engine is not running right after warm, movies and pictures included

[crazyoctopus]

Alrighty lets get to it.

car: 10/1972 240z with an L24 and an E88. completely stock engine.

I have recently been able to get my car to move under its own power, but it seems that problems keep coming about. Yesterday while taking her out for another test drive she drove fine for about 1/8th of a mile then she started to sputter, i gunned it and once i got past 3kish rpms the car pulled like I was hoping this car would be capable of. but as i started a to do some normal driving, 2k rpm cruising and 3krpm shifting the car started to sputter, lean pop, and backfire again and again.

brought her back into the drive way and started testing there. she revved fine and it seems that whatever the problem was it was gone. and then after i let it idle for awhile it came back. so i came back here and started looking at what to do. This is what I have done in hopes to stop the problem.

cleaned both of the carbs, replaced gaskets where needed

checked float - 10.31mm

checked timing - 0deg

set valve clearance - with engine warm .012 exhaust .010 intake

checked carb air balance - unisyn at idle

checked carb fuel - tried colortune on cyl. 1 and 5, but it kept acting up and resorted to the SU carb tuning tech on classiczcar

checked timing again - 0deg, and jumps to 20+ when at high rev.

then I let the car sit for a night because it was getting cold and damp. double checked all of my info and found that: the timing should be at 7-10 deg not 0, i should balance the carbs at 3k rpm not idle, and colortune at 3k rpm on cyl 2 and 5.

started the car up this morning, in hopes that it would all be sorted out with the inproper set up, but it obviously wasn't.

here is a vid of the first start up

that pop at the end is both backfire and a lean pop. awesome.

So I started to re-tune everything.

timing now set to 8ish deg

synced the carbs with unisyn, backed down all of the screws equally and set idle to 650-700 rpm. turned off the car, and then pulled the #2 plug

looks normal, and they are less than 20 miles old. stuck the colour tune on and here is what it is at idle

and then i set the idle to 3k and tuned it.

movie doesnt show it well, but color that I achieved, bunsen blue with hints of orange.

turned off the car and pulled #5 plug

tuned the rear carb at the same rpm and finally got the same color that I got in the front.

then I checked to see if my needles and nozzles were binding.

the rear piston is a bit harder to pull up than the front, so I am planning on dunmping the ATF and using some 10w30. To see how the carbs were actually balanced I used the lifting pin to see how the engine ran on only 1 carb.

from what I have read about the pins, the carbs look to be too rich, but according to the colourtune they are at their best. So meh.

Then I checked to see how the car revved through the power band. All of the jumping around is me playing with the throttle.

It seems that all of my problems were solved! So I took a photo of my temp gauge to show you all what "normal temp" is on the car, to see if that is what everyone else sees.

and while i was doing that the car started to act up again.

so i checked to see if both carbs were actually working, twice. and showed you the difference in nozzle richness.

So yeah... I have no idea what is wrong. please someone give me some advice. The only thing that I think it could be are the needles and/or nozzles, but why would it only happen after the car was warmed up, or under load?

[oldhemi]

WAG - dirty fuel or plugged gas filter?

[crazyoctopus]

fuel filter is about a week old, but i'll be replacing it today with a clear one so that i can see when it gets dirty. i'll also be pulling the pistons, and nozzles out of the carbs to get another bit of cleaning on em. pull the mech fuel pump off and see if there needs to be any cleaning done there.

going to re-set the timing to 12 deg, not 8ish.

i'll let you know how it goes after the morning's coffee

[GreenZZZ]

Throttle bushings leaking air or other vacuum leak?

[crazyoctopus]

Good idea; I'll check for it once I get everything back in place.

[crazyoctopus]

okay so I replaced the fuel filter with a clear one, re-cleaned my needles, piston, and nozzle; set my timing to 12 not 8, the richness to 2.5 turns down; then tried to start her up again.

with the lack of every bit of emmisions it takes a bit of work to get her running, but once she does start she is quick to turn over. once i got her running she was lean poping here and there so i made adjustments to both of the carbs and within about 5 min she was running normally.

I checked to make sure that the carbs were synced, and there were a hair off so I made the adjustment. checked the richness of the carbs by the method decribed in classiczcar, and then sat in the car and this is what is going on.

this is probably one of the best examples of what happens.

I am making a run to the parts sotre and picking up some brake cleaner to see if there are any vaccum leaks after i post this, and then check the float level (forgot to check while i was cleaning).

I am almost damn positive that it is a fuel at this point, and I am pretty sure it has to do with the rear carb. The reasons why I am moderatly sure that it is the rear is due to it needing a ton more richness. then again, it could be that vaccum leak and it needs a crazy amount of richness just to get the right mixture.

On a related note, I think, I am occationally hearing rod knock sound coming from the rear of the engine, cyl 5 & 6ish. This is my first pistoned car and am not really used to sounds like this, but from what I have gathered does this mean that the rear is running lean? it doesnt happen all the time, and I have yet to really pinpoint when it exactly does.

hopefully this will bring more light, and spark more ideas in your heads to help me figure out this issue.

[mlc240z]

Have you checked to make sure your choke isn't sticking?

Make sure the nozzles are fully up.

Are you running points or electronic?

[crazyoctopus]

yes i have made sure the nozzles are up all the way every time i make an adjustment to the nut. they occasionally stick, but it doesnt seem like it'll be an issue since i no longer have the cables.

I am running points; 3 week old cap, plugs, wires, and points. point gap set to .020, spark plug gap set to .035.

I cleaned and made sure that both of the floats were at 24mm through the blow through method; blow through the inlet tube and once it stops the air that is where it'll sit, measured twice with calipers. the float needle, or whatever it is called, is the one from thezstore and stamped with 1.7, the older ones that i has were both 2.0; dont know if that could help.

After i did this it seems that the car is running worse... i re-synced the carbs, adjusted richness on both carbs, and the rear is still much lower (near complete bottom) than the front.

also noticed that i am spitting some white smoke out of the back of the car, so I am sure that i am running rich somewhere.

tried to find if there was a vacuum leak, but the car never raised rpm wherever i squirted carb cleaner or brake cleaner.

also noticed that the engine slows down its RPM whenever i turn on the e-fan, would this also mean that the spark plugs are getting less juice, and therefore not getting enough to explode all of the gas in the chamber? I have been planning on the GM alternator as well as the 280z HEI mod, but was kinda waiting to get this problem sorted out before i went crazy with that stuff.

[73_240z]

I know I am going to catch a bit of heat for this....

My 73 was having some of the same symptoms. I would have it running good for a bit then I wouldn't run worth a darn. I replaced the plugs every fuel filter, took the carbs apart and cleaned them. I could not afford a set of rebuilt SU's so I bought an Arizona z-carb manifold and a brand new edelbrock 1403 with elec. choke. problem solved. the car runs amazing.

[crazyoctopus]

heh, if this problem keeps up for the next week I am gonna scrap these SUs and go with a tripple weber or mikuni...

[oldhemi]

White smoke COULD be a sign of coolant getting into the combustion chamber(s). Also hearing a knock or ping on cylinders 5 and 6 could indicate a bad head gasket.

Also, have you done a compression check yet? Bad compression does not mean that you have a head gasket leaking water into the cylinder.

Black smoke is an indicator of a rich condition. Blue is oil.

Edited March 10, 2010 by oldhemi

[Weasel73240Z]

heh, if this problem keeps up for the next week I am gonna scrap these SUs and go with a tripple weber or mikuni...

White smoke, along with the other symptoms, makes me think you're getting coolant into the combustion chambers. Maybe a leak in the carb warming lines, if you use them? I had that in my '73 when I bought it.

And if you think SU's are tough to tune, good luck with the triples!:classic: