Understanding head flow dynamics

[frankendat]

Gentlemen,

I am over thinking this, hopefully you will indulge and edify. Below are images of the head I am building. Neither online, nor in the FSM, have I been able to find a diagram that labels and explains the function of the holes in the cylinder head; the information may be attainable and I do not know where to search. I have placed colors near representatives of holes in  question.  I seek to know their function and aside from a pipe cleaner rogering, which passages would benefit from flaring. Included in this potential flaring, the water passages on the image of the bottom (red).

A few of the holes,(marked with yellow, have "steps" offset in the interior, that are not the complete circumference of the hole. Would there be benefit in removing these partial steps? 

Other holes have a uniform step around the complete circumference. Would there be benefit in removing the complete steps.

There are marks in the bearing channels, but the ceramic coated tri metal bearing purchased for this project address those imperfections.

Kanga Datsun talks about removing the sockets in the head, replacing with studs and polishing the interior of the head. I marked some of the spaces (as I understand them) in red. It looks different, more "boxy" then the area on the 240Z head on Kanaga. Are the areas marked with red the same type (provide similar function) of the 240Z on the Kanga website.

After two days of soaking in penetrating oil and using an impact wrench the socket plugs in the head stand fast. Has anyone ever removed the plugs?

Thank you for your guideance

 

[datzenmike]

 

Coolant from the pump enters the front right side of the block circulates around the cylinders and the only way out is up into the head. Well there is an outlet from the right side for the heater but generally it's not really part of the actual cooling system.

 

The red marked holes are to promote cooling or drawing away of heat around the exhaust ports on the left side. L series have more cooling on this side because the intake ports are also on this side and have to be cooled more. Coolant on the Z series comes up into the head and gravitates over to the right side. There is a main outlet at the front into the intake and to the thermostat and there are coolant runners out each intake port runner that are gathered and fed back into the water pump.

 

I would not be porting any of the coolant holes other than perhaps removing any casting flash that is visible. If there are any obvious restrictions Nissan has accounted for this in the design.

 

 

 

Orange.

Are small oil entrapment areas. The engine tilts up at the front so the oil is more to the rear in these areas, over flowing and working it's way to the very rear drain back hole on the left side. You can just barely see it to the rear of the top left head bolt hole and the top left cam tower alignment dowel. Depending on which is hotter heat will transfer. Oil is slower to warm so the coolant warms the oil.

 

Purple

These are simply openings to remove the casting sand when the head was molded. They are sealed and should be left alone.

 

Yellow

Are just two of the ten head bolt holes.

 

Green

Are the cam bearings. There's nothing to replace the cam rides directly on the aluminum head. Oil is fed to the hollow cam up into the center cam tower. You can see the hole near the bottom of the center tower. Oil is thrown onto both rocker shafts, rocker arms from the cam.

 

Cam tower bolts are fine and are not known for failure. Extremely important, like the L series, that they not be over tightened and the threads stripped.

 

Combustion chamber polishing is fine but don't waste your time on the ports. Remove any roughness or casting  flash in the bowl area below the valve seats. I found burs from the machining of the openings for the valve seats and a step or lip to the port walls. This can be sanded away and blended.

 

Generally the Z head is and never was intended for any high performance modifications so right off the bat it's got disadvantages that can never be over come. It does have cross flow, a hemispheric combustion chamber and dual spark plugs. These benefit efficiency and mileage and would benefit high performance if the intake and exhaust ports were higher and there was less severe bend at the valves into the combustion chamber.

[frankendat]

Thank you for patience and council, I value your guidance. Once again, I was attempting to screw up my stuff. At least, I show some signs of improvement. When the "casting sand plugs" didn't yield, even with a cheater bar. I thought to take a step back, instead of enlisting bigger impact drivers, a torch and whatever else, I have on hand to achieve victory over the plug. If history is a guide, I would have successfully removed the plugs and destroyed the head.

 

1. Is the picture below of the "rear drain hole? (The deepest hole in the pic) It seems prime for flaring or contouring/smoothing to allow for increased flow. Is there a downside to increasing flow?

 

 

2. In the same vein of smooth flow, in the picture below, wouldn't polishing the cast around the perimeter of the head, the area that includes the lines in the cast, stopping at the bottom small wall, have some benefit? (or at least no detriment) The polishing protocol, which I am referring, would greatly reduce, likely eliminate, the raised ridges.

 

On 4/1/2022 at 8:08 AM, datzenmike said:

Cam tower bolts are fine and are not known for failure. Extremely important, like the L series, that they not be over tightened and the threads stripped.

 

3. Is there another name for "cam tower bolts" ?

 

Thank you

 

[datzenmike]

1/... The drain back hole is how the oil gets back onto the oil pan. If you feel the need you could drill it out slightly larger. Has to go through the head gasket. I don't think there is a problem with the drain back.

 

 

2/... Rather than polishing you might paint it with Glyptal. It's a paint that oil doesn't stick to and runs off. Not going to run any better and oil run off isn't a problem that needs fixing really....

 

3/... Try Camshaft Bracket Bolt. #13058-W0400