Looking for ideas. My 55 Special, been sitting and getting driven rarely for the last 14 yrs. History of sticking valves a few yrs ago while cranking with plugs out, made a helluva racket from piston slapping valve back to seat. It freed up and ran decent. I ran some MMO in it and hadn't had any trouble since then. Only got run in driveway occassionally until just recently. I finally got a good transmission put in it and got it registered. Been driving around town just fine except occassional tap for 30 seconds on cold start but not every time. I finally got on the Interstate for a shake-down run. After about 6-8 miles at 70mph I started hearing a rapping noise. I pulled over and raised hood, noise on driver side. After idling 5 minutes it hushed up completely. Great, I took off again and in a few miles it started again, time to head back home. It rattled until I got off highway and quit again while driving thru town. I don't know the history on the engine but it is clean inside, looks like it had a rebuild before I got it. I pulled the valve cover when cold and cranked it up, luckily it had that familiar clack on startup. I located it by pushing down on #6 exhaust rocker at valve end. I pulled the rockers and intake, removed the offending lifter and took it apart. I cannot find anything wrong with lifter, the check works and seals good and the plunger is springy when dropped in the body without a spring and DRY. All the cam lobes are good and all lifter bottoms look good. I did find the damage done from sticky valves, both pushrods in #2 cylinder were bent. One was showing 1/8" wobble. Found 2 or 3 others were "tweaked", but not on the #6 cyl. Rocker shafts have a maximum of .006-.007" wear and I assume the rockers about the same. I opened up and checked another lifter, same thing, looks to be perfect. So what say you? I have never seen or heard of one doing this only when hot at speed. Yes, my oil pressure shows more than adequate. over half way on guage. John
Bad (weak) valve spring? Maybe it's not returning all the way back up, after being compressed? In 1975 , mine dropped a valve. Ruined a head, two pistons and cylinder.
Perhaps when the engine was "rebuilt" as you think it may have been when the heads were assembled the guides were made to tight. Without proper valve guide clearance and with the vehicle not being driven very often the valves stems could be dried out(or even slightly corroded from lack of oil?) making them stick? GL Derek
Great minds think alike! I am leaning toward putting it together with some more mmo and ease back into it again. If it does it again, I will be prepared to snatch the valve cover then and there to see which one it is. Maybe it will wear in or free up. John PS: The top end is not oiling very much, rocker shafts ok but valve tips seem borderline dry. I have checked the oil galleys down to cam and the rocker shafts are clean. I slotted the front pedestal bolts a little to improve flow, hope I didn't overdo it, will find out when I crank it back up.
The failure on mine was during a cold start. After being dormant for some time. We had the air cleaner off to prime the carb with Ether (two bad ideas) With the air cleaner off, it was getting PLENTY of air. Despite our priming, due to the lack of the air cleaner, a lean condition in the carb caused a backfire and the engine kicked back. Broke the business end of the starter and knocked a piston into the valve and cracked the head. That piston and lost it's skirt and gouged the cylinder. The adjacent piston also lost its skirt. I learned my lesson from that. Always prime the engine through the air cleaner snorkel. And use a not so volatile primer. (WD 40 instead of Ether)
Agreed! I have been priming mine thru the float check hole on the side of the 2 bbl with a BIG syringe. Pain to pull air cleaner and prime it every time it sets a couple weeks.
I've got an electric pump. I just haven't put it on... Float check hole.... hmmm, that's a good idea... I spray WD 40 down the nozzle of the air cleaner silencer
After the trans and a new set of tires, priority one was a cruise control. I got that done along with a tach on the column and was testing it for a road trip when this came up. Next up will be a wiper motor that actually works, rebuild or retro electric. Then Maaco and some interior work.
Can also fill the carb with gas through the vent tube, just did this on a '71 jeep that had dry fuel lines for who knows how many years. Engine ran great until the carb ran out of gas in the float reservoir. Friend used compressed air to pressurize the tank with just an air nozzle and a rag to seal in from the gas fill tube to force fuel through the lines, worked like a charm. Only took a couple of seconds to do as well, but before he forced it all the way he unhooked the fuel line before the pump and pressurized the tank until I seen fuel squirt out. Then the carb was refilled, the line reattached and pressurized the tank for a couple of seconds and we waited for it to stall, but it didn't and stayed running until the key was used to shut it down. The Jeep has 5/16" fuel lines which made it harder to fill the length from the tank to the carb, not to mention the roller coaster ride the way the fuel lines were routed under the hood! The line came up from the frame rail to the back side of the engine, and went across the engine and down to the fuel pump and back up to the carb!! ou: Almost anything else should be a whole lot easier to get fuel from the tank to the carb. Fill the float reservoir with gas through the vent tube, start car, pressurize tank for about 5 seconds and it should stay running afterwards? If not remove line from the pump that comes from the tank and have someone watch to see when gas starts coming through, reattach line and try again. That should make it easy to start your car after is sitting for a while and the lines go dry. GL Derek
There is a good chance that the heads were rebuilt with inadequate valve to guide clearance. That happened on mine even after supplying the specs. Or there may be a bent valve stem binding. Anyhow for now run some MMO through the carb until it is real smokey, shut down and let it set overnignt. Put 4oz MMO in a tank of gas and try that. For long term use I use 4oz of outboard 2cycle oil per tank. If no joy pull the heads: check valves for bends; guide clearance; valve stem height in head. Also be sure it was not rebuilt with 56 lifters and still using 55 pushrods which will sometimes sorta work if there is enough wear in the valve train components. You can increase oiling by using a dremel to cut a shallow groove from the oil feed area (at bottom) of the rockers to the spurt hole...be sure rocker shafts are oriented correctly.
Thanks for the reply Willie. Sounds like good advice. I am hoping IF it does it again I will be able to locate which one before it hushes. The cam looks to be steel. I measured the lifters and pushrods. The lifter is 1.993 to 1.998" and pushrods are all appx 8 9/32" long. John PS: I did get my underseat heater working.
