Monday, November 26, 2018

A Little Head work

Let's start this right, I am not an affiliate on any sites but the links below are the pages and parts that I have used for this head that is going into the 280zx.
We are working with a higher compression, and with that we need a cam shaft to move more air through this air pump. So what we have is a now built head.

The Parts

  • Head: Nissan N47 (from a 78 280z google)
  • Cam Towers: P90 (from an 82 Turbo google)
  • Cam Shaft: Nissan Motorsports 96666-E1031 Slalom Camshaft, .475" lift 275* duration (google
  • Rocker Arms: Datsun/Nissan Stock rocker arms, Refurbished (from a different 78 280z google)
  • Valves: Datsun N47 valves, stock with the head (google
  • Valve Springs: Crane 99884-12 (amazon) (crane catalog) (
  • Lash Pads: ISKY lc-175 .175 Lash Pads (isky)
  • Retainers: ISKY 1624ST-12 Chrome Moly Lightweight Retainers (isky)
  • Valve Keepers: ITM 051-304 Valve Locks (amazon)

The Head Work

The head had issues. When I bought the head off of CraigsList, it was at night, in a shed, in the farmland south of San Jose. I did not see the crack in the cam tower, or that the cam itself was broken, here is a pic.
I got lucky with finding a camshaft with towers on ebay, it can be found,  but patients is needed.
The head eventually made its way to the machine shop in 2017. At the shop they did a pressure test, fixed the holes where there used to be exhaust studs, and it was decked. Surprisingly very little material was removed from the bottom of the head. It was "pretty straight" and did not need more than .001" removed to be completely straight.
There was no porting done on this head, but the exhaust valve guides were replaced and the cam towers were checked for straightness.
The head checked out fine, so they did the valve job, installed the valves, springs, keepers, retainers, and torqued the cam towers to spec. The cam was put in, along with the rocker arms, but a lash job was still needed.

The Cam Shaft

The camshaft was a complete luck find. It was a craigslist ad, about 90 miles away from home, and it was a Nissan MotorSports part 99996-E1031. I have the paperwork that the seller had. It was a decent camshaft. It looked to be in good shape, and the seller told me how the car would come alive at 3000RPM and just pull all the way up the RPM range after that. 
The camshaft went to the machine shop with the head. During their checking of it, there was wear on a couple of lobes. They sent the cam out to be reground slightly, to be shaved so that all the lobes were the same. It was taken from .325 cam lift to .322 cam lift. This is not a huge change, it would take it from .475 valve lift to .470 valve lift. (.325 * 1.462 is as close as I want to get to the math) 
The cam is now installed, and a lash job is completed, check the above video
Though all practical measures that were attempted show that the cam is only getting .450" of lift. My measurements may be completely off though. 

The Assembly

The video above goes over the head assembly. I did not say it, but I show it. Use a good deal of assembly lube with the build. Check your measurements twice. Check your valve clearance. I will need to do this again, but I will need to do it on the lash not the cam next time. I will video that as well. 
Check where your cam is hitting your rocker arms as well. You want the wear on them to be as close to center of the pad as possible.
This goes for the lash pads, verify that the rocker arm is striking those pads as close to center as it can.  There have been people that mentioned that you can "move" the lash pad around, but I was not seeing a way to do that and keep the valve within lash spec.

Wrap Up

The head is together and sitting on the bench. Everything I have read, everything I have looked at, all the forum posts, the facebook posts, and the books show that everything should function fine. 
The camshaft is not a large camshaft, it is barely over stock size. If I do not like its performance I can also swap it out with another cam. If it wears too quickly or eats rocker arms, again there are ways to replace those.
There are things in this build that people say you should never do. I have done them because I had to or was too naive to know better, I will let you choose which one.
I swapped the cam towers out, because they were broken. There have been that shouted from the tops of mountains that this should never be done. Time will tell if it works or not. 
I replaced the rocker arms for a set found on ebay, I was also told that this should not be done at all, and either to get brand new, or maybe you can get away with your rocker arms being resurfaced. No mention of someone elses rocker arms though. 
I have no history of this head before 2014. I bought this head as a replacement for the stock P79 head and to hopefully get 10:1 compression out of my engine. I got disheartened when the head fell apart on me and I tucked it under the bench for almost 3 years before I decided that there would be no harm in having it checked out, and it might save a few bucks over getting the P79 shaved. 
I still might get my P79 shaved .080" down just so I can be like everyone else, but as for now, I am just gonna send it. 

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