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Art · Post by **Art** » Sat Aug 21, 2004 10:41 am

Well I guess its time for an introduction My name is Art Ashline, I have been hovering around this site for a couple weeks, I picked my first roadster its a silver 68 1600 2 owner with 55000 miles, but man was the engine tunning messed up, first off the alternater was bad so rather than mess around with that old crap I converted it to a internally regulated GM 63 amp alternater took about 30 min and I used all the stock brackets no cutting chopping or anything and best of all from now on I can get a reman replacement for $20. Next up valve adjustment, points, plugs, wires, timing, changed cracked exhaust manifold and lastly adjusting the carbs, and on that note I have a question is there a manifold available that I can use to convert it to a single carb? Once I was done with all that I still had a problem with it pinging real bad and running out of power around 3500 to 4000 in the 3rd and 4th gear I knew it was an ignition problem I just didn't know what it was. So I got out my meter and started shooting wires what I found I was only getting 5 volts to the positive side of the coil after cleaning the contacts voltage went up to normal and now it runs great however I'm going to check the carbs again. Next up is converting to electronic ignition just have to figure out what I'm going to use for a donor, a pre smog recurve kit and single carb if I have to make a manifold myself. I found a complete 69 2000 donor car and bought the 5 speed, driveshaft and mount for $50 so I guess I'll be putting a five speed. This is a great site I've learned allot. Thank you P.S that 69 2000 I mentioned has some good parts very reasonable if anyone needs anything let me know.

SLOroadster · Post by **SLOroadster** » Sat Aug 21, 2004 11:10 am

Art,
Why do you want to run a single carb? You can't pull anywhere near the power. With the 5 spd, you are going to have a nice freeway cruser but I think you might be a little overgeared (the 5spds are taller geared than the 4spds I think.) If you are looking for a fairly trouble free carb setup, get a set of Mikuni 40 Phhs. They are the closest thing to fuel injection that you can find without actually having it. Essentially you set them and forget them. Once you have the jets figured out, you only need to balance them every 3000 miles or so. Also you never see 1600s with the mikunis.
Just a thought,
Will

Russell Roach · Post by **Russell Roach** » Sat Aug 21, 2004 1:34 pm

If you guys are interested I have the complete gear ratios for every gearbox for the roadster letme know and I'll get it to ya

Russell

ambradley · Post by **ambradley** » Sat Aug 21, 2004 1:46 pm

Re: different carbs. There are a couple of options. You can get a Solex (Mikuni)/Weber DCOE/DellOrto DHLA manifold from Pierce Manifolds. Mike Young has this or a similar manifold on his stroker 67.5 1600, pictures at www.datsunsports.com. If you think tuning SUs is difficult though, wait till you get to those carbs. Sizing all the components and tuning is an art form to be sure.

You could build a downdraft plenum that bolts to the existing SU manifold rather than replace the manifold. I've seen this done to Z's. As others have posted, this will likely reduce performance, not improve it. There's got to be some reason that many 620/510 owners convert to SUs on their L-series motors when they hop them up.

If you're made of money, someone recently posted a link to TWM's FI throttle body replacement for SUs. A fuel injected R16 or U20 would be tres cool.

Re: your one wire alternator. Where did you mount it? It will fit in the stock location (under the exhaust on the driver's side) and the fan belt lines up perfectly but the excess heat at that location will fry the internal regulator. Been there, done that. I don't know if a heavy-duty heat shield and wrapping the exhaust manifold or header would reduce the heat adequately.

Art · Post by **Art** » Sat Aug 21, 2004 4:46 pm

After driving a couple hundred miles the carbs are more to my liking it's idling good and the plugs are all a pretty light brown so I think the carbs are pretty close now, however having built and owned many cars and bikes I know theres more than one way to skin a cat I don't believe for a minute that you couldn't take a another type of carb and make as much or more power and get rid of the SUs. I'll be thinking about that and maybe come up with something this winter until then I'm just going to drive and enjoy, as for the alternator I mounted where the air pump goes on the rt side as mine didn't have the air pump anyway it fit fine no problems works great I even went to the local U pull it and got 280Z top bracket and made a back brace the belt is a Gates 7890 although I think I'll try a 7880 next time. I think you meen 1 wire by taking the 2 that go to the regulator and running them to the battery terminal on the back of the alternator and then just one wire to the battery I didn't do that I got a diode and ran power from the old reguator plug I believe the black white striped wire (power from the switch) through the diode (to prevent back powering the coil through switch) to the small wire on the GM that way the regulator is not powered all the time which is not real good for them and will cause early failure. The pictures in that wonderful Clymer Datsun Sports car handbook/service manual (aka crap) show the air pump on the left and alternator on the rt so I don't think it would take much to swap sides so you can run the GM alternator on the rt side I could be wrong though, and I know you Cali guys have to have that smog stuff. Thanks

ambradley · Post by **ambradley** » Sun Aug 22, 2004 9:22 am

Could you tell me more about your alternator bracket? Did you fabricate a bracket to bolt to the block, or did you find one that aligns the GM alternator properly? If you fabricated, is it something the average guy (i.e. me) can do?

Also, regarding your wiring, are you saying you attached the alternator output to the factory wiring? Or did you wire it to the battery but differently than I did? Again, I'm not an expert so would appreciate any additional info (the mention of a diode means you know more about electrical wiring than I do!). The only "gotcha" I've heard about attaching the alternator to the original wire is that the Roadster wiring can't handle the 60+ amps that the GM alternator can potentially put out and you could fry your ammeter or your wiring harness. Did you do something that avoids that?

Art · Post by **Art** » Sun Aug 22, 2004 12:08 pm

On the brackets I just used the Roadster brackets and turned the lower one over for extra clearance the top bracket work perfectly and I needed to trim about a 1/8 inch off the back of the GM alternator pivot for belt alignment. As for the wiring the Gm alternator has 2 wires 1 big and 1 small, and a batt post on back of the alternator what you'll need is the alternator and a connector, what I did was go to upull it and get the alternator the plug and some extra wire for 15 bucks I figured the core was $15 on a remanufactured alternator so I'd be out nothing if it didn't work I could just go get a new one for $19.99 and I got the wire and connector for free. On the connector you take the big wire and run it to the batt post on back of the alternator (if you get it from you upull it will probably already be done) and then batt post to the positive battery post so now all you have left is the small wire I started off by wiring this directly to the Black wire with a white stripe on the Datsun regulator plug and everything worked fine till I went to shut it off and found that it was back powering the ignition thought the switch(would not shut off) I had the same problem with a VW cabrio so you can either take that wire to the batt post on back of the alternator again and have the 1 wire hook up deal or get a diode to only let power flow to the alternator from the switch I choose the diode it easier on the regulator. The last time I went to radio shack and bought a diode and wired it in worked fine never had any problem. This time I just took a good one from the old alternator and made a little plastic bracket and bolted in the old regulator position again worked fine, but a little more work. ThatÃ¢â‚¬â„¢s it for wiring except capping off the old alternator wiring to insulate it and protect from dirt or whatever or you can just remove it whatever you like I like to have the option of going back anytime I want. Now all you need is a belt, I took some wire and wrapped it around the pulleys and was off to the auto parts Gates 7880 or 7890 should work fine. As an after thought I got a 280z top alternator bracket and fabbed a back brace as GM did on many of there cars don't think I really needed it, but what the hell. ThatÃ¢â‚¬â„¢s it I came out of the whole thing under 30 bucks. Your amp meter will still work and only show what you car is drawing. I hate amp meters so mine is going the way of the dinosaur and will be replaced by a volt meter. I suppose I could do an in-depth how to on this if there was any interest in this conversion. Ambradly I will check on the stuff you wanted I think from talking to him before that I can get all of it for around $200, but I would have to pull it all myself and I have no idea what shipping would be.

ambradley · Post by **ambradley** » Sun Aug 22, 2004 4:08 pm

Ok, so it sounds like what you did differently than me is you put the diode between the "exciter" connection on the alternator and the black/white wire that came to the alternator, I guess to tell it to produce power. In my case, I shorted those two spade connectors together so it automatically becomes "excited". You can buy alternators preconfigured this way from auto parts stores but they cost more and as far as I can tell they do the same thing internally that I did externally.

So you use the car's original "exciter" wire to excite the GM alternator, that seems like a pretty good idea. I'd heard of people feeding back power like you said but wasn't sure how they did that since I never had that problem. The only connections I have to the GM alternator are the wire to the + terminal on the battery and a ground wire, no other wires attached to turn the alternator on.