Solex jetting

[69roadster]

Looking for some starter jets recommendations for my solex u20 . Not much to the engine..40 over solex with B cam. I saw Dean has a kit anyone have any experience with them.

https://www.datsunparts.com/2328

[Gregs672000]

As you probably know, there are a few different versions of Mikuni carbs, so we'll need more info. For example, what version of the carbs, what size main venturi, what are your current jets? Dave Premo knows theses carbs and cams well, and he may offer some suggestions (and supplies jets too).

Later versions came with 34mm venturi vs the early with 37s. People often set the accelerator pump in the bottom hole as the Mikinu accelerators tend to over fuel and that will reduce the volume. All engines vary, so while a change can get you closer, and maybe right on, it may be necessary to try a few different mains and airs to dial it in. Also, without a wideband O2 sensor giving you real immediate feedback, you're going to need to read your plugs and make sure you're not lean or rich. If you don't want to buy and install a wideband (requires welding), then another option would be to get the suggested jets, read plugs and make sure you're OK, and go to a dyno tuning shop and do a test pull with their O2 set up to make sure you're good and safe. They will be able to tell you what it's doing at different rpms and which carb system is operating (pilot vs mains), and likely suggest a step or two in either direction for jet changes. I suggest you familiarize yourself with how the carbs work in general via a mikuni manual or off the internet. All this is optional, but worth doing in my opinion. You have installed a system that is more tunable (Mikuni vs SU) but to get the best results ya have to tune IT!

To give you an example of why I love having a wideband, yesterday I was out breaking in my new engine and noted a stumble at times. I could immedialty look at the wideband and see it's a lean stumble, and it has to do with my accelerator system needing adjustment (not enough response) as the jets quickly catch up and air to fuel ratios go back to where I want them... There's a lot less guessing about where or what to tune, and I will be able to see my results with each change. After so many years of jetting carbs by reading plugs, this is awesome.

Hope that helps!

[bakerjf]

Dave Premo is the authority on Mikuni tuning, and will figure out what you need very quickly.

http://tuning4performance.com/

[theunz]

As mentioned save yourself some trouble and just contact Dave. He sent me all the jets and gaskets and they were spot on.

[69roadster]

Thanks, I will contact Dave

[Swimdad1960]

Dave Premo is the absolute expert! After screwing around for years with various jets for my NOS 44's type 4, Dave instantly quoted was seemed like an odd jet combination based on the available internet information. The car ran great but was clearly rich based on plugs and fumes. A quick call with Dave and he further diagnosed that my float levels were also too high. He was right (15MM down vs 18mm). The car now screams at all speeds and plugs look perfect.

[bakerjf]

Dave Premo is the absolute expert! After screwing around for years with various jets for my NOS 44's type 4, Dave instantly quoted was seemed like an odd jet combination based on the available internet information. The car ran great but was clearly rich based on plugs and fumes. A quick call with Dave and he further diagnosed that my float levels were also too high. He was right (15MM down vs 18mm). The car now screams at all speeds and plugs look perfect.

Yup. Having a resource like Dave available to the Roadster community is huge.