Box_Man

Has anyone ever done S.U. Carbs from a 240Z on their 7? I have a set, and I think it might be worth a shot, if they can make more power when properly tuned than a nikki.

Question #2, I know that Hurley made a really short manifold that I think used one carb for a Mazda. Would a longer runner be better. The carbs have to face the passenger side of the carb, as I can't get them close enough together to clear the alternator, and I don't feel like sacrificing AC to relocate my alternator.

Question #3 Would it be worth it? or should I just buy readily available carb? I'm worried that for some stupid reason I might lose power over the nikki (which is getting old anyway) on this endeavor.

P.S. What are common wear items on these besides throttle shafts and dampers? I plan to rebuild both of them If I use them.

84stock

iTrader: (5)

They are not great, ran them on a 240z back in my younger days (45 now), I upgraded to webers back then and they stomped all over the su carbs. The su's were a little tricky to tune whereas the webers were great.

stilettoman

iTrader: (1)

There is no big mystery to SU carbs. I had numerous cars with them back in the day, and they are very simple to tune ( Assuming you have two carbs. My E Jag had three, and that was a bit more tricky) Instead of taking the carb apart, replacing jets, reassembling and testing, you just turn the jet adjusting nut, up for leaner, down for richer. The adjustments you make determine the mixture from idle to full throttle. To change the relationship at various throttle settings, you have to install a needle with a different profile (taper). These are readily available from aftermarket sources. To change the throttle response, you can change the viscosity of the oil in the dampers.

The English made SUs were poorly made, although in principle they worked well. But the throttle shafts would wear out and they required frequent mixture adjustment to compensate for the air leakage around the shafts. When the Japanese bought the manufacturing rights, they immediately fixed all the problems, and the ones on the Z cars gave good service life. I bought my Z car with 100k miles, and the carbs were working just fine, did not need frequent tuning.

I had a 1964 Sunbeam Alpine with a lousy Solex 2 barrel downdraft carb, just could not be tuned to run well. I welded up a couple of 90 degree elbows and bolted on a pair of SUs from a Volvo. It ran great. The following year, Sunbeam installed a pair of piston type carbs as standard equipment (Stromberg, not SU)

The stock 240Z motor had 120 hp with the SUs, so you may not get a lot more than that from the rotary. I would think 150 hp would be about the limit with some porting. If you want more than that, you need to be looking at other alternatives.

I have a 1984 GSL with a street port 12a and an old RX-4 carb with a custom manifold I made. It showed 130 hp to the rear wheels, so should be running 150 plus at the flywheel. That is another cheap alternative. I am quite happy with it for street driving.

I think you would want a manifold that wraps up over the top, with the air cleaners on the left side. You might take a look at the manifold used with the Delorto.

Box_Man

Actually I wanted to run them to the right side of the car because of fitment issues with the alternator. I'm not looking for crazy power, just more than stock I'd be perfectly happy with 130 by the time I'm done. Porting the carbs? I'd be afraid that I'd screw something up.

cosmicbang

Possibly. The old Hitachi/SU carbs from a Z-car are about 10-15 years older than the SU carbs which were installed on RX-7's. Check which version of Hitachi/SU carb you have. Here is a link fyi:
http://www.zparts.com/zptech/tech_ti...ifferences.htm
No. The Elford Turbo had a single SU carb, but the manifold you are referring to was for two SU carburettors, model HIF6. Eamon designed the original intake for a RHD car, so it angles up. A LHD car has different clearance parameters. The HIF6 carbs are taller, but theoretically one could do a wrap-around (and the AC would also fit). I had several discussions with him about intake lengths, and also attempted a computational model and experimentation. Ultimaltely, what would be considered a "short" intake provided excellent results. YMMV with the different carbs. Exhaust and port configurations also come into play.
Depends on how you define "worth it."
What would you consider a "readily available carb"? One might say there is no "readily available carb" for an RX-7. SU carburettors were installed on millions of cars and motorcycles. They are simple, reliable, and easy to tune. Parts are available, and there are a number of specialist service businesses. There is also a Haynes manual, "SU Carburettors Owners Workshop Manual" by Don Peers, ISBN 1 85010 018 7 (US)

You could potentially lose power with any alternative if it isn't set up and tuned properly.

Box_Man

So my carbs are '69-'71 model carbs that came off of a '73. At least I know what gasket kit to buy now.