Stock E31 Head Factory Rocker Valve Guide "Lash Pad" Thickness

[jonathanrussell]

You have a beautiful car.

Those rockers are a disaster. Almost looks like the builder checked one wipe pattern of one of the good ones and then assumed the rest were okay. Equally concerning is the wear, gauging, ripples, etc on the rockers. Makes me wonder what the cam lobes look like. Makes me wonder whether all of the seats were replaced, the lash was initially set, and then no one ever re-checked the lash again. As the new seats become broken in the stems rise. When the stems rise the lash shrinks...or goes away. Was the lash severely low or zero when you checked? I wonder too whether zinc oil and molly lube were used. Great catch and decision to replace everything. Again....I find myself wanting to see photos of the cam lobes. Also, were the valve stem tips pounded any?

Or, could the valve springs be binding at full lift...causing the wear? Seems like there would be other side effects though.

Best of luck and again, beautiful car.

[Chickenman]

I'd like to see the cam lobes as well. Those are not good looking rockers. The scratching and chatter marks on the wipe areas are not good signs.  Saro, if you haven't already done it when you changed rockers, I'd recommend am immediate oil and filter change. Cut open the old filter and examine the filter medium for any metal debris. Scratches could also be from running no air filters or Air Filters that do not filter well and are allowing fine particle of dirt through. .

Post up some high res pictures of the Cam lobes.

A few questions:

1: What weight and brand of motor oil are you currently running?

2: What brand + type of air filter are you running. Independent tests have shown that K&N filters and other Cotton Gauze/Foam  filters are quite poor at filtering materials like fine dust. I've seen it on my own cars and only run the K+N filters on track days. DD gets high quality ( Factory Nissan filters are good ) paper element filters.

 

[Zed Head]

Some of the "chatter" marks look more like chatter from a regrinding operation.  Check lash after a few hundred miles, and then a few thousand.  If a lobe is going bad, it will show up.  

One thing that might be informative on the cam lobes though, pertaining to the valves, is if there is wear on the base circle.  If lash is set right the base circle will get a coating of brown, since the anti-rattle springs are lifting the rocker pad from the cam and there's a gap there (the lash).  If there's wear on the lobe base, there's a chance the valve seats have worn, or a valve stayed open and got "burned" or warped.

Really though, if it sounds good and runs well, you might as well just get another head ready to swap on.

[oemz]

Sorry for the late reply.

 

Johnathan,

The adjustments where close, and could have been adjusted, but the rockers looked like it was better to just replace them. The valve stem tips where fine and I didn't see anything that concerned me. It would have been best for me to have the cam regrind or an upgrade, but it was smooth and so I left it as is. I'll try to take some pictures when I run it some more an take the valve cover off to recheck.

 

Chickenman,

The oil was changed about 100 miles/30 days prior to the rockers & guides being replaced with conventional Mobil Super 10w-30 and a Factory Blue Nissan Oil filter. I am planning on changing the oil this weekend. I've never cut open an oil filter before but have heard of it being done. 

As far as the air filter, I am not sure what brand they are. They were on the car when I purchased it. If things check out well, I'm going to be installing the triple Mikuni's and then choose a good filter setup. I've been thinking of cutting two factory air boxes to fabricate one long enough to fit the triples, and give it a factory look. we'll see.

Zed,

Not sure if it's from a regrind, but you could be right. I just want to point out that they seem very pronounced in the pictures, but the surface is very smooth and looks almost as if the chatters are laminated or under a clear surface where you can see them, but not feel them. Regardless, I decided to replace them. 

I didn't check the base circles on the Lobes as you mentioned, but that's a great suggestion. 

I think I will recheck after a few miles and see how things are wearing in and check the lash and go from there. If there's any doubt at that point, I'm going to save up and send the head to Datsun Spirit for a STD Series head work. So far, things sound very smooth, and the Z is running very strong. 

 

Thanks

Edited March 29, 2016 by oemz