chaseincats

So if I'm understanding this right. When running leaner, it's better to use a BP5 plug since it will absorb cylinder heat better than a BP6?

Will do - curious why I shouldn't change to BPR5 or BPR7?

Well, the whole point of this thread was learning how to tune the stock system but thanks for letting me know.

is that something you just pop in or does it require a lot of supplementary tuning?

Never heard of that let alone it being used as a metric for engines. @madkaw

Sorry if this is a dumb question, but what does KPA stand for?

The air/fuel gauge connected to the o2 sensor that was installed gives you load readings that I listed above though.

I believe it burns some oil, but whatever it burns it isn't enough to affect oil level over the course of a year. @dutchzcarguy@jonbill Understood on the spark plug material. Which heat rating though (bp5, bp6, bp7)? Plug reading really isn't the way to go as long as you have an air/fuel gauge to see what the engine is actually doing. It's running at a 13.8-14.2 idle, 12.3 WOT, and 14.7 highway cruise. I will say, the other day I did catch it running VERY lean (in the 17s) so I pulled over and fiddled with it - not sure if that's when the plugs started looking like this or not though

Spark plug question. Plug image below. NOTE: cylinder 3's plug's ceramic was cracked so I pulled the valve cover and noticed that cylinder's exhaust valve was loose by at least .004 and has now been fixed. All other valves were sitting at factory spec. I pulled the plugs (they've been in there for a few years) and they're white on the top. I have been using NGK Iridium BPR6EIX-11 plugs. Since the car is running leaner than stock 280zs (14.7), should I change the plugs' heat to BP5, keep them at BP6, or change to BP7?

gotcha As a side note, there is some old/crunchy looking oil bits in there, should I try to pick those out or is that also, just an age thing?

Thanks for all the info! This whole thing spanned from me looking at my cam and seeing small lines on all the lobes. They are small enough that you can't catch your nail on it and wasn't sure if it was damage or 45 years of wear. I made a video of my cam with the valve cover off here: https://www.youtube.com/watch?v=MYNc7lrVUWk What do you guys think?

Gotcha and to make sure the hole is spraying properly I could just use a bent out paperclip and move it around in there, correct?

Hey gang, On a '78 I'm told the cam is 'internally oiled' (instead of using the oil spray bar). What does that mean and are there holes somewhere on the cam that spray oil while rotating or something? I looked but didn't see any... -chase

The air temp sensor is showing readings to spec on both the old and newer afm per the fsm which is good. I never found that sensor did much if anything since starting this process which I always found odd. Regarding adding a potentiometer on the coolant sensor, doesn't that only have ability to add resistance to the coolant sensor thus increasing richness? I don't believe you can lean the car out with a potentiometer on the temp sensor but I could be wrong.

Gotcha, so it wouldn't be the spring tension that would be different, it would be the circuit board?

Hi guys, quick question. Rockauto seems to have reman 5-pin AFMs in stock where the Canada spec one is half the price of the federal emissions (guessing that means USA) spec version. Anyone know what is the mechanical difference between these?

Bringing this back for a special "happy new year" edition of this thread with one new observation. Much like the 240z's big orange carb filter's "winter/summer" switch, I've found that adjusting the AFM requires a 1 tooth adjustment depending on the season (in order to stay within those air/fuel numbers). When it gets cold, richen it one tooth (clockwise) and when it warms up in the summer, lean it one tooth (counter-clockwise). I'm assuming this is due to cold air being denser and thus leans out the car, but I'm no scientist it's just what I noticed on the gauge after all this time. For me this means that the summer tuning is 3 teeth to the left of the stock tooth (that you should have marked) and winter decreases that by 1 tooth meaning that the winter setting is 2 teeth to the left of the stock configuration. Happy tuning my friends. Let 2024 be the year of 14.7

That is currently connected (the line from the tank into the carbon canister inlet port) to the carbon canister. Originally, when I noticed the fuel vapor smell in the cabin, that line was completely disconnected (but as it sits now, that is the only thing connected to the carbon canister).

That line is open with the inlet port on the intake manifold capped. I just don't understand how the fuel tank vapors are getting into the cabin since I can't find any leaks in the back...

So in this case it sounds like the check valve wouldn't be a leak point for fuel vapors - bummer

I changed my cap to a generic one from oreilly's since I wanted one with a lock. The original cap was on there when I got it and did not seal the tank vapors at all - with this one you can only smell them if you really put your nose to it so that should be fine I'm thinking.

Sorry, that's what I meant - the valve at the top doesn't hold vacuum, so it pulls in fresh air/vapor at all times, including at idle. When I started it after re-connecting the canister to the purge/throttlebody trigger vacuum lines, it ran poorly with the rich/lean number on my a/f gauge bouncing between 12 an 16 and it drove equally as poorly until I disconnected both vacuum lines (capped the purge hose on the intake and connected the throttlebody directly to the distributor like before.

Gotcha. If I smell near my gas cap, I do smell vapor - is that normal?

Thanks for providing this! Kind of odd, I noticed it went from easy to blow through (from the engine side) to hard with each successive time I blew through that line in the engine bay. According to this however it should be tough all the time? Also, it is kind of confusing as to why it should be hard to blow through when going from the engine to the vapor tank. You'd think that should be easy since the vapors are coming that direction (from the tank to the engine), no? -chase

Hi guys, I'm honestly not sure which sub forum this was supposed to go in but here we are. Periodically I smell gas fumes in the car. One of the main culprits was the old-style hose clamps weren't sealing the hoses to the vapor tank well enough. I changed them to modern belt-clamps which helped a lot but not fully. I've been testing the leak by blowing in the hardline that connects the carbon canister to the vapor tank and scampering back there to sniff around (which is how I originally found the clamps were a problem) but I'm still smelling some fumes while driving so it's not fully fixed. At this point I can't seem to pin down the smell point and even used a smoke machine but found no leaks. Could the check valve that goes from the vapor tank to the carbon canister have a bleed-off function? Also, any idea where that check valve is? I can't seem to find it. If it sits outside of the cabin then that might not be the leak though. Note: my carbon canister is disconnected because it doesn't hold vacuum. If I was able to use that system, I'm assuming this wouldn't be as big of an issue but who knows. Any ideas? chase