF I don't find a set of ugly "smacked up" pistons when I pull the head in the next couple of days.

 

[blue1]

Hi, When you did the comp test was that just dry figures or was that the best figures you could get with putting some oil in the plug holes and then testing?
To change the rod bolts it is HIGHLY recommended to resize the rods and to reuse your old rod bearings is not an option!
The compressions seem very low for a 30k rebuild and if they are all about the same across all cyl's i would try another compression guage first! this one might just be reading low! but i suppose you cant as you haven't a timing belt!!

 

[2bar]

If you do use your same pistons and re ring them, make sure to clean any and all carbon off the pistons, in ring groves and oil ring holes. usually soak them in a tub of carb cleaner to loosen all the carbon. Do not reuse your old rod bearing. look at the journals. measure them and if needed Polish the journals and install new bearings. Your just asking for another failure if you reuse the same bearings. Make sure to use the proper oil when braking in you new rings.

 

[TransAmConvert]

Why wouldn't you reuse the same bearings. Unless something is drastically wrong with your engine, the bearings will not wear. There is never any physical contact with the bearings to wear them.

Hell, i've even reused the rings on some motors before and ended up with 170psi. Not that you should do that, but if you're on a tight budget you can get away with reusing a lot of shit. If it ain't broke, don't fix it.

The amount of DSMers who insist on replacing components unnecessarily well before the end of their service life never ceases to amaze me. If you can afford to do that, then bully for you. I certainly can't.

Just my $.02

 

[Girvin]

Thank you for your input guys.

I took the head off yesterday and found that all of the intake valves were bent as well as a few exhaust valves. The cams survived the punishment and the pistons have minor marks on them. Just a quick stroke with a dremel smoothed out the piston marks.

I've talked to a few local machine shops about doing a re hone/ring and I've come to the decision that I'll just re ring and not worry about the rod bearings. As I mentioned before, this motor looks very clean inside and is low milage. I would be happy with getting another 30k on this setup as I plan on going bigger in the near future.