Engine Timing Driving Me Nuts

[ACK]

A while ago, my 4.1L was stuttering at low RPMs, so one-by-one, I did the following:

- New spark plugs
- Vacuum test
- Rebuilt carb, took apart 2nd time and recleaned again
- Replace ignition coil
- Remove inline fuel filter (has a new one in the carb)
- Went to clean inside of the distributor and found it has a Pertronix, so regapped plugs
- Replace vacuum advance and vacuum hose

Finally, I purchased a timing light with an advance. I marked TDC on the pully and found the timing was completely off the charts, so confirmed TDC again and once more after that. I've been adjusting the timing for over a week and having no success. I slowly pull the timing back, adjusting idle as I go, and when it's around 12 - 18* it doesn't run well at all, it needs a real high idle to keep from dieing and when revving the engine, it sounds like the vacuum is sucking in a whole lot of nothing then dies.

Right now, timing's set at 38* because anything higher seems crazy. Also, when I hook the vacuum advance back up, there's no change in timing.

At 38*, if I'm driving on flat surfaces everything is fine, but it pings going up hills and has no power. If I advance it further towards the original crazy high position, I have no problem with hills, but it stutters in the lower RPMs. I want to replace the current distributor with a HEI to see if it fixes the timing issue, but before I do, is there anything else I should look at to get the timing in line or is there much bigger problem?

[Corts60]

One of two things is happening here, either your harmonic balancer has spun from its original location or it is the wrong one. There were two types of balancers and timing covers made. The most common is the one with the timing marks that are off to driver side. There is one that has timing marks centered on cover and you have to look down behind the water pump. Sometimes people swap harmonic balancers and not the timing covers so they do not go together. Make sense?
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[Corts60]

Here is what you need to do:

Pull #1 spark plug and stuff the corner of a rag into the threads of the cylinder head. Don't push it all the way into the combustion but just enough to make it tight. Then carefully bump the engine over. Once you here that rag POP, that is #1 TDC. Now go check your balancer location and that is where zero should be. If the mark is nowhere near your timing marks, your balancer is wrong or busted.

And now it is time to check your rotor. Pull your dist. Cap and see where the rotor is pointing. It should be pointing at your number one wire.
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[Rufton]

Many ways to verify TDC. Last time my Dad simply put finger on #1 plug hole and when air stopped I stopped turning; it was dead nuts TDC.

My Pertronix has been working great for about 15 years.

I would not drive while pinging because of potential engine damage.

I would pull VC and verify timing chain on right tooth and verify pointer like others said.

[luvbowties]

Originally Posted by ACK

A while ago, my 4.1L was stuttering at low RPMs, so one-by-one, I did the following:

- New spark plugs
- Vacuum test
- Rebuilt carb, took apart 2nd time and recleaned again
- Replace ignition coil
- Remove inline fuel filter (has a new one in the carb)
- Went to clean inside of the distributor and found it has a Pertronix, so regapped plugs
- Replace vacuum advance and vacuum hose

Finally, I purchased a timing light with an advance. I marked TDC on the pully and found the timing was completely off the charts, so confirmed TDC again and once more after that. I've been adjusting the timing for over a week and having no success. I slowly pull the timing back, adjusting idle as I go, and when it's around 12 - 18* it doesn't run well at all, it needs a real high idle to keep from dieing and when revving the engine, it sounds like the vacuum is sucking in a whole lot of nothing then dies.

Right now, timing's set at 38* because anything higher seems crazy. Also, when I hook the vacuum advance back up, there's no change in timing.

At 38*, if I'm driving on flat surfaces everything is fine, but it pings going up hills and has no power. If I advance it further towards the original crazy high position, I have no problem with hills, but it stutters in the lower RPMs. I want to replace the current distributor with a HEI to see if it fixes the timing issue, but before I do, is there anything else I should look at to get the timing in line or is there much bigger problem?

Not sure how Pertronix affects advance; but, otherwise you are describing effects of a too short timing curve--like the mechanical advance is stuck or for some reason, not advancing with increasing RPM. I'd check advance weights to ensure they are free and swing out easily when you manually spin the distributor.
Sam

[ACK]

Originally Posted by Corts60

Here is what you need to do:

Pull #1 spark plug and stuff the corner of a rag into the threads of the cylinder head. Don't push it all the way into the combustion but just enough to make it tight. Then carefully bump the engine over. Once you here that rag POP, that is #1 TDC. Now go check your balancer location and that is where zero should be. If the mark is nowhere near your timing marks, your balancer is wrong or busted.

And now it is time to check your rotor. Pull your dist. Cap and see where the rotor is pointing. It should be pointing at your number one wire.
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I brought her to TDC, pulled the distributor cap and the rotor is pointing close to, but not on the #1 wire. Does this mean the oil pump position needs to be adjusted?

[brokenspoke]

[quote=ACK;6114406]I brought her to TDC, pulled the distributor cap and the rotor is pointing close to, but not on the #1 wire. Does this mean the oil pump position needs to be adjusted?[/quote

[Rufton]

Rotor should be aligned slightly CCW of #1 plug when #1 TDC compression.

[tincan1966]

Originally Posted by ACK

I brought her to TDC, pulled the distributor cap and the rotor is pointing close to, but not on the #1 wire. Does this mean the oil pump position needs to be adjusted?

So where is the timing mark in relation to the pointer? That will help establish if you've got a spun inertia ring on the balancer or a mismatch of cover and balancer.

[ACK]

Originally Posted by tincan1966

So where is the timing mark in relation to the pointer? That will help establish if you've got a spun inertia ring on the balancer or a mismatch of cover and balancer.

When the TDC marks I made are on 0* (about 2 o'clock), the factory mark is shy of 6 o'clock. The engine is a 1973 Mexican crate 4.1L.

The good news is I rotated the oil pump shaft and have the rotor pointing dead on to #1. The bad news, I've set the timing to 12* and there's power in park, but once it's in drive, the engine is sputtering and has no power. Any advice before I proceed to fiddle with the advance some more?

Thanks for heading me in the right direction!

[tincan1966]

Disregard any marks you made. When the engine is truly at TDC, not the rotor pointing to #1 on cap, where are the OEM marks?

#1 can be anywhere you want it to be on the cap, all that is needed is to following the firing order. That position on the cap is not set in stone, and has no effect on intial timing.

[ACK]

Originally Posted by tincan1966

Disregard any marks you made. When the engine is truly at TDC, not the rotor pointing to #1 on cap, where are the OEM marks?

#1 can be anywhere you want it to be on the cap, all that is needed is to following the firing order. That position on the cap is not set in stone, and has no effect on intial timing.

When the engine is truly TDC, the OEM mark is about 6 o'clock.

[jonzcustomshop]

I was having similar issues to what you are talking about, and it turned out to be a flat cam...

[ACK]

What has me scratching my head is the position of the OEM timing mark. A PO did some "creative" work to keep the truck running. I'm curious if they used a harmonic balancer that was sitting around or did the crank and cam gears skip so badly at one point that they're off by an unbelievable amount. The 4.1L doesn't have a chain, so I would think gears skipping is almost unheard of.

If I want to see if the crank and cam line up, the shop manual calls for removing the oil pan to remove the timing cover. I replaced the oil pan seals last month and the thought of doing it again is painful. Can the valves give me a clue as to what's going on if I have #1 at TDC?

[ACK]

Originally Posted by luvbowties

Not sure how Pertronix affects advance; but, otherwise you are describing effects of a too short timing curve--like the mechanical advance is stuck or for some reason, not advancing with increasing RPM. I'd check advance weights to ensure they are free and swing out easily when you manually spin the distributor.
Sam

I spun the distributor when I had it out this morning, hard to tell if the weights were swinging freely and didn't have time to disassemble. I'm thinking of getting a HEI next weekend to see if it improves things.

Jonzcustomshop - Don't even want to approach the accountant about fixing a flat cam, she'll make me sleep in the dog house for at least a month

[ACK]

I think I discovered why the engine is running poorly and could use some Pertronix help. The yellow wire runs from the starter's R terminal to the ignition coil, so the coil isn't getting a full 12 volts. Do I move the yellow wire from the R to the S terminal or is it better to remove the yellow wire all together and run a constant hot wire from the fuse box to the ignition coil? If it's best to run it from the fuse box, what gauge wire would you recommend and should I put in a breaker?

[geezer#99]

The yellow wire is there to provide 12v while starting only. After it starts you only need 7v to make it run. That's what the resistance wire is for. If you supply full time 12v to the coil they overheat and get fried inside.

[ACK]

Originally Posted by geezer#99

The yellow wire is there to provide 12v while starting only. After it starts you only need 7v to make it run. That's what the resistance wire is for. If you supply full time 12v to the coil they overheat and get fried inside.

Thanks Geezer#99, I was under the impression that the Pertronix needed a constant 12, points needed less to keep from frying.
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[Sharps40]

Assuming points ignition, you seem to describe a dwell issue, i.e. likely your points gap is off. As Cam angle/Dwell is increased as the point gap is decreased. It looks like you are compensating for a far out of spec dwell/point gap by spinning the dizzy to advance the timing.

There is a one way relationship between points gap (Dwell) and ignition timing.

Changing dwell changes static timeing...but not vice versa. Its why you always always set dwell/points gap before setting timeing. And its why changing timing never ever changes dwell/points gap.

Start at the beginning.

Find TDC on #1. Balancer factory mark should be close...if not, mark it at 0 for now with a silver sharpie to establish final accurate timing later. (It is not likely your balancer spun way far off.)

Set dwell (points gap) with a 16 to 19 thousands feeler gage or as specified in your Motors/Haynes. If the rubbing block is not on the high side of the cam, just loosen the dizzy and turn it slightly till it is...tighten the dizzy clamp then set the points gap.

Disconnect vacuum advance at the dizzy and plug the hose leading to the carb.

Reassembly cap/rotor, etc, and start the engine and fully warm it up, 30 minutes idle is about right. (Vacuum advance off and plugged)

You should be reading close to the right dwell...on a 6 it should likely be in a range of 30 to 35 degrees. Ignore the timing as long as it idles, even rough. Reset the points gap as needed to get to the Bottom of the specified dwell range (this allows the dwell to increase to the top of the specified range as the rubbing block wears in)

Once the dwell is perfect...put the timeing light on the warm idling engine, set the static timeing to the specified number by rotating the dizzy body...when set correctly, clamp down the dizzy. (Vacuum advance still disconnected and plugged.)

Reinstall the vacuum advance on the dizzy.

Now, check and adjust fuel mixture at idle and last, idle speed.

Go drive. Should be a Buzzin Half Dozen.

HEI is easier...TDC, warm it up, Set it for 10 to 18 degrees advance with the plugs gapped 45 thou, check mixture, check idle speed, go drive.

[ACK]

Thanks Sharps40. It's a points that's been converted to Pertronix by the PO. I went to the salvage yard this morning and they wanted $50 for a HEI ... Thanks but no thanks. So I went home and pulled out the volt meter to trouble shoot some more.

Don't get it, I would love a HEI for Father's Day, but the wife would be as happy as a wet cat if I gave her a new $300 vacuum on Mother's Day. Go figure.
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[Sharps40]

$84 from Tom Langdon at Stovebolts gets you an HEI, cap, coil set up for the 6 cylinders - and someone to discuss the install with. I believe they are rebuilt GM units. Love mine...best money I spent. 6 bucks gets you the hot plugs he recommends. The local houses had rebuilt units w/no cap/rotor or coil for the same $80 to $90. From what I gather, the pertonics units are simple points replacements and don't provide the hot burn and higher initial advance possible with the HEI.

[AcampoDave]

I once replaced many perfectly good parts trying to fix a Caddy. At first I was sure it was the carb not opening up the secondaries. I finally took it to a shop and they found the exhaust to be plugged up. My point is, sometimes your problem aint at all obvious or where you believe it to be. Consider other causes. Could you have a vacum leak. Is your intake properly sealed? Do you have a stock exhaust manifold with a heat riser stuck shut? If your dist has a functioning mech adv. and your timing is set, could your problem be unrelated and waiting for you to look more broadly as was the case with my Caddy?

[ACK]

I'm giving this thread closure in case someone comes across it down the road because they're having a similar problem.

Thanks to everyone for their suggestions and guidance, here's what I've learned ...

1. TIMING CHAIN: the 230,250, and 292 don't have a timing chain. The crank and cam gears mesh together, so it's rare (but not impossible) for them to be out of sync

2. FLAT CAM LOBE: Todays oils have way less additives that prevent metals from wearing away, if you don't use one, seriously consider a zinc additive. The easy, but not the most accurate, way to check for a worn cam lobe is to take off the valve cover and see if any of the lifters are barely moving up and down while the engine is running. If you want to get real accurate, get a dial indicator and rotate it by hand to see if a lobe is lower than the rest.

3. HEAT RISER: Located on the underside of the exhaust manifold, when the engine is hot, if the flat side is pointing towards the drivers side you're good and if it's pointing down, that's not good. Read this link for more info.

4. RESISTOR WIRE: It's suppose to be a white cloth wrapped wire. We'll, when a P.O. paints it gloss black, it' looks like all the other wires. When I started unwinding the black tape around the wire harness, I found out that I still had a resistor wire. The resistor wire's casing also yellows and even turns dark brown over time. I read many different opinions about the resistor wire if you have a Pertronix unit, one thing is for sure, it can create problems if it's not hooked up correctly. Below is the passenger side wire harness for a 64 C10 with the wires labeled.

5. HARMONIC BALANCER: GM made balancers with marks at 2, 2:30, and 12 o'clock, so you might be top dead center on the #1, but your timing mark could be pointing someplace crazy if it was replaced with the incorrect year. One way to test it to see if the rubber is separating is place a mark on the rubber part below the timing mark and hit it with a timing light. If it appears to be moving separately from your timing mark, time for a new balancer.

6. TIMING LIGHT: If don't need a pro timing light, get the one with the advance dial at Harbor Freight. Sure, it's inexpensive and the knob moves a little too freely, but having the advance control is fantastic. Avoid getting an older timing light off of Craig's list. If you do and they say "Well, it worked 5 years ago when I last used it", either test it before handing over the cash or ask if they'll give you your money back if you can't test it then and there.

All the above is just one man's experience, if any of this is inaccurate or could use some clarification, chime in. Now to end this tale. I ordered an HEI from Tom at Stovebolt Engine Co. and HALLELUJAH, my truck has been cured! I'm not going to speculate if it was the Pertronix unit or the camouflaged resistor wire, all I know is it feels like a new engine –*best $100 I've spent on the truck. Again, thanks to everyone for their help and advice.

[tincan1966]

So did you ever get it straightened out?

[Sharps40]

Tom Langdon is a good man and the dizzy you ordered will be set up right for the I6. Easy to install and I love the way it runs. Mine felt brand new when I put in his HEI as well. Yer right, best money I spent too...glad I popped for it.

Watcha runnin for timeing? I started at ten advance and finally wound up at the 18 advance that Tom told me to use in the first place. I also installed the plugs he sells/recommends. They are doin fine also.

Glad it worked out for ya!