1977 280z: Randomly running VERY rough

[ckurtz2]

Okay now for some preventative action.

 Now the only lead I have so far all circulates around the cam. I am running the 260s comp cam https://zcardepot.com/products/performance-camshaft-comp-racing-cam-240z-260z-280z?variant=19279549825137

I am still using the stock springs that the car had when I got it. So lets assume they are 45+ years old. Should I do something like swap to new 280z springs or slightly stiffer Gen 1 300zx springs? Do the valve springs really loose stiffness over time. I have read so far Isky or Schnieder springs are too stiff for such a small cam, but the 300zx ones are the best medium.

Now the comp cam did require a different lash pad. I forget the size now. Anyways, I read up that different lash pads require a deeper valve spring retainer... I am using the stock ones. I looked at photos of a stock valve train and the lash pad is indeed sitting deeper than mine. I am thinking this is maybe causing excessive play in the lash pad area. Mine did look pretty cockeyed where the rocker had pushed off it in the previous post. Here are photos for comparison of stock vs my lash pads and the rocker.

Does anyone have experience with this? Not trying to shotgun buy parts at all. 

@Zed Head you are good, hah. It would have been on me if I pulled the head. You at least got me off the EFI trend, man that was a dark hole... always is.

 

Edited October 31, 2023 by ckurtz2

[Patcon]

Well your lash pad might not be sitting deeper. If you went to thicker lash pads the wear surface would be taller compared to the bottom surface. So even if it sits on the valve the same way it would appear that its not sitting as deep. Did that make sense?

[Zed Head]

Have you checked the wear patterns on the rocker arm pads?  People have had the wrong lash pads installed and the cam lobe rode off the end of the rocker arm.  

Found a few old threads.