Topic: Issues getting the 390 to run correctly

[Matt1968]

Ok ,  the mustang sat for 3 years without running. Now,she would fire slightly but would not start so I thought I'd start with the basics.  Checked the spark plug wires for correct firing order. ( Never touched anything on that engine since it was rebuilt 6 years ago.  Ran perfect after the rebuild and ran perfect the day I parked it 3 years ago.)

All but a couple of the plug wires were incorrectly installed. (wrong firing order)  How  on earth could this possibly be?

All wires now correctly routed. Rotated the balancer to 0 degrees and had to radically rotate the dist to get the rotor to point to #1.  (Did not remove it)

She is now running, BUT at 20-25 degrees advanced at idle. Trying to get it back down to 10 degrees is impossible...starts to backfire and then stall.

How did this thing run so well with all the plug wires wrong?  What did the engine re-builder do?

Why will this thing only run at 20+ degrees?

When I parked this thing it ran like a raped ape,  and no one has touched it.

Could there possibly something going in the carb?  (3310)

[67gtasanjose]

There are some people who do not follow the guidelines of all of the service manuals or cannot for various reasons, to set up spark pug routing and/or firing order. My take on your description is your rebuilder did just that. He probably had the distributor timed incorrectly, so rather than pull it out and clock it correctly, he simply rotated the spark plug wires one to the right or one to the left in the distributor cap. This gets the engine running, then he times it by ear and throttle response after that. There is another possibility on why after you time it with a light it does not run correctly after setting up the plug wires correctly. If the outer ring on the harmonic balancer has been rotated (slipped at the rubber joint), it is no longer a usable way of setting up not only the firing order after an overhaul, but it will also not allow  you to time it with a timing light either. I have seen this many times over the years, especially if anyone might have used a nylon strap wrench to turn the engine over for any reason while working on it (e.g. accessing torque converter nuts). The rubber sometimes loosens up from a previous oil leak too, a backfire can snap a degree of rotation between the two pieces. Old engines translates to old parts/pieces with unknown condition.
Maybe somebody can help you identify if the two halves of the harmonic are aligned correctly with each other. The only way I know  to confirm perfect alignment of it is by side-by-side comparison of a known good one. If you notice a lot of wobble while the engine is running, can be a clue, but NOT proof by itself.

Hope this helps

[Bob Gaines]

There are some people who do not follow the guidelines of all of the service manuals or cannot for various reasons, to set up spark pug routing and/or firing order. My take on your description is your rebuilder did just that. He probably had the distributor timed incorrectly, so rather than pull it out and clock it correctly, he simply rotated the spark plug wires one to the right or one to the left in the distributor cap. This gets the engine running, then he times it by ear and throttle response after that. There is another possibility on why after you time it with a light it does not run correctly after setting up the plug wires correctly. If the outer ring on the harmonic balancer has been rotated (slipped at the rubber joint), it is no longer a usable way of setting up not only the firing order after an overhaul, but it will also not allow  you to time it with a timing light either. I have seen this many times over the years, especially if anyone might have used a nylon strap wrench to turn the engine over for any reason while working on it (e.g. accessing torque converter nuts). The rubber sometimes loosens up from a previous oil leak too, a backfire can snap a degree of rotation between the two pieces. Old engines translates to old parts/pieces with unknown condition.
Maybe somebody can help you identify if the two halves of the harmonic are aligned correctly with each other. The only way I know  to confirm perfect alignment of it is by side-by-side comparison of a known good one. If you notice a lot of wobble while the engine is running, can be a clue, but NOT proof by itself.

Hope this helps

+1. a 390 balancer is pretty common relatively speaking . Confirming it hasn't slipped by comparing the installed one with another using the crank keyway as index point also gives you piece of mind that you are on the right track. FYI running your balancer to 0 degrees is only part of the process. You have to remove the #1 sparkplug  and put a finger over the hole while rotating the engine (tapping the key or remote starter) and when you feel compression then you run it to Top Dead Center or the initial timing mark and make sure the rotor is firing on number #1. If you don't follow the compression part of the procedure you may be 180 degrees off. 

[Smokey 15]

 /\/\/\ All good advice. Also, the engine builder, or whoever installed the dizzy and wires, may not be familiar with Ford engines. May have used the correct firing order, but set it up like the engine was a Chevy with 'evens' on one bank, 'odds' on the other.

[Matt1968]

+1. a 390 balancer is pretty common relatively speaking . Confirming it hasn't slipped by comparing the installed one with another using the crank keyway as index point also gives you piece of mind that you are on the right track. FYI running your balancer to 0 degrees is only part of the process. You have to remove the #1 sparkplug  and put a finger over the hole while rotating the engine (tapping the key or remote starter) and when you feel compression then you run it to Top Dead Center or the initial timing mark and make sure the rotor is firing on number #1. If you don't follow the compression part of the procedure you may be 180 degrees off.

Let me ask you this....if it is 180 off,  would it still run?  I have got this thing running and starting right now.  Would it even start or run 180 off?

[67gtasanjose]

Let me ask you this....if it is 180 off,  would it still run?  I have got this thing running and starting right now.  Would it even start or run 180 off?

NO!

[Matt1968]

There are some people who do not follow the guidelines of all of the service manuals or cannot for various reasons, to set up spark pug routing and/or firing order. My take on your description is your rebuilder did just that. He probably had the distributor timed incorrectly, so rather than pull it out and clock it correctly, he simply rotated the spark plug wires one to the right or one to the left in the distributor cap. This gets the engine running, then he times it by ear and throttle response after that. There is another possibility on why after you time it with a light it does not run correctly after setting up the plug wires correctly. If the outer ring on the harmonic balancer has been rotated (slipped at the rubber joint), it is no longer a usable way of setting up not only the firing order after an overhaul, but it will also not allow  you to time it with a timing light either. I have seen this many times over the years, especially if anyone might have used a nylon strap wrench to turn the engine over for any reason while working on it (e.g. accessing torque converter nuts). The rubber sometimes loosens up from a previous oil leak too, a backfire can snap a degree of rotation between the two pieces. Old engines translates to old parts/pieces with unknown condition.
Maybe somebody can help you identify if the two halves of the harmonic are aligned correctly with each other. The only way I know  to confirm perfect alignment of it is by side-by-side comparison of a known good one. If you notice a lot of wobble while the engine is running, can be a clue, but NOT proof by itself.Hope this helps

I am familiar with a slipping balancer.  About 8 years ago I replaced the original just for preventative maintenance because the rubber looked bad.

[67gtasanjose]

I am familiar with a slipping balancer.  About 8 years ago I replaced the original just for preventative maintenance because the rubber looked bad.

Maybe true that you replaced the balancer 8 years ago.Was it NEW reproduction? NOS? USED? The situation I described above seems the most likely, that is going by the information you provided, assuming you checked everything by the book.

You mention it was rebuilt 6 years ago, so this sounds like it has been off the engine at least once.

Try doing as Bob mentioned above and bring #1 around on compression stroke. With the plug out, using a thin screw driver (or likes) to feel the top of the piston movement. Rotate BY HAND using the bolt in center of the balancer, back and forth till you find PHYSICAL top dead center as best you can feel. This can be difficult doing alone with the fan and radiator in. See where your "O" mark on the balancer rolls around on center of the movement back and forth or not. Best field test I know of.

[WT8095]

All but a couple of the plug wires were incorrectly installed. (wrong firing order)  How  on earth could this possibly be?

What order did you find them in?

To my knowledge, all FE cams use 1-5-4-2-6-3-7-8. If someone had installed a cam that used a different firing order, it would explain why it was wired in a nonstandard sequence. But I don't think such a cam exists for FEs.

Back in the 80's I consulted for a friend who restored a '69 GT convert with a 351W-4V. One night he called me from the shop where he and his mechanic were trying to start the engine for the first time, and it was sputtering and bucking and backfiring. I knew he had put a brand new cam in it. I told him to switch the plug wires around to 1-5-4-2-6-3-7-8 instead of the sequence isted on the intake manifold. It fired right up and growled like a tiger. He (and his mechanic) didn't know the 302 cam he put in it had a different firing order from the 351. But I did     (I wasn't being a jerk; I only figured out he had the wrong cam AFTER he called me!)

One more story: back in the 90's I had a '69 Cougar convert with a 351W-2V. Drove nicely, despite being somewhat "flexible" from the rusty floors. One day I parked it in the driveway, and came back outside some time later to go for a drive. It cranked and sputtered and tried to start, but just wouldn't go. It was getting fuel, the accelerator pump gave a nice shot. Also had spark at all the plugs. Just wouldn't go. I couldn't think of anything else to check, so I pulled the fuel pump off and stuck my finger in to check the timing chain (insert joke here  ). There was about an inch and a half play in the timing chain! When I tore it apart to investigate, it turned out the sprockets were off by a total of THREE teeth! Put a new timing set in, and it fired up and ran smooth and strong. Before the incident, it was probably off by one or two teeth and I didn't even realize it!

[Matt1968]

What order did you find them in?

To my knowledge, all FE cams use 1-5-4-2-6-3-7-8. If someone had installed a cam that used a different firing order, it would explain why it was wired in a nonstandard sequence. But I don't think such a cam exists for FEs.

Back in the 80's I consulted for a friend who restored a '69 GT convert with a 351W-4V. One night he called me from the shop where he and his mechanic were trying to start the engine for the first time, and it was sputtering and bucking and backfiring. I knew he had put a brand new cam in it. I told him to switch the plug wires around to 1-5-4-2-6-3-7-8 instead of the sequence isted on the intake manifold. It fired right up and growled like a tiger. He (and his mechanic) didn't know the 302 cam he put in it had a different firing order from the 351. But I did     (I wasn't being a jerk; I only figured out he had the wrong cam AFTER he called me!)

One more story: back in the 90's I had a '69 Cougar convert with a 351W-2V. Drove nicely, despite being somewhat "flexible" from the rusty floors. One day I parked it in the driveway, and came back outside some time later to go for a drive. It cranked and sputtered and tried to start, but just wouldn't go. It was getting fuel, the accelerator pump gave a nice shot. Also had spark at all the plugs. Just wouldn't go. I couldn't think of anything else to check, so I pulled the fuel pump off and stuck my finger in to check the timing chain (insert joke here  ). There was about an inch and a half play in the timing chain! When I tore it apart to investigate, it turned out the sprockets were off by a total of THREE teeth! Put a new timing set in, and it fired up and ran smooth and strong. Before the incident, it was probably off by one or two teeth and I didn't even realize it!

I learned all about Ford firing order over the last few days.  The 351 and 5.0 HO have that different firing order.  The cam the rebuilder put in my engine was a Comp Cams and there is no way possible it has and incorrect firing order.

The rebuilder was NOT a Ford specialists,  and more than once I questioned his competence during visits.

Also during the last few days I taught myself how to set float levels.  This exercise has forced me to learn new things,  but I am still puzzled on how the wires were all out of correct sequence and the thing ran.

[WT8095]

but I am still puzzled on how the wires were all out of correct sequence and the thing ran.

Me too. Do you remember the incorrect sequence? It would provide a clue as to why it would run that way. I assume you ruled out the possibility that someone was playing a joke on you or tampered with the wires for some reason? BTW, deliberately miswiring the plugs would be a clever way to slow down a thief...

[Matt1968]

What order did you find them in?[/b]

I am kicking myself for not taking a pic or vid of the wires because it might have answered some questions.  Plus now I'm questioning my sanity because I still can't believe it was running like that.

[WT8095]

What order did you find them in?[/b]

I am kicking myself for not taking a pic or vid of the wires because it might have answered some questions.  Plus now I'm questioning my sanity because I still can't believe it was running like that.

Well that happens, always easier to think of it afterwards. I think you should verify your cam timing relative to the crank. You'll have to pull the valve cover and spark plug, and check that both vaves on #1 cylinder are closed when the piston is at TDC. It's possible that you have more than one problem - could be cam timing + slipped balancer.

And I have to ask just to make sure nothing is overlooked; please don't be offended: you know which cylinder is #1, right? Front right (passenger side in U.S.).

[Matt1968]

Well that happens, always easier to think of it afterwards. I think you should verify your cam timing relative to the crank. You'll have to pull the valve cover and spark plug, and check that both vaves on #1 cylinder are closed when the piston is at TDC. It's possible that you have more than one problem - could be cam timing + slipped balancer.

And I have to ask just to make sure nothing is overlooked; please don't be offended: you know which cylinder is #1, right? Front right (passenger side in U.S.).

As already mentioned above, I am now very literate on my firing order and cylinder numbers.  It is all over google and my manuals.  I was hoping not to have to take the v/c off because they are gaskacinched glued to keep them from leaking.  A good test drive would tell me how the engine is now functioning,  BUT the reason I parked it years ago is because the clutch broke while hot rodding.  Not slipping , but something actually broke (another project coming soon.)

[WT8095]

As already mentioned above, I am now very literate on my firing order and cylinder numbers.  It is all over google and my manuals.  I was hoping not to have to take the v/c off because they are gaskacinched glued to keep them from leaking.  A good test drive would tell me how the engine is now functioning,  BUT the reason I parked it years ago is because the clutch broke while hot rodding.  Not slipping , but something actually broke (another project coming soon.)

Sorry, I feel bad for even asking!     Just wanted to make sure everything was checked.