So, I'm having timing issues with my 390. Admittedly self-inflicted. But I do still have to figure out what to do next.

Over the past couple months, I've swapped out the OE ignition for a pertronix HEI setup, overhauled the carb, replaced the timing chain and old balancer and done my best to RTFM. Every manual I could lay my hands on, that is, plus got as much advice at each step of the way, here and elsewhere. Most of it good, I hope.

I fired it up last night and got it to run real rough. When running "well", she's pinging. To get it to run "well" requires me to be WAY out from TDC - like maybe 30 degrees or so. Seems to ping more at low RPM than high.

When close to TDC, it back-fires if it runs at all. Tried all the usual tricks - verifying TDC between runs, checking for spark on each wire, checked connections. I even replaced the plugs once from .054" over-gapped platinums to .044" copper Motorcrafts. I swapped the wires 180 degrees once.

Same result. When running sort-of okay, the valve train makes noise. "Loud lifters" said a buddy I've dragged in. When put under a timing light, moving it back towards TDC makes matters worse until it eventually dies pretty close to where the pointer says TDC is at.

So, it seems like I must be off a tooth or two with the timing chain.

Short of tearing everything apart again, is there a way to figure if I really did get it wrong?

I was thinking I might learn something by finding TDC and then pulling of a valve cover. I've been trying to avoid going under those covers, but will do it if it will tell me for sure that all those hours worth of work will be worth it (I'm sort of a rookie, mind you).

 

How did it run before the work?
If it was okay, then something done durring the repair is probably the culprit.
Did you do all the work, carb rebuild, t/chain and ignition at the same time or were they done separately?
If they were all done at the same time you'll need to sort things out.
First, I don't think the ignition conversion is the problem. That narrows it down to carb or t/chain.
When I was reading your post, before I finished it I was thinking timing chain and I still suspect that, but because of the work that involved you need to eliminate carburetion.
Check for vacuum leaks at the base of the carb and all the vacuum lines including the brake booster (if power brakes) and under the dash (if fact. a/c).
After you eliminate carburetion/vacuum leaks that pretty much narrows it down to timing chain.
Without a dial indicator and knowing the cam timing specs really the only way to check the timing chain is to bite the bullet and pull the front cover and visually check that it was installed correctly.
I know that this is a huge PITA but I have a feeling this is where the problem is.
Good luck, and let us know how it turns out.
PS: You did double and triple check the firing order, didn't you?
Also, you mentioned "noisy" lifters. How is your oil pressure?

 

I was just thinking, one way you might be able to narrow it down to a timing chain problem is run a compression test. I would suspect that if the cam is off the compression might be down from what it should be.
Don't know for sure but it's worth a try.

 

Heres a post I made a long time ago. I hope it helps.

Moto Mel
Posting Guru Join Date: Jan 2009
Location: Va. Bch, Va.
Posts: 1,318


Assuming your distributor is stock and in good condition, here's an easy way to set your timing using a lighted electrical tester (it looks like an ice pick).
Turn the engine over by hand until the pointer on the timing cover lines up with either the advance mark or 12 degrees advance mark on the dampner. Loosen the dist. hold down bolt so you can move/twist the distributor. after making certain the #1 piston is at top dead center by looking through the spark plug hole. Turn on the ignition key on while having the wire end grounded on the engine or negative side of the battery you then put the point of the probe/ice pick at the base of the points, twist the distributor and watch for the light to flash. At that point the engine will have a static timing set of 12 degrees advance. And thats close enough to get it running.

 

Depending on what cam you have, you can tell if it's off by checking where the #1 intake valve opens.

During the intake stroke, the intake valve starts to open. Where it opens (how many degrees after, or even before, TDC) depends on the cam. If it's a mild/stock cam, it should open AFTER TDC, so if you rotate the motor until the intake valve starts opening on #1, and look at the timing pointer, it should be showing somewhere after TDC.

Report back with where it opens, and I'm sure someone here will know if that's correct or not. Off the top of my head, I can't say exactly where it should open. If you know what cam is in it, we can check the specs.

 

Thanks for all the feedback.

It was all done at the same time. Ran good before I got into her. (Seems to be a trend...) I think I'll approach it like this:

1. Replace the carb-to-intake manifold gasket, being liberal with the High Tack. Double check the vacuum hoses and quadruple check CCW 1-5-4-2-6-3-7-8: The brake booster was replaced along the way, so that's worth looking at. I've never really understood the EGR valve - will that hold a vacuum seal itself? I do get hissing on that when I shut it down...

2. Put a vacuum gauge on it and see what happens.

That's relatively cheap.

After that, I'll take a look at the camshaft and valve train.

I thought I was being damn careful while in there when replacing the chain. Even turned the motor a bunch of times. Guess there's supposed to be some "old mechanic's tale" about that or something.

Probably be a day or two before I check back in, but I will...

 

Check the EGR valve before tearing into the engine.
With the engine idling, apply a vacuum to the EGR valve, if everything is good the engine should start to idle rough then die.
If the engine is idling rough before the test, pull the vacuum line that goes to the EGR if it smooths out there is a problem somewhere in the vacuum circuit.
If all checks okay, pull the EGR valve and see if it is seating and sealing correctly. If not you MAY be able to clean it. If you can't, replace it.
If the EGR is okay, then it's probably time to tear into the engine's t/chain.

 

Sorry, mean PCV not EGR. There's no EGR valve on my engine. Looks like the brake booster valve was leaking... Will post video of the vacuum gauge in a few minutes (waiting for upload). Timing still may be off, but gauge may provide a clue or two for you old pros...

 

Here's a 5 sec video of the vacuum gauge after adding a .75 clamp to the brake booster and a couple of other places. I'm still way out on the timing, but won't have time to try to bring that in until tomorrow evening. Didn't start at wild guess at TDC. Had to back it out probably 15-25 degrees to get her to start...

Don't know yet about oil pressure, either. I skipped putting in the pressure switch... Heard they're unreliable and I put in an aftermarket remote mount oil filter setup that doesn't fit the replacement switches.

 

Did you put in a double roller timing chain that can go on 3 different way?
A lot of needle movement there. looks like there maybe valves leaking due to?
maybe T-chain timing off or leaking valves.. If you put in a roller chain the lower sprocket on the crank is set at (0) not 2* or 4* key way slot..
I put a 12" ruler as a straight edge for checking alignment. But working at odd angles over the fenders and so on does hamper eye balling things up some what.. With the #1 Piston all the way up intake & exh valves both closed the crank pulley marks should be at TDC with the pointer. If not your chain is off.
orich

 

Yeah, it's a three way. I installed it "factory" w/ a piece of white paper. Fenders and odd angles were involved, but I took my time with it. Still: wouldn't be surprised if I was off a tooth.

Gonna try to verify oil pressure somehow before popping the valve cover. Thx orich!

 

Paranoid now: anyone ever managed to get the distributor installed in such a way as to not engage the oil pump? (I have no reason to think so other than the noisy valvetrain.)

 

Also the way that vacuum gauge moves it may have a bad intake gasket..
check for any wet oily plugs, check for some blue exh smoke to..

 

It looks like a timing issue to me. I would bring #1 to TDC by using a pencil or wood dowel in the plug hole and verify the distributor rotor location at the #1 location in the dist. cap. Mark the distributor with a dab of paint, then check where the timing mark is in the dampner. If the dampner mark lines up near TDC when the dowel indicates TDC you are close. Then find where your dist. rotor is pointed, if it's just short of the mark on the dist. for #1, your timing is nearly correct. I don't think it is close at this time. When you get it nearly all lined up check your plug wires for proper order in the dist. cap and to the proper plug. I think you may have a couple of wires in the wrong places. If that dosent work I believe your cam timing is off by a tooth or more.

 

MM: I've done all of that stuff more than once, but that was before fixing the booster vacuum leak. I even rerouted the 7 & 8 wires to prevent cross-firing. Fixing that leak fixed the pinging at least...

At this point, I'm gonna paste the heck out of that carb/manifold gasket, recheck the wires, see if I can figure out whether I'm getting oil pressure (?), set the pointer back to TDC, and try again.

If all that fails, I'll put the pointer back at TDC and pull the valve cover to see where my #1 valves are at. If they're wrong, they're wrong.