Lugging under load, Clunks, and Backfires (long)

[fiveleaf]

I made it to Kingston! or... Limped into Kingston. Recently drove my dad's old project z across Canada -- Whistler, BC to Kingston, ON.

I use this as a daily driver in the summer, and walking to work/school is over an hour...

She has troubles:

A)

-Keeping a steady Idle

-Delivering power to the wheels at any RPM

-Will not coast in any gear before trying to cough and lug (1st is especially bad for this)

-Will cough/lug in any gear at low RPM even if throttle is given gently mid RPM

-Climbing hills in low-ish RPM (even 3rd)

C)

-Will backfire from exhaust many times if full throttle is given from pedal, especially at high RPM

D)

-Will clunk/shudder from below me (mid/rear), especially at low rpm when trying to give power to wheels. It sounds much worse than a miss, and is separate from the lugging.

She has no problem:

-Downshifting

-Revving in Neutral

-Coasting down a hill

-Cornering without applying power

I believe I have a few problems, which is why I've laid out the symptoms A-D.

My thinking/solutions:

A) New Distributor Cap for 280zx distributor. Plugs/Wires/Distributor is new. Coil appears to be giving good spark, but only if the main male terminal is held about 1/8 to 1/4" away from the female socket. When it is held like this, 1. you can see/hear every spark perfectly jump,

2. idle immediately rises by about 300rpm and is steady

3. the distributor cap was replaced last summer

4. No water/condensation/rust inside the distributor or cap, all looks good

5. Having spark issues driving here, all terminals to cap are coated in dielectrical grease. It seemed to improve spark, as I had the same "hold the plug wire away from the cap" problem coming across the prairies. Does this then point to the coil?

I hope to god that this is solved with my solution to problem A, as it must be linked to problem B.

I know, it sounds like a miss or a fuel delivery problem. But so much has been done to clean up fuel delivery recently

C) Triple webers running too rich. I'm really out of my league when it comes to finding the correct jet's for my webers. They are apart and on my living room floor for a cleaning (I thought they might be dirty or something may be inside them.) They are not dirty at all.

Plugs come out coated in carbon. Inside of tailpipe is coated in soot. Exhaust is sometimes black with carbon. Exhaust line is not cracked, broken, or loose.

D) Diff/loose nut somewhere? I believe this is a 3.54 R180 or R200, and will put the car up on a hoist and just look for any nut I can find to tighten, anywhere near the diff/mustache bar/U-joints? I need to research this subject more. Weird, because there is less than 10,000mi on this diff.

-------------------------

Car "went like stink" many times for 2hrs Whistler - Vancouver, with an altitude change from sea level to the mountains. I don't think the change in location messed with the carbs, and I don't know why they are running so rich now, and not earlier.

L28 (slight bore) with triple webers, Webers are currently apart in my living room.

New Noisier Carter electric fuel pump to replace the old Carter 4070. Regulated to 3.5 PSI

Fram HPG-1 Fuel filter, just replaced the cartridge. Supposed to be very good for these webers.

PS92 Ignition, 79-80' 280zx Distributor, all new wires and plugs.

New 10w30 full synthetic.

Not overheating, and only other problems are random electrical issues.

I noticed that the distributor from the 280zx has a vacuum advance on it; should I attempt to hook this up? There is a possible location on the cannon manifold to accommodate this, but it would need to be drilled.

The Ignition Coil has printed on it "For Use With CD Ignition ONLY"

Guess I can look at the fuel strainers immediately before each carb... "Banjo" is what I believe they are called.

Thank you all so much; any input is appreciated.

Tom

The cap came from 79-80 280zx. 81-83 NA (non turbo) may also work.

The one we used was your original, (the plug wires were still attached). I believe your distributor was 75-78 280z by the look of the innards.

Let me know what happens

Jim

[theramz]

The ZX dizzy must have a vacumm advance hooked up. Take the cap of and make sure the breaker plate will advance and return freely. Hook up a vacumm tester and check the advance. If either test fails you will have to replace the dizzy. Reset your timing if it passes.

[Zs-ondabrain]

Yup, I had similar issues with my triple 40DCOE's and advancing the timing helped a little. Different altitudes will also effect the timing. Advancing should also bring up your idle.

The only problem with running Vaccum advance on triples is they are not typically set up for Vaccum Advance. The VA has to be place before the buuterfly on the #1 Weber. If you put the VA after the butterfly, on the intake manifold, you'll suck your vaccum advance diaphram out or suck a hole into it, causing it to malfunction. I blew out my $30 diaphram on my Mallory Unilite by doing that exact wrong thing.

Dave

[theramz]

Yeah, the ZX had 1 throttle body so the tripples will have a different vacumm as will different cams. I figuered that the vacuum would be less with more carbs. If you don't have the right cam they will be to much carb anyway. You could test different locatons to compare vacuum I guess.

[fiveleaf]

I'm a little confused over ignition, spent a few hours looking online, and learned that buying new can look pretty expensive.

Just found a pretty good deal on a new PS92(coil) with HI-6(ignition), so the old PS92 is now replaced. Unfortunatly, the PS92 is only CD ignition, so I either need to ignore the HI-6, or look for a PS91. All crane arms.

I also have the XR700 fireball ignition (crane arms) that was [used with PS92 after old HI-6 failed?]. I'm not sure about this. It's bolted under the PS92, and was used with it... but disconnected when swapping the old (mechanical only) distrubutor out.

Too bad, because the crane arms tach adapter would work if I bought a PS91 and used it with the HI-6. Just not sure what to do with the XR700 ignition.

Anyways, to the vaccum advance.

It's the cannon intake manifold. Two possible locations to take vaccum from; one is used for the brakes and the other is undrilled, and past the first putterfly nut on the webers. I'd rather change the dizzy now than drill into the manifold (because if I ever change it in the future...)

So I guess I'm going to look for a new dist.; does anyone have somthing cheaper than the Unilite in mind? Or maybe comments if I were to look for a used unilite?

Thanks so much so far guys!

Edited September 18, 2009 by fiveleaf

[Zs-ondabrain]

here ya go. if you pay $200 or $300, you're still getting a deal.

http://cgi.ebay.com/ebaymotors/Datsun-240-260-280z-Mallory-Unilite-Distributor_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem3ca59e25b2QQitemZ260476642738QQptZRaceQ5fCarQ5fParts

[fiveleaf]

Wow, thank you!

Assuming that ideally, I should be running mechanical only off triples...

That Mallory unit also uses vaccum & mechanical advance... I'll bid for it at this price, but i'm really looking for the Mallory 4563901 (mechanical advance only). Though if I end up buying this, I wouldn't mind drilling into the manifold to install it (as I'm not going to replace it with something better).

[Zs-ondabrain]

The unit on ebay is an adjustable mechanical advance only. No vaccum to worry about.

As for drilling the intake, Don't do it!! That's how I blew out MY vaccum advance and it cost $30 to replace the vaccum pot. if you need a vaccum for the dizzy, you need to get it BEFORE the butterfly on the carb. taking it from the intake manifold is TOO MUCH for the vaccum on any dizzy. Unless you have a reducer of some sort (like a pinhole, no bigger than about 1mm or so.)

I wish I had mechanical when I had my triples. Oh well.

Dave

[theramz]

I had a Mallory all mech advance and it performed well but with no vacuum you get almost near zero advance at a normal driving start so you have to ride the clutch a little more until the rpms come up. I changed it for a ZX E12 and it runs perfect for a stocker. By the way Mallory is now made in China even though the cap says USA on the inside. When I have a built up engine like you guys I will get an engine management system, maybe MegaSquirtnSpark.