NGK BP6ES spark plug burn color OK?

[jalexquijano]

Just tuned both of my recently remanufactured by Ztherapy SU Carbs to 3 turns clockwise on my 1972 240z. I am getting this color of burn on the 6 spark plug wires (NGK BP6ES at .32mm gap). The car seems pulling okay. However if i get stucked in traffic, the plugs start to get black and the car rpms start to drop a Little bit more. I already made the following mods to the car and still cannot get a completely steady idle:

 

- Change pertronix coil and ignitor (3.0 ohms)

 

- Bypassed the ballast resistor

 

- Swapped the Far 311 Race cam to a 274F Schneider cam

 

-Changed rocker arms

 

-Retainer springs

 

-Lashpads

 

Am i still too rich and need to go down to 2.5 turns??

 

One of the mechanics says this non stable idle is due to a valve or couple of valves being damaged?? How come?? I did a compression test and the result was the following:

 

cylinder 6 --------------------- 175 psi

 

cylinder 5 --------------------- 180 psi

 

cylinder 4---------------------- 180 psi

 

cylinder 3 ---------------------- 185 psi

 

cylinder 2 ---------------------- 180 psi

 

cylinder 1 ---------------------- 180 psi

 

I do not want to keep on replacing parts that are not necessary. My aim is to bring the car to the steadiest idle and install an AC system.

 

Anyone????

Edited May 25, 2015 by jalexquijano

[240260280z]

yes try 2.5 turns.  The plugs are not bad, just a little rich.

[Zed Head]

That plug doesn't look bad.  The ground strap is getting hot and burning off deposits like it should and the center ceramic looks clean even though it has some color.

 

Why don't you describe a typical situation where the idle starts to drop. "Stuck in traffic" doesn't have any detail.  Are you driving down the road just fine, then hit a stop light, and the idle drops immediately?  Or does it take 5 minutes of slow driving before the idle drops?  Does the engine temperature increase as the idle starts to change,or is it steady, and the idle changes just from sitting?

 

Tell a story about driving in to traffic and what happens, with lots of detail.  Don't tell what you've done to the engine, just what the engine does from your view, inside.

[siteunseen]

Just tuned both of my recently remanufactured by Ztherapy SU Carbs to 3 turns clockwise on my 1972 240z. 

2.5 turns counterclockwise from the top.  Turn them towards the passenger's side until they're tight then back down towards the driver's fender 2.5 turns.  Put a scratch on one of the ears so you can keep up with your turns.

[jalexquijano]

I close them up clockwise until the nozzle is flush and then back it up 3 turns. After driving the car more tan 10 minutes, if i get stucked in traffic, the idle starts to drop and increase. It is not steady. the temperature changes to 3/4 of the gauge. If you speed up it lowers. It could also be a faulty temp gauge. Do i need to open the gap more?? ie .035mm??

[Stanley]

Are the carbs in tune with each other? To tune them you need one of these, if you don't have it already:

http://www.thezstore.com/page/TZS/PROD/classic07/60-9976

There's another similar tool, but I like this one better, it has numbers you can write down when you get the carbs tuned, so you can compare vacuum data at a certain RPM if you re-tune them. Also you need a copy of the FSM for the tuning procedure, if you don't have it. I suggest follow the FSM procedure exactly.  2.5 turns down is just the starting point before the tuning proceedure, and that varies according the elevation and temperature, see the graph in the FSM. There's also a tuning procedure you can download from Teglerizer. I like the one in the FSM better, to me it seems more clear and concise, but it's good to read both. The Teglerizer also explains the push-pin test, but maybe that test isn't extremely accurate. http://www.zcarz.us/TechnicalInformationPageCarburation.htm

 

Every time I check plugs, I clean them, unless they're perfectly clean.  Hit them with carb cleaner, use a small wire brush for about ten seconds, then another blast of carb cleaner, on each one. There are better ways to clean them, but that's fast. If there's oil on the threads, wipe it off. If any of the plugs are even slightly fouled, cleaning them always makes the car run and idle better, without doing anything else.

 

What happens to the idle after you drive at highway speeds for a half hour or more?

[jalexquijano]

The idle is kept fine. The problem is when you are stuck in traffic.

[Zed Head]

 if i get stucked in traffic, the idle starts to drop and increase. It is not steady. the temperature changes to 3/4 of the gauge. If you speed up it lowers. 

This is a better clue.  You're saying that the idle speed fluctuates, like up-down-up-down-up-down.  That's different than just idle speed decreasing.

 

I'm not a carb expert, let alone Z carbs, but this sounds like a carb issue.

[Zed Head]

High performance cams also do this but the 274 seems like a fairly mild grind.

[Diseazd]

Check your nozzles underneath.......push 'em up by hand. Many times when I get an erratic idle, it's because the nozzle underneath the carb doesn't return after choking the carbs. If they are hanging up, you can hear them snap back up when you push em up. This also causes a rich mixture.

[jalexquijano]

Already checked and they are fine. I have a 274F Schneider cam and should not have any erratic idle issue. the rpm should remain steady at 950 RPM in traffic jams and stop lights. With this cam isnt this posible? I strive for perfect idle.

 

I bought myself the following vacuum gauge to verify for any leaks:

 

http://www.amazon.com/ATC-Vacuum-Fuel-Pump-Tester/dp/B00SHPLT50/ref=sr_1_90?ie=UTF8&qid=1432657183&sr=8-90&keywords=vacuum+gauge

 

Where and how exactly will i need to connect it to test for leaks?

Edited May 26, 2015 by jalexquijano

[Stanley]

A vacuum gauge is useful, but a 240z only has a few vacuum hoses and other places that could leak vacuum, so it's easy to check. Maybe you have a  vacuum leak.  I had a big vac leak in the PCV hose on my truck and it was sort of like you describe but worse.

 

Bad hoses always leak on the side you can't see, otherwise you'd see it and fix it. There's the brake booster hose, the hose to the  transmission modulator if you have automatic trans, the PCV hose, and the little tube from the carb to the vac advance on distributor, and the connections for all the vac hoses. Old hoses leak at the clamps. Also could leak around intake manifold connections. If you have the smog stuff on the balance tube, maybe it could leak if it was shot, I don't know. If the smog was taken off, and the holes weren't plugged with the right thread (BSPT) it might leak a little, not enough to cause much problem, though.  If the PCV valve was clogged with gunk and stuck open, there's a vacuum leak. PCV's are cheap.

 

I posted a thread couple weeks ago about a vacuum gauge, you can see how I set it up under the dash by the steering wheel. You can also put the gauge right on the balance tube if there's a vacancy. Just need a BSPT/NPT adapter and some elbows, etc., from the hardware store. The instructions for the gauge  say to cut a vac hose and install a tee (kit probably includes wrong size tee), but I don't like that idea, especially if it's the brake booster. Not PCV hose, either, since the valve would mess up the readings.

Edited May 26, 2015 by Stanley