318 engine problems 67 Coronet 500

[mightymopar]

Went for gas this AM and on the way back home just cruising easy the engine suddenly started making a banging sound, lost almost all power and started surging and backing off. Towed it home and discovered the rocker arm was making contact with the valve cover on the pass side. It is the cyl. closest to the firewall on the pass. side. The second valve from the firewall. Took the rocker arm thinking it broke, but not. No bent push rods, all are going up and down, nothing seems out of place. Removed coil wire and spun motor over and no unusual sounds or actions. Whatch ya think, guys. I do pretty good mechanically but I have limited knowledge. Sure am anxious to get goin again, the first car show is this thur. nite. Thanks, Dave

 

[bluefury]

noise...

Went for gas this AM and on the way back home just cruising easy the engine suddenly started making a banging sound, lost almost all power and started surging and backing off. Towed it home and discovered the rocker arm was making contact with the valve cover on the pass side. It is the cyl. closest to the firewall on the pass. side. The second valve from the firewall. Took the rocker arm thinking it broke, but not. No bent push rods, all are going up and down, nothing seems out of place. Removed coil wire and spun motor over and no unusual sounds or actions. Whatch ya think, guys. I do pretty good mechanically but I have limited knowledge. Sure am anxious to get goin again, the first car show is this thur. nite. Thanks, Dave

It dosen't make sense that the rocker would make contact with the valve cover.... Is there a contact mark....? I would put it back together and run it with the cover off.... and if no noise then reinstall the cover...

It's not uncommon for the pin in the fuel pump pivot to back out. The pivot arm may cock and can contact the timing chain and make a noise like that.

 

[Coronet 500]

Can you tell if it was pushrod side or valve tip that was touching? If the roker was broken or bent enough it might flop around enough to hit it,but it would make a different noise and be obvious when you took it apart, assuming they are stock stamped. I agree with run with cover off, if you have another cover you can cut the top off to stop oil from flowing onto the exhaust, just rags are ok too. A compression test might be in order to help the diagnosis and at least eliminate issues there. I'm Buffaloed on this one.

 

[mightymopar]

Found the problem. One of the push rods on the drivers side broke thru the rocker arm. I had a couple sets of old ones that fixed me up. 1.5 ratio. Hope it will hold till I can justify a new set to wifey.

 

[greenmonsta79]

I was just getting ready to tell you what you found, this had happened to me once on a 318 72 Duster!!!!

 

[mightymopar]

Found the problem. One of the push rods on the drivers side broke thru the rocker arm. I had a couple sets of old ones that fixed me up. 1.5 ratio. Hope it will hold till I can justify a new set to wifey.

 

[The Satellite Cometh]

Use the 318 as a boat anchor and step up to something more "manly"

LOL. Just kidding.

Glad ya got the problem fixed.

I got a 318 in my Satellite right now. Good to know.

 

[Patrick]

That's a fairly common problem with stamped rockers big and small block. Mopar performance has a set of heavy duty ones for under 100$. You can get them from Summit or Mancinie.

 

[daredevil]

I went thru 3 rockers with a 450 lift cam in a 72 318 b4 I got the m/p stamped h/d rockers. worth the c note. If I were you I would pull the rocker shafts and inspect the push rod cups on all your rockers with a magnifying glass.I have a boat anchor in the garage from a pushrod poking thru the cup, then the cam kicked the lifter into the valley and the pushrod fell thru the lifter hole and was twisted thru the block by the cam breaking a lifter bore and busting a piston skirt on its way to the oil pan.

 

[mightymopar]

Man that must have hurt. One other question, if I put in roller rockers will I have to do anything else like push rods or anything?

 

[daredevil]

You will more than likely have to change to ball and cup pushrods depending on the rockers

 

[mopar42668]

One other thing to watch for is these older engines have soft valve seats. Prolonged use of "un" leaded will wear the seats allowing the valve to sink into the head. If your going into the engine, have the valves ground and hardened seats installed.