fatjoe10

No, the rings were installed out of the box without modifying any of the gaps.

Deckoz

did you measure the gaps atleast?

that's surprising, I've never seen a set of rings with propper gaps out of the box...you need one of these

fatjoe10

I measured the gaps a really long time ago.. I remember that the 1st ring was right on spec, but the 2nd ring had a slightly narrower than spec gap. I purposefully threw the kit on this engine as is to see how it all works out. The rings are NPR part No. SWH30466ZZ (K24 Accord/CRV/Element) as it comes with the Nippon piston kit.

I agree tho, for the next build, the gaps will be made proper with the proper tools. I appreciate the suggestion.

Deckoz

I don't know if I'll have anything else useful to add to discern why one cylinder has a higher leak down.

But the following should be added to your build process next time

• Once you have balanced your pistons
• You need to mate the pistons to a cylinder by their diameter vs bore.
• Test each ring about an inch down in each bore just to match rings to a cylinder, we only need guestimates or close enoughs/this ones better in that one here or there
• once you match the rings to the bore, clock the ring before pressing into the bore and push it down with the piston to mid bore. Check the gap, remove and file and de-burr. and repeat until the gap is spec.
• once all your rings are mated and spec'd, install them on the piston, and finish balancing the rotating assembly, ie Balance the rods, balance the flywheel, then mate rods to pistons so the combo of rod wrist pin and piston are closely weighted. then use those total weights of each combo to add to the rod jounal each piston is mated to, then balance the crank/flywheel/harmonic balancer with these psuedo weights installed.

fatjoe10

For this build, the pistons were matched with the bore when Inline did the machine work. The crankshaft was checked that it was balanced. As for the rings, I simply followed the repair manual instructions, although I admit the gaps could have been measured better. If this doesn't improve by 1000 miles, then I will pop that one piston out and see what the deal is. For now, I will let it ride ...

Charper732

Dude.... you are seriously playing with fire. If your ring ends touch it'll pop the top on the piston and that that motor will be done. There will be no warning.

fatjoe10

Here's how I see this situation:

If my mind serves me correctly, the measured gap for the 2nd ring was somewhere between 0.0017- 0.0018. I'm aware this gap is narrower than the F20 spec of 0.0024 - 0.0030. If we go by the commonly thrown around rule of 0.0050in x bore diameter for a "performance street engine" (currently 3.4350), we get 0.0017 suggested gap. While I feel the gap is safe as far as the ends touching is concerned, it may not lend itself to good performance, specially at high RPMs. The OEMs learned a long time ago that widening the 2nd ring gap led to more power, and this is what I think Honda was going for. We will know once I put the car on the dyno.

Noted the advice given. For the next engine, the recommended gap tolerances will be closely adhered to.

I'm already building the 2nd engine for when/if this one goes... I have plenty of spare blocks lol.

Charper732

Just so you know though, no piston kit i have ever seen, for any motor, has rings that are good to go out of the box...its not designed that way.

I would advise you go on the looser on even the oem spec. I doubt the metal alloy of nippon is identical to oem. Therefore, expansion rates will be different.
There is very minimal downside to running a wider gap. Im currently running a .022" and .028" on my motor albiet i make a lot more power, but blowby is not an issue at all.

and just food for thought, ive taken unopened oem motors apart with broken rings/ringlands.

gzob

I got OEM Honda piston rings (0.25) for the nippons just to be sure they are 100% FRM compatible. They are still available, although pricey as always. With cylinder bore at exactly 87.25mm, I measured first gap at 0,010" and second gap at 0,027". Although first gap seems low, I will leave it for the moment, I will just break in the motor patiently and the engine will not see any kind of endurance racing so I should be OK.

fatjoe10

Wow good info on the broken ringlands.

What ring gap do you recommend for an NA OEM like build? (Edit: add P/W rec)

As for the P/W, Inline stated the clearance should be fine for this type of piston, as they seemed to be familiar with it.