L20b Carb Options on 510 swap

[Grimlid]

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•  

   Im looking at buying a new carb set up for the L20b I'm having rebuilt.

   

  I have a chance to buy a Hitachi su carb set  similar to the one listed in this thread https://ratsun.net/topic/79997-l20b-carburetor/   

  they are set up for an 1600 sss but I can get them  jetted by Paul Silva. I feel confident they will fit since I don't have a brake booster (though if i could iI sure would....)

   

   I also found a set of Yamaha bike carbs with an intake manifold listed on ratsun classified https://ratsun.net/classifieds/item/1908-fs-yamaha-r1-carb-setup/   which looks similar to Datzemikes bike carb set up. (listed in the above thread and a few other pics Mike has posted (not sure if he still run these though).

   

  I could also buy a dcoe weber set up currently but obviously convenience and costly go together. Realistically They are more or less plug and play the dcoe setup would likely save all the trouble the other 2 set ups will present (I assume). All the weber will need is a tune up and jet kit. though hypothetically the other 2 sets might go just as easy....Pierce Manifolds  I heard these are made in 'China though (unconfirmed)   https://www.piercemanifolds.com/Datsun_510_L_Series_Weber_Conversion_K637_45_p/k637-45.htm

   

  If Datzenmike  is reading this ""How complicated was your bike carb set up to install and tune?"  I have some  good people to help make up for my inadequacies.  Im actually a high btu gas fitter so I understand the theory behind all this but my experience is with boilers and gas appliances' and only stationary equipment run in controlled environments. 

   

  At any rate what would you go guys go with :

   

  Hitachi su style dual carb set (looks new nearly, super old school cool but could be a can of problems to set up due to unknowns) 750 plus shipping

   

  weber dcoe dual carb set (new and expensive but simple and effective) from Pierce Manifilds    2 grand plus

   

  yamaha bike carb set with manifold (reconditioned but no user manual available). these look uber cool and I love the sound they make when running but could also present a lot of issues. you are the only human I am aware of running them on anything other than a bike. 500 USD plus shipping

   

  I also have the option  to set it up with the big old truck carburetor that came with it.  Tycot1 said it ran fine for him before he installed his KA . he gave me the old carb when he sold me his back up stock of l20 and l18 while cleaning out his shop.    300 cash installed and rebuilt

   

  Something other completely!!!????

   

  Thanks in advance for reading this far if you were able to and I owe you one if you can share your experience on this subject its a pretty major decision in my build.

  Thanks again,

  Russ Grimlid

   

   

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Edited March 13 by Grimlid

[banzai510(hainz)]

Sounds like you want sidedrafts.

 

Weber 32/36 dgv if you still have the intake manifold, down daft is EZ to install and get going.

 

that bike car set up is COOL but be nice is manifolds are all together as one unit. so later to work on motor you can take the carb and manifold and esp the lnikage OFF as all one unit.  The the Weber or Mikunis tyep set ups(just disconnect the cable to the throttle pedal

 

I remember a Byron that lived up there on the 510Realm He could assist you in making a choice

Edited March 12 by banzai510(hainz)

[datzenmike]

The R-1s are fine for the summer for me. They don't have accelerator pumps so you can't pump the gas several times to make it richer to start. Instead there is a pull cable that enriches the mixture for starting. Cold starts involves cranking several times till it fires and stalls progressively running longer and longer till it idles at 450- chugging away. It quickly warms and idles but when dead cold it won't rev up properly. There is an idle speed adjustment cable that I haven't sorted out properly that gives a fast idle. Perhaps the enrichment set up needs to be richer? Other than the slow starting it runs incredibly well and restart is a breeze the rest of the day. Idle is very strong and it's weird driving an engine that has zero hesitation at low speeds when you step into it in any higher gear. I noticed that above 4K the original carburetor climbs more slowly to 5k while the R-1s pulls all the way to 6k. I made and ran long air horns without filters and then shortened them till they did fit a 280zx air filter. The long pipes had more low speed torque. Sound was worth it. Looking in the ends with the slide up you can see the intake valve so very straight entry, much more efficient than dual SUs and way better than a down draft.

 

I followed the recommendations and re-jetted for richer on a larger displacement but my wide band read 9.6 which is as low as it would go and you could see black smoke out the back, ran really good though. Progressively going smaller and smaller I brought the air/fuel to high 12s WOT. Eventually it was almost the same as the original bike jets. Now seems to me that a carburetor just blindly mixes fuel with air and has no idea what displacement engine is drawing through it. X amount of air needs X amount of fuel. So I could have left the original jets in probably. Anyway, the take away is why would you need to change jets going to a larger displacement? An L20B at 2,000 rpms is the same as L16 at 2,500 rpms the carburetor doesn't know that.... the long road of enlightenment. 

 

Like the 510, the 710 also has throttle linkage. I changed to a cable because you can mount anywhere on the carb end. The R-1 throttle pull is smaller diameter than the pedal end so in effect a small pedal amount makes a large carburetor input. I wasn't putting up with that so I changed the pedal ratio so the travel was longer and more closely matched the original carburetor. This made the pedal less aggressive. Throttle cable will be a big challenge for you. 

 

I spent probably close to $400 trying stuff that didn't work and said to hell with being cute, and welded up a manifold for about $30 in scrap steel. That ended up being the easiest part.

 

If I were you I would run original carburetor or 32/36 Weber. Dual SUs look nice but not enough difference,

 

 

[Stoffregen Motorsports]

Unless you are having the head ported and installing a bigger cam, dual Webers or Mikunis won't give you much except a cool sound.

[Grimlid]

13 hours ago, banzai510(hainz) said:

Sounds like you want sidedrafts.

 

Weber 32/36 dgv if you still have the intake manifold, down daft is EZ to install and get going.

 

that bike car set up is COOL but be nice is manifolds are all together as one unit. so later to work on motor you can take the carb and manifold and esp the lnikage OFF as all one unit.  The the Weber or Mikunis tyep set ups(just disconnect the cable to the throttle pedal

 

I remember a Byron that lived up there on the 510Realm He could assist you in making a choice

Thanks I know Byron he lives near me . I tried bugging him before I posted lol he was too busy i guess

[Grimlid]

12 hours ago, datzenmike said:

The R-1s are fine for the summer for me. They don't have accelerator pumps so you can't pump the gas several times to make it richer to start. Instead there is a pull cable that enriches the mixture for starting. Cold starts involves cranking several times till it fires and stalls progressively running longer and longer till it idles at 450- chugging away. It quickly warms and idles but when dead cold it won't rev up properly. There is an idle speed adjustment cable that I haven't sorted out properly that gives a fast idle. Perhaps the enrichment set up needs to be richer? Other than the slow starting it runs incredibly well and restart is a breeze the rest of the day. Idle is very strong and it's weird driving an engine that has zero hesitation at low speeds when you step into it in any higher gear. I noticed that above 4K the original carburetor climbs more slowly to 5k while the R-1s pulls all the way to 6k. I made and ran long air horns without filters and then shortened them till they did fit a 280zx air filter. The long pipes had more low speed torque. Sound was worth it. Looking in the ends with the slide up you can see the intake valve so very straight entry, much more efficient than dual SUs and way better than a down draft.

 

I followed the recommendations and re-jetted for richer on a larger displacement but my wide band read 9.6 which is as low as it would go and you could see black smoke out the back, ran really good though. Progressively going smaller and smaller I brought the air/fuel to high 12s WOT. Eventually it was almost the same as the original bike jets. Now seems to me that a carburetor just blindly mixes fuel with air and has no idea what displacement engine is drawing through it. X amount of air needs X amount of fuel. So I could have left the original jets in probably. Anyway, the take away is why would you need to change jets going to a larger displacement? An L20B at 2,000 rpms is the same as L16 at 2,500 rpms the carburetor doesn't know that.... the long road of enlightenment. 

 

Like the 510, the 710 also has throttle linkage. I changed to a cable because you can mount anywhere on the carb end. The R-1 throttle pull is smaller diameter than the pedal end so in effect a small pedal amount makes a large carburetor input. I wasn't putting up with that so I changed the pedal ratio so the travel was longer and more closely matched the original carburetor. This made the pedal less aggressive. Throttle cable will be a big challenge for you. 

 

I spent probably close to $400 trying stuff that didn't work and said to hell with being cute, and welded up a manifold for about $30 in scrap steel. That ended up being the easiest part.

 

If I were you I would run original carburetor or 32/36 Weber. Dual SUs look nice but not enough difference,

 

 

Thanks for all the info and your frankness. I never considered the lack of a choke. Like you say I'm probably gonna mount the downdraft just because it's there and basically free. I have to find some numbers on the one that came with it. 

Thanks again you sure know a lot about these units. 

[Grimlid]

10 hours ago, Stoffregen Motorsports said:

Unless you are having the head ported and installing a bigger cam, dual Webers or Mikunis won't give you much except a cool sound.

Thanks. I think I've heard it enough to actually believe it lol.  I am likely to port the head and  do some cam work but my mechanic is already asking to just do a simple rebuild because he is super busy. May have to hold the whole project oover if I can't convince him to do what I'm looking for. Glad my l16 has only 33000 miles original

[datzenmike]

Speedometer rolls over to 00,000 after 99,999. Much more likely it's 133,000. Look for original muffler and shocks, wear on the brake pedal, driver's arm rest and seat and hinge wear on driver's door. 

[Grimlid]

On 3/13/2024 at 6:41 AM, datzenmike said:

Speedometer rolls over to 00,000 after 99,999. Much more likely it's 133,000. Look for original muffler and shocks, wear on the brake pedal, driver's arm rest and seat and hinge wear on driver's door. 

Ive had multiple old cars (Im mid 50s) and know all about the odo rollover.....honestly this was a barn find in Williams lake. The guy I bought it off worked for the city of Williams Lake. He watched the car sit since 1978 in a barn off the side of a rural road. It sat in full sunlight all day every day with no barn door. The front windshield was completely opaque from uv damage and the hood and roof had completely ruined paint from wind and uv damage. the car litterally sat for nearly 35 years exposed to sun and light rain and snow but only in the front half of the car. The guy (Mike is his name) tried to buy the car countless times the woman who owned it always refused as she was going to fix it. It was on the reserve apparently and he had friends there. She passed away in 2012 (or something) and he bought the car off her kids for a low price. He repainted it and tuned it up sold it to me (in 2015) after he fell in love with a mustang or something. He sold it me on the promise I never "cut it up". I had to race 2 other guys to get there with the money. we both believe it is 33k miles. the interior was perfect except for the cardboard and the c pillars. The seats werent  even cracked. Ive put 3k on it since I bought and my kids and I have done more damage because everything is so fragile from age. (seats are cracking now)i removed the original shocks (tt3 replace) and steering wheel (momo clone) though Mike removed the muffler and ran a straight pipe. break, clutch and accelerator are clean Its genuine 33k with basically zero rust. the Williams lake dust under the thing is like concrete though. Loooong story but its a lot km to account for lol. My dream is to hand it over to my son when Im too old to enjoy it.

Edited March 17 by Grimlid

[datzenmike]

My 74 710 (originally from an estate sale) had like Under 30,000K or 18K miles on it. (first year for metric speedometer) Had the original muffler fitted, no muffler clamps. No way they last 118K miles. Automatic brake pedal looked new, seat like new.

 

[Grimlid]

thats a definite classic whish I had seen the original to my car. The guy was a  mechanic at the city works and was able to bend the exhaust so he did and threw a resonator on it. I have to change it when I finish the swap its so obnoxious. loud pipes save lives but hurt kids ears.. 

so 73 was first year metric. Mine is in miles its a 72.

I was told also my car may be American made? the heater core I bought for it didn't fit right and my buddy said it was because the heater was for a  Canadian and the car is American. I was assuming that was why the speedo is in miles . he managed to get the heater to work but not with the linkages at the controls. I have to reach and manually open the valve under the dash. doesnt work worth a shit anyways.

Can anyone tell a way to know the difference between the american and canadian vehicles or  is this whole theory half cooked. All I know is the heater box said 72 510 and the fit up of the pipes was incorrect. I was under the impression from when i had my 510s in high school that they were made in mexico and america no one ever mentioned made in canada....

[datzenmike]

I think the only 510s built outside of Japan is in South Africa. The Canadian 510 simply got a HD heater that was optional in the lower US. There is an optional heater core, valve and a few other things to make it different from the standard one.

 

The first year Canadian 510 had amber turn signals like Europe they were red in the US. Later cars and trucks got a 60 amp alternator that was normally a 50 amp in the states. '78 and on 620 trucks, 280z, 810 did have an optional gear reduction starter for cold climates that was standard in Canadan models. I have an 810/Maxima gear reduction starter in my 710.

[Grimlid]

On 3/18/2024 at 6:51 AM, datzenmike said:

I think the only 510s built outside of Japan is in South Africa. The Canadian 510 simply got a HD heater that was optional in the lower US. There is an optional heater core, valve and a few other things to make it different from the standard one.

 

The first year Canadian 510 had amber turn signals like Europe they were red in the US. Later cars and trucks got a 60 amp alternator that was normally a 50 amp in the states. '78 and on 620 trucks, 280z, 810 did have an optional gear reduction starter for cold climates that was standard in Canadan models. I have an 810/Maxima gear reduction starter in my 710.

Thanks Mike. I've been asking around for 5 plus years and you are the

First to finally answer that one. Muchn

 appreciated