Jim (Dec 14 1999 7:04PM) What is the proper way to pull the plugs out of the sludge traps of a crankshaft? I don't recall ever doing it before, but I'd like to try to do it before I send this crank to the machine shop.

RE: sludge traps Jim, I think the last time I did that we drilled holes in the plugs which relieved the expansion and then pried them out. You will be amazed at what you will find in there. I never pulled them years ago and knowing what I know now, I am sure some good cranks died early because of not being cleaned out.

Bill M (Dec 14 1999 7:27PM) RE: sludge traps JIM.... a good machine shop will pull them and hot tank crank for you... but if you want to do it your self drill a hole in the middle of the plug screw in a metal screw and use a slide hammer like the ones that are used to pull dents in fenders works great

SteveM (Dec 14 1999 8:00PM) RE: sludge traps On my 1952 Merc the plugs were frozen in place. We drilled the plugs out because the slidehammer would not pull them out. After the crank was hot tanked the holes were drilled and tapped for screw out plugs.

rumble seat (Dec 14 1999 8:02PM) RE: sludge traps JIM: Drill a hole in them and install a large self tapping screw that's attached to a slide hammer and pull them out. New plugs are available, but I've seen several of them come out after a fresh rebuild. When this happens they can be put back in without pulling the engine, but it's a chore to do. Recommend tapping them with a 5/8 inch (I think) pipe tap and installing aluminum recessed socket head pipe plugs (Mr. Gasket makes them) with red lock tite. A word of caution: rebalancing is necessary when using this method. I STRONGLY recommend pulling and cleaning sludge traps or risk ruining a good crank and bearings.... rumble seat

RE: sludge traps JIM: My comment about threaded plugs was inaccurate. About 3AM this morning I realized it. I should have qualified my remarks by saying they are for a 4 inch Merc crank. And I said 5/8 inch pipe when it should be 3/8 inch NPT (which have a 5/8 inch O.D.). Aluminum socket head NPT plugs are sometimes hard to find. Mr. Gasket makes them. Their part number is #6352. Even though I use red lock tite, I stake them after they're in to assure they won't come out. Sorry about being brain dead.... rumble seat

billk (Dec 14 1999 8:54PM) RE: sludge traps On the big plugs in a merc crank I drill and tap for a 1/2-20 thread. then run in a bolt with enough thread to put on some big-holed washers and a nut. Then tightening the nut pulls them out. I've found that they are in pretty tight.

JWL (Dec 14 1999 9:08PM) RE: sludge traps First, take the torch and very quickly, heat each plug till the center is red. Allow them to cool completely. Then drill and screw for the slide hammer. Some of them might come out while you are trying to drill them.

RE: sludge traps The stock plugs are peened in place by the factory. I took a dremel and ground off the peen marks after having a problem pulling them with slide hammer. They came right out then. Look close and you'll see 3 or 4 peens on the edge to help them stay in place. I'm also going to tap mine and install pipe plugs. hotrod

RE: sludge traps jim thanks for the info on the cyl. head fire slotting. i removed the plugs in my merc crank by drilling inside the pllug in order to weaken the walls of the plug. i think i used a 9/16 drill bit.then i drilled an 1/8' hole in the bottom and using a long sheet metal screw and slide hammer, the plugs came out very easy. i then tapped the hole with a 3/8' pipe tap(a long one) and used internal hex pipe plugs with locktight. balancing is required whether you use steel or aluminum plugs.

JWL (Dec 18 1999 3:22PM) Crank plug removal Since a discussion occurred on this subject within the past week, I thought I would pass along a neat tip from a friend of mine. He told me he actually re-uses the plugs from 4'' cranks after he removes them. When I asked how he does that, he explained that he has a old 14 MM sparkplug shell on the end of his slide hammer shaft, and the inside of those plugs are the correct diameter to be tapped with 14 MM threads. Screw in the heavy duty slide hammer shaft a pull them out undamaged. Simple.

Jim Marlett 1/27/00 - 1:32:30 PM RE: Welch plugs for Merc crank Accessories I did get the plugs out of my crank. I carefully ground off the peened over areas with a Dremel tool and drilled and tapped them for whatever size all thread I had at hand. I broke them loose by turning a nut down on a washer on the all thread. This seemed to work better than starting with a slide hammer (stripped threads), but this was only good for a little ways. I then converted the all thread to a slide hammer (nut and washer on the end and a slide from a real slide hammer) and jerked them out. There was one which did not yield to this treatment. I stripped several sizes of threads out of it until I ran out of all thread/bolt/tap sizes which would fit. I ground the sides of the plug in two spots almost through (careful not to grind the crank) and collapsed it with a sharp punch. These are not ordinary brass freeze plugs. If you can't find the right things (I think Red's headers may carry them), I would suggest threaded plugs. I couldn't locate a 14mm tap quickly or I would have tried JWL's friend's trick which leaves them reuseable. Before you start, I would make sure the shop didn't already remove and the plugs and replace them. It's not really, really hard, but it's a little too much work only to find out it has already been done. If they didn't, charge on. There is a lot of junk in there.

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