Carburettor substitutes

[jcard]

I'm beginning to suspect the carb on my 521 may need some attention( backfiring through carb, balking, very light colored plugs - lean mix I'm assuming). Contemplating whether or not to 1) attempt rebuild should it need it - never have rebuilt carb before 2) try to find rebuilt carb ( I've seen Chinese carbs for the L16 although I'm leery) 3) get a beautiful Spanish made Weber carb.

 

I really enjoy driving the old girl. don't mind spending the dough for whatever is appropriate. I suppose if there was a place to send the carb to rebuild it well I'd do that. I just want to eliminate the carb as a problem. I figure after 159k miles I don't want to be cheap and skimp. I think my dad sometime before he passed either replaced the carb or had bought a new one as I'm pretty sure he had one at his house but due to an ugly move( long story) I lost it. Unsure if the carb on the engine is original, rebuilt or what.

 

If I were to stay with a oem type carb I'd rather find a used one, get a rebuild kit to rebuild it outside of the car then swap it out; I hate leaving dissembled car pieces laying around or a dead car in my driveway...

 

I know it's nuts but I see those dual DCOE 40 Weber setups and just drool.... those wouldn't be good would they??

 

Thoughts?

 

Jerry

[flatcat19]

Buy a timing light and a repair manual. 

[flatcat19]

If you're looking for an excuse to buy a carb, just get yourself a Weber 32/36 until you get a handle on what you're doing. 

[Charlie69]

Welcome. We need pictures Please!

 

Download this Factory Service Manual and save it to DVD for future use.

 

http://datsun510.com/manuals/Service_Manual_Datsun_Pick-Up_Model_521_Series_Chassis_and_Body.pdf

[jcard]

I have a timing light, pretty sure the timing is correct or close to it, somewhere I may even still have a dwell meter.

 

In the past I did have a 1973 240z that I'd bought new - maintained through 296k miles of driving ( a few parts rebuilds, many air pumps, alternators, balancing those way overly complex Hitachi SU carbs ), a 1981 510 wagon also purchased new and lastly a 1967 1/2 1600 Roadster that I rebuilt major parts of..

 

So I have a little experience...just not a lot with this particular carb ....hence the post...

 

Jerry

[mklotz70]

It may not be your carb.  I'd run a compression test and check your valve adjustment.  Backfiring through the carb is really only possible if the explosion in the cylinder is allowed past the intake valve.  It could be your timing being off and firing the plugs at the wrong time, but that would affect all cylinders.  It could also be your plug wires in the wrong position, therefore firing the wrong cylinder.  It could also be cross fire.....bad plug wires that allow the spark to jump from one wire to another.....firing another cylinder at the wrong time. 

 

I'd start by watching the plug wires in the dark to see if there's any spark jumping.  You can also pull each plug wire off the plug...one at a time and only one at a time.....the engine will run rougher since it will only be running on 3 cylinders, but if the backfire goes away when one of them is pulled, then you'll at least know which cylinder to look at first. 

 

You may have a carbon build up on a piston/cylinder that creates a hot spot and fires the mix at the wrong time.....or the build up is holding an intake valve open.  You can get the motor up to temp, then rev it up a bit and spray carb cleaner down the throat while it's running.  Obviously, the air cleaner cover is removed.  You'll probably get a ton of black soot coming out your tailpipe, so don't have a nice car parked behind it.   If this helps.....I'd get some SeaFoam an run that through the fuel system....it will clean up the carbon crap in the cylinders better than the carb cleaner.  I've seen guys use water to get the hot built up spots to break up, but it won't help clean junk in the carb like the cleaner will. 

 

You may still need a carb rebuild, but I wouldn't start with that...the carb won't....or at least shouldn't cause backfiring.  Even with a lean mix, it should affect all cylinders and it still needs something to ignite it.....and hot spots in every cylinder at the same time is pretty unlikely.

:)

[DanielC]

Mike eluded to it, but many carb problems are caused by something else.  It you have a factory service manual, it details an engine tune up, and carb adjustments are the last thinkg you do after checking and optimizing everything elsa.  A comprression check, valve adjustment, setting point gap, timing adjustment.

As long as a carb gets clean gasoline, and no water in the gas, they are pretty relable.