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Twin cam head for the L6 from Derek at Datsunworks


Derek

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I'm going to need a lot of piston clearance for this to work :)

 

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Deep drilling the head bolt holes. This stuff make my butt hole clench.

 

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Bottom all done. (I think)

 

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This is the ground flat bar that I'll use to set the rotational angle when I roll it over. That way I'm indicating off of the bottom surface.

 

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Well that's it for today. Unfortunately real work has got in the way.  Back at it tomorrow.

Edited by Derek
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+++ Infinity.  I know you say this head is being made for durability and not power but I cannot wait to see some figures even knowing there are obviously tons of variables at play.  If you can hit good numbers on pump gas I bet a lot of V8 guys would even get jealous over the 'cool' factor :) 

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Thanks everyone for the encouraging words. They do mean a lot.

 

So I got the top surface done.

I started out with a modified spark plug stop to use as a gauge. I used the end of the threaded rod that goes up through the head to touch off from. This let me know where I was in relation to the combustion chamber.

 

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I surfaced the top,did all the cam tower work, spot faced the head bolt bosses, bored the spark plug tube bosses to the correct depth, tapped the bosses for the tubes and drilled the oil gallery.

 

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Had to relieve one side of the cam towers for the ARP washers to clear.

 

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Set a few towers on for fun.

 

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Probably won't get much done till Monday. 

Edited by Derek
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And thanks again for sharing this process. I worked a short time as a machine operator/machinist in Fort Walton Beach FL for aero tech or something like that where we repaired jet engine cases. I really enjoyed doing the machine work even though it is primitive(operating a 42" vertical lathe ) compared to CNC creations like this.

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Not sure if this has been covered in previous posts, so apologies if it has - but, does the design of this head make any concession to the canting of the L-series engine block in the chassis?  

 

On the LY 'Crossflow' head conversion, Nissan canted the block over to the induction side (ie, induction side of head was higher than the exhaust side) by using a completely different LY-specific bellhousing and engine mounts. Different sump and oil pick-up arrangement too.

 

On the S20 twin-cam engined cars the cylinder bock is canted in a similar way; High on the induction side and low on the exhaust side. S20-specific bellhousings (for A type and later B type transmissions) were used, and engine crossmember is specific to S20-engined models.

 

I'm presuming that this custom-made head uses the stock cant of the L-gata block in non-crossflow configuration? With that being the case, does this impact the design and engineering of the oil system, and what knock-on will there be on inlet design (presuming that the inlet side will be lower than the exhaust side)?  

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Easy, use Z20/Z22/Z24 bell housing for roughly the same cant to the opposite side, or the KA24 bell housing to cant 20 degrees over to the exhaust side. I think Z-series block mounts will bolt right up, would have to modify the KA mounts, I think.

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I saw that the engines were tilted in the pictures during the design phase and wondered why. I figured it was for oil as I was having an issue using the stock L6 drain. Tony suggested a drain in the back of the head with a hose down to the oil pan and this is the direction I'm going to go.  That is probably why he was asking about it in post #230

 

Does the induction side need to be higher than the exhaust side? Is this for carb cars?

 

Thanks

Derek

Edited by Derek
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Does the induction side need to be higher than the exhaust side? Is this for carb cars?

 

 

Carbs like it better if they are mounted roughly level (floats etc) but some of that can be achieved through the inlet manifold shape as long as it does not become too much of a compromise. I would imagine some proportion of your potential customer base would like to run with carbs, and it seems to me that it would be worth catering for them.

 

Stock L-gata, LY and S20 were not tilted for oil draining reasons. On stock L-gata it was mostly about packaging (and not forgetting - as some Z specialist websites seem to - that the L-6 was designed and engineered to be used in more than one platform) and the need to fit in both RHD and LHD vehicles. LY was originally designed to be used with individual throttle-bodied injection, but also catered for carbs. A lot of the 'tilt' was about packaging, and again in both RHD and LHD form. S20 was designed and engineered pretty much solely for RHD use, and was designed, engineered and packaged accordingly.

 

Yes, you can move things around with different bellhousings and engine mounts as Xnke has pointed out, but that will have an impact on inlet and exhaust manifold shapes and I would think a 'one size fits all' approach might help to make your head a more accessible proposition cost-wise?     

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I agree, it would be far simpler to keep the tilt as is, and work the intake manifold to keep the carbs/ITBs level. There isn't exactly a *shortage* of room, but I can see where some would like to tilt the engine for longer intake runners.

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Here is a shot of my calculated standing oil level. The cam towers dictate how the draining works.

 

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The valve guides won't be standing in oil but they will be getting splashed a bit :)

Edited by Derek
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Actually, I bought a car out of Texas (Black Pearl, actually) that defeated the local mechanics who had done the "overhaul" of the engine but could no longer close the hood.

 

They had exchanged L & R Engine Mounts an the engine sat bolt upright! It was arduous duty troubleshooting that issue, something they gave up on almost 8 years prior as a mystery and unsolvable.

 

So a simple swap L & R Mounts puts it almost level....it needs to be determined if the head is shorter in this configuration than the L-Series.... Haven't seen dimensions, but that was my first step, second was as Xnke suggested: Z24/KA24 Mounts and bell housings are there...

 

Yeah...this is in the back of the shelf for when we come to that bridge...

Edited by Tony D
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There is a rendering on page 1. As soon as the head is done I'll start on that. Actually cams first then the valve cover.

I ordered a piece of 29 mm drill rod to use as a gauge rod for the cams. This way I can check the alignment of the towers and decide if I need to have them line bored.

Edited by Derek
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Derek, this is amazing work. This is one of the most exciting developments for the Z in many years. Hopefully it will bring back some of the lost interest in the L series motors. My only concern is if there is a sufficient market of actual buyers to make this economically viable. Thanks for taking the risk and doing such great work for all of us Z'ers.

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