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What would you pay for a dohc 4 valve head


JimmyZ

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If someone made a head like OS Giken used to what would you be willing to pay?

Yes, it's a hypothetical question and the performance gains are disproportionate to the money spent vs other ways BUT it is something to brag about.:)

What would it be worth and would you want a N/A head or one designed for forced induction? Any special features you'd like to see on such a head?

I imagine many people would hop on it if were between $1500-$3000,00 for a bare head. By bare head I mean a casting minus valvetrain having seats and guides installed. It would utilize the stock rockers which would not be included. (All major machining operations completed) Herringbone gears for the cams would be included and the stock chain could still be utilized.

On Z-car.com there was a fellow who built up such a head and there have been a few places doing variations of that over the years. It seems to have generated some interest.

Jim

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I'm sure there is SOME interest in reviving the idea of a 4 valve head for our L-series.

Sure, it would be easier to bolt in a V-8 or other engine but I'm talking about a certain coolness factor here.

Carl, If I knew some specifics about the ease of construction of the rotary valve head I'd definitely mention that as a possibility. I imagine there is some sealing going on between the cam and the head... More than could be had by just machining to close tolerances. Such a head would be way cool though.

So far I'm getting the impression that there is no real interest in reviving the 4 valve but I imagine there might be if someone made one.

The real question is how much could someone justify spending for the aforementioned "bare" head.

Maybe I need to make a poll.

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Yes that's it!

I cast aluminum as part of a hobby. Talking with Norm Simpers about this head got me wondering about taking a swing at casting such a head. Of course I'd have to make a much larger furnace and crucible but it could "easily" be done with a lost foam casting. I also have some light machine shop equipment which could tackle some aspects of the rough machining of said casting. I'd want to entrust the rest to someone with a Serdi machine and other high end equipment.

After looking at the simplicity of the OS Giken cam towers and hearing the gripes about the thinness of the OSG ports I'm just trying to get a feel of what changes would be needed to make a better 4 valve head. I've cut up a few 4valve heads and observed the thickness/cross sections of the parts. Having that knowlege make the task a bit easier. Designing the ports would prob find me just copying a similar heads ports.

If I were to be able to test and produce such heads I'm just trying to see what kind of interest there is.

Jim

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Some people would buy into it no doubt.

Performance gains I would see wouldn't be worth the cost. Though other modifications would take advantage over DOHC like a turbocharger.

But for that price, people would rather just keep their SOHC L motor, or get a V8 or RB/SR motor.

Hell, you can get a 4800 Vortec motor with everything except a tranny for $500 almost brand new. That right there gives you 300/300 stock.

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Some people would buy into it no doubt.

Performance gains I would see wouldn't be worth the cost. Though other modifications would take advantage over DOHC like a turbocharger.

But for that price, people would rather just keep their SOHC L motor, or get a V8 or RB/SR motor.

.

I mentioned this at the beginning of the thread.:)

The question is... How many of us would be interested in slapping a DOHC head on our Z's and what would be the price range desired? If one day you found one on E-bay what would you be willing to spend? (Knowing that the head was a proven design of course) Remember, this is more of a bolt on type of thing rather than fitting a whole new powerplant/drivetrain.

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Ummm.... I would say $2,000 tops.

Normal heads go up for $500, so I would say that $1,500 should cover labor, and parts. Though that includes everything.

Would I do this? I think that I would if I had money. I would have several different Z's tuned to much different specs.

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From memory the OS Giken head out flowed the standard heads by only 15% or so.

For the money these days in building a DOHC head, I'd say that a good head specialist would provide way over the 15% increase from stock at a fraction of the price of a DOHC head.

Now, for coolness factor, a DOHC head would look awesome in my engine bay or anyone's for that matter. Go for it, I'd be watching the developement unfold if allowed.

The rotary valve idea is not new. I remember watching a TV program years ago (10-15 at least) that was on this very subject. The guy who did it was a old chap from Italy who was trying to make one for the F1 industry. He had it working to a point but he was a privateer who had run out of funds to develop it further. I wonder if these guys picked up his ideas and ran with it. Red line was a huge 19,000 plus. That's what they doing now with valves anyway.....mind boggling isn't. If my maths is correct, that's a valve opening 158 times per second. 19000/60 = 316.66sec divided by 2 (four stroke engine) = 158

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not really. the Z432 had the S20 engine from the GT-R of the time. so it was an engine swap, and not a bolt on.

however, Nissan did have a racing head for the L series that was a twin cam if i remember correctly

Having a twin cam on my car would really be awesome. I wonder what sort of a difference in power it would be from stock, to direct bolt on of the new head...

and seeing 1 fast z's head on that car, and watch it fire up. that's engineering ingenuity right there. everyone was saying "oh that won't work blah blah blah" he did it anyways. I can't wait to see the driving videos

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A variation but most importantly a single piece new casting. I'm just debating whether to try an N/A version first or go straight to forced induction. It would be easier to make a non N/A head as far as port design goes.

Since the person buying it would obviously want to install valves/seats/cams suited to their needs it makes sense to leave those things out.

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Since the person buying it would obviously want to install valves/seats/cams suited to their needs it makes sense to leave those things out.

Yes and no. If they were off the shelf items, then yes the buyers might want to get them on their own, but a unique DOHC head would require cams that are designed for the specific engine and head layout. 1FastZ bought custom built cams. I'm sure those weren't cheap. Either the head would have to be designed to use some other manufacturer's valvetrain parts (i.e. Toyots Supra valvetrain), or the person making the heads would also need to supply everything required and build enough spares to have stock for years to come. :cross-eye

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Thyanx all for the lesson ^_^

I say go with the easiest first Jimmy and build the NA version then

build the Force induction 2nd if that makes since.

It sounds like it would be quicker to make the NA if you don't have to make the valves and stuff also.

Forced Induction sounds like theres tons of possiblities you can

opt out for that one though for all kinds of combinations and HP :)

Just my thoughts ^_^ ~Z~

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Carl, the rotary valve system looks VERY interesting. Are they building one for the L series?

Hi Mike:

No - but since they seem to have built a head for the M/B in-line six - the head for the "L" series can't to too much different in terms of the total design effort.

I have no idea what they would charge - but if they were to produce say 10 or more of them - it might help them get more publicity.... It certainly seems that the design is past the experimental stages, but still not broadly applied, nor fully proven by time and use...

Having the cams "be" the valves (so to speak) and getting rid of the entire conventional valve train seems like a great idea to me...

FWIW,

Carl B.

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Such a head would have better VE for sure. Tweaking it though...

I'd like to find out what the secret is to making a good seal on the "valve" face of such a head though. What about carbon on the exhaust side? Grinding a new seat/socket looks to be more like replacing the head. (Or at least sending to manufacturer for remachining.

It is extremely cool though.

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Heh, JimmyZ, I'm a home caster/machinist too. I've actually poured cylinder heads before, but a scale model of the L24 isn't quite the same...By the way, a 1/8 scale model of the stock L24 produces ~4.6HP, pretty good, I think. Next time i get to see that engine again, i'll take some pictures for you guys! (it's in a modeling museum about 20Hrs away from me...)

As to doing it lost foam, you'd get much better results that way. The best method to make the patterns is CNC, but you'd have to make the patterns layer-cake style. (not that that's a real problem.) the only worry that i would have would be getting the internal passages packed with sand fully, an internal blockage would be killer.

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N/A all the way baby :)

One question why doesn't someone make a roller rocker kit for the L6 series? Hell you an get roller rocker kit for just about every thing else and sorely there would be enough interest from us to have a smoother valve train?

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