Redmond49 Posted December 21, 2013 Report Share Posted December 21, 2013 The engine in my '49 plymouth has a knocking sound; I had my rose colored glasses on when I bought it and let the seller convince me it was a valve or lifter. My mechanic rules out the rods, and tells me he thinks the knocking is due to a piston skirt, and that fixing this is going to require pulling the engine and rebuilding it. That would also provide the opportunity to deal with oil leaks and a freeze plug that has a small coolant leak. He told me that if I'd like to enjoy the car a while and save up my pennies, he thinks it would be OK to drive it through the next summer and then tackle the rebuild next winter. I'm wondering if this is "piston slap" and whether you all think with a knock-in-the-block it would be ok to postpone and enjoy. Quote Link to comment Share on other sites More sharing options...
greg g Posted December 21, 2013 Report Share Posted December 21, 2013 Hows the oil pressure? 1 Quote Link to comment Share on other sites More sharing options...
54Illinois Posted December 21, 2013 Report Share Posted December 21, 2013 I agree on driving depending on oil pressure. Lots of cars knock or ping, and last for years! Quote Link to comment Share on other sites More sharing options...
Redmond49 Posted December 21, 2013 Author Report Share Posted December 21, 2013 He said it has good oil pressure. Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted December 21, 2013 Report Share Posted December 21, 2013 Don't rule out a wrist pin. But no matter what disassembly will tell the tale. Depending what your long term plans are and how much money you want to drop in the car repairs could possibly be done without engine removal. Quote Link to comment Share on other sites More sharing options...
William Davey Posted December 21, 2013 Report Share Posted December 21, 2013 My opinion - worth every penny. Noises like this do not get better with time and use. If it was mine, I'd tear the engine down now and fix everything before something catastrophic happens. An overhaul is much cheaper when cylinders have not been scored, rods/wrist pins have not broken etc. Also know that if my predicted failure occurs it will happen at the worst possible time and place. JMHO. Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted December 21, 2013 Report Share Posted December 21, 2013 he says good oil pressure....is the gauge not working now...??? closer evaluation of the engine's vital statics are in order to determine how deep you want/need to take the repairs.... Quote Link to comment Share on other sites More sharing options...
Redmond49 Posted December 24, 2013 Author Report Share Posted December 24, 2013 The gauge work, it seems to hold steady right about 40 on the gauge. Quote Link to comment Share on other sites More sharing options...
Tom Skinner Posted December 24, 2013 Report Share Posted December 24, 2013 Tyson, For God's sake man, buy a service manual, and fix it yourself. If its one bad cylinder Piston, Rings and Gaskets is still only a hundred dollars in parts or so. Why take any ones word for it, these cars are easy peasy to work on - borrow a few tools if need be. Good Luck. Tom 1 Quote Link to comment Share on other sites More sharing options...
DutchEdwin Posted December 25, 2013 Report Share Posted December 25, 2013 (edited) Tyson, I hope my case isn't the same as yours.... When I bought my car (long time ago and I had no idea what I was going into then) The engine sounded right and oil pressure was good. After I did some repairs and took it on a 10 mile test drive. I came to a stop after 3 miles, heavy engine knock and suddenly no oil pressure. After inspection I wished the previous owner stopped at first hearable engine knock. My crankshaft was worn for over 0.04 in. and the cam was almost round. Don't say it's the same at you engine. My problem were clogged oil channels all over the engine. This is what it looked like on the inside. Now, all moving parts (exept for the rockershaft and rockers) are replaced and it runs beautifull. Only I wished I had changed the freeze plugs then. Now two are leaking . So unless your sure, do the engine repair. Could save a lot of money. Just to add, it's true what Tom is saying, it's easy to do when you have some tools (invest in them) a service manual and this forum. Good luck, and do not forget, it's fun and rewarding too. Edited December 25, 2013 by DutchEdwin 1 Quote Link to comment Share on other sites More sharing options...
Redmond49 Posted December 25, 2013 Author Report Share Posted December 25, 2013 (edited) Thanks for the comments, all. I do have the shop manual. I took the car out with my dad today for a listen and although it was knocking slightly when I started it, by the time we came back from our drive, it had stopped knocking completely. We got out out a couple times on the road and the knocking sound seems to be gone. It sounds sort of like a sewing machine now. Perhaps it was a stuck valve that came unstuck? Edited December 26, 2013 by Tyson Quote Link to comment Share on other sites More sharing options...
Joe Flanagan Posted December 26, 2013 Report Share Posted December 26, 2013 Might be a good idea to get your hands on a mechanic's stethoscope and at least get a general idea of where the noise is coming from. Quote Link to comment Share on other sites More sharing options...
Tusler 49 New Yorker Posted January 4, 2014 Report Share Posted January 4, 2014 Mine does the same type of thing. When I firt start it cold if the eng races even a little I can hear a knock (like a Main Bearing) I found running the straight 30 w oil and starting the engine only once a week, sometimes longer the oil runs out of the bearing and it is dry. So I put some Lucas oil treatment in it, the stuff is a little sticky and stays on the bearing longer and seems to have fixed the knock for now. What is sad, is I know how to rebuild this L8 but where my wife decided to live teh people scream if i change my oil in my garage. Anyway I don't hear anyknock anymore but I am not counting my chickens yet... Quote Link to comment Share on other sites More sharing options...
busycoupe Posted January 4, 2014 Report Share Posted January 4, 2014 My car had a slight exhaust manifold leak that would make a ticking noise when the engine was first started, but would stop when the engine warmed up. this is a possible source for your noise, and has been suggested, a mechanics stethoscope will help locate it. Quote Link to comment Share on other sites More sharing options...
BigDaddyO Posted January 4, 2014 Report Share Posted January 4, 2014 (edited) Use a broom handle 3 or 4 feet long as a stethoscope, even a long screw driver. Stick one end on the block, the other end in yer ear, but not like the idiot in the 'Wax Vac' commercial. Obviously a little common sense is called for here. My dad told me not to put anything in my ear except my elbow. http://www.youtube.com/watch?v=ONvpWa-8moY Edited January 6, 2014 by BigDaddyO Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted January 4, 2014 Report Share Posted January 4, 2014 3/8 diameter wooden dowel 3 or 4 feet long works well as a stethoscope, even a long screw driver. Stick one end on the block, the other end in yer ear. My dad told me to never stick anything smaller than your elbow in your ear. Quote Link to comment Share on other sites More sharing options...
_shel_ny Posted January 4, 2014 Report Share Posted January 4, 2014 Can't go too far wrong with this http://www.harborfreight.com/mechanics-stethoscope-41966.html Quote Link to comment Share on other sites More sharing options...
Labrauer Posted January 5, 2014 Report Share Posted January 5, 2014 My uncle used a stick several times. He was a mechanic for a Chrysler dealer but had his own garage at home that he always fixed peoples cars. I have seen him use that stick and has had very good luck with it before he got the real thing. I on the other hand tried using one and can't tell crap just hear the engine running. Oh well I guess it takes some talent knowing what to listen to. Quote Link to comment Share on other sites More sharing options...
Tusler 49 New Yorker Posted July 8, 2014 Report Share Posted July 8, 2014 Just to update, I had a shop open it up and the #8 rod bearing showed the wear, it was the one knocking when I first started it, and the engine stillhad good oil pressure. I also found broken top rings on #1,2,&3 pistions. He honed the cylinders, I replaced all the rod bearings and rings, checked the valves and the head for flatness, all was ok so we put new gaskets in it and called it good.Even though I had broken rings it still ran ok and did not smoke...amazing engine. I watched a old Chrysler tech video about oil pressure and they said don't even worry about idle pressure as long as there is some. Above 30 I get 40lbs constantly so it'll last a while I guess. 1 Quote Link to comment Share on other sites More sharing options...
ledfootslim Posted July 8, 2014 Report Share Posted July 8, 2014 Yeah,my grandad was driving a 78 Thunderbird for a few years, and he noticed some engine noise. It was holding good oil pressure and still running good. A few years later he started to pull the engine and rebuild it for a truck, and found that two, yes I said two, of the piston arms were broken! Not trying to cause goosebumps, but I am always a little over zealous in quickly finding and fixing pings and knocks! :-) Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted July 9, 2014 Report Share Posted July 9, 2014 two, of the piston arms were broken! What is a piston arm? 1 Quote Link to comment Share on other sites More sharing options...
Lumpy Posted July 9, 2014 Report Share Posted July 9, 2014 (edited) I would guess the rod, but I never heard of an engine in use with two broken rods. Cracked perhaps? Or cracked wrist pins? Good question. Broken piston rings...revving up a cold engine will turn that trick real fast. Wow, that was one dirty Poly...seems every Poly I've ever met was like that inside. Now my question.....Dutch, you rebuilt an engine and did not replace the core plugs??? Or flush out the water passages? k. Edited July 9, 2014 by Lumpy Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted July 9, 2014 Report Share Posted July 9, 2014 (edited) I would guess the rod, but I never heard of an engine in use with two broken rods. Cracked perhaps? Or cracked wrist pins? Good question. Broken piston rings...revving up a cold engine will turn that trick real fast. Wow, that was one dirty Poly...seems every Poly I've ever met was like that inside. Now my question.....Dutch, you rebuilt an engine and did not replace the core plugs??? Or flush out the water passages? k. you can guess...but I am still waiting for clarification.....maybe all the ones I have keep them well hidden in the sleeves Edited July 9, 2014 by Plymouthy Adams 1 Quote Link to comment Share on other sites More sharing options...
Dave72dt Posted July 9, 2014 Report Share Posted July 9, 2014 I'll guess the piston skirts. Broken rods and still running sounds unlikely. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.