Piston not firing, compression tests seem normal - 1975 Comet

Maybe you should show up too

Jim, where in Dallas are you? I stay in Rowlett when i'm working in the Dallas area. Highland Park? lol

 

I showed up for one, then planned on the next two, but it always falls right in the middle of some project or test in my wife's graduate school program.

She should be done with school next year, so we have a better chance of making it.

That, and the car is now trustworthy enough that I can drive it rather than go through the hassle of trailering it.

 

Well, check this out - I assume that this could be one of the reasons why the second cylinder isn't firing, right?









Well, I am researching how to replace a bent pushrod. The major question that I have now is what could have bent that lifter in the first place!

I went through and checked the "play" on all the other lifters. There is one on cylinder 4 that I can spin just a little bit by hand. None of the rocker arms look bent or broken. I have to go out for an hour, but when I return I am going to see if the valves on cylinder 2 will move at all.

Can you replace a pushrod without taking the head off? Am I in trouble here?

Jim

 

yes you can replace the push rod without removing the head. you have to loosen all the bolts in the rocker arm assembley so that it can be lifted high enough to put the new push rod in. just make sure when you put the new one in it is sitting in the lifter cup and not on the side or something like that. and yes you need to make sure the valve that that came off of will move. if its stuck other repairs may be needed. let us know whats going on.

 

Congrats! that was easy!

Can you see what shape your valve seals are in?

 

I figured as much...Pull the whole rocker assy loose and check all the other pushrods.You can tap the valve with a soft face hammer and see if it moves, or pry against it with something to see if it moves up and down freely. (drop the piston down the bore a bit befor you do this)could have a bent/stuck valve.If its bent...Time to pull the head.

 

Jim, ain't mechanicing fun? I love it when a repair comes out that easily. hopefully that's all it is. This forem is absolutely great for that.

Welcome to the brotherhood (P.C. and sisterhood)

 

progress

well, I think I have good news!

I was able to unbend the push rod enough to get it out of the hole - I hammered it out and placed it back into the hole to see if I had a broken lifter or faulty camshaft lobe or something, and it looks like at least the lifter is moving up and down. Good news!

I have to order 2 push rods from Auto Zone, which will take a few days. Anyone know of a better place to order parts? Online or otherwise, I'm open to all suggestions.

Scooper, it appears as though the valve stem seals are okay - I see them all, and they don't seem to be crusted over or missing. Thank heavens for that, huh?

It appears as though what I have to do now is loosen up the rocker arm assembly bolts enough so I can re-seat a new push rod under the rocker push rod cup. I tried to push the cylinder down enough to just maneuver the rocker itself in position over the existing pushrod that I straightened out just to turn it over a few times, but I was unable to push the valve spring down far enough with the tool I bought. Oh well, I have a torque wrench, and I don't have far to go with the bolts.

My luck with this stuff usually isn't so easy. Let's hope it's just that bent push rod. I wonder what could have caused that. Hopefully it was a fluke occurrence!

 

LOL looks like a shifter linkage (but smaller of course)


You might want to compare the new one to a good old one. Take it with you to check it at the store.

 

if you have a napa near you check with them. they usually have internal motor parts like push rods and rocker arms.

 

update

I've ordered two new push rods, and I think they'll be in Tuesday or Wednesday. $7.99 each, not bad, so I ordered two just in case. When these things come in, it is GAME ON!

While I have the valve cover off, are there any preventative maintenance things I could be doing to prolong the engine's life? I planned on giving each of the push rod holes a short shot of WD-40 to clean and lubricate the lifters right before I fire it up with the new push rod. Anything else you guys recommend?

I bought some de-greaser to clean up the valve cover, maybe hit the block a little bit, as it's caked with old grime and grease. I figure anything I can do to improve her self-esteem would be a positive step! I'm going to give the valve cover a good scrub, maybe some paint. Do you think a spray enamel is acceptable in this application? I know that thing gets hot, but it can't get that hot...

I'm getting excited!

 

That should take care of you. Just make sure each of the push rods are cleared out. Looks like she is on the road to recovery!!!

 

May need to check the oil return drain holes to make sure they are clear enough to let oil get back to the pan and pump quickly..it looks a little gummed up up there...btw nice job finding the bent pushrod!

 

Did you figure out which valve it goes to and why it stuck? Did you get the valve loosened up? If not it will bend the new one the 1st time you turn the engine over.
Do not try and clean up the top of the head very much if at all. Not unless you seal all the holes around the pushrods and oil drain holes. If much gunk falls through to the oil pan it can clog up the oil pump screen and there goes the oil pump.
clint

 

you can use oven cleaner on the inside of the valve cover and on the out side of the engine. just dont get it in the motor. the best way to get the out side of the motor clean is to get a can of engine degreaser and goto a spray wash car wash where you put coins in and use a pressure washer. spray the engine degreaser on let it sit for 10 to 15 min then pressure wash it off. protect the distrubtor and carb from the pressure washer. every thing else should be ok to get wet.

when ive goten a used car with sludge build up like that in it i will put a quart of atf in the oil. let it idle for 20 min to 1/2 an hour. then do an oil change. i will repeat this once a week for a month. so it gets done 4 times. the atf disolves the carbon deposits in the motor.