83 L28ET Head Gasket

[subiegeek]

Hi everyone,

 

I am new to the forum, but have been lurking around soaking up everything I can about these old girls.

 

I picked up an early production 74 260Z about 6 months ago, and am just now starting to dig in. Very curious little car, with a mix of 240z, 280z, and a few of its own unique 260z bits.

 

After much deliberation, I decided to replace the tired L26 and build an L28 Turbo. Picked up an 83 L28ET that has been sitting in the corner of a garage for the last 15 years. Fortunately, the motor had never been opened or modified. It was removed and replaced with a V8 at the time, the owner built a car to compete in the Cannon Ball Run. Unfortunately, they blew up the motor, sold the car, and this motor has been buried away in the back corner of the garage since.

 

I plan on keeping the stock bore size, stock rods, custom forged JP pistons upping compression to 8.5:1. Custom exhaust manifold, custom ITB intake and throttle bodies ( using the Cannon ITB manifold I have and referencing MAP through the balancing tube. Garrett 3071R .62AR turbo (12-16psi boost), Full Haltech with A/F, EGT and Knock sensors. Looking to put down a reliable 400rwhp. Will be built for a weekend fun car and some track days. Would like to get some time at Seabring and Road Atlanta.   

 

Ok, so I started disassembly, measuring the components, and cleaning and prepping the parts for the machine shop. I am at the stage of figuring out what components I am going to use when putting it back together, but came across a rather interesting find.

 

When I removed the head, I noticed that the head gasket blocked off most of the cooling passages between the block and the head on the spark plug side. I have not seen this on the other motors, including the L26 and L28E (non turbo) I have. My assumption is that Nissan was trying to balance out the cylinder temperatures buy flowing the incoming coolant to the back of the head first, then move the warm coolant from the back of the head, forward to the other cylinders before it exits the thermostat. My assumption is that would help to balance out the cylinder temperatures since the forward cylinders would see more of the cool water otherwise?

 

I found a few threads where folks were wondering what gaskets to use based around other block head configurations, but I couldn't really determine what the correct / best gasket was as a replacement. Also, most were old threads. I know there are gaskets like Jeff Purdy version of the Cometic gasket, which i believe has every possible port opening available and recommends block and head modifications. I wasn't able to find much info on that topic. I know there is Felpro and the other usual suspects, but I was not able to locate the Nissan Factory gasket.

 

I guess what I am wondering is, why did Nissan block the ports and is there a better mouse trap? Aside from doing some of the external head cooling mods, is there ways to improve cooling? I would assume drilling more passages in the block and the head would be a better solution if more circulation was needed? What would be the best gasket for the application? Just for reference, I included some photos of the gasket from the Turbo and Non turbo motor, and a little diagram of how the F54 block and P90 head cooling passages lineup with the Turbo Head Gasket.

 

Sorry if this was a bit log winded.

 

Thanks,

 

 

 

[NewZed]

20 hours ago, subiegeek said:

My assumption is that Nissan was trying to balance out the cylinder temperatures buy flowing the incoming coolant to the back of the head first, then move the warm coolant from the back of the head, forward to the other cylinders before it exits the thermostat. My assumption is that would help to balance out the cylinder temperatures since the forward cylinders would see more of the cool water otherwise?

 

Seems like a logical assumption.  If it's a factory stock engine then a factory stock head gasket gets you back to factory stock specs.  Trying to second-guess the engineers, who have all of the tools and money to test the variations, seems a bit foolish.  Gasket restrictions are the same as port size restrictions as far as flow is concerned.

 

You might have seen the comment from somebody in one of those old threads about the fact that after he got his cooling balanced across all six, using the head drilling/plumbing cooling mod, that instead of popping the seal on 5 or 6 from detonation, he popped all six at the same time.  Something to consider.  Probably better to spend time on the cooling system as a whole before fine-tuning the spread across the cylinders.  Just an opinion.