What are the chances of getting a 87 Camaro started at 34* advanced? A mechanic set my bro in laws 87 Camaro IROC at 34* advanced and claimed that it is the sweet spot for his MSD Ignition box setup. From what I know, our timing cover contains a gauge that marks 1 - 10 degrees for setting the spark without the EST connected. So how can anyone know that the timing is set at 34*?

 

On gm efi engines you have to set the timing w/ the timing connector unplugged, so that would be initial(base) timing. He's probably talking about total timing at 34*. I don't know if he can achieve that w/ out setting the base timing really low. You'll need a dial back timing light (or a timing tape) to check it.

 

I told my bro in law the he needs to set the base timing but accordin to the mechanic, the Camaro wouldn't start at 8* so the timing was advanced 34*. 34* was the timing at which the Camaro would start.

 

It would start harder at 34 then at 8, think about it, slow cranking engines need less timing to start. At 34 the plug fire off before the piston is at tdc, try to push it back down.
You might have a slipped harmonic balancer.

 

I wouldn't worry too much about it...

Nod politely, keep your mouth shut, and move on.

Never argue with an idiot. THey'll just drag you down to their level and then beat you with their greater experience there. Besides, it's too hard for bystanders to tell who's who.

Meanwhile, if it RUNS good, it IS good; no matter what the "mark" says.

 

Nod politely and keep my mouth shut? Words of wisdom I guess.

 

The mechanic said it was the sweet spot? I hope he was using a dyno to determine that setting on that engine and not just guessing. Total timing on one engine may not be the same on another. The best total timing could be anywhere from 28* to 42*. My engine makes it's best power around 38*

It's hard to do with computer controlled distributors but older style mechanical ones can be adjusted with a recurve. You determine what your base timing needs to be. It's usually determined by the cam duration. From that, the mechanical advance is changed to give a total timing or full advance. Full advance will be the base timing plus the mechanical advance.

If your engine works best under load at 34* and you have 10* of base timing then you have 24* of mechanical advance. Don't worry about vacuum advance. That's only for part throttle operation and can be all over the place depending on engine load.

Also in the recurve is determining when the total timing should be. In a stock distributor, the number can be very high before the distributor reaches total timing. In a performance application, the distributor should be at full advance by 3000 rpm. The weights and cams in the distributor change how much mechanical advance there is. The springs change how quickly the advance happens.

If someone tells you to advance your timing until it pings under load then back it off a few degrees, tell them that the timing will be nowhere near close enough to make the most power doing it that way. All you're doing is screwing up your base timing and not changing the mechanical timing to set the best total timing.

Engines like mine are for racing only. We don't worry about base timing, mechanical or vacuum advance. My distributor is locked out to the total timing and I use a start retard to back off the timing so that the engine will start easier. Once the engine starts, it runs at full advance.

If your engine is basically stock, set the base timing to the stock setting. You could advance it a couple of degrees to see if it helps the total timing any.

Want to see what your total timing really is? Use an advance timing light. Aim it at the timing marks and bring the rpms up until the mark on the balancer stops moving. Adjust the timing light to bring the balancer mark inline to the TDC pointer and look to see what the timing light says the timing is. You only need to bring the rpms up until the timing mark stops moving because that will be the full advance. If you have a vacuum advance on the distributor, disconnect it before checking.

With an advance timing light and a recurve kit, you can easily recurve your own distributor by watching how much mechanical advance the distributor is making and at what rpm the advance stops. You can mix and match the weights and springs to fine tune the setting. There just isn't much you can do with computer controlled distributors unless you get into the software to reprogram it.

 

^^what he said^^

 

Very well said. Damb. But the IROC is a computer controlled dizzy. Does the info apply? It's a dumb question bu my large hei dizzy has no weights or springs and my bro n law has the small computer controlled dizzy.

 

If it's computer controlled, there's very little you can do. Unplug the timing connector, set the timing to stock specs then plug the timing connector back in. The computer will control the timing as it sees fit unless you get a custom tune for the ECM to change the timing curve etc.

I have no idea how the mechanic set or decided that 34* was where the best total timing was going to be since it's controlled by the computer.

There's a couple of different large cap HEI. Late model CC versions and older ones that had weights and springs under the rotor. I've pulled rotors off the old ones in the junkyard to find seized or worn out weights and cams. Makes me wonder how much the last owner cursed how poorly the engine ran when all it needed was a new distributor.

 

From what I was told, the EST wire is useless because the spark is controlled by the MSD box, not the ECM. So the mechanic told my bro n law that whether or not the EST was connected or disconnected, nothing would happen to the spark. My bro said the wiring goes from ECM to MSD to coil. It's got me confused because MSD or not, the ECM still has to control the spark right?

 

False.

Correct.

Tell him to find a new mechanic.