The Stovebolt Site Forums The Shop Area Engine Shop How Much Smoke On Engine Run Is Expected??

Finally got the freshly rebuilt 261 started. Ran for 25 min at 2,000 rpm & there was more smoke out of the tail pipe than I expected. Have repeated the engine run 3 times after cool down for about the same amount of time. The smoke out of the tail pipe is about the same on each run. Is this pretty much normal??? Should I expect the oil bypass to finally wear-in and stop smoking out of the tail pipe?? Thanks For Your Thoughts.

Almost none.
Oil level too high?

What kind of smoke? Oil, gas, water?

After the first few minutes of the break-in run to burn the oil away that was used to assemble the rings and pistons, there should be little or no smoke. Is the smoke black (gas) blue (oil), or white (coolant)? Assuming the smoke is blue, the next step is to pull some spark plugs to see if the oil consumption is from just one cylinder, or a more universal concern. Are you running a road draft tube or a PCV valve?
Jerry

** Smoke is blue & smells like I would expect oil smoke to smell like. Crank was serviced with five qts. of Brad Penn break-in oil plus one for the 1 qt. filter. Correct road draft tube is installed. Will pull the plugs and update first thing tomorrow morning. ** Just as a note the engine was rebuilt by a so called machine/over-haul shop but has been setting in my shop for a year covered up.

I'd suggest a little more run-in time before doing anything dramatic. Depending on how aggressively the cylinders were honed, it might take a while for the rings to seat properly. Ring seating also needs some time under load out on the road- - - - -the initial run-in is just for making sure the camshaft lobes and lifters establish the right wear pattern. Perfect Circle used to recommend 10 accelerations from 30 MPH to 60 MPH in high gear for ring seating. Do you notice more blowby than expected for a "new" engine?
Jerry

Did you check any of the work done on the engine? Meaning did you pull any of the pistons, check the fit in the cylinders, push rings down into the cylinders, get them parallel and check ring gap? Have you removed the oil cap to see if there is much blow-by? After the first couple of minutes there should be no blue smoke in an engine that was machined correctly. Will it idle decently? Have you checked with a vacuum gauge? What carburetor and has it been checked recently? If it is a Rochester B and the power piston is stuck it will be running greatly rich (maybe as much as twice too rich) and this won't help anything. Lastly are you using fresh gas or has the gas in the tank been sitting there a while? A couple of months ago I posted 3 images of gas. 2 of them had gone bad in 2 months time (one sitting in a new gas tank on my truck and one sitting in the lawn mower gas can). The bad gas burned more slowly and with notably more smoke and a lot of sticky crud left after it burned, albeit it was black and sooty smoke.

For Hotrod Lincolns thoughts ** I will more than likely have to wait to try your thoughts as I still have the front clip to install before it will be road ready. But will comply with your directions as to the power run. ** For Jon G thoughts ** I have not checked fit of the rings. ** Did not even think of checking the blow by but I will do that tomorrow. ** The engine idles really well & accelerates from idle to 2500 really well without hesitation. ** The carb used is a known good rochester. ** Prem. gas was used purchased two days ago from a supplier that probably pumps several hundred gallons or more a day. ** Thanks

What is the wt. of this "break in" oil? Keep an eye on oil level. As Jerry indicates, maybe more time is needed. Some yahoos put way too much oil in piston area and such during rebuild trying to be safe. Let's hope that's it. No blow by? Aren't you supposed to vary the RPM's?


Flat tappet break in:

6.Start the engine.
7.Immediately raise the RPM's to 3,000.
8.Vary the RPM's between 1,500 and 3,000 for the next 20 - 30 minutes. Use a slow, steady acceleration / deceleration pattern.
9.Shut down the engine and let it cool.
10.Drain the oil and change the oil filter to remove any metal particles from the break-in process

**For the bartamos reply ** The first engine run was accomplished pretty much as you suggested. Complied with just about the same run and method 4 times over several hours. ** Had about the same amount of smoke during the 4th run as the first one.** Will change the oil tomorrow.

Hope smoke goes away in time. You probably don't want to ask the builder after a year of sitting. I guess my idea of too much oil is wrong after a year of gravity. Great idea to check each plug. I think I would want to see oil on every plug. Just a feeling. It will be OK.

** I surely hope it all works out and the 261 performs like one would expect. Time will tell **

I would wait until you can get some seat time and the motor under load before you go to anything extreme. 261 pistons and rings can sometimes be hit or miss as to what is available at any given time. If the builder used chrome rings, which were not all that uncommon in the day and frankly are just fine to use in my view (I used them in the last 261 I did in 2015), they take a little more run in time to seat. So I would say take a deep breath and let that motor break in a bit and see what it is doing then.

Maybe I missed it cuz I ran thru this one pretty quick...but the only mention of a rebuild
that you posted was the "Crank was serviced with five qts. of Brad Penn break-in oil plus
one for the 1 qt. filter."
In other words, did the shop do a complete overhaul, like bore job, new pistons complete valve
job on head. If they simply lapped in the old valves to seal them and just roughed up the
cylinders and fitted new rings to the old pistons, then it wouldn't surprise me that it's smoking.
DG

** As far the quality and completeness of the over-haul I can't really say. Like probably most that take an engine to a machine shop and tell them you want a complete over-haul and your not there during the over-haul you pretty much have to take their word for it as to what was done. I guess my big mistake was not shopping around for a shop that came with good track record. For what I paid the shop one would think it would have came out as a blue printed engine. **** I did another 30 min. engine run this morning to check for bolwby. ** I could not detect any blowby at all at the valve cover oil filler cap. ** All six plugs looked about the same, all six were pretty black. ** One thing I did notice was the engine did not smoke but very little if at all until the engine was up to normal operating temp. ** I'm pretty much at a loss at this point I guess I'll wait until I get it on the road so I can put a load on everything and go from there.

Are the plugs wet black or sooty black? I am hoping for sooty black. That indicates over rich condition.

** Sorry to say all the spark plugs wettish black. ** I was surprised to see they all looked nearly the same. Looks like some oil is getting past the rings and into the combustion chamber. Guess my only hope is the rings will finally wear in???

I hate to keep harking back to this, but if there is any chance your power piston is stuck it will be causing much more fuel to be dumped into cylinders which at this point are going to naturally be sucking some oil past the rings...especially if they used chrome rings. The Rochester...had you looked inside to be certain the power piston wasn't stuck and was moving easily in the bore? Proper gasket where it mounts to the manifold (atop the phenolic spacer)? Not the gasket missing the vacuum opening? At idle that piston will have plenty of vacuum to suck it up and off the power valve. In fact, if you suck on the vacuum hole at the base of the carb (assuming there are no vacuum leaks at the airhorn) you can usually feel/hear that piston moving up and down. It will be bottoming out at the top of the airhorn, actually. It should only take maybe 8 or 9 inches of vacuum to pull it up.

Just a long shot but I have had it happen. Could there be oil left in the exhaust system from the old engine?

George

** The carb is the carb I took off my driven daily 3100 just to make sure I was dealing with a known good carb. I will check power piston just to make sure. *** The exhaust system is new stainless steel from manifold all the way back.