24 valve variable valve timing crossflow L series Cyl head

[Guest Anonymous]

well just kinda throwing this out there for thought and see what kind of interest there is in something like this. I am researching right now into developing a 24 valve dual cam Variable valve timing head Cyl. head for the L-28 engine. I am of course aware of the huge commitment to such a project and am wanting to know if anybody has some good advice (i.e from an engineer) Would anybody be interested in purchasing such a head? Obviously it would be fairly expensive but imagine having modern technology on your 25+ year old sport car.

Just putting some feelers out here to see who would be interested and anybody that could help me out.

Thanks

Ed

[280Zen]

Several folks here have looked into doing custom heads for the L28 series,

 

http://www.hybridz.org/phpBB2/viewtopic.php?t=20564&highlight=custom+heads

 

http://www.hybridz.org/phpBB2/viewtopic.php?t=20621&highlight=custom+heads

 

http://www.hybridz.org/phpBB2/viewtopic.php?t=23090&highlight=

[Guest bastaad525]

I"m sure there'd be interest but with the cost involved in putting that kind of modern technology into an old Z car, most people would probably rather just put something like the supra engine or an RB engine... RB engine blocks actually seem to be very similiar to Z blocks in a lot of ways, and the head they come stock with would be pretty much what you're looking into building. If you could produce the head and sell it for significantly cheaper than buying an RB longblock with the EFI system, and make it easier to install and make use of... then we'd be talking

[Clifton]

Those that would want such a head usually get the RB26. Not only does it have the head it has a crank that can take 8K and not shake the crank pulley apart. I don't see why one would spend that kind of money on a custom L head and keep the L block. You could build a couple bad RB motors for the $$$ it will cost for this head.

[turbobluestreak]

I'm intersted in the head build up just not VTEC DOHC I'm doing some reasearch on this build up and am going to start my cad drawings tomorrow.

 

 

 

tbs

[Guest Nismo280Z-L28ET]

Why Variable Valve timing....it is considered more for a fuel efficiency stand point and limits the power/torque curve feel you recieve. Anyone driven the Lexus IS300 or Celica GT-S...these engines only feel alive for like 2000rpms! In racing they remove it from the Supras and the IS's and in that celebrity race they use celicas without it also. If your out for fuel efficiency go for it!

[fl327]

Me, among others, would love to see a twin cam L motor. Realistically however, to me the head is just the start of the domino effect that would make a project like this far more than overshoot the cost of a jdm or domestic dohc I6.

I can see the head being built, thats one thing, next, you have to build the bottom end to take the new mid high rpm powerband, which is also very doable, BUT,

the balance work, associated parts like a damper and all is big $, considering that a STOCK rebuild and BnB goes for 3000 at any reputable Z engine shop.

Then theres the trans, sure there are tons of L five speeds out there and they go for cheap, but the newest ones out there are 20 years old now, and havent been rebuilt.

In my case, these are why I wouldnt do the DOHC head even if it came out, even if it was "cheap." (the crowd is stunned!)

I can see putting down 2k on a head, another 2k bottom end, and hopefully not to have to do any trans work, theres still more money to be spent in random parts and accesories mandated by such a change, like manfolds, pipe routing, throttle linkage, induction setups, blah blah, you know what im saying? It would be 7-10k easily from nickel and dimeage, and I havent even got rubber to burn yet!!!

I am not trying to dissuade you from your goals, If you really do go through with that dohc head I wish you the best, if you are going for originality I applaud you, If youre going for all out power, I would go with another route personally, either the RB or the JZ engines if you need a I6 Dohc turbo (or two!)

ANd if you really have to make your own head, I say go for it, the reasons above are just MY personal opinions on why I would use one.

I can understand why you would want to, since my personal mantra towards creating my cars is that I build them for me, and could really care less if somebody doesnt approve or like what I do with my steel!!!

 

Good luck either way.

[RB30-ZED]

Why Variable Valve timing....it is considered more for a fuel efficiency stand point and limits the power/torque curve feel you recieve. Anyone driven the Lexus IS300 or Celica GT-S...these engines only feel alive for like 2000rpms! In racing they remove it from the Supras and the IS's and in that celebrity race they use celicas without it also. If your out for fuel efficiency go for it!

 

I read posts all over the net were people say to get rid of the Variable Valve Timing. I can say from my own experience with my engine that VVT makes a big difference.

 

We all know that advancing the valve timing of the inlet cam will give the engine better bottom end power, Guys in Australia will RB30E's tell you that one tooth ( about 4deg) gives it a big bottom end lift and that they don't rev the engine that hard, so they don't miss the top end , Well I can say that with my RB30DE with VVT, that ive advanced the inlet timing about 6 deg ( the VVT cam pulley has adjustment, but its behind the pulley) for great low rpm torque and then to be able to have the VVT work to retard the cam 20deg ( think its 20 crankshaft degrees, 10 cam degrees) to improve the top end is worth every bit of trouble you have to go to keep the system.

My engine pulls strongly in from 1500 to 7100rpm, something that I don't think it would do as well, with out the VVT.

I'd just like to add that people seem to miss the point of VVT, yes it has been used lately to meet the demands of tighter emission laws, but as guys would say, "get rid of that EFI and put a good 4 barrel on it", guys are saying the same about VVT now, because they don't see or maybe haven't worked with it to see the true picture.

 

At low rpm the air speed through the port and valve is slower, so we try to have the valve reach its point of maximum lift at the same time the air speed reaches its maximum speed, for the best volumetric efficiency.

But as rpm increases the air speed falls behind the increasing engine speed and torque drops off, but if we retard the inlet valve timing we can match the maximum valve lift point to the maximum air speed which is now later in the cycle, this will increase torque at higher rpm.

 

So as you can see the engines torque can be increased over a much wider band (and torque times rpm equals HP) with the use of VVT, for any reasonable cam used.

Steven

[Guest Won'tletmyzDie]

Yeah I saw a brochure for the 280z on ebay the other day, it had a parts listing and everything included on how to convert your 280z to DOHC. The z it was done to had its compression raised to 10.01 to one and ran about 329 rwhp. That was all they stated, I was skeptical at first too but thy had pictures of every page of the book, just not in focus enough to get the plans out of them. Sadly I did not have the $100 to buy the book either and it is gone, I am trying to find a way to look up ended auctions in ebay and e-mail the guy with that book before he sends it off, then I could tell him to make copies of it and sell them off too!