I'm chasing an oil leak and have the valve cover off on my 300 (FI converted to carb, supposedly from 87 according to the PO). I figured I should probably set the valve lash, but then I realized it uses hydraulic lifters. Then I noticed some of the pushrods are bent. I'm used to shimming overhead cams. So, how do you set the valve lash on the 300? The rockers just have a bolt that holds them into the head with a small plate between the rockers and the head.

Mainly, what should I do about these pushrods? I have pushrods and lifters on the way, but I don't understand why the pushrods bent in the first place.

 

And that there is the 64 dollar question?
What valves intake or exhaust or both?
This truck / motor new to you?
If yes how long has it been sitting as bad gas can make valves stick and bend push rods.
That is just off the top of my head.
Dave ----

 

As FuzzFace mentioned, sticking valves are usually what does it. The lobe pushes up on the lifter, the lifter pushes up on the pushrod, the pushrod pushes up on the rocker arm, and the rocker arm pushes down on the valve. If the valve doesn't open, something's gotta give, and it's usually the pushrod.
Gummed up lifters can sometimes do it, but it's gotta be pretty sludgey inside. The lifter doesn't drop back down when the spring closes the valve, loses contact with the lobe, and then the lobe comes back up and rams it.

You may need to pull of the lifter cover on the driver's side of the engine and inspect. Pull all the lifters and clean them (make SURE they go back in the same hole they came out of). Replace the bent pushrods, etc.
Inspect all the valve stems for broken springs.
Then, with the rocker arms off, take a rubber mallet and pop the tip of each valve to get it to move.

Change the oil and run some Marvel's Mystery Oil in with it to clean up any gunk and varnish to keep it running clean.


The rockers on that head are non-adjustable. You just torque down the bolts to... I think.... 25 ft/lbs if my memory serves.
Any adjustment is done by changing the length of the pushrod.

 

Where did you hear that "bad gas" can cause a sticky valve ? Do you hear the valve "squeaking" while driving before the pushrod goes ?

I bent a pushrod because of a stuck/sticking valve. I had switched my reserve tank that had 2year old rusty gas, and after a few runs the pushrod bent on a cold startup. I've still got the engine apart, looking for what happened.

 

4 year old thread man,the op's Last Activity: 06-03-2023 06:21 PM so it's doubt full he will see your post

 

I have not had it happen with bad gas but think the gas coats the valve (exh?) when hot and as it cools it sticks.
With todays gas they say it starts to go bad in 6 months, 2 years you are lucky it even ran LOL
Dave ----

 

Yeah, if you know the truck is going to sit, might as well add some fuel stabilizer. Not Sta-Bil red - if you use Sta-Bil, use the green (marine) version.

 

todays 10% junk starts to break down in 3 weeks,

heres a link to what happens
https://www.onallcylinders.com/2014/...-classic-ride/

 

Thanks charlie. That was an interesting read. My gas is said to be "ethanol free" at the station, and after sitting in the tank for 10 or more years here in hot-as-hell Texas/Oklahoma, it looks and smells like Turpentine - as best I can relate it to. I read once that Turpentine was made from pine tree sap from the old timers - maybe from heating and distilling - and so maybe it can be evaporated down from gasoline over time in a heated container like we have here in the south with 110 degree summers...in the shade !

 

About the only automotive fuels, these days, that seem to have a stable shelf life are competition fuels (race gas like Sunoco/CAM2 and VP) or aviation fuel. I have a five gallon can of 100 Low Lead aviation fuel that's a couple of years old and it's still OK. I used to use it in things that sat (outside, in the shed) over the winter (lawn mower, motorcycles, etc.). I never had an issue. But, as you discovered, all fuel has an 'expiration date'.

The fun part will be draining the tank of that 'turpentine' and disposing of it. Check for rust while you're at it.

 

True on the race fuel.
I had 5 gallons of 110 race fuel sitting in the trunk of the drag car for about 10 years.
When I sold the car I kept the fuel, was not going to let $50+ of fuel go if I could still use it.
It did not smell bad at all and I mixed it 50 / 50 with good fuel to use in the garden tractor.
Every time I use the tractor I go thru 4 gallons so the old race fuel went fast.
Dave ----