I seem to be having a small timing problem on my '82.

Several months ago I did a very nice intake job, and I marked everything before and moved nothing during. However, when I went to check the timing it seems like the colors on my seemingly original looking wires didn't match up at all with the color codes noted on the underside of the hood, so I just left them all connected. When I put the light on the timing mark, it ran it's best when it was off the scale - probably 14 degrees or so. Any less than 12 or so and it would backfire under rev.

A few months after that the timing seemed to have moved - the car would backfire with a to-the-floor rev of the engine - although nothing had moved (distributor was still tight and in the same position).

Knowing about the nylon coated timing gear, I just bought a new timing chain set. I suspect that either the previous owner, who had obvioulsy been in the engine before, either missed a tooth, or that the gear has lost a tooth or two. I am at 65k miles, by the way.

Any suggestions from anyone about this? Anyone had a similar situation with missing teeth/bubba'd timing? I have an interested buyer for this car who seems like a real Corvette guy AND this will be his first Corvette, and I want to be sure this car is working properly before he takes off down the road in it.

 

I would get the engine at TDC on #1 cylinder and then retrace all the plug wires to be sure none are crossed. Then, I would set the distributor so that I had around 35-36* total advance with the vac advance disconnected and all the mechanical advance in. Record what the initial advance is just for reference. It really doesn't matter what it is, it's the total advance number you're looking for. Also check your advance curve to see that the mechanical advance comes in smoothly and is all in by 3000 RPM.

Once you have confirmed that all this is correct, you may want to chase other things if the problem still persists. From your description of the work done, you didn't get something in the ignition back in the proper spot. This is easy to screw up, especially if you haven't done it a few times. It's actually very simple once you understand what you're doing. All service manuals will have a distributor installation section. Follow these directions closely and you should solve your problem.

 

AARRGG!!!!

82's are computer controlled....No curves.. No vacuum...

There is a disconnect plug near the distributer that you have to pull to set the timing, if you don't you can't set the timing...

Sorry, it's late, and I can't remember all the steps, or even exactly where the plug is. I'll pull out the book tomorrow and fill in all the details.
Unless someone else helps here sooner...

 

Sorry 62fuelie, I wasn't mad at you....

It's just every 82 question seems to get all the wrong answers...

 

Dawg's right. The 82 HEI advance is not controlled by springs or vacum. It is equipted with (EST) Electronic Spark Timing. All timing and advance functions are carried out by the (ECM) Electronic Control Module. It monitors various engine sensors and the (KS) Knock sensor to adjust for maxium advance without spark knock (detonation).

It's been a while but I believe it is a tan wire that has to be unhooked, sorry I don't remember exactly where it's at, but I remember it's right there around the dist. (someone correct me if I'm wrong). Start the car and set base timing to the spec on the underhood sticker, shut the car off and replug the wire. Recrank the car and the computer will take over from there.

 

Yes, Dawg. You are correct that this engine is a little different than a regular 350 with a carb slapped on top. There are load of extra wires and sensors here and there that I am not familiar with and don't want to just go yanking around.

Here is part of my problem: the underhood sticker says that in order to set the timing, I must "unplug the tan wire with black stripe".

Well, when I look at my distributor from the driver side, on the left is a 2-wire connector with white wires, the right side has one large orange (possibly tan? No black stripe...), and behind those is a 4-wire connector that the sticker says to NOT unplug.

If you guys are looking at your distributor from the driver side, which connector is it? The orange (tan) one on the right?

I still swear something internal has moved though, so I won't be starting it again until after I pull the old timin chain off on Saturday. The backfire during rev concerns me because that indicates a valve is at least slightly open at the wrong time, right?

 

the tan black is the hei disconnect, it's part of the wiring harness and it has a brown connector on MOST 82's, however some early ones didn't have it, in which case you have to install one yourself. IT's part of the EST harness that goes into the back of the distributor base, not the 2 connectors (+ & -/tach) for the coil. There's only 1 tan/black wire in there, the connector is dark brown. The backfiring during rev is not internal most likely, it's the timing.

 

You really ought to check your harmonic balancer - do a TDC verification and see if the balancer has slipped. This is an very common problem on these cars. I've done 4 or 5 '82-'85 Vette slipped balancers so far - all came to light when trying to set the timing and the car would not run right at the spec timing setting.

Normally, the ECM controlled cars will have an initial timing at idle on the readable part of the timing scale, even with the ECM wire hooked up. If the car won't idle on the scale (even with the wire hooked up) you most likely have a bad balancer.

The tan/black wire with the black disconnect connector is located on the driver's side of the engine near the power brake booster. To check timing, unplug the connector and set timing at idle to the spec number shown on the emissions tag. If it won't run at this setting, I'll bet your balancer has slipped.

 

Hi,
I'm curious, what does the harmonic balancer do? How does it effect engine timing?
Thanks,
Tom

 

The balancer has the timing mark on it. If it has slipped then it won't tell me the right story when I put the timing light on it. I hope mine is ok, because a new one is $140...

 

Here is a picture of what the connector looks like. The wire is tan (although it looks orange) with a black stripe.



If you don’t disconnect the wire before reading/setting the timing you will never get close. On my other ’82, I clipped the wire (disconnect the battery first!) and inserted a quick disconnect lead between the ends to facilitate easy disconnect in the future as (I believe) the other three wires should remain connected while setting the timing.

As you can tell from the photo, I’ve not done this to my current ’82…I wonder when the last time the timing was checked on the car as there are no breaks in the tan/black wire…

 

That's not the correct connector (although the est bypass wire is in that connection, clearly visible), if you disconnect that (EST connector) the engine won't run at all, the connector is on the single tan/black wire. As I said before, early 82s didn't have the single connector to bypass the EST, you can isntall one yourself, later oens have them. I should have a pic of the lead somewhere..let me see.

 

The 4 wires w/ the to ECM comment are the 4 you see in above connector


still haven't found the pic.....

 

2-tone, my '82 looks exactly like yours!

Check out the Corvette Album at photos.yahoo.com/leeloo67

 

It's an 84 obviously but the wiring harness is identical (the engine harness) and that connector is roughly in the same area as on the 82.

 

Everyone here is awesome. I remember Twin Turbo also helped me with some great tips when I did the intake job!

 

On the 82, the wire to disconnect comes out of the firewall just below the MAP sensor on the drivers side. My connector is black, wire, because of age, looks very faded yellow, or should I describe as a yellowed white wire. Connector is only, say, two or three inches at the end of the wire coming from the firewall.

 

You guys think this is the wire (circled at bottom right)? It is kind of brown coming out of the firewall, and kind of dirty white going into the distributor:

 

Yup, TT is right…I’m passing bum scoop in the post above. Following is a picture of the correct connector. It’s located way down, almost looks like it goes to the tranny…



Your car is very nice. Is it early or late production? Mine is somewhat early in production; # 6,058. My other one (I've owned two, note my signature) was in the early 5,000 sequence. She was identical in color and most options but very high mileage.

Bill

 

Listen to Lars! The harmonic balancer on my '82 slipped so far back against the timing chain cover that the timing mark wasn't even visible when I went to check it! I bought a new one from AutoZone for about $80.