Divot worn in Valve Stem Options

[frank_c]

Hello,
I started replacing the Pushrod Tubes yesterday, and I noticed that the top of the stem of #4 intake valve has a divot worn in it from the rocker (#4 valve stem & rocker adj screw photos below). The other three valves on this bank are fine, and I haven't pulled the rockers on the other bank yet.

I purchased the car about a year ago, and here is some engine related info based on an engine build sheet, the receipts that came with the car, and what I can see:

• 2.0 with euro P&C
• Weber 40 IDFs
• WebCam #86
• Standard Aluminum pushrods
• Standard 2.0 rockers

I do not see valve springs listed on the build sheet, so I am assuming that the single spring currently installed is the OEM spring, and not an HD spring.

So, I have two goals here:

1. First is a short-term fix as I plan to take this car to the Hill Country Rallye in Mid-March - so no big tasks that might go off-script. Car will be driven 600-700 miles during this event.
2. Second is post-rallye where I plan to move to 1.7 rockers with swivel-feet, chromoly PRs, set valve geometry, and whatever else folks might suggest while I'm in there (solid rocker spacers?). And can this valve be saved? Am I looking at pulling the head to either repair or replace the valve?

For the short-term goal, if I leave things as-is this will obviously make setting the valve lash on that valve challenging. So I would like to hear folks' opinions on the use of a Valve Cap on that one valve (and any others with similar issue I may find). If I install a cap, should I replace the rocker adjustment screw for that valve as well? Or is there any other short-term option that does not involve pulling the head? Or just run it as-is knowing that #4 intake may not be getting full lift, and tear into it after the event?
Example valve caps: https://www.cbperformance.com/product-p/1522.htm

I also have some questions regarding the long-term fix, but I'll leave that for another thread when that time comes.





Thanks,
Frank

[Ninja]

I'd rate that as toast...

Unless you know the age of the valve springs, I'd replace them before I ran it again.

On that I'd expect R+R heads, valve job, new valves (as required, auto change any sodium critters), springs, retainers, keepers, swivel feet adjusters and guides as needed.

Pull heads, clean the crap out of the combustion chambers, and look for cracks before spending any money. Exhaust side near plug is the usual propagation point.

It MIGHT be possible to machine the damage off of that stem, but it looks trashed to me.

Put it back together as is and drop a valve at 4500 RPM...


I've got a box stock 31K 914 that runs OK and I won't run it again until I replace the springs/retainers/keepers. Some of mine sat open (in compression) for 33 years.

Too many resurrection threads on here have been terminated over dropped valves.

[Ninja]

I would not use steel pushrods in this application.

There are two levels of upgraded aluminum pushrods available. You need the cheaper version.

Most of the time the steel rods require a cold adjustment of zero lash.

In my book, this is a recipe for disaster.

The cams base circle has to be DEAD NUT perfect and if the valve or the seat wears AT ALL the valve is now held open on base circle.

Burned valves will be the final result.

I tested my stock 31K mile stock 914 camshafts base circle and came up with a variation over .002"!

If you have .006" valve clearance this variation effectively means nothing and is not service affecting.


As the engine heats up this clearance increases when steel pushrods are used so zero cold does not mean zero hot but it's still a BAD idea.

There is no margin for error with zero lash. (IMG:style_emoticons/default/ninja.gif)

[frank_c]

Quick update:
I pulled #1 & #2 rockers tonight and all the valves on that bank look good (whew). So, maybe I should have asked this question at the start - what might have caused this issue on just this one valve? Insufficient oil getting to it? Valve stem not hardened properly? Too much valve lash?

Regarding the valve stem caps, I looked at the valve more closely, and it appears that the length of stem exposed above the keepers is shorter than the height of the caps. I'd have to get measurements to be sure, but I certainly wouldn't want the cap pushing down on the keepers instead of the stem.

@Ninja ,
Thanks for your replies. I'm aware of the zero lash requirement with steel pushrods (and the inherent danger of such), but I suspect most folks will recommend that I move to heavier valve springs due to the non-std cam, and most everything I've read states that if HD springs are used, it is best to also use steel/Chromoly PRs as the AL ones may bend.

If/when I go through the effort of pulling the heads, then I would simply replace the valve (probably all of them) at that point. Of course this quickly becomes a slippery slope because I have a displacement increase on my future to-do list, and I would be very tempted to just do the bump while I have the engine that far apart.

[Jack Standz]

Thanks for your replies. I'm aware of the zero lash requirement with steel pushrods (and the inherent danger of such), but I suspect most folks will recommend that I move to heavier valve springs due to the non-std cam, and most everything I've read states that if HD springs are used, it is best to also use steel/Chromoly PRs as the AL ones may bend.

There are better options these days. For example, you could run beehive springs which is a way to control valve action without overly high spring pressure or dual springs. If this is for you, do some research as there are different beehive springs available and you will need to perform some customization.

But, if you go with HD springs or dual springs, you can still run aluminum pushrods (we run them on our 2056 with HD springs and plan to do so on our 2615 project motor which will use a cam similar to yours). There are different types of aluminum pushrods. Some "standard", some quite heavy duty pushrods, tapered aluminum pushrods, etc.

BTW there are 911style adjusters available for 2 liter rocker arms, so no need to go to 1.7 liter rocker arms.