Timing issue

[nhall80 10]

Replacing the distributor while installing electronic ignition (351w) and found a issue. When I'm on TDC, my timing marks on the harmonic balancer don't line up. When the marks are in line, the #1 piston is down. Motor has been running fine, so I don't assume anything is seriously out of time. I thought by moving my distributor I could fix the half time issue.

 

What thoughts do you guys have? Can I just reinstall my distributor on TDC without timing marks lining up?

[blueblood 26]

Sound like the outer ring of the balancer has moved.

You can replace with an aftermarket version or maybe someone local reconditions them?

[Midlife 814]

You sure you are measuring TDC on the right piston? It should be the forward-most one on the passenger side (unless you are in Australia...).

[nhall80 10]

Yes. TDC is on right piston. I assume the outer ring has moved. It isn't noticeably loose, but I may go ahead and replace it.

 

thanks

[69gmachine 15]

You say it was running fine, but that was before you replaced the distributor, right? It sounds like you installed the distributor 180 out, meaning instead of being on the compression stroke, you were on the exhaust stroke. I would re-check the position of the rotor after verifying it is on the compression stroke.

[nhall80 10]

It was running fine, and I haven't tried cranking it with the new distributor. In fact, the timing marks were off before I pulled the distributor...I just always assumed I was on half-time. I just thought that I'd take the opportunity to put timing right while I was dropping in a new distributor. Instead, I found the timing marks not lining up while on TDC.

 

I'll probably go ahead and drop the distributor in the same the way the old one came out and replace the harmonic balancer later. I will triple check the piston position though

[69gmachine 15]

OK, if the marks were off the same amount before and after replacement, then yes it could be that the outer ring has moved. However, if the outer ring is moving then it will have a vibration problem as RPM increases because the offset weight is also moving.

 

How are you determining TDC with the heads on? Is it possible you aren't getting an accurate measure of TDC?

[mwye0627 44]

Perhaps it's not a 1969 engine (or harmonic balancer).

In 1970 they moved the lower radiator hose to the drivers side for better cooling.

That meant changing the water pump to left side inlet and moving the timing pointer to the right side. If it is a 1970 or later engine or balancer, then I would expect the timing mark on the balancer to be on the right side of the engine when #1 piston is @ TDC on the compresion stroke...

[nhall80 10]

Put it back together today and its running well. I'd still like to have accurate timing marks so as to adjust it properly. Right now I'm guessing based on how it's running and starting. I found TDC by removing the valve cover and checking the rockers arms when piston was up. That's how I determined between compression stroke and exhaust. When in this position the marks are nearly on the opposite side of the balancer.

 

And the engine is a '73 351. I only assume the harmonic balancer is as well. It has the lower hose entering the passenger side with the timing tab on the drivers side. Maybe I have earlier balancer?

[69gmachine 15]

If the harmonic balancer is from a 73, it should have a 4 bolt pulley and will not line up with the other pulleys on a 67 - 69 small block. You would need the '70 up water pump that has the inlet on the driver's side and the '70 up water pump pulley, alternator and PS brackets. The alternator belt is in front of the PS belt on the 70 up whereas it is behind the PS belt on the 67 - 69. The '70 up 4 bolt balancer has a different offset than the '65 - 69 3 bolt balancers so it would be difficult to mix and match parts.

 

Using the rocker arms to determine the compression stroke is fine, but you cannot determine TDC by them. There are too many variables in the cam timing events to use this for TDC. If you are off by a few degrees the timing marks will not line up.

[j69302 11]

To properly find an accurate TDC, with the engine assembled you with need a screw in piston stop, and a degree wheel.

 

I just ordered a summit racing kit which came with those plus a dial indicator. You can by them separately.

 

I believe the summit degree wheel was about 15 bucks and 12 bucks for the thread in piston stop. The kit was about 85-100 if I remember correctly.

 

Of course, you can get really close by removing the spark plug, getting it on the compression stroke, and either look at the piston with a flashlight (assuming you can get your eye down there) or carefully stick a screwdriver in the hole and feel for when the piston stops moving. Turn the crank back at forth, and try to zero in on the dead spot when the piston stops moving.

 

Don't trust the marks on your balancer or your timing pointer. If the pointer was removed and reinstalled at one point, it is likely not in the correct place. I know mine is off a little bit.

 

I just bought a new balancer, and the degree wheel kit so I can accurately find TDC, and reset my timing pointer to point at 0.

[nhall80 10]

I made my own piston stop from an old spark plug and was able to find TDC and make by own mark for it on the balancer (The marks line up on the passenger side when on TDC...which I'm guessing means that it is an earlier balancer than the '73 engine).

 

Here's my next question: what is the best timing placement and how do I find it? I set the idle timing exactly at 0. I understand that I need to advance the timing a little or check the timing while the engine is at 3500 rpm or so, but I'm not sure what I'm looking for.

 

I understand also that my distributor will have a certain amount of mechanical advance but I don't know what that will mean either.

 

Should I advance the timing? How far? How do I determine it...at idle...at high rev?

 

Will advancing the timing help my engine run cooler or hotter? (its crazy hot and humid in MS in the summer and I need all the help I can get)

[j69302 11]

Long story short, the highest initial timing which does not create hard starting, detonation or excessive temperatures will give you the best throttle response. Along with the highest total advance which does not cause detonation.

 

The simplest way is to adjust the initial timing, until you see no more than 36-38 degrees total. If it detonates or pings here, back it off a couple degrees at a time until it stops.

 

This is how timing works:

 

Initial timing + centrifugal = total timing.

 

Vacuum advance does not add to total timing, it just manipulates the curve at which the distributor advances during part throttle operation.

 

First if it has a vacuum advance, you need to disconnect it from the distributor and plug the line.

 

Now set your timing to 10-14 degrees Before TDC. This is called initial timing.

 

Once this is set, slowly rev the engine up. You will see the timing advance. This is the mechanical aka centrifugal advance doings it's job.

 

Continue to rev the engine until the advancing stops, and holds a constant timing.

 

This value will be your TOTAL timing. Your total timing should be around 34-36 degrees at 2800-3000 RPM. Any higher and/or sooner, you start running the risk of detonation. Of course, there are many factors that affect this and is something that you will need to determine what is best or good enough for your engine.

 

Once you are done adjusting the timing, shut down the engine and reconnect the vacuum advance line to the distributor.

 

So, lets say you set your initial to 16*, and you measured a total of 40.

 

16* + Unknown Centrifugal = 40

Centrifugal = 40 - 16 = 24 degrees mechanical advance.

 

If you experience detonation with this specific example, I would reset the initial timing to 12* for a total timing of 12+24 = 36*.

 

Setting the initial timing is just the baseline. Your distributor has springs and weights (centrifugal aka mechanical advance) that further advances the timing as the engine RPMs increase.

 

If you really want to fine tune your timing, you will need to have your distributor curved. This way you can decrease the amount of centrifugal advance. This will allow you to set a higher initial advance, while still maintaining a proper total advance setting.

 

My distributor, puts in a whole lot of advance real quick to where I have to set the initial timing way below ideal. If I set my initial at 14, I have over 40 degrees total and this is way too much. Therefor, I am getting ready to re-curve my own distributor. I am going to use BOSS 302 specs. I have heard this can increase performance and mileage.

 

My goal is to have a total of 36 degrees at 3000 RPM with as high as an initial as I can without any side affects.

Edited July 7, 2013 by j69302

[nhall80 10]

Thanks for the clear and detailed response. Very helpful. I understand now the role the distributor plays and it makes sense why you'd want a low centrifugal advance for power at low rpm. Ill consider adjusting this after some research.

 

Ill need to add timing marks to my harmonic balancer in order to get these numbers dialed correctly. Other than that this will probably be a pretty easy procedure.

[j69302 11]

Since you want to curve your distributor, here is some more good info for you.

 

http://www.bob2000.com/dist.htm

 

http://www.fordmuscle.com/archives/2000/03/timing/

 

Ford distributors actually have 2 sets of centrifugal advance cams... Called the reluctor plate.. Seen below.. You'll notice there are 2 different numbers on each side. Only 1 side is used at a time to limit the amount. This is the amount of DISTRIBUTOR (not crankshaft) degrees that these will allow to advance. The reluctor plate can be pulled off, and flipped 180* to utilize the other sides setting. The length of the cutout is what actually allows and limits the movement.

 

In this pic, it has a 10* (top, not used) and a 15*(bottom, in use) reluctor plate. This example is setup for 30* mechanical advance.. That is way to high. The plate can be flipped around so that the 10* (or 20* at the crank) can be used instead.

 

If you look at the slot on the bottom 15* side, you can see there is a little tab inside the slot. This is the side that is in use.

 

 

Remember, the distributor rotates and 1/2 the crankshaft speed so Anything specific to distributor degrees or rpm, will need to be multiplied by 2 for it to equal crankshaft degrees.

 

So a reluctor plate that says 10, will actually be 20 degrees advance. 13 will be 26, etc..etc.. Same thing for RPM, if 2000 RPM at the crank is actually 1000 at the distributor.

 

If you have a mity vac hand vacuum pump, you can even adjust the vacuum advance(assuming you have a adjustable one) after your centrifugal is dialed in. Simply hook the vac pump directly to the vac. advance, with a vacuum gauge, and you can apply small amounts of vacuum to see how much it will advance as well. I am going to use this method to tune mine to BOSS 302 specs once I get the rest of the parts.

 

Keep in mind, while this can be done on the engine with the distributor installed, if you flip the reluctor plate to engage the other side, this will throw your distributor 180* out. If you do this, you will have pull the distributor out enough to rotate its shaft 180 and reinstall and reset the initial timing. This is because the breaker cam, and the rotor all attach to it, and since they only fit one direction, you will have to spin the entire thing to correctly clock it.

Edited July 7, 2013 by j69302

[nhall80 10]

Follow up question: I did as j69302 recommended and can't get the car to start once I put the vacuum line back on the distributor. I was able to set the initial timing on 10 and the advance timing is about 36. Ran great until I put the vacuum line back on. Car wouldn't start. I was only able to advance the timing 5 degrees and still crank the car. It runs well, but I think it ran just as well when the initial timing was set at TDC.

 

Thoughts? What am I missing?

[j69302 11]

sorry to hear.. Not really sure.. vac adv. doesnt really do anything at idle.

 

Did you have 1 or 2 hoses going to your distributor? Does the vac advance canister only have 1 hose nipple or is there 2?

If it has two hose connections, it is a dual diaphragm, the outer hose connection is for the vacuum advance which should be hooked to a special timed vacuum source on the carb. The second, inner hose connection is for a vacuum retard, I beleive this hooks to a regular manifold vacuum( not positive about the connection) but it's purpose is to retard the timing during start to make it easier to start..which is why these were installed on high compression engines.

 

If you completely pulled the hose off and plugged it at the carb, did you verify if it is hooked back up to a timed vacuum port and not a manifold vacuum port?

 

Just throwing some ideas out there.. Vacuum advance should be doing very very little, if anything, during start/idle.

 

Ill be trying this in a couple of days.. Ill let you know if I run into the same thing.

Edited July 10, 2013 by j69302

[nhall80 10]

I realize now that I plugged the vacuum port on the distributor but not on the carb. Could that have been the issue?

[j69302 11]

During the adjustment, you should have plugged the port on the carb. Either putting a cap on the fitting on the carb, or plugging the line itself.. I actually use a golf tee to plug the line.. Works pretty well. Of course you can get a proper vacuum cap/plug kit from a autoparts store as well.

 

Once the adjustment was done, the line should be hooked back up to the vacuum advance on the distributor. As long as its hooked back up correctly, it should not have affected anything.

[j69302 11]

Finally got around to doing this. I mapped out my original timing specs and had over 40* advance!!! (advance, not total)... That was ridiculous.

 

I also put a new harmonic balancer on and used a degree wheel and piston stop to positively find top dead center. My timing pointer was off by 6 degrees, not able to adjust the pointer over, so I took this all into account during my adjustments.

 

I managed to get really close to the BOSS302 specs. Pretty much identical except I have all the timing in at about 2800RPM instead of 4000.

 

I plugged the vacuum port on the carb, and hooked a vac pump up to the distributor and tuned my vac advance too. The car isn't drivable right now but throttle response in neutral seems much better.

 

Nhall80 - Did you get yours running again? I didn't have an issue with mine.

[nhall80 10]

I reset the timing while the vacuum port on the carb was plugged this time. Same story. Was able to set the initial timing to about 10 while the range tapped out around 36 at 2800-3000 rpm. Seemed to run and rev great.

 

But when I hooked up the vacuum line, the car would barely start. When I finally started it, it ran like trash and showed timing at nearly 45* advance. So, I left the vacuum line connected and reset the initial timing until the engine smoothed out...which ended up being 5* advance. It revs quick and runs strong. I have no idea why it is doing this but I'm very happy with how's it running now. Ill probably run it like this for a while and see how she does long term (like with engine temp). Any other thoughts about why this is happening would be great.

 

 

j69302 - Glad yours worked. Ill be looking into the boss 302 distributor adjustment as well.

[j69302 11]

Your vacuum advance diaphragm might be way off. Mine was. I used a mity vac vacuum bleeder to apply a vacuum to the diaphragm while the engine was running. By the time I got it in spec, the amount of advance it was giving was cut in half. My diaphragm was adjustable with a 3/32 allen through the vacuum port. Counter Clockwise decreases the advance. If you have an original style diaphragm, the fitting for the vacuum line should unscrew, and you can add or remove shims to adjust it.

 

It was quite easy to do, I used my idle screw adjustment to hold the engine at 2000 rpms, applied the vacuum, and checked the difference of timing. If I needed to adjust it, i set the screw back to idle, shut down, made the adjustment, and retested. Took me about 3 runs to get the vacuum curve set to the middle tolerances of the boss specs.

 

I just through in some lightweight springs (Some crane yellow springs) and used the idle screw to set some RPM increments and have a total of 37* all in at 2750 RPM.

 

Hopefully I can have enough of the front end back on the car to be street legal so I can see how it drives.