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Harmonic balancer installed and timing mark question
Yesterday we installed harmonic balancer. I taped the timing tape zero mark to the notch on the balancer and they line up perfect. After we turn the crank to line up notch on the harmonic balancer to the zero mark on the timing mark on the timing cover, rotor is pointing almost half way mark from number one wire terminal and number 8. From the paper I read TDC on compression stroke should line up with number one spark plug wire terminal. Since we bought the car used we do not know if someone changed the distributor cap and didn’t install it correctly. Should we pull the distributor out and align rotor to number one plug and drop it back in? We couldn’t find the TDC locator tool and have one coming soon. We also verified both rockers are flat and at the highest position on number one cylinder.
You really can't install the cap wrong. Eyeballing the rotor direction with the #1 plug is a guesstimate anyway. Fire it up; if it starts and runs well, cam to distributor placement is just fine. Then check timing.
If you turn the crankshaft one complete turn, the rotor will be pointing to #1.
Sorry to push back, but the OP says the rotor is 1/2 way between #1 and #8 on the cap now with the mark aligned. A full turn on the crank is going to place the rotor between #6 and #5 so those are firing while #1 cylinder is purging and refilling. If the rotor is close to #1 when both valves are closed, it's on the compression/firing stroke.
The only other error would be the distributor out 180° but the valves would not both be closed at the same time.
Sorry to push back, but the OP says the rotor is 1/2 way between #1 and #8 on the cap now with the mark aligned. A full turn on the crank is going to place the rotor between #6 and #5 so those are firing while #1 cylinder is purging and refilling. If the rotor is close to #1 when both valves are closed, it's on the compression/firing stroke.
The only other error would be the distributor out 180° but the valves would not both be closed at the same time.
thanks for reply. I am going to take the TDC on the balancer and timing mark more seriously than where the rotor is pointing at TDC. I figure rotor can be adjusted to point to number 1 cylinder after pulling it out and slipping it back in. I was hoping the rotor was pointing more close to number 8 wire connector so I can just rearrange firing order but it smack in between 1 and the 8. Cap can’t be 180 degrees out for sure because if it did, vaccum can does not have space to be placed. Before the balancer swap, car started fine and ran okay but with little roughness in low rpm. Right now, only way to have rotor point to number 1 wire connector is to have timing mark on 34 degrees on the tape.
Last edited by riverwabbit703; Dec 19, 2021 at 05:38 PM.
Reason: More info
You really can't install the cap wrong. Eyeballing the rotor direction with the #1 plug is a guesstimate anyway. Fire it up; if it starts and runs well, cam to distributor placement is just fine. Then check timing.
Thanks for reply. So, you’re okay with where the rotor pointer is now and time the car? Can started fine before the balancer replacement.
Right now, only way to have rotor point to number 1 wire connector is to have timing mark on 34 degrees on the tape.
Distributor rotor is closest to the plug wire terminal when at full advance and the farthest away with no advanced at the time it's ready to fire. All distributors work this way. Sound like you're good to go.
Last edited by Fly skids up!; Dec 19, 2021 at 06:12 PM.
2020 Corvette of the Year Finalist (performance mods)
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how are you telling what post its pointing at? I have an old cap I cut the center out with a hole saw and its cut right up to the base of the posts so I can use it for adjusting lash as well. If you are sure its half way between 1 and 8 pull the distributor and re-stab it and see if you can get it between 2 and 1, you are looking for zero and enough room to get advance in it not retard. then run the wires and hook it up and see how it runs and times out.
What I usually do with my fancy hole cap is, with the motor timed the way Like it, i rotate the motor a bit to line up the post dead center on what ever post is close, then i mark the post and the base of the dizzy so when I put it back together I can get it almost perfect again. You can do the same thing by making yourself a fancy cap, lining up the rotor and marking the cap then adjusting the oil pump slot and re-stabbing until it lines up with the post so you know you are gaining ground and not continually adjusting the whole distributor and hoping its going in right
how are you telling what post its pointing at? I have an old cap I cut the center out with a hole saw and its cut right up to the base of the posts so I can use it for adjusting lash as well. If you are sure its half way between 1 and 8 pull the distributor and re-stab it and see if you can get it between 2 and 1, you are looking for zero and enough room to get advance in it not retard. then run the wires and hook it up and see how it runs and times out.
What I usually do with my fancy hole cap is, with the motor timed the way Like it, i rotate the motor a bit to line up the post dead center on what ever post is close, then i mark the post and the base of the dizzy so when I put it back together I can get it almost perfect again. You can do the same thing by making yourself a fancy cap, lining up the rotor and marking the cap then adjusting the oil pump slot and re-stabbing until it lines up with the post so you know you are gaining ground and not continually adjusting the whole distributor and hoping its going in right
with the dist cap on I made a line dead smack in the middle of the wire terminal. When I put the cap back on it us dead smack in the middle between 1 and 8 terminal when timing tape and market lines up at zero.
sonds like you got a mark you trust. re-stab it and see where you go
cant start the car right now. In middle of fan shroud removal radiator started to leak. Have to wait for new radiator and hoses to arrive. Radiator price has shot up since i last check few years ago. Man oh man. Gotta get timing straight first before I can even try tuning the carb.
Sorry to push back, but the OP says the rotor is 1/2 way between #1 and #8 on the cap now with the mark aligned. A full turn on the crank is going to place the rotor between #6 and #5 so those are firing while #1 cylinder is purging and refilling. If the rotor is close to #1 when both valves are closed, it's on the compression/firing stroke.
The only other error would be the distributor out 180° but the valves would not both be closed at the same time.
Distributor rotor is closest to the plug wire terminal when at full advance and the farthest away with no advanced at the time it's ready to fire. All distributors work this way. Sound like you're good to go.
If I can some what recall, last time I set top dead center on my old 74 vette in 2014 was I think I advanced timing marker to 12 degrees from TDC and lined up number one rotor to the number one wire terminal. So when I fired up the engine, I already had 12 degrees initial. So what I find little odd here is that when number one rotor is pointing at number one terminal, timing marker is at 34. Which leads me to believe previous owner could not get the engine to run right, he may have advanced the distributor too much and let it sit for years and sold it to me. I couldn’t get proper timing done on this vette because harmonic balancer was slipping. I don’t even know if car can start with 34 degree initial timing?
If I can some what recall, last time I set top dead center on my old 74 vette in 2014 was I think I advanced timing marker to 12 degrees from TDC and lined up number one rotor to the number one wire terminal. So when I fired up the engine, I already had 12 degrees initial. So what I find little odd here is that when number one rotor is pointing at number one terminal, timing marker is at 34. Which leads me to believe previous owner could not get the engine to run right, he may have advanced the distributor too much and let it sit for years and sold it to me. I couldn’t get proper timing done on this vette because harmonic balancer was slipping. I don’t even know if car can start with 34 degree initial timing?
You're looking at this the wrong way. Distributors don't fire the plug when the rotor is lined up with plug terminal, it fires when the points open (or when the pickup is aligned). You have a centrifugal advance mechanism that advances when the plug is to fire. The rotor moves along with this. Coupled with a vacuum advance system it's impossible for the rotor to be always perfectly lined up with the plug wire terminal. It's sort of a compromise. The greatest demand on the ignition system is at a higher RPM so it makes sense to have the least amount of Gap between the rotor and spark plug wire terminal. If you bring your engine to TDC try to manually turn the rotor to the mark that you made in regards to the number 1 plug wire terminal, the rotor should be able to reach the mark. I hope this explanation helps. It's kind of difficult visualize.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
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I understand what you are saying now. so you are at top dead center with no advance set in to the distributor. I thought you got 34 degrees with the light and couldnt get more. So y, your balancer is probably shot if its that far off. You can paint a line down the center so you can see if it slips again and put a timing tape on it to mark the new zero so you can tiime it and get it running now and then replace the balancer when you get a new one
Riverwabbit, I think you're good to go on the distributor and harmonic balancer job. (It's a new balancer, yes?)
Once you get the shroud & radiator out - a knuckle-scraping, patience testing exercise in itself - and all of that back in, drop a note to let us know how the engine started and runs. (There are ways to use a circuit tester to static time the engine if you are really unsure of distributor position. If you're interested I can look up the paper I used to initially time and start my engine after its rebuild.)
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Originally Posted by riverwabbit703
From the paper I read TDC on compression stroke should line up with number one spark plug wire terminal.This just provides an indication that the timing tab 0* mark is aligned with the notch in the balancer with the piston at TDC on the compression stroke but is not the way to do it. You'll just have to wait for your tdc tool to arrive as this is the ONLY way to determine the alignment of the timing tab and balancer notch. If they don't line up, adjust the timing tab so that they do and make sure the balancer hasn't slipped on the rubber ring. Better to buy a new balancer to be sure.
I wouldn't waste anymore time on the timing until you get your tdc tool.
Riverwabbit, I think you're good to go on the distributor and harmonic balancer job. (It's a new balancer, yes?)
Once you get the shroud & radiator out - a knuckle-scraping, patience testing exercise in itself - and all of that back in, drop a note to let us know how the engine started and runs. (There are ways to use a circuit tester to static time the engine if you are really unsure of distributor position. If you're interested I can look up the paper I used to initially time and start my engine after its rebuild.)
I assumed the balancer he installed was new. What is the condition of the timing chain set?
quicky TDC check since valve covers are off. rotate engine past the TDC mark. look at the valves on #6 and #1 cyls. the exhaust is just closing and intake is just opening right at TDC on either cyl. one or the other cyl. the other cyl is at compression-firing at the same point. this is not dead-to-rights, but it will tell you if you are close.
If it ran OK before and you haven't moved the distributor then it can't be that far out. How close are the pickup teeth to lining up? If you didn't move the distributor they should be close to lining up something like 10* BTDC.
If it seems way off, check the TDC mark on the balancer first before messing with the distributor.
Harmonic balancer installed and timing mark question
