john compono Posted April 27 Share Posted April 27 Guy's I just completed my 55 buick century crankshaft because I had a bad leak coming from the rear main seal after changing 2 seals prior. Believe it or not after putting the crank back in with a new rear main seal it still LEAKS ! can't believe it. Rebuilt crankshaft and new rear main seal and it still leaks. Anybody have an idea why it would still be leaking from there ? everything else is dry as a bone on the engine. Link to comment Share on other sites More sharing options...
Mike "Hubbie" Stearns Posted April 27 Share Posted April 27 Sounds like either the wrong seal or an undersized crank journal at the seal. Mike Link to comment Share on other sites More sharing options...
c49er Posted April 28 Share Posted April 28 (edited) Rope type? I would only use the old stock type rope seals...not the new ropes being offered. Crank out...use a packing die the same size as the crankshaft seal portion diameter of the crank. Spend plenty of time carefully working packing down the rope into the block and the cap. The ropes need to be worked in so as to rub slightly 100% 360 degree's around the crank seal surface. Yet not be so tight as to cause excessive drag on the crankshaft with no rods connected. I fab up, use what ever tooling I need to be sure the ropes properly fit the seal retainers to crank or the block groove to crank. If possible I will use a .002" feeler gauge and check to see if it slides between the rope seal and shaft...better not! Many style rope ends usually need to stick up .010"- maybe .015" max and not be frayed.... they must be perfectly cut straight. When the cap is is installed the ends will be compressed and not caught between the mating surfaces. Main cap side seals have to be carefully packed tight too. A lot of Buicks used a stiff wire forced into the side seals to expand them tight to prevent leakage. Image is of a MoPar style rear main seal...external retainer type rope seal being formed..then test fitted to the block and crank...to three to four test fits for final assembly. Rope rear main seal jobs are slow as she goes..take all the time and effort needed to prevent leakage. Edited April 28 by c49er (see edit history) 1 Link to comment Share on other sites More sharing options...
john compono Posted April 28 Author Share Posted April 28 Thanks, c49er. like I said I just had the crank redone but I did use a modern rear seal. so I just found a brand new N.O.S. rear main original rope seal and I'm going to replace the one that's in there now. Hopefully this works. Will keep you posted and thanks for the info. Appreciate it. 1 Link to comment Share on other sites More sharing options...
john compono Posted April 28 Author Share Posted April 28 Mike HUBBIESTEARNS like I said I used a new modern made seal so I got the original rope and going to try that one. Hopefully it works. thanks. 1 Link to comment Share on other sites More sharing options...
john compono Posted April 28 Author Share Posted April 28 c49er hopefully changing to the rope seal will do the trick. thanks. Link to comment Share on other sites More sharing options...
c49er Posted April 28 Share Posted April 28 I did read up on the 322 Buick rear rope seal in Motor's book. Thry only state a way to replace only the cap rope and to cut it flush. I stated .010-.015...probably too much stick out on a firmly properly packed rope. Flush to .005"...tough to get .005" but meaning to just make sure rope ends push tight together. The upper rope can only be serviced by removing the crank of course. Oil the rope too. Side cap gaskets supposedly were cork. The only Buick rear seal I did years ago was a 1969 350 with the rubber and steel pin side gaskets. Good luck! Link to comment Share on other sites More sharing options...
Frank DuVal Posted April 28 Share Posted April 28 Funny, I always used an oiled hammer handle with good results... Yes, cut rope square with a sharp single sided razor blade, left slightly above the metal. I guess I have been lucky, never rebuilt a Chrysler with a rope seal.😉 Link to comment Share on other sites More sharing options...
john compono Posted April 28 Author Share Posted April 28 thanks c49er. Will keep you posted on how it turn's out. thanks again. Link to comment Share on other sites More sharing options...
john compono Posted April 28 Author Share Posted April 28 Thanks frank DuVal seem's like to cut the rope straight is important. Link to comment Share on other sites More sharing options...
c49er Posted April 29 Share Posted April 29 Some crankshafts also have a machined oil slinger thread or groove to help pull weeping oil towards the crankcase side drain back hole in the main cap. It has to be open. Link to comment Share on other sites More sharing options...
john compono Posted April 29 Author Share Posted April 29 c49er what I'm going to do before I change the seal is drop the tranny and let engine run, this way I can see everything that's going on and maybe find why it's leaking. I'll keep you updated. Link to comment Share on other sites More sharing options...
c49er Posted April 29 Share Posted April 29 That is the right thing to do...positively find the starting place of the leak...maybe using oil leak dye..that will pin point the leaks origin. Link to comment Share on other sites More sharing options...
EmTee Posted April 29 Share Posted April 29 Refer to @old-tank's method here: http://www.buickrestorer.com/rearseal/rearseal.html 1 Link to comment Share on other sites More sharing options...
DonMicheletti Posted April 29 Share Posted April 29 One other leak path is the seal at the sides of the bearing cap. Getting that right can be difficult. I hate that part of the job. Link to comment Share on other sites More sharing options...
john compono Posted April 29 Author Share Posted April 29 Yes c49er I will definitely use the oil leak dye. thanks. I'll keep you updated. Link to comment Share on other sites More sharing options...
john compono Posted April 29 Author Share Posted April 29 Thanks DON I'm going to check that also. Link to comment Share on other sites More sharing options...
playswithbrass Posted April 30 Share Posted April 30 Back in the 70’s worked at a Chev/Olds dealer. When I had an Olds With a leaking rear main,rope seal .The trick was to use a flat punch and hammer the rope up into the top half of crank,then on the cap cut the rope long enough to go up into the void left by you hammering the seal.Worked really well because you can never change a upper rope seal with crank installed Link to comment Share on other sites More sharing options...
john compono Posted April 30 Author Share Posted April 30 Thanks playswithbrass. Going to try different methods. One of them has to work. Link to comment Share on other sites More sharing options...
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