Which Melling Rocker Arm

[harmsway]

Hi all,

I have a stock 302 with OE cover. one of my rocker arms broke due it being not driven for many years. I've gotten a few different answers when trying to find a replacement. Does anyone know which Melling rocker arm is the same as the stock? I've narrowed it down to either: MR-886, or MRK-610.

 

[Broncobowsher]

What year is the engine? Keep in mind it may not be the same year as the Bronco as it may have been replaced sometime in the past with a different year. Or just the cylinder heads might be a different year. Was very common for machine shops to stock rebuilt heads. Walk in, swap them out, put it back together the same weekend. A lot of heads interchange.

 

[harmsway]

It's a 73. My father was the original owner, but did have the motor rebuilt.

 

[armynavy17]

I'm sure you already have, but did you take a good look at the rest of the engine?

I'm not sure I like the "rocker arm broke since it wasn't used for awhile" line...

I'd be suspicious about both the valve and the lifter.

 

[Broncobowsher]

The last broken rocker arm from an engine sitting I owned was a stuck valve. The rocker arm broke first, which is a better option than other stuff that could break (like cam shaft, timing chain, etc.)

 

[harmsway]

We hit the spring a few times and it wouldn't budge, then after a few more it seemed to break loose. We lubed it up and hit it for a good 10 minutes and it seemed to be moving more freely. Swapped out a rocker arm from another valve to see and was working ok. I may need to get the valve machined again, but seeing as how the engine was left unused for aout 5 years I'm hoping it was just bound up. Prob optimistic, but not sure which arm is the same. This is all relatively new to me.

 

[jamesroney]

Hi all,

I have a stock 302 with OE cover. one of my rocker arms broke due it being not driven for many years. I've gotten a few different answers when trying to find a replacement. Does anyone know which Melling rocker arm is the same as the stock? I've narrowed it down to either: MR-886, or MRK-610.

Hello,

I don't understand the question. The MRK-610 is a rocker kit that inludes the MR-886 rocker arm, ball, and nut. The MR-886 replaces Ford part number C6OZ-6564-B and is the standard positive stop rail rocker used on every Bronco 302 from 69-77. So are you asking whether you should buy the kit? Or are you asking if the MR-886 is the correct rocker for your Bronco?

I think my question will answer your question.

And if you have decent compression after you unstuck the valve, it will run fine. (until it sticks again...which it may never do.)

 

[Rustytruck]

might want to think about using some marvel mystery oil or a half quart of ATF in your oil 300 miles before you change your oil. I had a friend swap on a used set of heads once without rapping the valves first. cranked over the engine and bent a full set of hardened push rods. he was lucky could have done much more damage. was a used head run for a short time then stored for a couple of years. the head shop we took them to said this was very common with heads and tight valve guides sitting too long.