Could some one tell me what the stock piston ring gap is supposed on my 89 6bt? Im putting this engine back together and the only book I got from work is for the 6bt cummins engines i work on in our heavy equipment. If I go by their ring gap spec ,,Im out..And looking online I saw somewhere that its supposed to be 0.26mm-0.36mm, Not what this book says.. Im getting mixed info where I look..Any help on this? Thanks Mike

 

#1 .0160-.0275 / no side clearance available
#2 .0100-.0215 / .006 side clearance
Oil Ring .0100-.0215 / .005 side clearance

 

Well going by that, then im out of spec. This engine you could eat off of and was supposed to be a good running engine. Im measuring the top ring @3.5 inches from top of cylinder at 0.028 or so. Now I dont have the tool to measure cylinder bore. The piston doesnt seem to have any kind of excessive play in the cylinder and it had a perfect looking crosshatch pattern in the cylinder..So could it just be it needs rings? I dont mind replacing them if so. I want to put this engine together ONCE!

 

Depends on piston to cylinder clearance. Take it to a machinist to be measured if you don't have the tools. Easier to do it once.

 

Im going to see how much the tool cost. That way at least ill know if its the cylinders or just the rings. That and ill call Cummins and see how much rings,mains,and rod bearings cost.I priced out those parts from autozone,But after looking around on here,Just about everyone seems to say go with the cummins parts. Sounds good to me. You just never know with these aftermarket parts. Ill keep posting on the outcome of this issue.

 

OK Just an update..I have the cylinder bore measuring tool coming that attaches to my dial indicator..Once I measure the bore Ill know where I stand.

 

Ok I have reinstalled the pistons. I bought rings from cummins. Its amazing how much an almost unnoticable thickness between the old rings and new rings drastically decreased the gap. Looking at them on top of each other I had doubts until I checked the new ring gap. All the bearings in the engine are also from Cummins. I just didnt feel comfortable using aftermarket parts for the internals of the engine. SO now Im working on the head,and should have that installed sometime this week. Thanks for the info..Mike