Evening
I got a 1098cc engine, been bored out to +20. Im doing an engine rebuild, whilst my bores are ok, i rehoned them to take away the glazing before i fit new piston rings. I cant seem to find the set of 5 piston rings, only the set of 4. I ordered two sets of 4 rings instead hoping to use both oil control rings. But to only find the 5th groove on the piston has a locating peg.......
Do i need the 5th ring as the 4th is a segmented oil control ring?
Do i buy new pistons with new rings instead?
Do i knock this peg off and add 2 segmented oil control rings?
Thanks
5th piston ring
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philthehill
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Re: 5th piston ring
Before doing anything you must check that the new piston rings are correctly sized for the piston groove.
The piston rings must not have too much clearance in the piston groove. Fit each piston ring and measure the clearance between the top of the ring and the piston body.
Excess clearance will allow the piston and rings to pump oil. If excess new pistons I am afraid.
The clearance in the groove for top, second and third rings is 0.002" - 0.004".
Clearance in the groove for slotted scraper oil control rings is 0.0015" - 0.0035".
Specification taken from BMC wksp man general data for 1098cc engines.
As you have different (segmented) oil control rings the fitting instructions should give an oil control ring clearance.
To check if the oil control ring grooves are worn you can put a slotted scraper ring back in the groove and measure the clearance. If excessive there is little point in fitting a segmented oil control ring.
Make sure that the piston rings are fitted the right way up - 'Top' usually marked with a 'T'.
The 5th ring below the gudgen pin was introduced to help reduce the amount of oil getting up the bore to the other oil control rings. The 5th ring was discontinued on later pistons and the number of piston rings over the years has steadily reduced to the three now fitted - but of course better pistons and better rings. So to answer your question it is not imperative that the 5th ring is fitted but it is there for a purpose and you may find the oil consumption is slightly more without it.
Do not attempt to knock out the 5th piston ring locating peg as there is a good chance that you will damage the piston.
The peg is there to stop the 5th piston ring from rotating around the piston and catching on the split skirt of the piston.
Phil
The piston rings must not have too much clearance in the piston groove. Fit each piston ring and measure the clearance between the top of the ring and the piston body.
Excess clearance will allow the piston and rings to pump oil. If excess new pistons I am afraid.
The clearance in the groove for top, second and third rings is 0.002" - 0.004".
Clearance in the groove for slotted scraper oil control rings is 0.0015" - 0.0035".
Specification taken from BMC wksp man general data for 1098cc engines.
As you have different (segmented) oil control rings the fitting instructions should give an oil control ring clearance.
To check if the oil control ring grooves are worn you can put a slotted scraper ring back in the groove and measure the clearance. If excessive there is little point in fitting a segmented oil control ring.
Make sure that the piston rings are fitted the right way up - 'Top' usually marked with a 'T'.
The 5th ring below the gudgen pin was introduced to help reduce the amount of oil getting up the bore to the other oil control rings. The 5th ring was discontinued on later pistons and the number of piston rings over the years has steadily reduced to the three now fitted - but of course better pistons and better rings. So to answer your question it is not imperative that the 5th ring is fitted but it is there for a purpose and you may find the oil consumption is slightly more without it.
Do not attempt to knock out the 5th piston ring locating peg as there is a good chance that you will damage the piston.
The peg is there to stop the 5th piston ring from rotating around the piston and catching on the split skirt of the piston.
Phil