3&4 cylinder rich

[torker]

Been checking out my sons car some. I looked at the plugs/ Autolite 63 and the two middle plugs are rich. Outside four are ok. I noticed that the intake has shared runners on 1-2 and 5-6 and that 3-4 have their own runner. A PO has changed to Webers and elec. ign. But it looks like a stock coil/ still has a condenser, didn't see a resistor. This car is really coldblooded and you can tell it is trying to drop a cylinder at low rpm when not warmed up. If I keep it at 2000 rpm or so it smoothes out but not too good. No. 3 is actually a little wet.

I haven't checked compression or timing yet. Just wondering if this intake design may be contributing to this. Or if I can lean out the carb a little. Even the outside plugs aren't burning what I would call clean. Dark tan, some buildup and only the tip of the electrode is clean. Also wondering if I can go one step hotter on the plugs or is that a nono.

[SteveJ]

Is the setup a triple carb? I don't know why 3 & 4 would be shared otherwise. Of course, that could just be my own ignorance...

[torker]

No it is dual Webers. I just looked through the FSM and it looks like the stock intake. It is just that the front 2 cyl. share one intake runner- same as the back 2 cyl. and the middle cyl. each have their own runner. I was thinking this may be causing the rich condition on the middle cyl.

I am going to try and come up with a methodical approach to this cause I am out of money to put in this right now. First chance I get I am going to degrease the heck out of it and then start with timing and compression. And ohm out the plug wires. See where I'm at.

[SteveJ]

[

No it is dual Webers. I just looked through the FSM and it looks like the stock intake. It is just that the front 2 cyl. share one intake runner- same as the back 2 cyl. and the middle cyl. each have their own runner. I was thinking this may be causing the rich condition on the middle cyl.

I am going to try and come up with a methodical approach to this cause I am out of money to put in this right now. First chance I get I am going to degrease the heck out of it and then start with timing and compression. And ohm out the plug wires. See where I'm at.

Okay, I misunderstood what you said in the first post. My bad.

When you say the plug is wet, does it smell like gas or could it be oil? Can you post pictures of your plugs? Also is the Z in question the 74, or is it another year Z car?

Have you tried using NGK plugs? Do that, check your timing & plug wires, and then balance the carbs.

[ChrisZ]

I suppose when you say dual Webers, it is like the ones i the attachment.

I have a feeling that this is ignition related, have you tried to pull a plug wire when the car is at idle, just to confirm you have a spark ?

I 2nd on NGK and remember to gap them correct, to much of a gap your spark will be to weak when running stock points / coil.

Start with a fresh set of plugs and check your dizzy to see if the advance mechanism is frozen up.

Chris

[torker]

Yea, those carbs look exactly like mine. Just about as dirty too:) This is a 74-260

I was looking at the dizzy. It has the reluctor and pickup. This is electronic right? Also the rotor is pretty hard to twist/advance by hand so I am sure this is going to need to be freed up/ cleaned and lubed. Any thing special I need to know before I yank the dizzy. Is it like a smallblock Chevy? Only go in right or 180 deg. out or like some Fords with the hex shaft?

It is my sons car and tomorrow is my last day off for awhile but hoping to get started on it. Been reading the FSM and it looks like I have to jumper a vacuum hose and also an elec. connector to check timing. I hope I am reading this right. Any pointers here would be great.

Also do plan on new plugs. What # NGK ? The parts stores never seem to be able to find anything for this car. So far they've given me wrong ujoints, only show 4 coolant hoses for the engine, none of the formed hoses. Yesterday a guy looked to see what battery it called for and a 260-280 wasn't even listed. WTF Been fun. So all help is really appreciated.

Oh and the plug was wet with gas. #3 And #4 was black but firing a little better. Now the car was cold, I had just ran it for about a minute after changing the battery. I'm sure it cleans up once the car warms up as it does run ok when it is warm. And it starts good always. Just rough till it warms up.

Edited January 21, 2010 by torker
add

[torker]

Ok a little elec. contact cleaner freed up the advance till I can get it out and do it proper. I attached some pics of the carb tag, dizzy and coil. If the dizzy is electronic do I need to upgrade the coil. Seems to me the old points setups used the resistor in line. I shouldn't need that with electronic should I?

Looks like NGK bp6 is the plug # Not sure if I should get Iridium. vpower or what.

Edited January 22, 2010 by torker

[SteveJ]

1. Go with the base plug, BP6ES.

2. Your ignition seems to be getting most of the cylinders. The wires for 3 & 4 are next to each other. Is your distributor cap in good shape? Also, check the wires. Both are cheaper than replacing other ignition components.

[torker]

1. Go with the base plug, BP6ES.

2. Your ignition seems to be getting most of the cylinders. The wires for 3 & 4 are next to each other. Is your distributor cap in good shape? Also, check the wires. Both are cheaper than replacing other ignition components.

Awesome, I like the base plug better than those with tiny little electrodes. I will ohm the wires next. And separate 3 & 4 I remember on smallblocks we would separate 5 & 7 The cap looks new but I will ohm the wires through the cap.

[SteveJ]

Just an FYI, I noticed from surfing the NAPA website that you might need the stock number, 7333, to find the correct plug.

[torker]

Yep you're right. I found it here. http://www.sparkplugs.com/results_app.asp?productTypeID=1&AAIA=1209181

A pretty good cross reference for a lot of brands. Dang Autozone didn't have them so going to pick them up tomorrow.

[torker]

update: Finally got a little time to work on the z today. I did a compression check and all cylinders have 125 to 130 except 3 which has 120. A little low but fairly even across the board.

Before doing that I pulled wires with it running and 3 didn't drop rpm as much as others. Although the spark looked good. I could back the wire almost an inch away from the plug before it would lose its arc and it was nice and blue. No real suprises.

I ohmed the wires and they show 1.2 ohms? Not sure if thats right . Seems good though. The old plugs were gapped at .030 I gapped these at .035 Hope that is not too wide.

I drove the car and it runs fine. Still coldblooded but it does ok if you feather the throttle and keep it about 2000 rpm till it warms up a little.I did notice it idles about 1000 rpm when warm now. A little higher, maybe due to the wider gap.

Still haven't got a timing light on it. Maybe tomorrow..

I think I have finally got my son convinced that this car / engine was not designed to drive 3 blocks to school and shut off using the choke all the time. This needs to be his evening / weekend car. I'll educate him on this old school hotrod yet:cool:

Need to do some more reading and make sure I've got the procedure right for checking timing. And I'd like to check valve clearance. I expected this engine to make a little racket with a mechanical cam but it is quiet. Normal? It looks like it should be .020 in. and .025 ex. cold I think.