Carb Issue **Hitachi SU's*

[paradoxx]

Hey guys, I have an issue thats making me crazy.

 

 

• The thing is this. Its eating gas like a V8, half the tank is enough for 5 days, running like 25km daily.
  

 

• When im in traffic and idle it tries to shut down or decrease the revs, around 800-700 and I have to accelerate.
  

 

• The left hand carb is the one that's burning spark plugs, they come out black and some times they got wet and fail.
  

My hipothesis, an air leak is affecting the left had carb, maybe thru the throttle axis or a problem with the Pertronix.

 

How do you know the pertronix magnet is in the right position? Why do I say this, because the very first time that I installed it, I read the timing on the 4th cyl intead of the 1st cyl, until I started to change positions of the magnet.

Edited July 7, 2009 by paradoxx

[banzai510(hainz)]

when you fist put the Pertronix on did you mount it on a different distributor also.

 

sometimes if you installed another distributor or you put the oil spindal in 180 deg off the rotor will be facing 180deg off.

 

Thats why set everything up at TOP DEAD CENTER install the rotor and where it points will be #1 and #1 plug will go to #1 spark plug.

then time it with a light to say 14 BTDC as that what SU like I believe.

 

As for SUs I dont like them. they are almost 35-40 years old already

[datzenmike]

Assuming left hand carb is for the 1 and 2 cylinder? This carb is running too rich.

 

Is the choke properly releasing when in the off position?

 

Is the carb flooding from a bad float setting or dirt preventing the float needle from closing properly?

[paradoxx]

No I didn't change the distribuitor since I rebuilt it. But I have the feeling that the timing went wrong somehow. This weekend is has oil change, I will disassemble everything and check the timing as you say.

 

Or the solution is to put my most recent acquisition, a Weber 40 sidedraft with Lynx manifold. I really like the SU's because they are simple, but maybe youre right.

 

How are the timing marks on the crank pulley marked?

[paradoxx]

Assuming left hand carb is for the 1 and 2 cylinder? This carb is running too rich.

 

Is the choke properly releasing when in the off position?

 

Is the carb flooding from a bad float setting or dirt preventing the float needle from closing properly?

 

yes thats right, carb for cyl 1 and 2. the choke is ok, I dont even use it to start it.

 

The float thing you say Ive already checked it, even I have the, I dont know how you call it, the black thing where the gas comes in and you adjust the amount of gas, almost closed!

[datzenmike]

Maybe carb #1 has the wrong jet/needle size? There are over 340 possible jet/needle combos with the SU.

[banzai510(hainz)]

How are the timing marks on the crank pulley marked?

 

this is a common L16 set up.

 

Most left is Zero as in the photo then every notch is 5 deg up to 20 degs on a L16 crank. pully

I have a old English Datsun 1600 book thet list 14DBTDC but not saying that a little more or less will not work. But if you have cyl 1&2 going black what is the common factor? The front carb. and the rear clyinders 3&4 are OK, so it most be firing electrcally OK.

 

Be honest if your car has been running fine all these months I think its carb related not eleltrical.

Edited July 7, 2009 by banzai510(hainz)

[damon]

I am not saying this is whats wrong with your car but I had similar problems with mine when I bought it and I kept thinking it was carb related. It originally had a weber 32/36 and wouldn't idle at all. Then I switched to S.U.'s and it still wouldnt idle so I kept fiddling with them and fiddling with them. I got it to idle but would load up after a while and start to die.

Finally I took out the distributor and swapped it for another ( I ran the same Pertronix in both) and right off the bat it started up and idled perfect.

I drive my car about 35 miles a day and fill up once every 2 weeks.

And I drove to Canby this year using only a half tank of gas.

L-18, A87 head, S.U.'s and Z 5-speed.

Edited July 7, 2009 by damon

[paradoxx]

How are the timing marks on the crank pulley marked?

 

this is a common L16 set up.

 

Most left is Zero as in the photo then every notch is 5 deg up to 20 degs on a L16 crank. pully

I have a old English Datsun 1600 book thet list 14DBTDC but not saying that a little more or less will not work. But if you have cyl 1&2 going black what is the common factor? The front carb. and the rear clyinders 3&4 are OK, so it most be firing electrcally OK.

 

Be honest if your car has been running fine all these months I think its carb related not eleltrical.

 

 

sure, im honest, around a few months ago maybe 3 months it started like this. ive been changing sparks BP5 and now BP6, wire sets, from cheap to expensive and nothing worked. I will change that carb with one of the other 510 I have and see what happens.

 

I am not saying this is whats wrong with your car but I had similar problems with mine when I bought it and I kept thinking it was carb related. It originally had a weber 32/36 and wouldn't idle at all. Then I switched to S.U.'s and it still wouldnt idle so I kept fiddling with them and fiddling with them. I got it to idle but would load up after a while and start to die.

Finally I took out the distributor and swapped it for another ( I ran the same Pertronix in both) and right off the bat it started up and idled perfect.

I drive my car about 35 miles a day and fill up once every 2 weeks.

And I drove to Canby this year using only a half tank of gas.

L-18, A87 head, S.U.'s and Z 5-speed.

 

I would like to change it, because its starting to nod a little bit.

[datzenmike]

Can't see the dizzy being the cause. It either works or not. Now a bad cap or wires maybe. If you don't have new cap, rotor and wires then time to replace them but first check out a too rich condition on the carb.

 

Does black smoke come out the exhaust? Is the tail pipe black too?

[paradoxx]

Can't see the dizzy being the cause. It either works or not. Now a bad cap or wires maybe. If you don't have new cap, rotor and wires then time to replace them but first check out a too rich condition on the carb.

 

Does black smoke come out the exhaust? Is the tail pipe black too?

 

cap, wires and rotor are new changed it a few weeks ago.

As I said above, the fuel pass adjusting nut just below the carb is almost totally closed, I still dont know how to call it. And yes I can smell the raw gas out the exhaust and the black muffler tip.

[zerow]

Are the dome springs sticking? With the air cleaner assembly off the carbs, watch the piston for the front carb. If the piston is not moving consistantly with change in throttle range, then I would check for a bad dome spring, sticking piston, or bent needle all of which would cause the mixture to be waaaay off (rich) on that front carb.

 

Did you also check the dashpot oil??

[DISLEXICDIME]

did you check the dash pot oil ? maybe you have a bent needle !

[damon]

Can't see the dizzy being the cause. It either works or not. Now a bad cap or wires maybe. If you don't have new cap, rotor and wires then time to replace them but first check out a too rich condition on the carb.

 

Does black smoke come out the exhaust? Is the tail pipe black too?

 

If the mechanical advance isn't working properly, say a broken spring, it will still somewhat work but not idle. My car was fine above idle but had a broken advance spring which caused it not to want to idle. So it isn't that a dizzy either works or doesn't.

[banzai510(hainz)]

Damon this is correct.

Thats why I tell people to time their motor using a light.

One can telel if a weight or something is erractic as the timming marks will be bouncing all over the place as the advance is searching. But I think once a dizzy becomes a electronic ignition most likely they work or they dont. but he did say the other 2 clyinder are OK. So that means its triggering at the right time on those and the plugs are OK. So Im thinking carb proplems.

 

But Paradox does have another car and he could swap in the other dizzy in a few minutes then he will know his proplem.

 

Only other thing is maybe there is a HUGE ohm ballast in there causing a weak spark and carb is bad just enough to make it a huge proplem on the first to cylinders.

[damon]

On that note. Make sure and check that the fuel nozzles are set correctley and that the lever that moves them for the choke isnt sticking or jammed.

This will cause it to run way rich on that carb and cause your issues. Also make sure they are trully synced. It could bt that one balance screw is way off from the other.

Basically you need to check and adjust everything. make sure the pistons move freely and make sure the floats are good. I thought I had good floats and turned out one was half full of fuel.

[paradoxx]

Damon this is correct.

Thats why I tell people to time their motor using a light.

One can telel if a weight or something is erractic as the timming marks will be bouncing all over the place as the advance is searching. But I think once a dizzy becomes a electronic ignition most likely they work or they dont. but he did say the other 2 clyinder are OK. So that means its triggering at the right time on those and the plugs are OK. So Im thinking carb proplems.

 

But Paradox does have another car and he could swap in the other dizzy in a few minutes then he will know his proplem.

 

Only other thing is maybe there is a HUGE ohm ballast in there causing a weak spark and carb is bad just enough to make it a huge proplem on the first to cylinders.

 

I have both ballast resistors ever since. Do you recommend using only one resistor when using a Accel Coil?

 

Are the dome springs sticking? With the air cleaner assembly off the carbs, watch the piston for the front carb. If the piston is not moving consistantly with change in throttle range, then I would check for a bad dome spring, sticking piston, or bent needle all of which would cause the mixture to be waaaay off (rich) on that front carb.

 

Did you also check the dashpot oil??

 

they are good, they dont get stuck at the top and both are moving at the same time.

 

did you check the dash pot oil ? maybe you have a bent needle !

 

They are a lil bit low, but the issue that they give when the oil is low is that they accelerate so instead of being idle on 950 they go up to 1100.

Bent needle..mmmm gotta check with a glass.

 

On that note. Make sure and check that the fuel nozzles are set correctley and that the lever that moves them for the choke isnt sticking or jammed.

This will cause it to run way rich on that carb and cause your issues. Also make sure they are trully synced. It could bt that one balance screw is way off from the other.

Basically you need to check and adjust everything. make sure the pistons move freely and make sure the floats are good. I thought I had good floats and turned out one was half full of fuel.

 

Fuel nozzles is the word! thanks. the choke lever is good, I dont even use the choke. I will test them again with the unisyn to check that thing again. I will start from scratch.

[damon]

you dont have to have the choke hooked up to have a fuel nozzle stuck in a slightly choke on condition.

an easy way to check for a bent needle or binding piston is to remove the air cleaner and push up on the piston then let it drop it should drop quickly and make a solid clunk sound as it bottomms out on the base.

Edited July 8, 2009 by damon

[paradoxx]

you dont have to have the choke hooked up to have a fuel nozzle stuck in a slightly choke on condition.

an easy way to check for a bent needle or binding piston is to remove the air cleaner and push up on the piston then let it drop it should drop quickly and make a solid clunk sound as it bottomms out on the base.

 

Well, in that case I dont have a bent needle. Let me double check the nozzle.

[banzai510(hainz)]

I run the stock ballast resistor which is 1.6 ohms

and the ballasts resisstor which came in the SUPER COIL kit which is .7ohms

 

Mine works fine.

 

 

Do you have aAccell "SUPER COIL" or just the Accell Super "STOCK" coil as there is a ohm difference.

the Super coil is .7 ohms(as in the photo)

The super STOCK is about 1.4 ohms close to the stock Datsun coil

I run this on all 3 of my datsuns

Edited July 9, 2009 by banzai510(hainz)

[paradoxx]

I run the stock ballast resistor which is 1.6 ohms

and the ballasts resisstor which came in the SUPER COIL kit which is .7ohms

 

Mine works fine.

 

 

Do you have aAccell "SUPER COIL" or just the Accell Super "STOCK" coil as there is a ohm difference.

the Super coil is .7 ohms(as in the photo)

The super STOCK is about 1.4 ohms close to the stock Datsun coil

I run this on all 3 of my datsuns

 

I have the same configuration as you, so I guess theres no problem. that's a good coil, I have them since 1999.

[paradoxx]

tomorrow I will be working on this issue, I will let you know the results.

[paradoxx]

Well, I started all over again with the rimming issue.

 

some pics for start.

 

 

Everything as told, it leaves me to that spindle position, so I took a chance and put it as it has to be, disregarding the marks on the oil pump.

 

Now the question is, can I damage the engine by putting the oil pump that way?

 

After a short Carb adjusting y took it for a ride, I still have to wait to see the sparkplug result.

 

got some videos.

 

 

[banzai510(hainz)]

The spindal looks off put long as Rotor points to #1 plug wire and you have adjustment in the timming plate it will be OK.

 

Car sounds GREAT!!!!!!!!! both vedios

[zerow]

I've watched the first video 5 times - The front carb has a hard time coming up to the top of the stroke and some binding when you let off the throttle. Do this: First, push the piston up until it stops and let it drop. Do this a few times to see the dynamics of this full drop. Next, loosen, but do not remove, the dome screws on that front carb. Move the dome within that the loosened screws allow. Push the piston up again and let it drop. Did it bind any? Did it drop faster? You want consistancy between carbs, and I see that the rear carb is working better than the front. Once you have re-centered the dome and piston, tighten down the dome screws. I can't see this causing all your problems, but it most certainly will help her out.