What is the best head for a NA Calais for performance. like whats better the RB25 or .......... and do you know the prices???

like your signature suggests - RB26 is GOD, but i assume u don't want turbos. To keep it NA though RB25 would be the best, one without variable valve timing would be easier. Could cost about $4000 to install, i read it in a magazine anyhow. The major worries lie in fitting a new timing belt, and putting in new tensioners. Also wiring in an RB25 computer which is not an easy thing to do. Other wise the head just plonks on top.

That cost sounds like it was off the Zoom magazine. That cost was labour inclusive so doing it youself would save you a lot of money,I have priced up an RB25DE package for $1550.

whenever you mention the rb25 head thing ppl just say nope forget it way too expensive but it has never been explained to me why it is so outrageously expensive that it shouldnt be considered.

Cause to do it properlyyou need bigger injectors than what will come in the RB25 head, then you either need the ECU remapped or an aftermaket ECU + tuning.

Is there a gigantic difference in flow rates between the rb25 head and the rb26 head? Just another query... Ive asked around a few places and it seems as though the rb26 head by itself is very rare and you usually have to purchase the whole motor? True?

I don't know about flow rates, but the RB25 uses a single throttle body and hydraulic lifters, and the RB26 uses 6 throttle butterflys and solid lifters. I would presume the RB26 head flows more. I also guess people would want to sell the full RB26 engine because although everyone would want the head, what would you do with the block without it?

Quote: Originally Posted by ScKoTTeY Is there a gigantic difference in flow rates between the rb25 head and the rb26 head? There's certainly a gigantic difference in availability, and price! 8O Methinks unless you have an unlimited budget you'll get more bang for the buck out of an RB25 + modifications for the price you'd pay for a stock RB26 head. I gather the RB26 head doesn't come into its own until you're doing high revs. Note also that the RB26 was (AFAIK) only available with twin turbos, so it's quite possible that an n/a engine can't flow enough at sane revs to make use of its capabilities.

Unless your pushing the engine above 7000rpm, the RB26 head Is not worth considering, go for the RB25 head with variable valve timing. This will give you better fuel economy, more torque, and the power should continue upto 6500rpm.

Yeah Like ppl have said the RB26 head is the clear winner, but way too expencive unless for a race application. The RB25DE head is def the way to go and costs bugger all to fit. All the cost is in the ECU and tunning.

Performance, Go turbo. Thats all you cann do. Paying 3k for an extra 20kw at the wheels via some n/a stuff is stupid, where you can have an extra 50kw minimum at the wheels with some turbo work. If your on a budget, convert your n/a to turbo if you have a series 2 block. Everything bolts straight up no problems.

Quote: Originally Posted by darkstar Performance, Go turbo. Thats all you cann do. Paying 3k for an extra 20kw at the wheels via some n/a stuff is stupid, where you can have an extra 50kw minimum at the wheels with some turbo work. Depends what you want. Turbos are great if you want giant hp with some degree of streetability. However, you lose throttle response and (via reducing compression) fuel economy. For me, quick throttle response is one of the main elements in the pleasure of driving a car and particularly if it's a manual (which mine is soon to be). I also use mine every day and am not looking for huge hp. For my purposes an RB25 head will give me as much power as a stock VLT in more controllable form with better fuel consumption than I'm getting now. It's a more useful package *for my priorities* for the same price as going turbo. The other possibility is to supercharge it. With a Roots blower (plus intercooler?) you get more bottom-end grunt and again power instantly available. You won't get as much power as a turbo but in most circumstances it would be more useable. $1800 from Castlemaine Rod Shop... Now if I wanted to stay with an auto, go heavily into drag racing and not use the car every day you bet I'd be going turbo! Horses for courses, as they say... Some original photos have not been recovered yet.

So the rb25 will increase your bottom end power cause I don't get much power out till the top end? Quote: For my purposes an RB25 head will give me as much power as a stock VLT in more controllable form with better fuel consumption than I'm getting now. It's a more useful package *for my priorities* for the same price as going turbo. And I agree with you on this oldf@rt I drive mine for work so was mainly looking at changing the head bigger cam chip computer get it portered 2500-3000 stall 5spd with the other little performance bits. Does anyone know how much Kw that'd bost me up to I was hoping to get into the area of 130-150 but I don't know if you should tell me I'm dreaming ops: Some original photos have not been recovered yet.

I don't believe your dreaming you would need to tune your engine to give more top end hp, and if n/a make sure you have higher compression ratio. Rb30-zed mentioned that VCT should increase torque at low end and keep it going up over 7000rpm. Some original photos have not been recovered yet.

Does anyone know ball park figures of what it would cost to do this? Any idea at all? was mainly looking at changing to the twin cam RB25 head bigger cam chip computer get it portered 2500-3000 stall 5spd with the other little associated performance bits

someone said b4 that the RB25 injectors aren't big enough? What injectors suit it then? How much power do you reckon you could get out of a N/A with RB25 head? Or what power increase will an RB25 head give over a RB30 head?

They are not big enough if you go turbo, RX7 injectors suit, and it depends on the type of rb25 head + other mods + tuning. I think if you have a RB30ET then for more power the headcam conversion is the next big step. The valve springs on the rb25 head are soft and people say that they need to be replaced. I`m more concerned about the engine management system since it's a hybrid engine. Other then that a 20 - 30kw increase should possible.

so if u stay N/A with the rb25 head the N/A rb30 injectors are suitable? also do you need the plenum from the rb25? i'm thinkin that u would. Can we get a lost of everything you need coz my dad is gonna start flyin to japan and i reckon i'll be able to get an rb25 head cheap as chips over there.

just turbo it

thats the plan for me anyway - awaiting funds