Jump to content

Twin cam head for the L6 from Derek at Datsunworks


Recommended Posts

O-Ring seal on the back of the manifold to the head? Or gasket? That Throttle Body and Trumpet almost makes me want to go N/A.






It's going to be O-ring. And I'm not looking forward to it. 3/32 end mill in an old Bridgeport in cast aluminum...Ugh... 5500 RPM spindle can be a little restrictive with small bits.


The stacks and hardlines are going to give it exactly the look I want. Which kind of makes sense since I'm building it for me:)



Haha! The art of tracing will never die! :)


Looks awesome...


I have a $20,000 white light scanner and I still use the tracing method all the time. Now though instead of a flatbed scanner I just photograph the tracing with my phone. 


Thanks for the compliments everyone. I'm chomping at the bit to get back at it tomorrow:)

Link to comment
Share on other sites

Some suggest a 3.4 is what you need under that head to make power at 8,000 or so....

That should make for more than enough breathing on an L28 at 9K+


Big Bores, Short Strokes, Long Rods breathe nicely!

Hm... How about this?

L28 block bored .040 over, L24 crank, 87mm Mahle PowerPak RB30DET Pistons (32.10 pin height), 140mm FJ20 rods or aftermarket H-beams. This combination yields 2629cc's with a 1.90 Rod/Stroke ratio. The pistons will stick out the bore 1mm, but could be milled or use a 1 or 2mm head gasket.

Edited by Z-Dreamer
Link to comment
Share on other sites

About three milimeters shy in bore sizing. 89 or 90....


This is not a head you want to cobble together pistons and scrap parts to assemble.


The smaller engines will need a lot of Revs to make use of the breathing potential of the head.


A 3.4L would be supported to 7,000+, a 3.3 to 8,000+... see the trend forming?


Remember these  heads were centered around a 600cc cylinder displacement...

Edited by Tony D
Link to comment
Share on other sites

I think on any NA setup you are going to need custom pistons to make any kind of power. The K20 has a large combustion chamber and even ones that have been welded extensively are still 47 cc's. This is a head with a 47cc chamber done by theoldone.com




I'm going to pattern the raw castings around this design since all of the chambers will get machined to order. I think from a off the shelf piston standpoint the turbo people will have a better chance. 

Link to comment
Share on other sites

Making some progress.

Got the manifold to head flange done. I still need to de-burr the sharp edges but I'm happy with the results.






Hard to tell in this picture but the ports match really well.





1/3 of a money shot:)







Should be able to finish up the other 2 tomorrow. Now If I could just get my valve cover I'd be set for a while.

Edited by Derek
Link to comment
Share on other sites

And then there were three.....






Here are some process shots for those of you that are interested.



After rough surface and fly cutting.





Outlining the flange.











O-ring groove.




Port matched and injector clearance machined in. I'll hand finish the injector area. 



Edited by Derek
Link to comment
Share on other sites

I forget the stock C Chamber size, it was fairly low given what most modify them to accomplish for N/A.

The 47cc chamber is right there for a 500CC swept volume 3.0 turbo. Most of the HOMO guys are running 10:1 on their turbos, and N/A is easily run 12:1 on pump gas.


Even from that perspective, an L28 with a bigdome would have better torque characteristics from the high static CR.


The nice thing is the flow is achieved at relatively low lift, meaning  stability at higher rpms and long valve spring life.


Looks to be coming along well.

Link to comment
Share on other sites

Is that a Honda O-Ring, or a generic A-XXX O-Ring going in there?

Might try to see if there is an A-Series O-Ring that fits that groove acceptably, it will allow you to buy a bag for a couple of bucks and not have to buy two Four-Cylinder Kits and have two sitting around forever...

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...