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Twin cam head for the L6 from Derek at Datsunworks

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This is all Tony D’s fault:)   Hi everyone. Some of you know me from my  DIY EFI manifold project http://forums.hybridz.org/topic/63445-making-my-own-efi-intake-the-first-casting/ &#

Machine work finished!   I can relax a little:) Just got done with their first bath. Still need de-buring and edge finishing but the majority of the work is done.    

Yes, the exhaust port 'could' use some work, the as-cast cleaned intake is flowing within 10cfm of a 4 hour port job on an OS Giken head.   Those numbers outflow most max ported SOHC heads

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I'm in a industrial complex and naturally most of my neighbors know what I'm up to. I was talking to one of them who has a classic car resto shop. He was commenting on how good it sounded from his place. I mentioned that I hope it wasn't as noisy when I get it on the road and he replied " it will be better when it's not an open header" To which I said it's running through a resonator and a muffler already.


Between the exhaust and the induction noise it's really loud at 5000 rpm:) 

But it's a good loud.


You have likely found your torque peak right now... That's the curse of the Honda's, the induction bark is FAR louder than the exhaust. CHP continually cites Hondas for "illegal exhaust" due to the noise and when tested it's rarely over 85-90 dbA... it's all induction bark. "It will be louder and lower under load"!

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finally, I'm curious about you running it without load.   a lot of people say not to rev an engine without load.  I looked it up quickly, and I've not found a basis for this, except for revving it till you hit or pass the redline.  Now i know you're not going to blow it by over revving (then again i'd be curious as to what over-revving this head would be;  at what RPM would you expect valve float to start? same as with the original honda head?)...

The float issue would be dependent on if you have all the stock stuff in there. The rationale behind the head was the copious aftermarket support for good things made of Titanium and other lightweight materials. There are billet rockers, titanium retainers and spring keepers, valves that are feather light.... Frankly, it may really be overkill for the bottom-end restrictions of the L-Series but there may be some durability advantages to some of those billet followers they make...who knows? With all stock, I would assume same float not that I've heard a lot of issues with valve float on the Hondas. Their valve train seems to be very stable.


The caveat on free-revving relates to pumping the oil out of the pan and starving the bottom end. On a VW Type1 it's not an issue in stock form. But put a lightened flywheel and hot cam with some induction and not increase that 2.5 qt sump and it is VERY easy even under load to accelerate the engine fast enough to suck the sump free of oil and pump it to the top end before it can physically drain back from the far reaches of the engine. Engines blowing at the top end of the drag race track can sometimes be traced to it... those deep 7QT sumps came out for a reason, aside from lowering the level away from the crank for decreased windage.


The BMW Engine recently had issues with it. They dubbed it the "Damocles Engine" due to owners hot-rodding free-revving. Thing is the tach needle had more inertia than the rotating assembly and "Boom!" Our Bonneville L28 would go from idle to 8,000+ faster than you think giving a WOT mash of the throttle. In fact, the cam we had in the SOHC Head was stable without float issues to over 12,500 rpms. If your tuning in right, it should zing right up there... 



Edited by Tony D
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  • 2 weeks later...

"Did you put forged pistons in that thing? You will be sorry." Tony D to Bryan Blake after his triple itb cammed engine was up and running....


I posit, this will be similar. It's way too much head for the L28 in base form unless you twist it tight. But if you can twist, this thing is going to SING!


One thing which will be interesting is to get feedback on what difference the compression being low has overall. In VW's it was really overplayed and many of the best performance engines were in the high 7's to make the heat manageable, especially on the street. The torque you get down low is nice... but really it may not pay as big a dividend as many think. Other than  to the High Test Gas Company!

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Just a quick update. I finally have the car on the road. I ended up doing a lot of rewiring and re-routing of things. No videos yet as I'm still in the rudimentary tune stage but so far it's running great. 


My definition of running great is it hasn't exploded:)



Fantastic to hear mate!!! Cannot wait for videos.


I'm happy to say great isn't exploded all down the road either!!

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Thanks everyone. 

Stuck doing a bunch of bids right now so I don't have time to do the last couple of things to get it totally road worthy.


Here is a couple of shots of the engine bay mostly tidied up. The PCV system is still in Beta so don't judge:)








I still have some final tucking of the engine bay wires but it's nearly there.

Edited by Derek
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Hey. Quick question.

With a head like this, do you expect power gains accross the rpm band? Or would you expect mimimal gains low down but sigbificant ones high up, for example?

Im just thinking whether a head like that would be good mostly for high revving racers or if it would be great for a street motor, giving it plenty of torque...

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Well I just got back from a drive and right now it's like someone flips a switch at 5000 RPMs which is what Tony has been saying the whole time. The head needs something to make it flow. Having said that my tune down low may not be perfect, the cam timing may not be perfect etc etc. I'm not saying it's a dog down low but up high it's pretty impressive. The potential is there for sure. Baby steps for now:)

Edited by Derek
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As usual Derek, amazing work, and the attention to detail is quite impressive.

Thanks. Having the delay on the cams paid dividends on detailing time. 


I feel stupid, but what could a "something" be to make a head flow?


Are we talking a turbo to help air along, say, or a set or specially designer headers (yours are kickass, i'd sacrifice 20hp for them!!!)?

That something is displacement and RPM if it's NA or else forced induction. Tony worked the numbers and you need like a 3.3 liter that you can sling up to 9000 RPM's to fully realize the heads potential with NA. 


I'm optimistic that I can make a little power with this setup. 


The sound is just amazeballs at 6 grand i must admit.

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What CR are you running?  Hopefully around 12-1 with a pent roof.  I have not read this whole thread to know.


Put a turbo on it and join me in the 750+ HP range  :).


This motor only has 8.5:1. When I build my stroker it will have at least 11.5:1.


I can't afford to play in your league:) I'll stick with my (hopefully) 250 -300 HP NA stroker range. 

Edited by Derek
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Im building a 400+ NA one now.  Should sound good with a fully counterweighted crank at 10K  :)


Do you have some quench in your head with tight piston to head clearance?


The block is just a .040 over flat top piston. The combustion chamber is racetrack shaped which leaves 2 quench areas of approximately  .6 cubic inches on the intake and exhaust sides. That is if I'm defining quench properly. I'm just the pattern maker:) 


If you are building a 10,000 RPM L6 then you really need one of my head castings:)

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