stock SU cfms??????

[PetesPonies]

as I think about alternative carburetion, I wonder what is the cfm ratings of the stock carbs on a 1970 240Z? Holley makes the 390 which is expensive, but being a Ford person, I am quite familiar with Ford carbs that are similar to Holleys. The Autolite carbs have small cfm rating and bolt up the same as a Holley. There are 441 and 480 cfm versions. There are even 2V versions that are 356 cfm etc. These would be dependable inexpensive carbs that could be bolted to a Holley type manifold. So what doe sa stock system flow??

[John Coffey]

I think both carbs flow a combined 290cfm. But, I question your basic premise. Many folks have tried the 2/4 barrel conversions on Nissan L6s and are extremely lucky to get them to perform as well as the stock SUs.

Familiarity with certain carburator designs may make this a more comfortable choice, but why pass up the chance to learn something new? SU carbs are as reliable as any Holley, Autolite, Carter, or Rochester when setup correctly and are as unreliable as the same carbs when setup incorrectly.

[Royce]

I think John is correct regarding CFM for the SUs, they are a little less than 300 stock.

Before changing anything I suggested you talk to the folks at www.ztherapy.com and Rebello Racing, don't remeber their web site but I added it to the links here on this 240Z club site a month ago or so.

Z-Therapy specializes in SU rebuilds, not just for Z cars. They have enginered many specific modifications and special parts for the Z SU's to make them perform even better than new.

Rebello builds Z motors from 3.2l stroked and bored Z motors as well as good 2.4l ITS and street motors. Rebello is in Pacheco, CA and they rebuild the SU's as well as have experience building custom Turbo, FI and Mikuni setups.

According to both of these sources the SU's with little modification can be more than sufficient for the largest stroker L motored Z cars. Even thought the other carbs may be good, when you add an adapter plate to the Z manifold you are probably going to loose more than you are going to gain. I think for about $600 bucks either of these sources will rebuild your SU's to be better than when they left Nissan new and will probably perform as well as anything else out there. And for nothing they can provide a lot of tips to get your carbs set up well and the magic of how they flow.

Have fun!

Royce

'71 240Z series II

'75 260Z (12/74 parting out!)

Orangevale, CA