I’m starting to get ready to assemble my engine, and I’m measuring the piston ring end gap right now. I squared the piston inside of the bore with the new piston, and I took some feeler gauges and found that my compression ring end gap is 23 thousandths, and the spec according to the service manual is 10 thousandths to 20 thousands, meaning the brand new rings out of the box for 60 over pistons is just very slightly out of spec.

My main question here is, should I worry? I know 3 thousandths of an inch isn’t much, and I feel like it’s within the realm of being okay, even though it’s just slightly out of spec. I’m not sure if I can get “file and fit” rings for my 2.5, so I’m not sure if I should just leave it or get “file and fit” style rings

 

You can't file it to fit the gap is already to big . I would talk to the shop that did the work on the bore and the place you got the rings from .

 

To expand a bit on what Tech said.
​​​​​​ realistically that much out of spec probably won't make too much difference BUT:

Either the rings are off, the cylinder diameter is off but the piston/bore clearance is ok, or the piston/bore clearance is ok but the piston diameter is off or the piston/ bore clearance is off ( the cylinder diameter is too big.)

in any case something is off and I would want to make sure the piston clearance is correct before I put that thing back together

Edit: it does occur to me that if you got it bored 60 over for whatever reason and that's about the biggest oversize piston available if they messed up the bore size you're SOL.

 

Just did a search for piston ring gap on google...many choices. Firstly what type of pistons...stock aluminum or hyper-eutectic? Also a hair on the big side is ok. They also say measure gap at lower end of bore, not top. Talk to your engine people but also do your own research. .060 over is a big jump, why so much? Did you make sure you could get a head gasket with that bore

 

.023" is definitely a bit on the large side for a gap. General rule of thumb is take bore size and multiply it by .0035 to .0045 to get ring gap.

 

.023" is actually perfect. This way, you can comfortably turbocharge the engine later down the road.

 

You may have already done this but if not, just for grins...
I'm guessing you checked the gap by measuring it in one cylinder.

1)Using the same ring check it in all 4 cylinders. Get the same answer?

2) check different rings in one cylinder. Get the same answer?

Would be interesting. I have little faith in machine shop QC and parts QC

 

When assembing something complex like an engine that has been machined, I wouldnt do it without taking my own measurements with inside & outside micrometers and bore T-gauges

Writing down all results, its time consuming, but its blue printing and can save your backside, and at least guide your decision making

a set of T-gauges and an outside mic can be very inexpensive, they pay for themselves with one use

 

1

 

Sorry it took me so long to respond. For some reason the forum wouldn’t let me log in for a while now.

Anyway, I checked the same ring in all 4 bores, and this time I did it lower in the bore, near the end of the ring travel, which is what the service manual recommends. The ring gap didn’t change much across the 4 cylinders. It was .023 on 1, 0.021 on 2, 0.022 on 3, and 0.021 on 4.

I then tried another ring from the top compression ring set, and it was the same measurements. I’m wondering if maybe the feeler gauges I’m using were trash, because they’re actually older than me. I’m debating on using another set to see if the measurements are the same.

Regardless, it seems that my block is very slightly over bored from what the machinist said he bored it to. I want to check the size of the bore, but I haven’t had the time to check it just yet. There’s nothing I can do if it is bored over too much, so I’ll just have to continue. I’m not going to scrap the block over an end gap that is very slightly too much. I know some people won’t agree with this decision, but the only option I have is trying a used block and taking my chances with having it worked on.

Anyway, we’ll see what happens. I doubt I have anything to really worry about

 

1) seems like a pretty sloppy bore job based on the gap variation
2) measuring at the top or bottom of the cylinder only matters in a used/ unrebored cylinder as the top wears more than the bottom. Newly bored cylinder should hopefully be .....a cylinder.
3) Although as you pointed out there's nothing you can do if the cylinder is oversized, the ring gap is not the big issue, it's the piston-bore clearance. You can live with some piston slap... until the skirt breaks off . I would still measure this before you put this thing back together.
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If the machinist said he bored over then he should fix it for you and if it need a new block , Did you ask him how can it be fixed ?

 

Yeah, that’s my only concern. I haven’t got the pistons installed on the rods just yet but once that’s done, I’ll install the pistons and check piston-to-bore clearance.

But would you measure that with a feeler gauge?

 

Given that you've already decided you're going to run it the way it is I'm not sure why you're asking but:
1) no, you don't use a feeler gauge, look in your shop manual.
2)not that you could if you do it right but you don't measure piston/bore clearance AFTER you have the pistons installed. What would be the point?
3) this is a question pertaining more to the shop that did the work. Did they tell you to have the main bearing caps installed and torqued when they were boring/honing the block?

 

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