Piston ring end gap

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Apr 2, 2023 | 05:33 PM

#16

exasemech

Senior Member

Joined: Sep 2016

Posts: 978

Likes: 480

From: North East USA

Year: 2000

Model: Cherokee (XJ)

Engine: 4.0

Quote:

Originally Posted by pineapple_tree

I see. You don’t use a feeler gauge. You use an outside micrometer to measure the size of the skirt, the box they come in tell you where to measure it and what the measurements should be, and then you take the actual bore size(or in my case that it’s not exactly what the machinist said it was) and then subtract the two and then you have your piston to wall clearance.

And yes, i torqued the main caps down according to the service manual before I sent them the block. I want to measure the bore with a dial bore gauge and make sure that I’m not measuring the end ring gap wrong. If I can get concrete numbers, then I’ll call up that machine shop and try and work something out. I’m a little nervous with how it appears the bore job is sloppy, and I want to make damn sure it’s not me measuring wrong or using defective tools

That sounds like a somewhat better plan than throwing it back together and seeing what happens.

Apr 3, 2023 | 04:52 PM

#17

pineapple_tree

Thread Starter

Senior Member

Joined: Aug 2021

Posts: 514

Likes: 74

Year: 1995

Model: Cherokee (XJ)

Engine: 2.5

Well, I used the shops dial bore gauge and found out, there’s no issue. I measured each cylinder from 4 different places, marked it, and found absolutely no variation. If anything, the bore was within 1 thousandths of the rest of the bore. Every cylinder was the same measurement in all 4 of the places I measured it at.

So, I re-measured the end gap with a new set of feeler gauges off of the tool truck, and come to find out, it was just enough in spec at 18 thousands for the top compression ring. I also installed the second ring on the piston, and used that to make sure my piston was flush in the cylinder. I haven’t measured piston-to-wall clearance, but I’m sure it’s okay as I’m now within spec. I’m guessing either I never squared the rings up right, or the feeler gauges from 1960 were worn out. I’m really relieved that the machinist didn’t do a botched job.