76 280Z Project - First Start in 5 Years!

[pogden]

When I first started the restoration of my 76 280Z, I figured it would take a couple of years. Five years later, I'm happy to say that Andrew and I were able to get it running this past weekend! The first start was actually Friday, but a janky (new) mechanical fuel pump prevented it from running for more than a few seconds. Spent most of Saturday troubleshooting that. Installed a(nother) new fuel pump yesterday and was about to get it warmed up.

As it came up to temperature, it started smoking really bad.. Blue smoke, so we shut it down. I pulled the #6 plug and smoke poured out the hole. I removed several others, no smoke. All plugs were heavily sooted (black), I'm sure due to not having the carbs adjusted at all, and/or never getting the engine warmed up. #6 seemed to be wet, but so were 5 and 4.

Any thoughts on next steps?

A couple of other observations:

1. A small amount of coolant pooled in the freeze plug on the driver's side near cylinder #2. I wiped it off, but it kept reappearing as we were turning over and firing the engine. Over time, it seemed to actually get better (not as much coolant pooling in the plug). It's hard to tell for sure, but it looks like it's dripping from the head gasket (as opposed to seeping around the plug itself). Early in this project we had the head off for repair. Reinstalled with a light coating of copper sealant, same gasket (it had maybe 50 miles on the engine rebuild), and torqued in three stages according to the FSM. Yesterday, during the warm up run (maybe 2-3 minutes), there was still a bit of coolant in the freeze plug, but less than before.
2. The oil looks ok - it's brand new, and shows no sign of gas or coolant.

[Randalla]

The link below is helpful in narrowing down your issue. Pull the #5 and #2 plugs and compare them. They should look identical. Obviously, #5 is fed by the rear carb and #2 by the front. Let us know what you find (take a picture) and then we can help further. Also, pull the dip stick and see if you smell gas on it. Your freeze plug issue is probably a leaking plug. Did you replace them in the process of building your motor? RE-torquing a head gasket is iffy, even a new one.


http://knowhow.napaonline.com/exhaust-s ... ack-white/

[pogden]

Thanks, Randy. I'm pretty sure the smoke was blue (oil), maybe mixed with black (mixture) - again, no tuning has been done whatsoever on the carbs. I was just trying to get the engine warmed up before starting the tuning exercise.

When I have a chance I'll fire it up again and let it run for a bit (increasing my carbon footprint significantly). When it's warm, I'll pull the plugs and take a photo.

Regarding the motor, it is a Doc-built 3.0L stroker commissioned by the previous owner. He sold the car to me shortly after getting it running (with Doc's help), but *after* breaking an exhaust stud and then munging the head while trying to extract the broken stud. First thing I did was pull the head; Doc had it welded for me and I reinstalled it. If I have to replace the head gasket, so be it, but I'd like to be a little more sure that's required before going down that road.

One other observation - when "idling" (at about 1000-1500 RPM) I could hear a distinct mechanical "rattle" from the back area of the engine. I know that the L6 is known for having an noisy valve train, and that localizing a noise in a running motor can be tricky. Since I've never really heard a Z engine running, I would welcome a second set of (experienced) ears to tell me whether it sounds normal or not.

[Randalla]

Peter, call me when you will be around and I'll swing by and give you my two cents. 602-312-4038

[pogden]

Thanks Randy. I'm away until Sunday afternoon. If that works for you, I'll give you a shout around 4:30pm. If that's no good, we can do it late next week or on the weekend.

[Randalla]

I should be available.

[qz16]

peter,
If the smoke is blue then perhaps you might consider doing a compression check.

[pogden]

peter,
If the smoke is blue then perhaps you might consider doing a compression check.

Good call, I’ll do that this weekend.

[pogden]

Messed around in the garage a bit on Sunday. The car started right up, ran like a tractor for a minute or two, started smoking again so I shut it down. Never got the temp off the peg, but ... decided to do a compression test anyway. Here are the results:

Cyl 1: 195 psi
Cyl 2: 200 psi
Cyl 3: 185 psi
Cyl 4: 195 psi
Cyl 5: 180 psi
Cyl 6: 180 psi

Since 2, 5 and 6 were the "outliers", I measured them twice - same results. Took a picture of the plugs since they were out, see below. When I reinstalled the plugs, I started the car again and it ran ... better. The idle is still high (I think I may have a linkage issue, more on that below), but I was able to get it warmed up. And, no smoke!

A few more observations:

1. If I stop the engine with the choke still on, fuel slurps out of the front carb. Doesn't seem to do it with the choke off. At one time it was happening with both carbs, but I think I disconnected and reconnected the choke cables since then. Methinks I many not have the choke cables adjusted quite right.
2. While it was "idling" (if I can call it that), the RPMs gently fluctuated between ~1000 and ~1500 RPM. Carb float level issue? Fuel flow issue? Maybe "just get the carbs tuned properly and it will go away" issue?
3. I need to convince myself that the throttle linkage isn't part of the high idle problem. The "high idle" screw (the one high up on the linkage) is backed all the way out; the idle mixture nuts are at 2.5 turns down, and idle won't go below 1000 RPM.
4. The vacuum advance on the distributor does not seem to be working, at all.
5. Hooked up my timing light, it shows about 20 deg BTDC at its current high idle, and it's retarded to the limit. I'll futz with that some more when I'm able to get the idle down to something reasonable.
6. Still need to figure out how to wire up the electric fuel pump in a safe way.

And, two questions:

• The fact that cylinders 5 and 6 gave the lowest compression reading make me wonder if maybe there's a leak in the head gasket between them. But in that case, wouldn't the numbers tend to be even lower still?
• The FSM lists "Retightening Cylinder Head Bolts" in the Engine Tune-up section. Is there any reason I shouldn't do this? I wouldn't loosen them, just check that they are all tightened to the "3rd turn" value of 47 - 61 ft-lb.

[Randalla]

95% sure I know your issue, at least one of them, related to the idle. Just for grins, take the air cleaner off, start the car and while you're looking at the pistons in both carbs, blip the throttle rod slightly so you can see if the pistons are rising at exactly the same time. I'll bet that they don't (linkage issue and a balance issue). Also, I bet the vacuum advance is not working, unless you have already verified the canister is holding vacuum. Not a problem if it does not. We will set total timing and the car will run better anyway, though perhaps it will be slightly less fuel efficient. Let me know when you want to get together this weekend. The fuel coming out of the carb when choked tells me your floats may not be set properly.