jamesbob02

Ok before I thought that my timing was changing (very little) because my clamp was loose or my plug wires were pulling too tightly, but now I'm absolutely certain the cap is not moving.

Every time I've reset it and go put a load on it, the timing changes a LOT (~50 deg), and I've made marks to make sure the cap is not turning.

Seems like the problem would be obvious to those who have been here....is the gear on the bottom of my dist stripping or something?

ShiftyCapone

iTrader: (7)

Your timing is supposed to change like that with the EST connected. You need to set the base timing and go from there. Unplug the EST, set timing, and plug it back in.

IROC_385Z

That is true about the computer changing the timing, but not +/- 50 degrees!! I had this same problem where I set my timing and then it was like 60-90 degrees off next time I checked...the balancer had busted and the two parts separated! Take 10 mins and check to make sure that your dampner is ok.

jamesbob02

Maybe I should have mentioned that I knew about the EST connector.

I'm talking about the base, mechanical timing.

Also, my damper is new, and the damper moving anyway will not change the timing.

Come on guys, what would cause this?

dimented24x7

iTrader: (2)

50 degrees of base time would cause serious problems, the motor may not even run with all the overall timing. Same thing if the base timing was going to ATDC. How does teh engine behave? Oviously if it still runs the same and the dist. isnt moving then there is something wrong with the balancer or how your measuring the timing. Might be a problem with the timing set but there the motor wouldnt run, either.

jamesbob02

No no, I'm absolutely sure the timing is changing dramatically. I can tell in the way the motor is running, and can tell on test drives...i noticed immediately when it slipped again on a test run....the car barely ran. When it was worst, it wouldn't run at all.

Also, the balancer is new and is one piece, so the outer ring can't slip and mislead me on the timing (like the last balancer). Also, I'm quite sure the timing light works perfectly.

I'm 100% positive of these things: The timing is slipping when a big load is put on the engine, the dist cap is NOT moving, the balancer is fine.

Basically, I'm waiting for someone to say "oh yeah, that means your distributor gear is stripping" or something like that, because I'm sure its obvious to someone who's been there, but I don't have the experience.

I know it can't be the timing chain, because I would be destroying valves, along with the rest of the engine.

Mods, what do you think?

dimented24x7

iTrader: (2)

I dont know. Are you sure?

From the sound of it there is definatly something wrong. Have you pulled teh distributer to have a look at it?

jamesbob02

Just to clarify, let me give an example of what I'm experiencing:

I notice the timing is off, so I reset at and mark the cap position, and rev the engine to see if the condition changes...well now it runs like a champ in park, when before it struggled to rev at all.

So I take it for a test run and, after making it to a stop sign, I speed up a bit and allow 2nd gear, then peg the throttle to downshift and feel the high rpm power. Immediately, I can tell the difference, it runs great, but almost immediately as well, the car falls flat on its face and barely runs at all. I look for the SES light, but it doesn't come. I assume the dist has slipped again, and limp the car home.

When I get it home, unplug the EST again and check the timing....its at 60 deg BTDC, changed from 8 deg BTDC 5 minutes prior (and yes I'm sure about the EST wire). So I look at the dist cap and it has not moved. Just to make sure, I reset the timing to 8 deg BTDC, and the marks are nowhere near each other. Clearly, something is slipping down there, and it's not the timing chain (catastrophic engine failure).

What now?

jamesbob02

I can't pull the dist for a couple of days because I have a headliner appt tomorrow, and I know I can limp the car there without putting much load on it.

I'd like to know "THIS is the problem" so I can prepare to fix it immediately when I get the car back.

Stekman

So the BASE timing is getting thrown by ~50°? Advance or retard? You say you put the engine under load THEN it changes. Does it change during the load itself?

What balancer did you use? It may be a one piece but where is the timing mark in relation to the crankshaft keyway? It may not be able to move, but that doesn't help much if it isnt in the correct spot to begin with.

Have you yanked the dizzy to inspect the gear? If it is retarding, what condition is the knock sensor in?

IROC_385Z

I believe you about it not being the balancer but let me just say that my BRAND NEW balancer did this to me!

Its been a few years since I've had TPI, does that distributor have springs for mechanical advance?

dimented24x7

iTrader: (2)

I would help but I forgot my crystal ball[<-insert humor here...]

Its not the computer for sure. It can only retard teh timing at the dist. jsut slightly past 0 deg and its out of the loop with the EST disconnected. If I had to put money on it Id say maybe the gear on the dist. is chewed up. Of coarse teh gear on the cam may be in equally bad shape.

Stekman

Yank the dizzy (after marking the rotor location) and look at the gear. Work from there.

jamesbob02

Like I said, about 50 deg BTDC, so advanced. And this is BASE timing, so it has nothing to do with the computer.

As far as the load, let me put it this way...it seems that the timing is changing BECAUSE of the load, like when I'm revving high and accelerating a lot (on the street), the power and load are causing the gear to slip or strip, is what I'm picturing.

Basically, I would assume it's either the dist or cam gear, I just want to know if these is even possible and does it happen, you know?

For the balancer, its a Fluidampr, one piece, and I remember when I installed it was the first time I was able to get my timing right on this car, and was the strongest it's ever ran, but this was like a year ago. And with the way the balancer lines up with the key in the crankshaft and because it's a one-piece, there is ZERO possibility of the balancer being off. Also, I was sure to check the first time that the TDC mark is in the right spot, according to the piston, distributor, and balancer.

Also, the dist and timing (beyond base) is entirely electrical, so no points, springs, or mechanical/vacuum advance of any type.

jamesbob02

I'll pull the dist tomorrow night when I get the car back from the headliner shop, but until then I'd still like to hear if anybody has had this happen, and whether or not the dist or cam gear actually is the culprit.

Honestly, I couldn't imagine it being anything else, but I've never been down in there.

neat

If the cap is not moving, and the timing is changing that dramatically, the gear must be slipping. Either the cam gear is shot, the distribtor gear is shot, or you some how have a cam with the wrong type of distributor drive gear.

I guess it would also be possible for the rotor to somehow not be properly affixed to the distributor shaft, but I've never heard of that.

gmgod

Thats weird because load at the crank isnt going to create more load on the camshaft gear. Is there metal particles in the oil?

jamesbob02

Good thinking.

Actually, the FIRST time it changed dramatically under my watch was in park, revving a bit.....at the time, though, I thought my ecm was going out and didn't touch the car for two days because I was disgusted. So I guess it doesn't matter if there's an actualy engine load or not.

I'll change my oil in a few days and see what's there.....til then I'll just take it easy and try not to go above 2k, and take a look at the dist gear then as well.

Thanks for the help.

94-6spd

I'm having a similar problem. My base will be 8 to 10 and at idle it'll rise to 18. I think the problem may be camshaft endplay.

Your problem could be that the teeth are worn on the distributor gear causing the timing to move but I don't think it could make it jump 50 degrees though. Did you ever pull the distributor yet?

five7kid

iTrader: (14)

Sounds more like putting the timing light probe on the wrong spark plug wire.

Anything that would change timing based on mechanical drive would tend to retard the timing. Loose pickup is one possible exception, but it should get whacked and fail completely if that were the case.

Another possibility is spark jump within the cap. Cap & rotor been inspected/replaced lately?

jamesbob02

I have not changed the oil yet (will try to fit it in tomorrow)

I yanked the dizzy tonight, and it had minimal wear on the gear, so I'm concerned it's the camshaft gear.

five7kid,
I'm definitely not putting the light on the wrong wire....my wires are arranged in looms and it's impossible to not grab the #1 wire lol.

I think you're right about any mechanical change would result in retarded timing, but for some reason this isn't the case.

Regardless, I can confidently rule out anything intermittent, like jump inside the cap, or crossfiring, or a bad pickup, because there is a DRASTIC change happening, and it doesn't just "go away."

After looking at the dizzy gear, I put it back in and timed it properly (EST disconnected), and took it for a spin just to make sure I wasn't crazy (EST connected). Again, first time I stepped on it hard, the engine went crazy and started pinging hard, so I limped back in and checked the timing (EST disconnected), and it was way off again, between 50-60 deg BTDC, and the dist cap had NOT moved (I marked it in a few places)

My guess now is that the cam gear is shot, and that it is slipping one tooth at a time, because every time the change happens it looks to be the same amount. This makes sense, right?

And since the car ran fine for two years, its safe to assume that the cam gear was right at first, and not the incorrect one.

There is one last possibility, but I don't think it holds much water. If the source of this problem was the timing chain jumping teeth, at 50 deg off at a time, wouldn't this quickly result in total engine destruction with pistons hitting valves? That's what makes me think it has to be the cam gear now.

Is there any possible way that the pickup is causing this? I'll put my old one on tomorrow just to try it out, but this problem screams mechanical.

dimented24x7

iTrader: (2)

The cam gear is the most unlikely. Once something goes wrong there the motor stops running. It could be maybe the rotor is spinning on teh shaft. There is a sort of plasic key on it that locates teh rotor on the dist. shaft and if it was somehow damaged then the rotor could move all on its own. The reluctor moving around on its own in relation to the shaft could feasibly cause the same thing but I dont even remember how it was attached or if it would be possible for it to move. Carefully inspecting the dist. would either prove or rule these things out so you could move on.

TMX

Mark everything. Seriously.

Bring your timing mark on the balancer to 0 degrees TDC, remove the cap, and mark a straight index line across the reluctor and stator. Make another mark on the distributor body that corresponds with the position of the rotor tip, and then make one final index mark between the distributor hold-down area and the intake manifold. Button it up, drive it until it happens, go home, bring the damper to TDC, pull the cap, and then see what doesn't line up any more.

-Bob

Apeiron

If the reluctor ring was slipping it could retard far enough that it would begin firing on the next cylinder's pole, but since the position of the cap hasn't changed it still gets routed to the current cylinder and appears advanced.

I hope that makes sense.

jamesbob02

The problem is I don't know anything about the other parts on the distributor...reluctor, stator, stuff like that is foreign to me. I can vouch for one thing, and that is that the rotor is not moving in relation to the shaft...the key notch it sits on is still well established and they fit snugly.

I'll try to do a little research on the dist parts and see what I can learn, but until then, does one of you have a picture of the top of a dist they don't mind labeling and posting? That would help a lot.

Stekman

http://www.rustpuppy.org/ignition2/Ignition%202b.htm

That's a start...good break down info.

jamesbob02

That's interesting, but it looks nothing like the dizzy I have, which is entirely electronically controlled. Thanks for the link, though.

Anybody have a breakdown and info on a divorced-coil, late model HEI distributor without all the vacuum or mechanical advance?

dimented24x7

iTrader: (2)

Although its a non-CC hei dist. its similar to the construction of yours. The CC one doesnt have and weights, vac adv. canister, or the other stuff but the way it comes apart is similar to my knowlege. The dist. isnt too hard to take apart. The part about the shaft being hard to get out with an old dist. is definatly true. Mine had so much gunk on it it wouldnt even budge without a good cleaning.

Red Devil

Did you by chance check the diameter of the new balancer to that of the old? Also, did you check the condition of the key on the crank?

IROC_385Z

(in a sarcastic tone)

You mean there is a key for the crankshaft?

J/K buddy.

jamesbob02

Yeah I'm sure I got the right one. Like I said, the whole combination worked great for 6 months or so, so something went wrong. I'll take a look at the key when I get down there, but I would consider that quite a distant possibility, considering the nature of how the timing is jumping, which is not random.

Tonight I'm going to change the oil and see what I find.

A friend of mine who dabbles in racing and has engine building experience told me that the cam gear can "pull away" from the dizzy at high rpm, especially if there is slop in the connection, and that a "cam button" would prevent that. I've heard of a cam button before, but didn't really know what it did. Do you guys consider that a possibility?

Regardless, I'm probably still going to pull the cam anyway just to make sure the gear isn't trashed on it, so I can either rule the possibility in or out without wondering....and I'll install a cam button when I put it back in (or when I replace the camshaft I might say).

IROC_385Z

I see that you have a 92 L98, is your block still the factory roller block? If you are running a factory-type roller cam than no, you already have a cam retainer plate that works the same as a button...unless you never put that plate back on?

jamesbob02

I've never been down that far to see (I wouldn't even know what to look for), but it's possible, the engine has been rebuilt (but before I owned it)

jamesbob02

Ok for various reasons, I haven't gotten around to changing the oil or pulling the cam, but my uncle who is an old hotrodder came over and checked it out, and suggested all the same things you have and he couldn't think of what could have been causing it, so he just pulls off the cap to take a look.

So we're messing around with what I assume is some sort of magnet related to the pickup, that is concentric on the shaft, and he's able to turn it a few notches, which to me is not something significant (I don't understand the stuff under the cap). So he says "pull it, let me get a closer look"

So I pull the dizzy and we look at it....he sees the same things I did....small wear on the gear, pin is intact, and (using two channel locks) he decides that the gear and the rotor shaft are not separated.

So he looks at the shaft and says it appears to be "sunken a little low" and proceeds to use all his strength to pull the shaft out, which separates it from all the top pieces, and that magnet comes off the top. It appeared to both of us that this was something that was not supposed to happen, and decided that the magnet was slipping and so the pickup was misreading the dizzy position (or whatever), and that was able to screw up the timing without the cap actually moving, which to me makes sense.

Either way, I'm going to get a new distributor, but does this make sense to you guys? Just wanted to see what you thought....if I don't get many replies I'll probably start a new post.

jamesbob02

I ought to clarify, that after seeing some pics, it appears that the gear is supposed to come off the shaft so that you can pull it out the top of the dizzy, but in my case, the MAGNET came off, and I was able to pull the shaft out the bottom with the gear on it.

I'm guessing that the magnet's hole was factory toleranced smaller than the shaft, and was pressed on, and not intended to ever come off...am I right about this? Thanks.

dimented24x7

iTrader: (2)

Thatll do it... The reluctor works much better when its firmly affixed to the dist. shaft.

Apeiron

Yup, that's what I thought.

jamesbob02

Awesome, I'm glad you guys agree. What should I be able to get an old camaro dizzy for at the junkyard? Just wondering if it's worth it to go ahead and get a good one like a DUI....I don't really need it for the high revving, but if its gonna be a miniscule price difference, I might as well do it. I already have their coil and module.

SLEEPER 86

are you sure you didn't shear a timing chain gear(some were nylon)or a crank key?I'd be pulling the timing cover before blaming other things.
Eric

Apeiron

If there was a valve timing issue he wouldn't be able to reset the ignition timing and be on his way.

jamesbob02

Right.

Like I said earlier in the post, I was able to tune it back to the right timing and it would run GREAT....so the valves were not out of sync with the crank. I lost a total of 150 deg, so if the problem was in the timing chain, I would have had engine destruction a while back.

jamesbob02

YESSSS!!!

Got a used dizzy at the local camaro junkyard for $55 and swapped it in tonight....and it worked! The car runs GREAT! I love a perfect ending to a car problem.

sellmanb

I've been following this thread since it's been up cuz I have been eager to learn what was wrong with this... 40 posts later, and it was a bad distributor heh.... for educational purposes... what could have gone wrong in the distributor that made it advance the timing like that?

Very glad you got it fixed man :lala:

Apeiron

The reluctor was slipping, probably a manufacturing defect.

jamesbob02

Basically, the reluctor that is hard pressed on the shaft that is picked up by the pickup to show dizzy position was slipping at high rpm. Basically, this is not supposed to be a possibility because it's supposed to be toleranced so tightly that it never moves. Obviously, in my case it has. I can vouch for the fact that my uncle, in all his years of SBC hotrodding, never saw this before.

So what was really happening was everything was staying in the position it was supposed to (real timing was not changing), the reluctor was confusing the ignition module and telling it the wrong dizzy position, so that the spark was occuring at the wrong time.

jamesbob02

EDIT: I'm a moron

At least I'm a moron with a properly working engine now lol

Thanks guys :hail:

Apeiron

Ahem...

TMX

Another ahem.....

Admittedly not as specifically focused as Apeiron's post, but definitely including reluctor misalignment in the realm of possibilities.

-B

jamesbob02

lol....I guess the biggest thing is I didn't understand what that meant at the time. My uncle was the one who actually showed me what the thing was. Sorry guys, I guess I just didn't understand.