rket56

On a previous post about which side of the timing mark would the pointer be if the timing were advanced, it was determined that viewed from the front of the engine, the timing mark would be nearer the passenger side. If I understand this correctly, the rotor in the distributor turns counter clockwise so I believe rotating the distributor clockwise would advance the spark, CCW would retard it. I am observing that the timing mark is on the bottom side, driver side of the pointer, the opposite of where it is supposed to be. The engine slows down when I advance the timing so the mark is closer to the pointer and will not keep running or start if the timing mark is above the pointer, as it is supposed to be. Since the timing of the valves/piston is locked in via the timing chain, could the distributor be installed one tooth off of the cam gear? Comments suggestions appreciated, Thanks, Chuck

gs72

The rpm should increase when the timing is advanced at idle. Try turning the distributor the other direction and see if the rpm comes up. Then try adjusting from there. You might also want to make sure your harmonic damper hasn’t slipped. Bar the engine over to TDC and make sure the timing mark on the damper is on the zero mark.

sysmg

Check what direction the water pump fan turns (the blades will push the air back from the radiator to the engine when the engine is turning the right direction. The balancer turns in the same direction. When the balancer is turning Before Top Dead Center (BTDC) would be in the opposite direction from zero that the balancer is turning. After Top Dead Center would be in same direction as the balancer is turning. So if the balancer is turning towards you as it cranks that BTDC would be in the direction away from you from the 0 mark. Typically cars fire BTDC so there are more timing marks on the tab in that direction than ATDC. I haven't worked on a 56 Olds but 1966 had a few notches and two marks 0 and 10. 10 was BTDC.

oldcutlass

No there is no such thing as the distributor being 1 tooth off in relation to how the engine is timed. Being 1 tooth off is an esthetic issue where it may lead to the vacuum can interfering with something preventing you from rotating the distributor to get proper timing. In other words the can will hit the firewall or an engine component. If the engine rpm is declining so is your timing while rotating the distributor..

rket56

Thanks guys but I'm still confused. Since I did have the balancer rubber replaced, it is possible that the timing mark is not in proper alignment with the key but years ago when I checked it out with the piston at TDC it seemed to be ok. But, if you will reread my post about the rotation of the rotor, CCW am I correct in that rotating the distributor cap CW advances the spark? Please see if you agree with this. What I didn't mention is that the distributor is not located in the factory position. Do to interference with the custom linkage on my 3x2 carb setup, the distributor is rotated 15-20 degrees clockwise from the factory position. The plug wires were rerouted to new locations on the distributor cap to correspond with firing order with the rotor position at TDC. Item # 2, it seems to me that it would be possible to be one tooth off with the distributor. The valve opening and closing is timed to the piston movement and the cam gear on the cam shaft has only one position in which the valve opening/piston position and ignition firing is correct. If the engine is not at TDC, but a fraction off, the distributor would go in and maybe the cap can be turned far enough for the ignition to fire, but be out of phase with the valve/piston opening and closing. Please forgive me if my reply/questions seem terse, I'm just kind of frustrated but I really appreciate your input. Thanks again, Chuck

oldcutlass

CW advances timing. The only thing that happens when a distributor is 1 tooth off is that it is not in the factory position when the timing is set correctly. You basically made the distributor a few teeth off by setting the position to avoid interference with your throttle linkage. The engine does not care what position the distributor is in as long as the firing order and ignition timing is correct.

joe_padavano

Your statements are correct. The rotor turns CCW, so turning the distributor body clockwise advances timing. When facing the front of the engine, the crank (and thus the balancer) turns clockwise. At TDC, the scribe mark on the balancer is aligned with the pointer. As the timing is advanced, the scribe mark will move to the passenger side of the pointer.

From what you describe, my first inclination would be to verify that the scribe mark and point actually do line up with the piston at TDC. It's entirely possible that the outer ring with the scribe mark has slipped on the hub, which would cause all timing measurements to be incorrect.

rket56

Thanks Joe: I was trying to avoid taking off all the extra stuff I have to remove to take off the valve cover to confirm TDC when both valves are closed. But, I guess it's the only way to go to gather more info. Taking out the distributor isn't a walk in the park either, have to remove some of the custom linkage mounted on the firewall to remove it. Sigh, well even though it is an Olds, some of the mods I've made have made it even harder to work on. : ) Thanks again, Chuck

OLDSter Ralph

You don't need to remove the valve cover, because both valves closed is not accurate enough. You don't have to remove the distributor. You need to know when the PISTON is at TDC on the COMPRESSION stroke.

joe_padavano

^^^THIS. Use a piston stop that screws into the spark plug hole. It doesn't matter if the cylinder is on compression or exhaust for the purpose of checking TDC on the balancer. Be sure you get a piston stop that has threads for the Oldsmobile 1988 spark plugs and not the more common 14mm Chevy threads.


https://www.summitracing.com/parts/cca-4792

rket56

I think we are on the same page but on different paragraphs.. I agree that in order to just confirm the timing mark it can be done on either the compression or the exhaust strokes, and the rotor position if near the # 1 contact will confirm that it is the compression stroke. I will have to pull the cap to confirm the rotor position at TDC. My previous comments were about if I had to remove the carb linkage/ distributor if the rotor was not in the correct position. Sorry I was not too clear about that and thanks for the info on the piston stop. Chuck

oldcutlass

Why are you going through this exercise if the engine is running?

rket56

After many years of working on other items, I have just started focusing on performance. I just discovered that the original PV in the center Holly 94 in my 3x2 setup was faulty and I have been trying to select the one that works best. With the correct one now installed, I am still finding hesitation and back firing upon acceleration. I installed new accelerator pump seals in all the carbs along with booster springs under them that were missing. All passage ways and orifices are clear. I checked the "squirt" of the pump with mineral spirits b/4 installing it, so it is working properly. The pump link is in the center position for stroke, it may need to move to the longest stroke position if not enough fuel is present during acceleration. The timing/ignition is most likely the cause and the anomaly of the timing mark on the wrong side of the pointer seems to show that.

sysmg

You mention needing a longer acceleration pump stoke during acceleration. If you are back firing during acceleration, you do not need a longer acceleration pump stroke. Back firing does not happen during a lean condition. You can't be changing thing ***** nilly and expect to resolve your problem. You will only cause other problems that will complicate your ability to resolve the initial issue.

Back firing can be due to an overly rich mixture, an ignition timing issue or improper intake valve opening during ignition.

If you want to resolve your issue. Get a Wideband A/F mixture meter and see what's happening when you are back firing.

rket56

I mentioned the position of the pump linkage only as a point of reference. I didn't think I was changing things in a "willie nilly" fashion. After making sure the carb was working correctly I am now focusing on the timing issue, which was the problem I first posted about. The suggestion I just received to start with establishing that the timing mark is actually at TDC is the next step and as Joe had suggested I ordered a piston stop yesterday. After determining if the timing mark is correct I will proceed from there. Thank you for your input. Chuck

rket56

Good idea but I'm offering a correction to the info you provided. I ordered the tool per your link and discovered that it is incorrect for 1956. The correct size is the 14 mm tool, CCA 4795. No fault being assigned to this, I should have checked my plugs b/4 I ordered. I wonder if the size went to 18 mm with the 1957 engine changes? Thanks Chuck/
PS. I couldn't get at the bolt on the balancer to turn the crankshaft with my custom fan shroud and flex- fan. I had already removed the plugs but also had to loosen the rocker assemblies to take the tension off of the valve springs b/4 I could turn the crank with just the belts.

oldcutlass

If the engine runs, then the firing order is already correct. Just turn the engine so that the rotor is pointed to the #1 spark plug wire and see where the timing mark on the balancer is located to the timing tab.

Vintage Chief

?? No one uses a chop stick any longer ?? Weird

rket56

The correctness of the firing order was never an issue. If you read carefully my first post my question was is it possible to install the distributor so that the rotor is out of phase with the piston/valve train ? Since the distributor can be rotated so the #1 plug is firing please explain why the although the #1 plug is firing the valves may not be opening/closing at the proper time. That is why I am trying to establish if the timing mark on the balancer is actually at TDC. I'm sorry if you didn't understand my question. Thanks Chuck

OLDSter Ralph

You CAN'T use the distributor to confirm the piston is at TDC of the compression stroke. You are exactly bass ackwards, you need to verify that the timing mark on the harmonic balancer is at TDC "0". From there, you connect a timing light to #1 spark plug to see where the #1 is firing the spark plug. THEN you adjust the distributor to advance the timing.

rket56

Guess you didn't read one of the later posts stating that I'm waiting for the correct piston stop in order to establish that the timing mark on the rebuilt balancer is at TDC. Thanks Chuck

OLDSter Ralph

I read a previous posting about the waiting for a piston stop. I read and responded your last post (#19) where you circled back to the distributor.

Have you looked at your CSM to see where the timing mark on the harmonic balancer should align at TDC ?

rket56

Sorry, I don't recognize CSM, please explain. Thanks, Chuck

OLDSter Ralph

Chassis Service Manual Its the manual that dealership mechanics used as a reference to repair a particular year automobile.

Get a used manual, not a reprint.
https://www.google.com/search?client...Service+Manual

rket56

I have an original, thank you for the clarification. Chuck

rket56

OK guys, I have confirmed that the timing mark on the balancer is dead on, using a piston stop. Since the timing light will continue to show the mark is on the wrong side of the pointer, what else can it be other than the the distributor is installed one tooth off? So far no one has explained to me why this can't be since the distributor is not mounted in the traditional, ie; radial location. My theory is that it could be one tooth off, thus explaining the timing mark on the wrong side of the pointer. Since the distributor can be radially located, independent of the rotor location to point at the # 1 plug, it would be firing with the valves not totally open/closed. Any ideas on what to do at this point other than remove the distributor and engage at another point on the cam gear ? Main problem with doing this is trying to also rotate the oil pump to a new position without dropping the pan. Thanks Chuck

oldcutlass

See posts 4 and 6. Valve timing is controlled by the cam which is mechanically connected to the crank through the timing chain and sprockets. If they were installed correctly, then the issue you are having is with your ignition timing setting.

rket56

Your thinking is correct up to a point. Assuming the timing chain etc are all installed correctly, the cam gear timing is synchronized to the valve and piston. However, with the distributor removed, I can put a wrench on the harmonic balancer and turn the crank slightly. I can then reinstall the distributor, rotating the rotor until it meshes with the cam gear but now the rotor is out of phase with the cam gear and therefore the valves/piston. I can then rotate the distributor until the #1 plug is in firing position. Thanks Chuck

oldcutlass

No, my thinking is not correct up to a point, that is how it works. The engine does not care where the rotor is pointing if you restab it anywhere within 360* as long as the firing order is wired accordingly and the timing is set right. The only thing that changes is the position of the distributor body and the wires. The cam controls the valve timing and is fixed mechanically to the crank. The distributor controls the ignition timing and is adjustable, they are 2 separate operations.

rket56

I guess we will agree to disagree. How do explain that the timing mark is on the wrong side of the pointer? When the timing is advanced toward the pointer, the engine dies. What do you suggest the next step should be? Thanks, Chuck

joe_padavano

Look, it isn't physically possible for an engine to run correctly with spark timing AFTER top dead center, which would be the case if your timing mark is on the "wrong" side of the pointer. Do you have a dial-back timing light? If so, is it possibly set incorrectly? In any case, have you tried a different timing light? Are you 100% sure you are sensing the correct plug wire?

oldcutlass

Without seeing what you're looking at I can't... How about some pictures of your timing tab and balancer position at TDC.

rket56

I got lucky and after a little trial and error, managed to show the CW & CCW rotation bracketing the timing mark using the piston stop. I have a regular timing light and the plug I am using is the plug closest to the radiator on the drivers side. Thanks, Chuck

sysmg

If you moved the distributor one tooth (for arguments sake lets say there are 36 teeth, 10 degrees per tooth) then if you left the cap in the same place you're timing would be 10 degrees off and the car would likely not run. So you'd have to turn the cap 10 degrees too. Now the timing would be exactly the same as it was, nothing would be accomplished except the distributor would be 10 degrees different. Perhaps if your distributor (maybe vacuum advance) is hitting something and can't be turned enough to get the timing right, then you need to move the distributor a tooth or two to get rid if the mechanical interference.

The distributor is geared to the crank, when the crank turns the rotor in the distributor turns in lock step. What the timing is, is that the points open just as the rotor is getting near one of the terminals inside the distributor cap. When the points open a pulse of high voltage is created which the rotor passes to terminal, that is adjacent to the tip of the rotor, in the distributor cap. That pulse needs to happen a few degrees before top dead center for each cylinder. The only thing that sets the timing is the relative position of the cap/points to the rotor. The rotor position is fixed by gears to the crankshaft. The relative position of the rotor to the cap can only be changed by turning the distributor body/cap relative to the rotor/distributor shaft. You can do that now without pulling the distributor by loosening the hold down and twisting the cap.

Now that you've established that TDC is correct, what leads you to believe that adjusting the timing so it moves into the correct position (BTDC instead of ATDC where it is now) is wrong? Does the car run bad? Does it have problems starting? Perhaps something else is very wrong, like your centripetal advance or vacuum advance over advances your timing when you hook everything up. So the car only runs OK when those are hooked up with significantly retarded timing.

Also I am not familar with 50s ignitiion setup, are you following the right procedure to adjust the timing (probably vacuum advance plugged and at a set RPM)?

rket56

Thank you for your time and patience in trying to help me sort this out. Now that I have established the timing mark is correct, I will have to tighten up the rocker arm assemblies to activate the valves since I can't get at the balancer bolt to rotate the crank and had to use the belts to turn the crank. After establishing that I'm on the compression stroke I'm sure the rotor will be at or near the # 1 plug contact. But then what?
What is confusing is that in the past the timing mark was showing in the correct position. The only change I made in that area was when 2 years ago I removed the distributor to remove the electronic ignition and put points/condenser back in. That's why I was wondering if somehow it was not on TDC when I reinstalled the distributor.
The engine has never really performed the way I expected but it always seemed to be the carbs. Many reasons for that conclusion. Right now the # 1 and # 3 carbs are blocked off. I discovered that the power valve on the center holly 94 was never working and the cause of the engine running rich and not idling properly so I have supposedly now installed the correct one . The only trip I made using the newest PV was to the gas station and back. A lot of hesitation, missing and backfiring; I couldn't tell if the backfire was thru the carbs or the exhaust. This was not a brand new situation, just seemed to be worst. At this point I started trying to adjust the timing and found the timing mark now on the wrong side of the pointer. It starts fine, engine revs quickly under no load, vacuum advance is working correctly. Turning the distributor to advance the spark, i.e. moving toward the pointer results in the engine slowing down/ stopping and no start. I am certainly open to suggestions Thanks Chuck PS. yes vacuum line was blocked

oldcutlass

Set the timing where it's supposed to be and look elsewhere for the issues. From the above description the issues may very well be in the carbs.

rket56

From my first post : I am observing that the timing mark is on the bottom side, driver side of the pointer, the opposite of where it is supposed to be. The engine slows down when I advance the timing so the mark is closer to the pointer and will not keep running or start if the timing mark is above the pointer, as it is supposed to be.

rket56

The point that I was trying to get across was that it seems to me if the engine was not at TDC when the distributor was installed, the rotor would be out of phase with the piston/valves closing. You can rotate the distributor until the contact fires the # 1 plug but it will be firing when the valves/piston are not in optimum position. Thanks, Chuck

joe_padavano

Look, you apparently don't understand how the distributor works. What matters is the relationship between the rotor and the cap. If you move the gear one tooth, the effect is exactly the same as rotating the body of the distributor (and thus the cap) the same angle in the opposite direction. Many have told you this and you apparently still don't believe it, so rather than wasting time posting here, why don't you simply pull the distributor, move it one tooth, and see what happens.

Vintage Chief