I removed the heads from my 1968 427 and had them reworked (valve seals new hardend seats) I placed them back on the car but I can't get it to run right. I have dropped the distributor in at least 20 times and always have the same problem. The car will run, but I get backfiring through the carb and poping out the exhaust, it also belches "tons" of unburned fuel out the exhaust, stumbles when heavy gas is initially applied, and strangest of all, runs best at about a 24-26 degree advance, it will barely run at a 4 degree advance. To make the problem more complicated the car is equipted with factory original TI ignition and a replacement coil. Why can't I properly time this car? Any thoughts are greatly appreciated. -jfarmer
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Re: Ignition/timing problem
Jack-----
Did you remove or replace the timing set (chain and/or sprockets)?In Appreciation of John Hinckley -
Re: Ignition/timing problem
No, that is what is so strange. I did use a breakover bar to "spin" the engine over to TDC to drop the distributor, and in the process of going back and forth I did loosen the nut holding the pulley, which I tightened right back up. But, I don't think that would move the timing mark.
Thanks!Comment
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Re: Ignition/timing problem
Did you verify that you were on TDC #1 compression stroke by observing the #1 inlet valve close as it approached TDC?
The other problem could be spark plug wires. Verify with the '68 Chassis Service Manual that the #1 wire is indexed in the proper cap terminal and that wires are installed clockwise from that point in the firing order and that all wires are properly routed to the correct cylinder. As long as the dist. is out verify that the dimple in the drive gear is pointing the same direction as the rotor tip.
Bring the engine to 10 degrees BTDC #1 (be sure you are on #1 compression stroke, not #6). Drop the dist in and rotate the housing until the pole pieces are aligned. At this position the vacuum can should be about halfway from the interference points on either side and the rotor should be pointing at #1. If everything is properly indexed, the engine should start. If you can't get the pole pieces to align after you drop it in the shaft it is probably a tooth off.
DukeComment
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Re: Ignition/timing problem
Two things to check come to mind.
1. The vacuum advance may not be working. I used to have trouble getting my Mustang to idle. I finally timed it by ear and it ran pretty decent. I later determined the vacuum can was not working and I had been running the car with 24 deg of initial timing. It sounds similar to your description.
2. The other thing could be the that the harmonic balancer ring has slipped or disbonded, and the timing mark on the balancer is not actually at TDC. You can set the #1 cylinder to TDC on the compression stroke and check to see if the timing mark is aligned with the timing index tab.Comment
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Re: Ignition/timing problem
This link is a good technical tip on how to install your distibutor, it worked for me
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Re: Ignition/timing problem
'68 might have ported vacuum advance. First year for 49 state emissions.
DukeComment
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Re: Ignition/timing problem
Duke,
I don't kow what a ported vacum advance is, can you describe how I can tell if I have one and how I can tell if it is functional?
Thanks
JfarmerComment
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Re: Ignition/timing problem
Duke,
Thank you, good stuff for me to check on. This website is really great, filled with good, no-nonsense advice. I was not aware that the distributor cap has "assigned terminals" for the plug wires, that may be where I have failed. The distributor cap is a replacement and has no markings designating a spot for the number one plug wire. However, I know I have them in the correct firing order.
Thank You,
JfarmerComment
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Re: Ignition/timing problem
Doug,
I'll check them both!
Thank you.
JfarmerComment
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Re: Ignition/timing problem
Mike,
I,ll check it out.
Thank You,
JfarmerComment
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Re: Ignition/timing problem
Ported vacuum advance is an emission control strategy. The port for the vacuum signal to the vacuum advance is above the throttle blade at idle, so there is no vacuum advance at idle. You can test by connecting/disconnecting the vacuum advance hose to see if the timing changes. Your '68 Chassis Service Manual Emission Control System Section will have a good discussion on all the emission control systems on your car.
DukeComment
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Re: Ignition/timing problem
Duke,
Thanks, the vacum port appears to be below the blade, it is a early 3X2 car.
JfarmerComment
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Duke - Ignition/timing problem
Duke,
I checked the dimple on the ditributor and it is 180 degrees out from the rotor tip, also it can't go in any other way as the cap has a square hole on one side and round hole on the other, is it possible that I have an incorrect cap and rotor? Are some reversed on the square and round holes?
Thanks,
JfarmerComment
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Re: Duke - Ignition/timing problem
What you need to do is tap out the roll pin that holds the drive gear to the shaft until the gear is free to rotate on the shaft. Once free, rotate the gear 180 degrees so the dimple points in the same direction as the rotor tip and tap the pin back in. The last guy to install it installed it "backwards"!
This is a common problem with GM distributors. It's been discussed numerous times on this Forum, but there is nothing about properly indexing this drive gear in any distributor service information I have ever seen published by GM. It's something that you learn by experience - "system knowledge". My education on this issue was back in about '65.
The drive gear has as an odd number of teeth, so if you install it backwards, you throw everything off half a tooth and often cannot achieve the recommended initial timing before the dist. interferes with something. It can also cause other problems, but I don't want to get into that discussion again.
Once you have the gear installed properly and follow the other instructions for wire indexing and installation, you should not have any more problems.
DukeComment
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