Datsun Roadster Forum-311s.org

Based on the video, I would guess a timing issue. The hotter coil may have been able to ignite the charge but just not at the optimal point in the stroke. Moving the distributor side to side, as Greg suggested, while it is running/stumbling may help diagnose.

When it is running, albeit poorly, do you smell gas? Are the throats of the carbs wet with fuel while running? Excess fuel in the cylinder (wet plugs), black smoke out exhaust, are symptoms of timing being off - either ignition or cam timing. Pull the valve cover and look at the valve positions at #1 TDC.

Last thoughts is the eDizzy matchbox module may be faulty. It happens... You said you had another distributor - is it a points version? Maybe try it again?

Agree with Joe. I also may have misspoke regarding the carb adjustment screws, in that the individual throttle plate screws basically act as a "stopper" for how closed that plate can go. When I used to balance my SUs, as I recall I would disconnect the linkage at the dog bones, then set those screws so both carbs were drawing equal air but such that it would idle at about 600rpm with the linkage disconnected, then snap the dog bones back on (idle screw loose) and make sure the dog bones themselves don't change the throttle plate(s) position due to their lengths not being equal, then set the idle to 900 or so via the idle screw, making sure the carbs continued to draw equal air.

Have you PERSONALLY seen this engine run and rev prior to you freshening it up? If not, is it possible that something else YOU didn't do is causing some issues (carb linkage, fuel delivery, some weird electrical issue?). For example, an SU set up I bought for my L-series as a kid had screwed up linkage that would not allow me to adjust the carbs correctly. A decent Z car shop owner helped me with that or I would never have gotten them to work. Sometimes it's not your doing...

Also, while it's running put the timing light to it and try to rev the engine slowly to see if the timing is advancing, or if it's dropping spark. It didn't look like it wanted to rev at all, so just be slow and nice to her...

This is frustrating I'm sure... these damn engines are not that complex!!!!

I also want to be sure... if I end up saying stuff that's kinda "obvious" or already known to you it's only because I don't know what your level of experience and understanding is regarding this stuff, so I'm trying to make it as straight forward and clear as I can. I'm no expert and make plenty of mistakes, just been messing with these engines for a long time and I'm always happy to try and help

Your posts have been great and you have followed advice well. Keep slugging away, we will get it one way or another.

nismou20 wrote: Thu Mar 20, 2025 11:59 am You have checked the float levels I presume.

This would be my next check if it was me.

Where'd you get that fan blade ? ,50° angle of attack ? ...it's possible it sucking all the air from the carbs looks like it's capable / puts out 130lbs of thrust

PROGRESS!! As with most problems, it is not just one thing - it is EVERYTHING!

I went back to the carbs. Took them off. examined everything. Found a sticky needle valve on the front carb float for one thing, and a sticky choke, and after much massaging I reassembled my best matched pair reworked for smooth action and the beast came to life. Now to check the timing.

Timing is way retarded. firing pretty late, so I loosened both adjust screws on the dizzy (top and bottom) and twisted clockwise to advance the spark. I was able to get it closer but the best I can do is maybe around TDC (+/- 5 degrees as my painted mark is 16 BTDC and so this is an estimate). Anyway cannot get to 16 BTDC. I disconnected the vacuum hose but the idle is higher than I would like, to keep it running smoothly.

SO, I think I need to pull the dizzy again and try to rotate the oil pump and drive gear one tooth counterclockwise to give me the range I will need to get a good timing, but wanted to get an opinion before going there because it is a royal PITA to get everything to drop, as y'all know. Since timing would advance at a higher idle, I don't think lowering my idle speed will help me get better timing with the current setup, so I think that is my next step, then when the timing is close, I can dial in the carbs, and do a final timing check. Do y'all agree? Thanks for the helping hands and heads. I think I am on my way, and your help is invaluable!

By the way, the fan blade is simply an early stock blade from maybe a '66. I hate the whirr the 7-blade fan makes and I have a few of these, Cools pretty good too. It is a two piece fan blade.

Hey Mike congrats, great perseverance and news. I'll let the timing/dissy experts help you get the last 5% dialed in, but nice to hear you are close!

Good News on getting the beast running! I agree with your approach. Here is some info from Zcar Guide on carb tuning (https://zcarguide.com/tuning-adjusting- ... rburetors/)

Before tuning carbs first check:

• ignition timing
  Spark plug gap level and condition
  Cylinder compression
  Valve clearances

Of these, the most significant is the condition of your spark plugs. To be perfectly honest, you can do a little bit of carburetor adjustment without doing a spark plug replacement, but it will be impossible to tune the carburetors properly if even one of your spark plugs has fouled

Joe, thanks for the link. Great article. You can never get good enough at tuning these carbs. I have all the right prerequisites in place now because I had a good morning in the shop. After re-dropping my drive gear (it went easily for once) I am now able to time it at 16 degrees BTDC and it is running very smoothly. On to the carbs and final tweaks. You guys really walked me through everything and gave me the determination to do it all one more time, which is often what it takes. Once I have it perfect, I'll post another vid. Before and after.....

Nicely done, Mike. It is often hard to work through the frustrations. Now, sit back and enjoy a home brew. Best of all, enjoy your roadster!

Does the beast have a name?

Great idea. I do have a new batch of homebrew that I made with a friend's hop harvest from last year. I wanted to showcase his hops so I did a simple pilsner that I killed with fresh hops. In the mash, in the boil and a dry hop. Lagered it at 48 degrees for about 10 weeks before bottling. It may be the best pilsner I have ever made. Wish I was as good with roadsters as I am with beer!

Woo hoo! I'm a little late to the party being that I've worked the past two days, but it looks like we have engines a-running and beer a-brewing... awesome! Congratulations on your persistence and success. You have proven to your Roadster that you truly love it... may there be smooth sailing from here on out (ya, just like any love relationship eh!)

Thanks Greg. You kept me on task. Very thorough analysis and logical progression. They will run if everything happens at the right time in the right amount. BTW I am going to visit my daughter in Puyallup in June. I''ll PM you and buy you a beer.

Celebratory beer. Nothing better.

roadsterdude1600 wrote: Sun Mar 23, 2025 7:00 am Thanks Greg. You kept me on task. Very thorough analysis and logical progression. They will run if everything happens at the right time in the right amount. BTW I am going to visit my daughter in Puyallup in June. I''ll PM you and buy you a beer.

Cool man, I look forward to it... I'll even drive the Datsun and if you have time and the weather cooperates we'll run up to the top of Rainier!