Rocker Noise

[FirstEliminator]

    Hey guys,

    After  year or so, I finally got the 445 stroker assembled and into the Comet. It has a Survival Comp cam 236/242@ .050 hydraulic roller. The engine was started, timing was set and the initial carb adjustments were made. If you run the engine around 1500 or so, you can hear what sounds like rocker tapping fading in then fading out. We pulled the valve cover and checked to see if there were any loose pushrods as each lifter were on it's base circle. One seemed to have just a tad of play. For the heck of it, we re-adjusted each rocker. Except this time we went to 3/8 of a turn preload instead of 1/4 turn. I didn't hear the noise as much. However, after road testing the car today, cruising along I would sometimes hear the rocker noise fade in and fade back out.  In the past I've never had this "problem". But, I've never used a hydraulic roller cam or a cam with lobes quite this intense.
     One of the things that I question is the rocker oiling. The tech at T&D said if I have oiling through the pushrods, I should block off the oiling through the pedestals completely----which I did.   We used an old chrome FE valve cover to cut a big slot into---about 2 1/2" tall and almost the length of the valve cover. With the engine idling using the windowed valve cover I was able to see that we had what appeared to be a sufficient amount of oil coming through the rockers. Towards the low side, the back of the engine, there was a steady flowing stream of oil going down to the drain back hole. Although it looks like enough, I would like to take a video of the amount of oil coming through for a 2nd opinion. If the engine were running in 12 second intervals, I would think the amount is sufficient. Yet, this car is going to be doing a lot more cruising around the streets which makes me question if there is enough oil to sufficiently cool the valve springs.

    Hopefully I can find time to take the movie of the oil flow this weekend.

   thanks,
     Mark

[jayb]

You don't need to worry about cooling the valve springs in my opinion, unless you are running at high RPM for extended periods.  The springs will be just fine with minimal oiling at 3000 or 4000 RPM.  I restrict oil to the heads on all my FEs except the SOHC engines, and have never seen an issue.  The amount of oil you are describing seems just fine.

Hydraulic lifters are funny about the preload in some cases.  If you had an improvement going from a 1/4 turn to 3/8 turn, you might try going to a full 3/4 or 1 turn and see what effect that has. 

[FirstEliminator]

Hey Jay,
  Thanks for the quick reply. I guess I was a little cautious with putting too much preload on the lifters. I've never experienced what can happen with too much preload. But, I've heard the lifters can pump up at higher rpm's causing a valve to not close properly----is there truth to this myth?


   thanks,
      Mark

[jayb]

Hydraulic lifters can definitely pump up past 5500 RPM or so.  If they do, they will hang the valve open.  And it can hit the piston if you don't have sufficient piston to valve clearance.  By adjusting the preload so that you have a minimum preload on the plunger in the hydraulic lifter, you minimize the amount of pump-up that can happen.  So it is good to run at a minimum preload.

However, if you look at the actual dimensions involved, the difference between 1/4 turn and one turn of preload is pretty minimal.  Most FE adjusters will move about .040" for one full turn.  So at a quarter turn of preload, you are at .010", which is the amount that the lifter can pump up (unless you blow the clips out the top of the lifter, but that's another story).  Add in the rocker ratio and a pumped up lifter means that you will lose .0176" of piston to valve clearance.  You've probably go way more than that.  If you go a full turn on the preload, you will lose .040" X 1.76, or about .070" of piston to valve clearance.  You've probably go way more than that too. 

Bottom line is that running up to one full turn of preload is not real risky, even in a lifter pump-up situation.  A lot of times the lifter pump up deal hurts guys who are running non-adjustable rockers; they might have .100" or more of pre-load but never know it because the rockers aren't adjustable.

[FirstEliminator]

    Is it a possibility that links on the roller lifters can make some ticking noise at cruising rpms?