The Stovebolt Site Forums The Shop Area Engine Shop leaky 261

A couple of years ago I bought a rebuilt 1959 261. I finally got around to firing it up and it started easily and ran well on a stand . I noticed before starting the there was goop of some sort oozing out around the crank and main bearing cap . I cleaned it up and then fired it up using a flex plate instead of a fly wheel so as to see if the seal was leaking, it was . About one drop a minute for around an hour, and when I was done there was more goop and some solids which I suspect was parts of the rope seal.
I plan to open it up to see whats going on and want to know if I'd be better using rubber seal made by Best or another rope seal or what ever else one might suggest short of machining it to accept a one piece seal.

Thanks

JOHN

What was da "goop"? Maybe the seal dried up from sitting a few years? At least its on a stand and should be easily serviced as opposed to being in a veh..

If it is a 261 from a 59, ditch the rope seal, Best Gasket makes a neoprene lip seal and they work, my 261 rebuilt last summer, couple hundred miles on it been in the garage three months not a drop on the floor. https://bestgasket.com/rear-main-seals/
Pricey but will take care of the problem, installed about 4 in the last couple years on 55 and later 235 and 261s.
Steve

Once you get the main bearing cap removed where you can inspect the sealing surface of the crankshaft, check for grooves or rough spots. If the surface isn't smooth, any seal you install is going to get torn up in a very short time. Neoprene seals in particular are subject to damage from a rough crankshaft surface. National Seals, SKF, and a few other companies make a 3 7/8" Speedy-Sleeve that can be installed on a stovebolt crankshaft, but the shaft would probably need to be out of the engine to get a good installation.
Jerry

Thanks Jerry , I got it on a engine stand and the fluids drained today , tomorrow I''l pull the pan and main bearing off and see what I see .

When you get the seal straightened out you might do a search on the correct way to install a pcv valve. All my machines (forklift, gas compressor, generator) didn't leave big pools of oil but all were nasty dirty and with a few drips per hour of running time. The pcv helped a lot in keeping them clean.

This motor is out of a two ton and came with a pcv system along with a bypass thermostat housing and full flow oil and filter.
I got the rear cap off and found the gap between the two seals at about two oclock with the motor upside down and about a 1/8 th in. gap , lots of stuff in the pan which seems
to be parts of the rope seal and a little bluing on the crank where the seal seats I'm guessing the seal did some rotating along with the crank. I see no damage other then the bluing
I also noticed the timing cover has two bolts from the inside and read this could be changed, would tapping the cap to a one size larger bolt be advisable so as to have all the bolts on the outside??? I'm guessing I'll have to remove the cover to lift the crank far enough to reinstall a seal .

John

That myth about tapping the main bearing cap assumes you're going to be replacing the front seal or the timing gears frequently. I see no point in doing it. The reason for doing things that way in the first place is a holdover from the 216 engine, when it might have been necessary to adjust the main bearing clearance with shims, and having the lower timing cover bolts accessible from the crankcase side made it simpler to remove the front main cap. Some designs of front motor mount made getting the bottom bolts out of the timing cover from the front very difficult. I've always been able to lower the crankshaft sufficiently to change a seal by simply loosening the other main caps. Since your engine is on a stand, it might be necessary to wrap a strap or an old fan belt around the crankshaft and lift it a little with an engine hoist.
Jerry

Thanks Jerry , then I'll leave well enough alone . So I take it there is no need to remove the timing cover , I was curious if lifting the rear of the crank would have a negative effect on the timing gears.

John .

It's only necessary to lift the crankshaft a little to relieve the pressure on the seal. Then a Lisle "Sneaky Pete" kit can be used to remove the old seal and install a new one. I'd choose the "Best Gasket" seal, either the rope or the new lip seal they introduced recently. They're expensive, but they seem to work well. When the old style rope seals with the asbestos fibers became unavailable, replacing that style of seal became a pretty risky process with frequent failures.
Jerry

The pan gasket I removed was a one piece rubber one , I've found the Best rubber lip seal on line but not the one piece gasket, any ideas??

John

Couldn't find a best gasket seal in Canada so I ordered one from Vintage gasket , should get it next week .

John

Well I got my new rubber best gasket rear main seal and started to install it but noticed they seemed to be a touch to long , about a 1/16 of an in. the portion in the block seems to be flush with block at both ends but the portion in the cap while flush at one end sticks out by about a 1/16th at the other . Is this normal???

Also while I had the pan off I noticed the caps on the connecting rods had been ground off a bit but not evenly on the ridge between the bolts on 5 out of 6 caps . Also the heavy parts of the crank had similar grind marks. Is this an attempt at balancing ?? The motor was a fresh rebuild done about 3 tears ago but never used .
I bought it privately but it was done at a machine shop which I don't have info on so I'm on my own .

John

1959 261 used precision bearings that did not need shims.

Maybe someone ground caps to make-up for bearing wear?

Wait to hear from others regarding this jackleg-mechanic speculation.

It's not uncommon to find grinding marks on weight-matched rods. The rebuilder uses a fixture to hang the rod by the small end and weight the big one on a triple-beam scale or a digital one. Then the rods are weight-matched to the lightest one, and they're swapped end for end and the small ends get the same treatment. Most inline six crankshafts are very close to properly dynamic balanced, but some shops spin the crank without bob weights and do a final tweak to eliminate any vibration. It sounds like somebody has gone to a lot of effort to do a very good buildup job. I weight-matched rods on the race engines to a tolerance of 1/10 gram. A dollar bill weighs one gram.

I usually like to rotate a lip seal a little so the parting lines of the seal and the block/cap junction aren't at the same place. Best Gasket rope seals are intentionally over length, and must be trimmed to fit. Don't try that on a lip seal!
Jerry

Again thanks Jerry, I will now continue putting it back together with confidence .

John

Well I got the motor together with the new best gasket rear seal and although I haven't put it under load yet I've run it a few hours without a drop out of it , also it turns over
easier so I guess the other seal was to tight which would explain the bluing on the crank where the seal sat .

John

The seal is purposely long so the parting lines will crush together to seal. Best advises against any sealant between the two seal ends. I have installed the seal both ways with it even with the block and the last couple of times offset the seal about 1/4" or so. both ways worked out well.
Just put together a 235 for a buddy and it too is without a drop on the floor, although the soft plug in the rear of the engines main oil gallery was leaking like a sieve. Appears the machine shop installed it wrong and damages the soft plug on installation. I ended up tapping the main oil galleries, IMHO there should be no soft plugs used where there is oil pressure. The machinist agrees with me when I told him I had to yard the engine out because it was behind the bell housing. You just cant remove the bell housing simply in a AD truck, such is life, live long enough you learn all these tricks others had learned years ago and died without passing them on. This is why you listen to old timers when they speak about such things. The wisdom learned in their years of experience is without a doubt one's best resource.

Steve

The only reason the manufacturers used cup plugs to seal off oil galleries was the "baby chick" concept- - - - -they're "CHEEP- - - -CHEEP- - - -CHEEP!"
LOL!
Jerry

Good one Jerry.