Inability to retard timing under 10 degrees

[sideshowbob]

This car's going to drive me mad.

In addition to the other wacky problems I'm having the timing just can't be adjusted lower than 10 degrees, at this setting it runs like hell and pops quite a bit (SUPER RETARD!). Ahem. Anyway, I have this odd feeling that this isn't caused by the oil pupm/dizzy shaft being out of whack, but instead maybe the chain has jumped a link (I STILLL really dread removing the front cover, due to my garage being a parking lot at the moment) and the damper mark has shifted as a Result or Consequence of this little occurence (damned infuriating, really). The chain itself is rather loose on the right hand side of the engine and tight (due to the tensioner, no doubt) on the left. In my previous experience with domestic vehicles, this is incorrect :dead: . The chain and sprockets show very little wear so i'm forced to question it's position and not the pysical shape it's in. Also, I can get by TDC several times before the timing mark on the cam sprocket aligns, is this also normal? I've never had to adjust this in-vehicle. In my previous and only rebuild (a 302) I had the luxury of an engine stand and set the adjustment from scratch, which is amazingly easier than diagnosing this with the cover on the I6. Thanks, again :classic:

[jmortensen]

This car's going to drive me mad.

In addition to the other wacky problems I'm having the timing just can't be adjusted lower than 10 degrees, at this setting it runs like hell and pops quite a bit (SUPER RETARD!). Ahem. Anyway, I have this odd feeling that this isn't caused by the oil pupm/dizzy shaft being out of whack, but instead maybe the chain has jumped a link (I STILLL really dread removing the front cover, due to my garage being a parking lot at the moment) and the damper mark has shifted as a Result or Consequence of this little occurence (damned infuriating, really). The chain itself is rather loose on the right hand side of the engine and tight (due to the tensioner, no doubt) on the left. In my previous experience with domestic vehicles, this is incorrect :dead: . The chain and sprockets show very little wear so i'm forced to question it's position and not the pysical shape it's in. Also, I can get by TDC several times before the timing mark on the cam sprocket aligns, is this also normal? I've never had to adjust this in-vehicle. In my previous and only rebuild (a 302) I had the luxury of an engine stand and set the adjustment from scratch, which is amazingly easier than diagnosing this with the cover on the I6. Thanks, again :classic:

There are 2 TDC's. TDC Power stroke, the real TDC, and TDC on the exhaust/intake stroke, which is TDC for #6 IIRC. So you should get 2 TDC's on the pulley for every one time the cam lines up.

The chain jumping would change the cam timing, but it would not change where TDC is, so when the pointer points at the 0 mark on the pulley, you'd still be at TDC, but the cam wouldn't be in the right position.

If the rubber in the harmonic balancer separated that can allow the outer ring on the balancer to spin relative to the inner, and that will cause problems finding TDC.

I would start by pulling out the #1 spark plug and use a pen or a piece of welding rod to follow the piston up as you turn the crank. When it tops out, then see if the pulley shows TDC. If not, then you know that your harmonic balancer has come apart. If it matches up, then check the cam mark. If they look OK, then I think your distributor drive is in the wrong spot.

[sideshowbob]

This I know, I replaced the balancer last month due to the seperation problem. In my case it was banging against the block! Good point abou the cam timing... the electrical shouldn't be affected because the spark is controlled by the rod and.... argh. Ok so it must be the rod, or the new pulley isn't as new as I wanted it to be. Well, at least it doesn't jump around. The mark is quite steady even under a good twist of the throttle. The cam lobes, however, isn't what I meant. I'm speaking of the bright links on the chain lining up with the number on the cam SPROCKET. If one has moved, the other might line up and I wouldn't know where the second bright link is. I'm saying the link seems to take an inordonate amount of turns to reach the position it should be in to check chain stretch with the little V mark anf the dash on the cam retainer plate (washer?). Though this may be due to my impatience and not that it's turning too often. I should probably have mentioned that this motor isn't exactly stock (f57_n42_n47) and I haven't a clue as to what's already been mangled within the deep, dark confines of the block and head. I think maybe someone tried to mate it with another motor to produce little l28's in an obscene and seriously damaging way.

Anyway, what I'm sayin here is.... is... that I've been in the sun too long.

[sideshowbob]

No, wait. The rotor and the #1 wire line up at TDC, when both lobes are up and when the pressure from the plug hole pops my finger OUT, not sucks it in (this i use instead of a pen or wire that might concievably scratch my piston surface (the wire, the pen is safe )) Lovely nested comments, no? So... I'm at TDC two or three times (I forget) before the bright link and the sprocket line up with #1.

You're going to tell me to pull the front cover, arent you?

Seriously, thanks. I'm most likely making a very basic mistake here somewhere (see my rather lenghty post about rapid compression loss that I figured out 10 minutes ago!)

[jmortensen]

The bright links on the chain are only for initial assembly. Once you have the engine assembled you should never have to worry about them again. The cam timing should be checked by looking at the notch and dash in the cam gear and the plate behind it and observing how they line up. What are you trying to measure or accomplish with the bright links on the chain?

You mentioned the V and the notch. How do they look? Lining up correctly?

Scratch the piston??? That's pretty out there. ;-) You aren't going to damage the piston with a pen or a welding rod stuck through the spark plug hole as long as it doesn't fall in or get stuck in there sideways. If you keep one hand on the pen and the other rotating the crank nothing will get damaged. You should use something that you can set on top of the piston though, because pressure on your finger won't get you a very exact measurement. There's quite a bit of crank rotation where the piston barely moves up or down.

I don't think you need to pull the cover, unless you have to replace the chain due to wear. Otherwise I think you'll be able to adjust the chain with the cam gear, or maybe just leave it alone entirely and focus on the distributor drive or the crank pulley.

[Victor Laury]

Why are you attempting to adjust the timming under 10 degrees BTDC? Is that a spec you read in a book. Are you sure what the initial advance is on your dizzy? There are several different advance cams that may be installed in your dizzy. You need to confirm, either by direct observation or by total advance adjustment. If you carefully unscrew and lift the breaker plate and look at the advance cam below, You'll see a number stamped on the flat area before the slots. Typically a 9.5 or and 11 sometimes a 7.5 and as high as 15. This number indicates the total dizzy advance. To get total advance, you mulitply that number by for example 9.5 X 2 is 19. Now, on pump gas, and 8.5 CR and stock cam, You do not want to exeed 35 degrees total advance. So, 35 -19 = 16 So the optimal timing for this dizzy is 14 ~ 16 BTDC. If it was an 11 dizzy, optimal would be lower, 11 ~ 13. In reverse, if it was a 7.5 unit, 7.5 X 2 = 15, 35 -15 = 20 so 18~20 would be the range. If you car sound "Super Retarded" at 10, It just very well might be.

[sideshowbob]

I'm trying to determine if the crank spun one link or tooth without the cam following it aka "jumped a link". With such a loose chain on one side it doesn't seem too far-fetched. But then, you're right that that still wouldn't affect the dizzy timing unless the damn shaft that connects it to the oil pump did the exact same thing somehow. I've never been much good at diagnosing rough engines It can be rather frustrating. EX: the old coil caused a miss that could bee seen when the timing light was on, it hesitated for a fraction of a second sometimes. I replaced the coil once and it was just slightly better. Did some other fiddling and so forth for a while and came back to the coil, an accel coil was worse than stock so i was luckily able to trade it in for an MSD coil and the stutter dissapeared. Engine's still rough though, mostly due to the injectors but this strange timing behavior has me scratching my head a littl too much: I feel the bald spot forming already. At the moment I've tuned it by ear to just above that crappy stumble/pop crud to avoid the detonation that I can't hear even when the timing is maxed out (though it runs badly with a great amount of advance, of course). That, I suppose, is due to the large amount of underhood noise I get, some of which will be fixed as soon as I install the new manifold gasket tommorow or maybe this weekend.

Excuse me, I tend to babble on about this car.

[sideshowbob]

Victor,

Due to some ugly problems I'm having I was attempting to get a baseline tune going on. The dizzy is from an '83 Maxima (or at least it uses the Cap for one, yep found out where it came from and if i'm not mistaken it uses the odd e12-93 unmarked TFI unit). Good point about checking the total mechanical advance, though. I assumed it would be the usual 8.5(STX?) or 9(ATX?) found in the ZX, but since it came from an entirely different car you're probably exactly right, thanks! If the vehicle it was pulled from had a different mechanical advance curve due to slower idle timing then the readings I'm getting would be around a couple hundred RPM's off! This can advance the timing very significantly in some cars and is no doubt why I'm getting such a high reading at my relatively high (800) rpm idle. Oh, and I have no clue as to the INITIAL advance on this thing.

[rzola]

Adjust your lower distributor (not dizzy) plate. This is a slotted plate with one bolt (bolt threads facing up), has the degree marks on it. I could not back my timing below 15 degrees initial on my 1970 240. My total advance was in the way too high range as well! I had to run premium fuel in my stock engine to prevent spark knock. When I tried to back the timing down, it was at it's limit. I pulled the distributor out to see if the shaft was in wrong, or I jumped timing chain. This is when I saw the timing plate adjustment slot on the bottom of this distributor housing. I loosened the bottom bolt and centered the plate. I re-installed the distrubutor and set my timing to 10 deg advanced initial ( 3 degrees more than my service manual called for). The car now runs great on plain old 87 octane regular unleaded. Give it a try.............

[sideshowbob]

That's probably it then, thanks!

Unfortunately I can't do it right now as the fuel rail is sitting on my desk (meeting with glares from my wife). I've gotten these things to stop leaking before but the problem is back again . I'll have to grab up some replacements after I've taken care of this ticket I picked up on monday unless I can get these to hold pressure for more than a couple of weeks at a time .

[richard1]

I am not a guru at this matter but I have never understood why my 72 240 adjustment has always been 0 deg. The engine performs well only when set in "the middle" with full power at any load and speed range with still plenty of power on the freeway at 90 mph.

I bought the unmolested car at 32K five year ago. Now, it has 87K.

It's still unmolested and fully stock and the timing set up is still the same after all this mileage.

I don't know what is the key to this amazing situation other else than regular maintenance ( twice a year) of the stock distributor components (points, condensor, rotor, cap, proper lubrication, no matter the mileage beetween each interval).

In the same preventive maintenance approach, I take care of the carbs that have never been rebuilt since the car has been out of the factory . Once a year, I remove the pistons, clean them and the chambers and make sure that everything works properly with no visible defect.

The only thing I do is I run the engine with octane booster on every gas tank and change oil at 3K without adding additive.

Maybe I am just lucky for a so reliable early Z.