A few years ago I found the completely rust-free, orange 240 Z of my dreams.  (This is the third Z that I've owned but my first 240.) It had been sitting in barn since about 1992, about 700 miles right after the previous owner swapped the engine for a 28L with a 4-speed and rebuilt it with Mikuni carbs. I have fun working on the  interior, some chassis work, electronics and other "soft" stuff, but I turn to my mechanic to get this thing running right. The problem is, I bought this because of the rust-free unmodified body, but I've never had any intention to race this thing. In fact, I really just want something fun to tool around on nice days. So, I now realize that these Mikuni carbs are probably not the best choice--especially at the lower end. Is there a way he can modify or tune them to make this car drive better and more reliably for my use? Will this car ever be good for the way I want to drive around the city? Should I swap out the Mikunis for a stock carb set up? Is fuel injection an option? I know this talk is probably pains some of you to even hear--but I want this Z to be a little more practical for my needs. Thanks for your help.

Edited July 11, 20186 yr by CleZ

Mikunis are fine for everyday use. You need to describe what aspect of the power train makes it not a daily driver. Mikunis were sold as kits to bolt in to stock Z’s like putting a 4 barrel on a Chevy. It’s not the Mikunis but the whole package. They could be tuned wrong or you have other engine issues

1 hour ago, CleZ said:

 I turn to my mechanic to get this thing running right.

So, I now realize that these Mikuni carbs are probably not the best choice--especially at the lower end. 

Did your mechanic tell you that?  Power band is controlled more by cam profile and/or cam timing.

My mechanic definitely thinks of them as more of a racing carb. He never said anything about swapping them out. That's more the feeling I get after reading about them being hard to tune, and making some other inferences about "racing" carbs. I was under the impression they are not good for stop and go, daily driving. I have not had the opportunity to drive this much. I've had it for a couple years, but I've been taking care of some other issues--fuel lines, gas tank leak, alternator and a few electrical problems. I finally had this on the road the other day for a test drive, and it just didn't feel right to me--really puttering at low RPMs, and stalled when I was pulling into a parking place.

He's working on the valves now, but maybe I'm just overthinking this. So, correctly tuned these should be fine for a daily driver?

I should add, this only has a 4-speed tranny. I'm thinking of swapping it for a 5.

Edited July 12, 20186 yr by CleZ

I would be happy to buy those Mikunis

The key I remembered in my research about getting a set of Mikunis or any triples is they need to be tuned by someone who knows what they are doing.  Have the valves adjusted, make sure the timing is good and, if at all possible, tune them on a dyno.  I found someone who did all of that and my Mikunis run like champs.  A well tuned set of SUs will perform great on the street and will do 90% of what a set of triples will do performance wise, it's that last 10% when you're really laying in to the throttle that triples perform.  On the other hand, you could probably sell the triples and buy a set of ZTherapy SUs which would be easier to tune and give great daily driving/autocross performance.  Make sure you get a good heat shield for either setup, my SUs vapor locked more easily than the triples do but it was always something I was paying attention to, especially in the summer.

If you decide you or your mechanic rather do SU carbs I have a clean set I’d trade for the Mikunis. If you were closer I would offer my services to get the Mikunis running. They can actually be set up off the car, but final adjustments need to be on the engine running based on the motor build

Hi I’m also wondering if you’re considering of selling your mikunis. And maybe if you have pictures of them. I know it’s been some time. But consider selling them. Thank you.


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I'd consider it, but the problem is there are so few mechanics around here who could help me do a swap and then I'm concerned that I may be opening myself up to a whole new set of problems. I'd have to do more research.

Have you spoken to Lanny at R&R in Kent about the Mikuni's. 

https://www.facebook.com/510Restoration/

Edited August 27, 20195 yr by Jeff Berk
added URL

small venturi ~28mm to 30mm makes for a nice street setup

I'm not familiar with R&R, thanks for the suggestion, and the tip about venturi

 

Mikuni's are similar to Webers. This site might help you:

http://240260280.com/Tech/Carbs/Weber/DCOE Theory Operation and Tuning.html