Which carb(s) to choose?

[7D124DZ]

I have a 71 240Z that I have owned since 1990. 3.90 R200.  Engine is F54 blk , flat top pistons, N42 head.  Supposed to be around 10.5 cr, head studs and Schnieder 260-70f cam. Have good set of SUs, but figure I need more air to run this baby.  Don't really want the headaches of triple webers as I don't like tuning all the time, don't know about 390 Holley either.  Just want a reliable  setup to play a little with , but be able to take on 1000 mile cruise if desired.  I'm looking for suggestions,  Anyone running a similar setup and engine. Reliability is number 1.  Am considering an efi setup, which one ?  Got my first Z, a 76 280 in 1980,  My track car is an 86 300zx with lowered suspension, poly bushings, adjustable rear camber mods and 3.7 LS diff.  Have aluminum LS 5.3, but waiting for TK600 because of $$$ lolol, aren't we all. Am almost 61 yrs old and have found that "not fast enough 20 yrs ago is NOW fast enough. Can't decide on the 240z fueling method. Will SUs be enough for this engine or?  Thanks.

[crayZlair]

I think that I would go with the EFI. Once you have it dialed in (a good dyno tuner shop) you'll never have to worry about it again. It will start in any weather, no choke to play with. However, I'm a little older than you, and it's never "fast enough"! ?

[Diseazd]

I would definitely go with the SU’s. They are so simple and absolutely no problem feeding your set up. Get Ztherapy to build a set for you. They do a great job on my 3.1 Stroker Motors.

 

Edited March 15, 2020 by Diseazd

[siteunseen]

If the SUs are getting their proper fuel you can't beat them. I finally got mine right and cannot make them stumble for anything. Believe me I've tried.

 

[AK260]

I have a very similar engine to yours but with shaved E88 head. SUs are producing a measured 232bhp at 6200 rpm and the tuner said he thinks it would be over 240 if he had taken it to 6800 but backed off as he is used to dealing with British Layland cars ;) also it was going a little lean.

 

While getting lean at the top, it had no trouble breathing. The right needles will sort that out. I’m still in the process of finding the ideal needles as the tuner was modifying my SM needles while we were unaware of several air leaks behind the carbs. ZTherapy thought that my engine should be fine on SM, so that tells you something also about SU carbs. I think either lightly modified SM or unmodified MC would be correct for my car but I have yet to find the time to fine tune.

 

ZTherapy run their SCCA car revving to 8K rpm on stock sized SUs with modified needles and producing big numbers.

 

The beauty of SU carbs is low and mid range throttle response and power for the 70% rest of the time you’re not WOT. Also a piece of cake to set up.

 

So my advice is get your carbs properly tuned but EFi is of course king when it comes to perfect fulling maps. If you go efi and cost isn’t a big factor, consider the Jenvy Throttle Bodies ...

 

 

https://store.jenvey.co.uk/nissan-datsun-cknn03-1

 

 

 

And of course if you want the triple look / sound with EFi, then there is this ...

 

 

https://store.jenvey.co.uk/throttle-bodies-and-components/throttle-bodies/heritage-dcoe

 

 

[SteveJ]

SUs will work nicely, and if you decide you really want EFI instead, you can convert the SUs into throttle bodies with a kit from Patton Machine. http://www.pattonmachine.com

[240260280]

 

[7D124DZ]

Thanks for all the great input.  Didn't realize the SUs would be enough.  Think I will go with them for now since they are in great condition. As far as the future, who knows.  Thanks again.