Valve Seal replacement

I didn't want to Pirate the thread posted by ROXJ, even though this is simalar. My '75 with a 285 sometimes smokes on start up, but as it warms up, the smoke goes away,, good compression, acceleration, smooth running etc, It sits for a long time between using it, and I am thinking that itis my seals,,, How much of a job is it to replace the seals??

 

I have not done this job ... but I know it can be done in the car.

The usual (easier) approach requires an air compressor. Buy/make a fitting to go in the spark plug hole, and pressurize the cylinder to keep the valves seated. Then use the valve spring compressor tool, and remove the springs, retainers and keepers. R&R the rubber seal. Put everything back, paying close attention that the keepers are properly seated. I've read that you can also use a length of rope - feed it into the cylinder through the spark plug hole leaving enough hanging out so you can retrieve it, and turn the engine to squish the rope against the valves.

 

What Tim said.
I’ve done this several times in vehicle and the air compressor hose to spark plug adaptor is the way to go. Never heard of the rope thing though, think I’ll stick with the air compressor method.
A couple of helpful hints though.
1. If you’re having troubles getting the spring retainer to let loose take a small hammer and tap at the edge of the spring retainer. Sometimes the locks get wedge in the retainer so tight they don’t want to let go. Tapping around the edge of the retainer helps to break them loose.
2. Once reassembled remove the air chuck to spark plug adaptor and take a soft faced mallet then pop the end of the valve stem several times. Hit it straight down so the valve opens and the spring slaps it back shut again. This makes sure the retainer and locks are all in place and bedded in so that they don’t go flying apart the first time you start your engine. Just make sure you’re hitting straight in line with the valve stem as hitting it on the side can bent a stem.

 

I've used the rope trick to break loose the crank pulley on old Gravely engines but not for holding valves. I see no reason it woudn't work, though. Use very limp rope like the very fine strand braided mooring line stuff. It'll fold around and fill better than stiff rope.

I have done the air compressor method and it worked well. I'd still turn the engine to TDC when working on a particular cylinder just in case you pop the valve off its seat. It'll keep the valve from dropping the whole way into the cylinder, requiring you to pull the head.

 

I second valve seals as mine has a new pvc and great compression but still smokes on start up and while descending long hills on the trail. Ill be taking care of this pretty shortly and will let you know how it goes.

 

In the next few weeks depending on how work goes anyway.

 

The rope trick works good. I've used it myself. One thing though, if you do use the rope, turn the engine over by hand to bring the cylinder up on TDC. Using the ignition could cause more problems.

Walt

 

My 1973 CJ5 with the 258 only has 37,000 miles but sat in a barn from 1981 -2010. It burned a quart of oil every 150 miles, plugs would get loaded with deposits until they misfired. Mostly start up/deceleration. I changed the valve seals the other night. About a 4 hour job start to finish. I used the air compressor method. Trickest part was unsticking the keepers. Had to put the end of an 18" 3/8 extension on the holder a whack it with a hammer to come lose. The results have been impressive. No smoke on start up, deceleration and havent burned any oil. It's a PIA, but highly recomend.

 

You shouldn’t have to go too crazy to get the locks to let loose of the retainers. Using an overhead spring compressor pull the spring tight and pop the handle of the spring compressor with a soft face mallet or dead blow hammer (my favorite). If you’re hitting it hard enough to open the valve against the air compressor stop, take a small hammer and tap at the edge of the retainer. Usually just a little tap at one edge then the other is enough to break them loose. If you can’t get them to break loose doing that then it might be time to consider taking the head off and hauling it to a machine shop.

 

I tried two different brands of spring compressor thinking the same thing, but alas the keepers were not budging. However hard I hit them, it worked on all 12 valves with no damage. Went back together fine and is running better than ever.

 

That’s the main thing right there. You just don’t want to whack it so hard you damage something.:tea: