I'm currently rebuilding my BP 26 engine and have already started the assembly process. I put the pistons in, rod/main bearings, crank, oil pump, front and rear main seals, and the oil pan. The engine turns over just fine, BUT---

It makes a noise when the piston reaches TDC, and not just one. They all do it.

Even though I can search my mind and vividly remember nearly all of the assembly process, there are a few instances during the piston install where I was having trouble with the ring compressor. The distraction creates gaps, and doubt.

Even though I'm 99% sure it's correct, the stakes are so high that I'm stymied.

The only thing that could be wrong is if the ring gaps are not aligned properly, or if the oil ring ends overlap, and that wouldn't account for the noise that I'm hearing.

I guess what I'm asking is, how do you keep it all straight so that when you're done, you know you're done. If an unexpected noise happens, then what? Thanks for taking a minute to answer. It might mean the difference between making progress today and just sitting around watching tv.

 

I don't have the head on yet so I can see that the pistons are all oriented correctly.

 

Your asking piston enging advice on a rotary forum? Thats like instaban

J/k, my first thought would be, did you hone the cylinders? I wonder if theres a ridge near TDC that the rings are hitting and giving your sound

 

Bored em 0.020 over.
Installed 10:1 Miata pistons, also 0.020 over
New rings.
engine lube + 30 weight oil all over the place
new rod/main bearings

I could ask in other forums, but I like it here. My question is actually about assembly in general. I suspect that the level of expertise among mechanics on this forum is higher due to the specialized nature of the RX7.

 

Whats the noise sound like?

 

 

you set the video to private

when you roll it over by hand, can you feel it in the crank when the sound is happening? as in, does it get harder to turn?

if your thinking you staggered the rings, high chance that you did, but, even if they weren't, you wouldn't notice until you start the engine and you can't get it to stop smoking and its blowing oil out everywhere

You may be just over worried, this your first engine build?

are you 100% positive that you torqued everything internally down? Sure your not just hearing the oil sloshing?

 

Yea, my first engine build. The video should work now.

 

that sounds like the wrong bearings installed in the connecting rods. too small. can you move the big end of the rod on the crank end?

 

You got me thinking. I started using the breaker bar instead of the ratchet so I could change directions back and forth. I hear the noise even at mid stroke. I don't think it's the bearings because the sound is coming from the top of the motor, or the piston rings. There's no slack at all when I change directions either. I'm starting to wonder if the rings are not the right width for the pistons grooves. Since both the pistons and rings are new, I'm going to call the outlet where I bought them and ask if they are compatible.

I just revisited my sales receipt and everything looks in order. Maybe I should call.

 

honestly, it sounds normal to me Its been a few years since I've had heads off a motor, but I seem to remember it sounding like that, even with the "water droplet" sound

 

+1

on second thought, you may be on to something about the rings not being wide enough. it almost sounds like the rings are "folding over" when the pistons change directions.