The Stovebolt Site Forums The Shop Area Engine Shop valve stem seals 261

hi everyone, my 261 is freshly rebuilt by a reputable shop, and i have driven it for about 400 miles now. soon after i had the engine in and running i took it to the machgine shop that did the work, i was just showing it off, i mentioned to the man that it would smoke a lil when i first started it up and he asked me if they did a short block for me, meaning that i had to assemble the head to the block myself, i told he i did put the head on and the pushrods and arms, they assembled the valves . anyways he then looked under the hood at the engine and he pointed out that i did not have an air cleaner on it, at that point i had only 35 miles on the engine and was going to get one as soon as i could find one to fit the carb, this was his gue to start in on i may have a smoking engine for ever now, i am like what ever dude, i know that smoke when start up is valve seals, common since tells me that, not debree from not running an air cleaner.

i am going to take it back to him tomorrow and talk to him again, hopefully he will try and rectify this problem of mine, since i did spend 1700.00 for the engine and head work.

what do you guys think about this smoke issue, could it be valve stem seals?

thanks
jeff

Unless you've been running those 400 miles in an Iraqi sandstorm, there's probably no damage- - - -yet. That being said, even starting a new engine without a functioning air cleaner is beyond stupid. I was in a Detriot Diesel seminar for luxury houseboat owners a few years ago when one of the participants asked the Detroit field engineer "Just how long will a Detroit engine last"? The answer- - - -"Long enough to eat 10 pounds of dirt"! Whether that's 10 hours, or 10 years doesn't matter- - - -dirt is the deadly enemy of any engine, gas or diesel.

The rings on your engine probably haven't seated yet. Get a proper air cleaner on it. and run at least 1,000 miles before you start chasing a smoking problem. If it doesn't improve, or gets worse, there's a problem. I think the smoke will probably clear up in a few miles.
Jerry

i have put an air cleaner on it after the first 35 miles, an i never driven it on any dirt road or anything like that, i just removed the head cover and pulled the spark plugs, i noticed that this head does not have valve seals on it, i used a flash light to see thru the spring and there is nothing there, just the valve stem and guide, i have looked on the net at valve seals and there are several types, my old 235 had umbrella style seals , the auto parts store sold me these felpro oring style seals today, there seams to be no seal on these stems!!!!

could there be something differant, there that i dont see? as far as a rubber seal of any type teflon rubber ect ect there not there... the number 5 plug is a lil smokey and all the others are just right, i was wondering why just that one and i started the engine to see what the oil flow over the valves looked like.
that tappet is getting a lot of oil flowing down the spring as its running.

is there any other seal even to todays standards that dont look like a standard seal, all i see is a round metal guide like thing at the bottom of the valve stem.

thanks
jeff

when you are working with oil baths and the like, my stepvan had an elbow diverting the air cleaner to the side of the engine compartment, and that was missing, like i said 35 miles on a clear day and no dirt roads, driving it easy, soo stupid i may be, none the less i was very easy on it.

jeff

The original-equipment type oil seal is under the valve spring retainer, a square-cut O ring that can't be seen without removing the keepeers and the retainer. There is also supposed to be a sheet metal cover over the top of the spring that deflects oil away from the top of the guide, along with the O ring keeping the oil fron running down the valve stem.

Umbrella-type seals, or "positive" stem seals that attach to the top of the guide are aftermarket parts, not original equipment. If you choose to install them, be sure and remove the original seals, as too much sealing can starve the guides for lubrication, and cause very rapid wear.
Jerry

one quik question, i pulled the valve shaft off the rear of the engine, since its two pieces, front and rear, i noticed that i have the oil hole on the top, so i then was looking at the front shaft and the oil holes are on the bottom, which one do i have on wrong, the oil hole to the top, or bottom. i am thinking that the holes need to be on the bottom, and if so could this be my problem with the number 5 valves having excessive amount of oil puddeling and cause it to smoke when i start it up.

thanks
jeff

superpieboy,

I'm pretty sure that the oil holes go DOWN, or to the bottom. This was how they were on earlier engines, although the later 261 might be 'new and improved'.

The interface between the bottom of the rocker and the shaft is the high wear area, as the springs are trying to shove the whole shebang up, so the oil hole is positioned to pump (drip) into this location.

Stuart

i rotated the one shaft, like i said i had one shaft with the holes up and the other with the holes down, i have them both down now and hope that this will clear up my smoke on start up.

thanks for your help.
jeff

PUT THE HOLES IN THE ROCKER SHAFT DOWN, AND I SURE WOULD
CONSIDER INSTALLING AFTER-MARKET POSITIVE VALVE-GUIDE/STEM
SEALS. I USED PERFECT CIRCLE WITH GREAT RESILTS. DON'T
EVER USE MORE THAN ONE TYPE OF SEAL ON THE VALVES AND THEY
WILL BE STARVED FOR OIL AND WILL WEAR RAPIDLY. GOOD LUCK
ON YOUR EFFORTS.

i bought a spring compressor today and changed out two seals that were on the cylinder that had a smokey spark plug, i was hoping that this would solve it. i drove it around a lil to get it warmed up and brought it back home and parked it for 10 minutes, then i started it back up and it smoked till it burned off, i dont know how many miles i have on this engine yet, but i have put two quarts of oil in it and about 45 gallons of gas.

lets say i get 12 mpg that would be 540 miles i have driven estimated, since i dont have a speedo cable yet, do i just need to drive it another 500 miiles to seat the rings,

my 235 head i have from the old engine i pulled oout of this 62 chevy had both umbrella seals and square faced o-ring style, so i dont know about that one, except i wanted to mention it anyways!

I dont get smoke when i start it cold,only when i restart from a drive, i dont know its kinda funny when it happens, when i rev it up warm and let it decline to idle it will smoke a lil, but there is no load on the engine either, i am under the influence that load and pressure is from driving and not a simple rev sitting still.

i will just throw this out there to , could it be a head gasket? i had to retorque the head down again when i first installed the head cause i was getting oil in the water only, i flushed the radiator and and have not since transfered any fluids, but can oil get into the combustion chamber thru the gasket.

thats all i have for now, at this point i will drive it for another 500 miles and see what happens.

thanks for reading
jeff

here it is almost 3 months since i last posted to this topic. My new engine stills smokes, and i am convinced that it is because i dont have umbrella style valve seals! i will go get some tomorrow and start putting them on.

my only question is that i have read several places that the square cut o-ring and the umbrella are used simultaneously (hope i spelled that correctly) lol the old 235 i pulled out of the truck had both umbrella and o-ring, it dont sound right and u would think that the valve guides would wear out faster and ppl would be quick to say dont use both, nonetheless i have read that youu use both.

thanks

jeff

I have always only used only the umbrella seal but I have never seen instructions either way (only umbrella seal vs both umbrella and regular seal). A Google search is inconclusive, except that most links state replace regular with umbrella.

Just to play it safe, I squirt the valve stems with a little oil every time I adjust the valves.

Tim

If you are refering to the umbrella seal that slips over the end of the valve guide, I don't see anything wrong with using both seals on your engine. Those seals were originally an after-market seal that was installed in addition to the O-ring at the tip of the valve. The umbrella seal became original equipment 2-3 years after its introduction as a service part to reduce oil consumption through valve guides. I think Perfect Circle Corp. developed those seals- just for historic interest. Originally you had to cut the outside diameter of the valve guide to accomidate the seals, but before long the guides were cut to fit the seals at manufacturing.

Also, for historic interest, Chevrolet stopped using the metal umbrella cap that covered spring and the valve tip when they began using valves with the O-ring seal, sometime in the mid/late 1940's, but I can't say with any certainty when that happened. Valves without the O-ring groove were still available for service parts until the mid-1950's, but were seldom used. The metal cap also contributed to valve noise.

Harvester