So, after 100-150 miles I started to notice more noise on the bottom end than I had at the beginning. It wasn't horrific but more that I expected. I thought that I might have spun a rod bearing so I pulled the motor to take a look. All the main and rod bearings are pristine. Cam is beautiful and everything is straight. I pulled the plugs and noticed that most of the pistons heads are caked with carbon, some with a touch of wet oil. I assume that what I'm hearing is a result of the rings not being set yet.

Is this normal this early on? Might there be something wrong with my piston ring sizing? The carb is tuned right and I see zero sign of coolant in oil or vice-versa.

 

Are you certain your not running rich and diluting the oil?

If auto maybe loose converter nuts. Bad balancer, stickie belts (after using a treatment).

 

Not sure of anything, how does running rich dilute the oil? Blow by from unset rings?

Truck is a manual with new clutch, the balancer and flywheel were balanced to the engine. Maybe something is off with the clutch.

Spark plugs are neither black or white, so I think my mixture is good. Just a bunch of black on piston heads. I do get a little knocking when under load and engine is warm but not full temp, running premium fuel and at 5400 ft so I'm guessing it's the result of the carbon on the pistons. Compression should be around 9.5:1. Didn't start until about 50 miles in.

Thanks!

Think I'll just put it back in, run 15w40 and see where it goes. From my inspection nothing is worse for wear.

 

If your plugs are tan you are probably good on mixture. Too rich of too much choke can dump fuel into the engine that can get by the rings and dilute the oil.

When do you notice the noise i.e. all the time, high rpms, under load?

Possible exhaust leak?

 

Rich mixture is heavy air, heavier that the right mixture, it can't light and combust properly as well as it cools the combustion chamber losing effectiveness or combustion, as a result on certain engines like boats and air planes, a rich mixture is not too bad, engine always has a load. On a car engine, engine idles at a stop light, sucking all the residual heavy air in the intake, then sucking all the rich mix in while coasting, like going down hill, and that gas won't burn. It will pass by the rings, mixing with oil, Now oil is dilluted and gets introduced into cylinder walls via valve guides and rings.

 

So how long should it take for the rings to fully seat and for the engine to stop burning oil? I've read that you shouldn't switch to synthetic till then, but when is then? Is there a certain mileage or is each engine different?

 

Well, depending on ring types, bore condition, driving habits, my local shops recommend 3000-5000 miles. that should seat most modern type assemblies in the old blocks. A lot of variables. My old 400 powered engines start right up and wait for quite a few minutes to gain operating temp, my EFI 460 even though bigger and more metal to heat, it reaches operating temp half time of the smaller older 400. They say start up and warm up is the most accelerated wear, in an engine, Good luck. I Have seen engines seat in almost immediately, and then I have seen them seat in for upwards of 10000 miles. I startedon my new builds doing a very thorough cleaning of the bores, like hot water as hot as I can stand with gloves on and detergent, a cotton rag, then immediately follow with 15w40 new engine oil and clean rags until rags are no longer showing any color at all of grit, dirt, hone material, then I wipe with ATF and clean rags, until clean. It is surprising how much grit and material and contamination is in there even after 2 hot tank sessions.

 

Depends on the rings, cast iron bores and cast iron rings shouldn't take long at all. The basic general routine on a rebuild is have everything dialed in beforehand - carb and ignition timing so it starts right up without any drama - break the cam in at a fast idle - maybe 2000 or 2500 RPM for 20 to 30 minutes. Then no more idling till rings are seated, get engine under load, rings will never seat at idle. The risk of excessive idling prior to ring seat is cylinder glazing, a hard slippery varnish like coating. Basically full throttle accelerations from cruising speeds - say from 20 or 30 MPH up to 50 or 60 MPH, and decelerations back down. It's the compression gases while under load that forces the rings outward to closely fit with the cylinder walls. The cylinder hone crosshatch design is part of that process, it holds oil. When a cylinder glazes over it is smooth as glass, blowby and poor compression results and it will be an "oil burner".

 

Each setup is different. I've had some seat within 100 miles and some take thousands of miles. All comes down to the setup.

 

What kind of noise is it making anyway? Pings?knocks? Clunks? Any indication of rings butting together? I slather assembly Lube on cyl walls before each piston install. The oil ring scrapes off excess and the top two rings get lubed during startup. It's usually about 200 miles before seating on my builds now. And I change oil every 500 miles till I change plugs at 2k then I change oil every 1500 miles and plugs at 3k miles as I'm running nitrous. No spray till at least 500 miles though to be safe.

 

The noise running is a diesel noise, knocking. I imagine that is due to the carbon build up on the piston heads. The bottom half of the engine is pristine so I'm pretty sure now anything I'm hearing is coming from the top. Cam and lifters are also perfect. The bores still have cross hatch and no glazing. I do see signs of some piston tails sliding on the walls, I have no idea if that is normal or bad.

So this is where I stand. I have excessive carbon built on all piston heads, some worse than others. I'm almost positive it's oil, I can see oil on the plug threads. Oddly, the plugs are pretty clean. I think it can only be coming from one of two places, up past the rings or down past the valve stems. It only has 100 miles on it so rings are most likely not set.

Here are my new questions:

Could the fact that I have been running it without the spring damper and just the allow excess oil down? Will installing them help? I'm using comp cam springs. I left them out at first because I thought they were dual springs not spring and damper. Rubber comp cam seals are installed.

Do I have to clean the carbon off the pistons at this point or will it burn off with time once the issue is fixed?

If I do have to clean the pistons, do I have to pull them from the motor or can I do it installed?

Is there anything I could be missing? I'm not sure if the ring are pinching or loose, I just trusted that when I bought the short block the KB 40 over pistons would fit the 40 over bore.

 

So, after thinking on it I just ordered some 40 over TMeyer Pistons. No more screwing around with the modified Cleveland pistons that came with the block. If they get crusty I'll know it's the heads. The bores still have a decent cross hatch so I'll just swap them off the connecting rods and toss it back in the truck.