Types of Mikuni/ Solex 44

[Danny_Vilato]

I know there are several versions of the Mikuni/Solex 44 carbs.
http://www.wolfcreekracing.com/carbid.html" onclick="window.open(this.href);return false;
The question is, do they all work for the U20 Roadster?
I have seen some with the fuel lines on the sides and some on the top.
Does it make a difference the placement of the fuel line?
Is that something that is interchangeable?

Thanks, Danny

[SLOroadster]

All 44pHHs will work, it just requires the correct linkage, and jetting. I'd imagine that Todd has the correct linkage, and perhaps an intake as well. He knows his stuff, and has lots of it.

Will

[Danny_Vilato]

Will,
I bought a set from Todd. It has the fuel tubes on top. But when I see some (most) of the pics of the forum, they have the fuel tubes on the side. I wanted to know if I can move them to the side, like the original Roadster type.

[spl310]

If you find someone with the other float covers, you could swap. I believe that you could drill and plug the covers to move the inlets, but it seems like an inordinate amount of work for appearance...

[SLOroadster]

Did you get a set of old style carbs, or the later type 4/5 with the rectangular jet cover? There are a few variations of the new style, but non of them affect the performance of the carb. As for the jet covers, I wouldn't worry about it. I'd set the front fuel inlet T so the top of it faces the back of the carb, and just run it. It will function just fine, and will keep the clutter down.

Will

[Danny_Vilato]

Will,
I have the newer style carbs 4 or 5. I don't know which.

solex carbs.jpg

I had wanted to use the fuel t that is attached to the manifold/head.
But I think the fuel line will have to a big loop.
Otherwise cancel the fuel t and loop the fuel line from the bracket in front of the valve cover

[SLOroadster]

Those look like type 5s, the way you tell is the # of screws holding down the float cover. It looks like you have 5 so they are T-5s. I would recommend getting a single inlet for the rear carb however. You don't need the fuel return with Mikunis. I have never had a hot start fuel issue, and the return line is just another thing to clutter the engine bay. I tried running mine as I have the float bowl coolers on the bottom of my carbs and the way they work is by taking cold fuel and running it through the coolers to the return. The only problem was that the fuel would vaporize before it got back to the return, so I would just end up pressurizing the tank all the time. That caused some strange issues. I abandoned the idea, and removed the top of the return line and capped the end.

Even running at Thunderhill in July with track temps close to 120, I had no vapor lock issues.

Those do look sweet however.

Will

[spl310]

The Japanese domestic market cars had a fuel return valve on the rear carb unless I am mistaken. (been known to happen) Rallye has one that may work:

http://www.datsunroadster.com/PIC_PAGES ... 161-B2.htm" onclick="window.open(this.href);return false;

[drewnamis]

For the U20s, I read how there are "early" solexes and "late" solexes. What's the difference?

[SLOroadster]

Ahh, the early late question. The 67.5 2000s came with what is known as the early style. They look similar, but the jet cover is a kidney shape and is held in place with 2 screws. The early style carbs are also made of Antimony, a mixture of lead and tin. This has some good benefits and some strange downfalls all at once. The good is that they don't heat soak well, the bad is that they will distort some when they get warm sometimes causing strange running and a tendency to move out of tune. They also have no quick way to adjust the float level. The later style carbs have a rectangular jet cover with a single screw in the center to hold it on. The type 5 carbs have externally adjustable floats. They are also made of Aluminum. All in all, the new style carbs are best. Mikuni continued to improve the design until they quit making them all together. The early type 5s say SOLEX and Mikuni in smaller font on the jet covers. The later ones just say Mikuni on the jet covers. Mikunis do have one flaw in them that only comes up if you are racing with a high flow head. The carbs will flood the vents and cause the engine to hack and gag on the fuel flowing through the air jets, and other places where it shouldn't be. It only happens through right hand corners however. It clears up as soon as the car is returned to straight line running or a left turn. The fix is to seal off the vents under the jet cover and drill a new vent in the top of the float cover at a high point. I had to have this done on mine. The difference between the type 4s and 5s is the number of screws holding the float cover on, and perhaps the external float adjustment (however some if not all the type 4s could have this) I know one of the sets after the pHH2s (old style) had the later float covers, but didn't have the adjustable floats.

Will

[gtrbg]

Just wondering if you have any pictures of the fix you mentioned for the vent flooding? Just raced my Datsun 2000 with Mikunis on the track for the first time after buying it out of long term storage and doing some rehab and maintenance.

Have a issue at lime rock coming out of the big right hand turn at the end of the straight. Bogs and runs rich per air flow meter as I try to accelerate at the end of the turn. Seems to clear on the straight and then one of the few left hand turns that comes up right away. Definitely seem to have an issue on hard rights if accelerate but then again most of the turns are to the right.

Your fix or lowering a notch on the accelerator pump rod was what I was thinking of trying.

Very helpful post. Thanks.

[gtrbg]

Picture of my carb with jet cover removed.

[david premo]

You have the 2nd generation of 44’s the fix is pretty strait forward. I recommend you verify correct fuel level as well as the type 3 which is what you have, do not have external float adjustments so you will need to verify the level and shim the needle valves accordingly. After you have corrected the fuel level you may or may not need to do the modification to the top cover.
Dave

[gtrbg]

Thanks for the info. Do you know anyone that has shims to adjust the floats? Carb say n44phh-a11 on side but it looks to be using 40 jet blocks and air jets. As you pointed out do not see an external float adjustment. Also a bit weird as it’s has 180 air jets outboard and 165 on the inside throats.

[david premo]

I have the shims in stock and most all the parts except the bodies castings and float cover castings. Inner ventures, jet access covers and most all the other internal parts are in my inventory.
Dave