Datsun Roadster Forum-311s.org

We all go a bit mad from time to time.

Since my R16 has undergone a rebuild, and since the cam needed to be reground anyway, I had it sent out to Isky cams for a DR-66 grind. And since I have a bit more lift and duration, I figured, maybe replace the stock SUs. Was thinking, what? DCOE, Z Therapy SUs? then I ran across This place http://v-performance.com/products.html .

Volvos wear SUs as well so a kits are available to convert to Mikuni HSR42 or 45 carbs to an existing SU inlet manifold. I had an email exchange over a couple weeks, and decided on a HSR42 carb kit came with 2 carbies, adapters,linkages, and K&N filters.

The stock throttle cable anchor point looks okay but I think I'd like to get it a bit closer to the lever on the throttle linkage. Chokes may be a bit more challenging. Here are some photos of the setup:

That looks like a great start. I am looking forward to reading more on this one.

Steve

Cool find on those adapters. On paper this looks like a great swap, functionality like the SU with a more modern design. And the bore is wide open without the steps inside the SUs.

Interesting. I can understand the Think Different aspect, but wonder how much a performance benefit there will be on a stock R16. Any plans to dyno the finished product?

Will there be a decrease in MPG with the Mikuni 45's vs the stock SU 38's? Might be something to thing about considering a rebuilt set of SU's from Ztherapy is $630 vs $900 for this setup. If the Mikunis equal or better the SU MPG, then this would be a terrific upgrade.

How about clearance? Do the Mikunis have a smaller height than SU's?

That is one cool looking setup. That choke cabling is going to be tricky to find a pivot point for that slide movement.

interesting. I can understand the Think Different aspect, but wonder how much a performance benefit there will be on a stock R16. Any plans to dyno the finished product?

Not quite stock. Mo change in displacement, but there is a hotter (ISKY DR-66) in. The problem with the ZTherapy carbs, if I were to go any different than rebuilding my stock units, is the core charge which gets us back up to what these are. price wise I believe. AS far as a performance benefit if any, that remains to be seen. Not sure if I want to go to the fuss and bother of dynoing with the SUs then re-trying with the Mikunis, will probably be depending on the Butt-Dyno

Another advantage I anticipate with the Mikunis is being able to go down to the local harley shop for needles, parts, etc. But this is, after all, an experiment.

autoquick wrote:That is one cool looking setup. That choke cabling is going to be tricky to find a pivot point for that slide movement.

That does look to be the trickiest part. I have a cheep snowmobile cable for dual mikuni chokes on order. The cable outlet to the choke is near the top of the carb pointed towards the back, and full travel is only about 1/4 inch so it should be interesting.

I was thinking of trying a set of the Harley SU Eliminators if I can scare up a set cheap. The V8 is on hold, but I have an H-20 on the stand...
The Mikunis are nice, as you said, parts availability is a plus.

dbrick wrote:I was thinking of trying a set of the Harley SU Eliminators if I can scare up a set cheap. The V8 is on hold, but I have an H-20 on the stand...
The Mikunis are nice, as you said, parts availability is a plus.

dbrick - watch out for the eliminators kits. Some do not include the choke, rather they recycle the choke from the CV carb. that they expect your replacing. Read the kit numbers. Some Mikuni kits include the full choke setup and some don't. And getting that little item is a pain in the tailpipe because it's a cable, plug/pin and return spring.

That should be a nice setup! I have quad 40mm flatslides and they really flow! Do you have any clearance issues with rear carb and steering shaft? Just curious as my #4 carb is further back than your rear carb and thus the float bowl hits the shaft. I had to set the carbs further away from the mani by about 1.5 inch.
You will probably be fiddling with several emulsion tube sizes and jet needles to get them dialed in but it should be fun. Keep us posted.
Now we need some one to experiment with a pair of 45 or 48 on a U20!

nismou20 wrote:That should be a nice setup! I have quad 40mm flatslides and they really flow! Do you have any clearance issues with rear carb and steering shaft? Just curious as my #4 carb is further back than your rear carb and thus the float bowl hits the shaft. I had to set the carbs further away from the mani by about 1.5 inch.
You will probably be fiddling with several emulsion tube sizes and jet needles to get them dialed in but it should be fun. Keep us posted.
Now we need some one to experiment with a pair of 45 or 48 on a U20!

Engine is out of the car but they look to occupy almost the identical space of the SUs. I'll stick the heat shield on, refer back to photos of SUs in, and see if any problems crop up there.

Well I've fabbed up a dual choke cable for the Mikunis (most of the way, anyway.) I ordered a dual mikuni cable from a snowmobile outfit, mainly for reference, everything was too short. Travel is short, around 1/4 inch or 6 mm. I decided to use the knob from the snowmobile cable for the time being. Bought some raw lined cable housing from the same outfit, and have some stainless cable and copper cable ends from my work. Had to make some special little brass barrel shaped cable stops to interface with the carb. I'm hoping soldering will provide sufficient holding power. Here are some pics:

This end goes to the carb (there are 2)


Here are the guts of the controller end. compression spring is from the snowmobile cable ass'y.


Assembled control


Control knob (for now)

How did this experiment end?