Hi

I have a `85 inline six cylinder and just had two push rods that fell out of loosly tightened rocker arms and got bent up. I replaced all the rods but i am unclear about the required torque for the push rod bolts. According to the Haynes manual it says like 27 inch-pounds. They definately were on tighter than that in seems. Is this the right spec? Is it suppose to be foot-pounds? What would happen if they we over torqued since i dont want the rods to slip out again. Please help.

Thanks.

 

According to my Chilton's Manual, the 1985 300 6 cylinder engine uses adjustable rockers. This is different from some of the other engines that use the positive stop rocker mounting studs. With the "positive stop" studs, you just tighten the rocker arm stud nut to a specified torque and you are done.

The adjustable rockers use a more involved process. With them, you use the process:

1) Crank the engine until the TDC mark on the crankshaft damper is aligned with the the timing pointer on the cylinder front cover.
2) Scribe mark on the damper at this point.
3) Scribe 2 more marks on the damper each equally spaced from the first mark. You will end up with 3 marks on the damper that are 120 degrees apart from each other.
4) With the engine on TDC of the compression stroke, ( first mark aligned with the timing pointer) back off the rocker arm adjusting nut until there is endplay in the pushrod. Tighten the adjusting nut until all clearance is remove then tighten the adjusting nut one additional turn. To determine when all clearance is removed from teh rocker arm, turn the pushrod with your fingers. When the pushrod can no longer be turned, all clearance has been removed. Do this for both valves in cylinder #1.
5) Repeat this procedure for each cylinder turning the crankshaft 1/3 turn to the next mark (clockwise as viewed from the front of the engine) each time and following the engine firing order of 1-5-3-6-2-4.

Basically, this procedure is having you work one cylinder at a time and rotating the engine until the valves in the cylinder are both closed.
If you are doing this work and if you have had pushrods come loose, you probably will want to replace the rocker arm stud nuts. If not replaced, they might come loose again.

- Ron

 

Actually, many 300's came with the positive stop rockers also. My original 68 300 had adjustable, but my rebuilt 72 engine has positive stop. According to what I've read, many or most of the newer models used the positive stop rockers. You can tell by looking at the rocker studs. The adjustable stems are straight with no enlarged shoulder. The positive stop studs have a slight shoulder that is wider than the main dia of the threaded part. "I think I have this right anyway, and hope I'm not backwards"...Myself, I converted my positive stop setup to adjustable, by adding an inverted rocker nut on top of each normal rocker nut. I use the inverted nut to lock down the "main" nut, once the lash is set. One thing about positive stop rockers...The valve setup and geometry is critical. Also pushrod length. You don't want to run any valve more than 1 turn down from zero lash. If you do, you risk burning exhaust valves. If you adjust positive stop rockers, and you end up more than one turn down from zero lash, that means the head/valve work is sloppy. IE: need to adjust pushrod length, etc...By using my inverted nut trick, I can set my lash where *I* want it. Which is usually about 1/4 turn down from zero lash...Factory specs say no more than 1 turn. But I consider a full turn down as kinda tight for my tastes. 1/2 turn down is a good "average" setting. MK

 

BTW....One other comment. I always prefer to adjust my valves with the engine running. yes, it can be messy at times, but it's *much* more accurate if you want to know *exactly* where zero lash is. Setting valve lash on a cold engine is ok when rebuilding, etc, but I prefer a final check running. The problem with cold adjustment is knowing exactly where the zero lash point is. It's vague when you are trying to do it using your slimy greasy fingers to judge when the rod quits spinning, and you actually have zero lash. The average person will tend to set them too tight, which again, can burn exhaust valves if you are too much farther than 1 turn down. Setting them running, finding zero lash is a no brainer. When it quits ticking, thats zero lash. "adjust real slow, and always give a few seconds for the lifters to stable out before turning farther. " If you want truly accurate valve adjustments, I'd do them with the engine running. I set my valves on the loose side, which may cost me some high rpm power, "the valves don't open quite as far", but I sleep better at night knowing my exhaust valves are happy and cool. On the other hand, looser valves usually increase low rpm power a bit..MK