Distributor & Ignition Timing Woes

[Kennymonster]

First off, Happy Father's day to all.

Recently I had just finished the daunting task of front timing cover removal / tensioner reset, following the all so common rookie mistake of letting the chain slack, during a cam install (stock regrind @ Schneider .460 270/280)

Thanks to the abundance of information on here, I 'thought' I was being pretty meticulous on reassembly, verified the crank/cam timing/TDC to be correct, however the end result is the distributor/oil pump being off by a tooth or two:

What happened: It's a '72 with a 280zx distributor, my mistake was interpreting one of the reference pictures where the rotor hat aligns with the vacuum diaphragm, not realizing the diaphragm on my dist. was actually one spot over (at #5 and not #1). It also had a nice yellow dot on there to seduce me into thinking it was #1.... I searched and few others seemed to had the same issue.

It started/ran fine once I shifted all the plug wires one spot over, but at this time I've maxed out both adjustment screws and it's still way too advanced (40+ at 3k, trying to get it to 34, specs: l28/n47/44h mikunis). Pulls ok until 3k, does climb to 6.5k but very slowly.

So as it stands, I'm assuming I have to clock the dizzy correctly in order to gain the adjustment needed to properly set the timing, couple of questions.

- This may sound idiotic, but does the oil need to be fully drained in order to remove the oil pump? Or is the oil mostly in the pan and I have enough slack to remove and reinstall, with the car jacked up from the front leaning the fluids to the rear.

- Even with the timing being way advanced, I'm not getting much pinging under load, the compression r is around 8.7:1 on n47 maxima head with n42 block, and the 44h triple mikunis are nice and throaty with 3psi fuel. Does overly being advanced 5 - 10 degrees result in actual power loss, as I'm witnessing, in addition to just detonation? I would think anything other than optimal combustion will lead to lack of power, I just wanted to confirm this fact to rule out other parts being an issue for poor performance.

I appreciate any feedback,

-Ken

[madkaw]

I guess i am understanding that you used the rotor to line up your timing?

You want the dizzy removed and look at the drive tang and make sure it is at 11.25 oclock at TDC. No you don't need to drain the oil.

You need to get things TDC again and drop the oil pump and reinstall until the tang is in correctly. There is a dot on the shaft that lines up with a mark on the oil pump to helpn you initially line things up. Then it's kind of trial and error until you reach the 11.25 position.

40 degrees advance is a lot and you might not hear the detonation over them triples;) So your initial timing is sitting at 23 degrees right now, which she might not want to start easy on them hot days. I would want to get back to knowing where your at and being adjustable.

as far as specs-not sure there is specs for that combo, it's what makes it run good.

FYI, my car didn't put out anymore HP at 38 compared to 34 on the dyno.

Hope this helps

Edited June 17, 2013 by madkaw

[madkaw]

I would add that you could probably enlarge the slot to get more travel on the adjustment for now until you can do it proper

[Kennymonster]

Thanks for the feedback Steve, it's much appreciated. I don't post much on here and only lurk, but I have quite a bit of your posts bookmarked when referencing/diagnosing the mikuni's jet settings.

Since this is mostly a weekend toy for autox and whatnot, I think I should just fix the root problem. Believe it or not it actually starts very easily, usually on the 2nd turn over. The base timing, difficult to get a reading being somewhat jumpy, seems to be between 10 - 15... at 900 rpm. I wonder if I have that 'bad version' of the zx dizzy with a huge gap in the curve.

Here it is sitting at TDC, notice the vac diaphragm and the yellow dot.

The shaft - definitely needs to be rotated clockwise.

The CORRECT reference pic I'll be going by now:

I just doubled checked to see if it's the cam timing that's killing my 3k+, it was at #2 slot before the cam on stock motor (it was bought that way) which still had a good powerband upto 6k with the triples.

Even with the new 270/280 cam, I put it back to where it was at #2, since it was just the right amount of advance for my driving. The notch seems pretty close to other reference pics I found, as I understand it, at #1 should be slightly left of the mark, and the #2 slightly more being another 4 degrees of advance. Let me know if this looks out of wack:

[madkaw]

Okay, let's clarify things- are you running vacuum advance?

There is a thread on here that Walter Moore put out on all the advance curves of the dizzy s based on model number. Your numbers don't jive with mine as far as a zx dizzy. My dizzy only gives 17 mechanical degrees. So your dizzy is different or you have other issues or your vacuum advance is involved .

Yes it looks like you need to re spot the dizzy. As far as cam , I have degreed my cam and have an adjustable sprocket, so I'm not going to try and define your set up by a pic. Myself, I couldn't really feel much as far as going from one hole to number 2. I was dialing in by a cam card.

You could always reset the valve timing to # 1 hole at TDC to verify timing- if you are POSITIVE you know where TDC is on your crank pulley. Then it's an easy adjustment to #2

[Kennymonster]

Okay, let's clarify things- are you running vacuum advance?

There is a thread on here that Walter Moore put out on all the advance curves of the dizzy s based on model number. Your numbers don't jive with mine as far as a zx dizzy. My dizzy only gives 17 mechanical degrees. So your dizzy is different or you have other issues or your vacuum advance is involved .

Vacuum advance plate fully works, but I have it plugged. I did see a chart that Vic put up, the emission ridden /'worst' one out of the group had something like 6 idle / 35 full so I'm thinking it might be that one.. however I did not have any complaints before on stock cam, pulled like a beast.

Yes it looks like you need to re spot the dizzy. As far as cam , I have degreed my cam and have an adjustable sprocket, so I'm not going to try and define your set up by a pic. Myself, I couldn't really feel much as far as going from one hole to number 2. I was dialing in by a cam card.

You could always reset the valve timing to # 1 hole at TDC to verify timing- if you are POSITIVE you know where TDC is on your crank pulley. Then it's an easy adjustment to #2

I started from #2 so my thought was just leaving it the same, I supposed to really verify I can readjust to #1, but after that chain slack incident, even with the MSA wedge tool I just bought I'm a little gun shy about taking that sprocket off now

To start with I'm going to attempt the correct adjustment on dizzy and go from there, I appreciate the help Steve.

[Kennymonster]

Yup, running the correct dizzy alignment did the trick. Ended up somewhere 35 - 36 degree full advance where it seemed to be most happy, 91 oct. Cam timing seems right as the torque feels good early on and still pulls to 6.7 - 7k.

Also serviced my rear drums with new shoes and cylinders, I can lock up all 4 wheels now vs. just the fronts, awesome.

For those of you searching distributor position posts and coming across this... my advice is don't even bother with moving spark wire orders to mask the real problem, with another helper up top, getting the gear alignment correct will take less than a minute.

Quick video of an offramp pull, cam specs also listed on there:

2nd Gear - YouTube

Can't wait to take her out at the next AutoX.. it's been couple months and I'm tired of driving my buddy's miata ;(

[madkaw]

Glad to hear!!!

[kensval]

I'm going to jump on this thread with a similar but reversed problem. I can't get more than 4 deg advance at idle with the vacuum line disconnected from the distributor and plugged. I was pretty sure I had the dizzy in the right place. It's a 1976 280Z, original engine (N42 block/N42 head) rebuilt with flat-top pistons in place of the original dished ones. It doesn't detonate, but then at only 4 deg BTDC with 94 octane gas, it shouldn't! Under normal circumstances, I run with the dizzy vacuum teed into the same vacuum line that goes to the charcoal canister from the ported temp sensing switch on the intake.

So, do I pull the dizzy and move it over (counterclockwise?), or do I use the internal adjustment to get another 4 deg or so?

[Zed Head]

Actually, you'd have to remove the oil pump and shift it over a tooth. The distributor only fits one way on to the quill.

One thing to do before going too far would be to verify that the timing mark is at zero at TDC. Your damper might be bad.

Why would anything have changed? Have you had the oil pump out? Rebuilt recently? Some background on what's been done recently might give some ideas.

By the way, the line to the charcoal canister is ported vacuum, only applied when the throttle is off idle. It's the right place for it. And the thing on the intake manifold is probably the top gear solenoid. Doesn't help your problem, just adding.

[Kennymonster]

+1 on verifying TDC. If you unbolt the dizzy and look at the angle of the spline, with all things TDC, there should be a clear answer on whether you need to realign the gear tooth or not.

When you say 'can't', by that do you mean ran out of adjustment space on the main 10mm bolt? If so, have you messed with the smaller 8mm adjustment bolt behind the dizzy?

I always thought the concept of base idle/timing is all iffy in regards to performance aspect, I would maybe try to check the full advance timing at 3k+, and then work backwards from there.

[kensval]

First off, I was wrong when I said the vaccum line to the dizzy was going to the ported switch on the manifold. Brain fart. It's hooked up to the front vacuum port on the throttle body/BCDD, and the canister is teed into the same line. That's as per the FSM. The back port on the BCDD goes to the ported switch on the manifold.

As for "can't", yes, the dizzy runs into the end of the adjustment slot and I physically can't move it any more clockwise.

The engine was professionally rebuilt, but they had the dizzy in all wrong. Even had the #1 cylinder position marked on the wrong hole on the dist cap. They were one too far clockwise. So I pulled the oil pump, got the engine to TDC on #1, and reset the dist driveshaft position, then put the wires in the correct holes on the cap. This was all before I had the induction system and exhaust back in place last summer, and I've been driving it ever since, and it's been feeling fine to drive. I timed it by ear at first because I was too cheap to buy a timing light! Only decided to get farther into setting the timing correctly because I'm planning a trip to California this Sept. for a Jap car show at the Queen Mary in Long Beach. Since I've got higher compression than stock (about 10:1), I'm a little worried about detonation once I get down closer to sea level, hence the need to check on the timing. Also switching from NGK BPR6 plugs to BPR7s, one heat range colder.

I don't recall seeing another adjustment bolt behind the dizzy. Doesn't mean it's not there, I just don't recall seeing it. What does it adjust? I know I can adjust a bit inside the dizzy, maybe get another 4 deg in there. Really I think I'd rather get the dizzy drive set correctly. Right now with the timing light on the damper, and revving the engine up but without a tach to look at, and no offset timing mark, I'm guessing my total advance to be about 30 deg.

Like I said, the car is not running badly, but I just want it to be right. It dynoed at about 20 hp over stock recently, and gets excellent gas mileage on the highway. As for coming down to sea level, and not being able to find high octane gas when I get there, I'm hoping that if I just take it easy on the acceleration and RPM I won't cause myself any trouble with detonation.