d,
Was there anything really different between the old transmission and the new one that might be causing the problem ? Different converter which might be putting more load on the engine ? Etc.

Does the distributor have a vacuum advance on it ? If not, you should replace it with one that does. I know the discussion has been endless but personally I do not think you can get the proper ignition curve for a STREET DRIVEN engine without having vacuum advance on the distributor. Your total of 32 degrees might be way too much under certain rpm/load conditions. That is where the vacuum advance comes into play. If you got a "tighter" converter with the trans swap, it could be loading the engine down at that rpm.

I would not personally feel real comfortable with someone that has a chassis dyno, and yet cannot figure out why an engine is detonating Where are you in Va ?

 

Of course nobody ever cracked a cap lowering a engine to change a transmission??

 

Thanks. I am in Chesapeake/Virginia Beach. The tranny swap and converter were the same. I just had a rebuild. The stall is around 3 grand. As for the timing, it used to run perfectly with 14 initial and 36 total using the same MSD distributor that has a mechanical advance. I thought about changing the springs to heavier ones but the curve seems good and gradual. I have backed off the timing and it still pings.

John, I even changed the dist cap. No luck.

See the video:

 

I would be tracing down all the vacuum lines from the engine. If they cracked the vacuum modulator or didn't hook it back up, your transmission may still shift OK but now there is a vacuum leak.

 

Would I have a vacuum line on an HEI MSD that would cause pinging if it is damaged?

 

The line would be for vacuum advance. If it were leaking it would just pull in less advance so you'd have less timing at part throttle but no change at wide open when VA drops out. However, it would still be a vacuum leak as far as the engine were concerned.

 

cracked cap to check first- is there a rise in coolant temp since trans change if so that will point you in direction of cause

 

Thanks. I will check the vacuum lines. That's not going to stop the pinging, is it?

And the cap was changed, Darrell. Everything has been changed. Wish I could figure it out.

 

Yes, a vacuum leak can cause pinging.

 

Even with an HEI MSD?? It's a mechanical advance (springs internally).

 

Could it be from you last load of gas in the tank ?
Try some octane booster.

 

Thanks. I even tried a full tank of 100 octane. It helped a lot, but it still pings.

 

You're getting hung up on the distributor part. If a vacuum line going to the distributor is leaking, that's a vacuum leak.

Also, which MSD HEI do you have? If it has a vacuum can on it, remove the vacuum line and plug the port on the carb that the vacuum line is coming from and take it for a spin to see what that does.

 

I have the MSD 8360. The vacuum port is plugged on it because I use mechanical advance. The carb is hooked up to intake vacuum and the brake power booster.

 

The MSD 8360 has a vacuum advance can on it.

Steiner was trying to explain that any vacuum leak can cause pinging. This is not related to your distributor.
Vacuum leaks cause the air/fuel ratio to lean out and this causes pinging.

 

Ohhh. Gotcha! I will def check that. And the MSD gives you the option for vacuum or mechanical advance. Mine is mechanical. I will def check the vacuum lines though!!

 

Ohhh. Gotcha! I will def check that. And the MSD gives you the option for vacuum or mechanical advance. Mine is mechanical.

I thought that distributor has a vacuum can, but it does have the option of "locking it out."
I wouldn't do that ! It will kill your gas mileage.

 

Good point! But I only drive it 100 miles per month at best. And you are correct. I locked it out.

 

Well, the vacuum lines didn't seem to be the issue. What's next?

 

I can't tell from your video so this may sound crazy...Are you sure it's "pinging"(detonation) and not a header leak or arcing plug wire. If there is any doubt you could induce pinging(it won't kill it!) for comparison.

 

Nope. Not a crazy question. I think that if it were a header leak, I would hear it at all RPM's. it would just get louder. A few other folks, including a mechanic, felt it was a "pinging". In the attached video, it is pinging AND "breaking up". It actually got worse with new plugs. Before I changed the plugs, it was just pinging. I replaced the plugs with the exact same brand and part number (Autloite AR3933). Immediatley afterwards, it got worse for some reason. I looked at the car in teh dark. No arcing was evident from the wires nor plugs. I actually bought some Chamion plugs just to try one more plug change for comparsion as I threw the old Autolites away without thinking. I should have put those back in. What is the likelihood of having a bad bacth of Autolites?? Probably remote. Thanks for all the suggestions and help. I am at my wit's end. I mayhave to send the car off to an expert as crazy as that sounds for a naturally aspirated Gen 1 block. It should be a simple fix on such a simple motor.

 

BTW Beth is correct - you should be running both vacuum and mechanical advance on most street motors. Not sure if this will help this particular problem but your motor will perform better. The link in the second post of this thread is a great article that explains why: http://www.camaros.net/forums/showthread.php?t=191842&highlight=vacuum+advance

 

I've been reading DeAnglo's thread on the side for anything I may have missed when I looked at it last year. Let me add the symptoms I had found,

Not a symptom, but, a beautiful burgundy '67 with a black deluxe interior, chrome appearance pkg, console with gauges.

The harmonic balancer is labeled correctly, ie, zero is zero degrees.
Measured 14° BTDC initial timing, reset the mixture and gained 1.5 inches of vacuum, read then, 15 inches.
Engine has a 160°F thermostat and a young alum radiator.
Cylinder compression is about 175 PSI., checked two, I believe, memory eludes at the moment, maybe DeAnglo remembers.
Went for a ride, I listened, yes pinging, just like in an '80's vehicle.
Traveling at any rpm, 2000tro 4000 rpm and nail it, pings.
If slowly depress the pedal, no ping.
Returned to the driveway, took out both vacuum adv by plugging the hose, and installed heavy centrifugal springs.
The above step took the total timing from 36° at 3000 to 20° at 4000.
Rode again, still pinged.
Put everything back the way it was and the same results, one ride is a carbon copy of the other ride.

I suspect either the wrong head gaskets used as in too much quench, camshaft advanced too much, or maybe a bad batch of Autolites.

 

Thanks, Everette!!! You nailed it!!! Weird that this happened after 2 years of PERFECT running. Now it has been 3 years of aggravation.
And yes, I think the pressure was 175 psi.
I am going to install a set of Champion plugs this weekend for the heck of it. ya never know. The wires are Taylor, 8 mm. They were replaced 2 years ago and only have a 1000 miles on them max. I only put 100 miles at most on the car per month during great weather. I wonder if my MSD distributor has a bad internal part. Thanks again!

 

I know some may question this, but have you run any really good carb/injector cleaner? I like you don't drive my camaro more than 1000-1200 miles in a season and carbon buildup on the edges of the piston/combustion chambers can cause detonation due hot spots created by the carbon buildup. I had an issue like what you are discribing years ago on a different car, ran some strong fuel cleaner in a couple of tanks of fuel back to back to clear the carbon and the problem was solved. I now run cleaner in all my vehicles from time to time to keep things clean. If you haven't tried this, what's the harm in trying something you haven't tried yet. Good luck and I hope you can find the problem without having to send the car out for diagnostics.

 

Gotta ask, why did you retime it from 14 down to 11? I would think that would cause it to ping worse. Try bumping it up to 16 or so. Is is possible that the timing marker has been bumped and your advanced further than you thought?

 

Like Everette said. Less timing should cause less pinging.

That a gess ? what is it and at what rpms?
And what AFR do you have?
Its been on the dyno so they must have those....
And does it ping/detonate at part or WoT or cruise?

The AFR averaged 12.8. And it only pings at WOT.

I know some may question this, but have you run any really good carb/injector cleaner? I like you don't drive my camaro more than 1000-1200 miles in a season and carbon buildup on the edges of the piston/combustion chambers can cause detonation due hot spots created by the carbon buildup. I had an issue like what you are discribing years ago on a different car, ran some strong fuel cleaner in a couple of tanks of fuel back to back to clear the carbon and the problem was solved. I now run cleaner in all my vehicles from time to time to keep things clean. If you haven't tried this, what's the harm in trying something you haven't tried yet. Good luck and I hope you can find the problem without having to send the car out for diagnostics.

Chet, I actually used a can of Seafoam to make sure that it wasn't carbon buildup. That's supposed to work on that. I will still try a can of carb cleaner. You never know! Thanks!

Here's a good way to check for a vacuum leak:

Get a small propane bottle and install a heating tip. With the engine idling, crack open the propane bottle (don't light it !) and move it around the base of the carb and where the intake meets the cylinder heads.

If the idle speeds up, you've found a leak.

That is a great idea. Is is possible to have a leak occur when those parts have never been off?

Had not thought of carb cleaner to the gas tank since I have not seen Wynn's Carburetor Cleaner on the shelves since early '90's, and yes, it did work. Certainly could be carbon buildup or a protuding piece in the combustion chamber glowing red hot during the compression stroke starting as compression heats up anything.

Reduced timing lowers the combustion pressure by delaying the point of ignition creating less heat reducing pinging, the collision of two flame fronts in the combustion chamber. One front started by the spark plug, the other front started by a super-heated protrusion, or heated carbon deposits, in the chamber.

Remember, at cruise, engine is creating a vacuum, less air pressure in the combustion chamber than at WOT, atmospheric pressure (no vacuum), more air pressure. More air pressure, higher combustion pressure.

Thanks, Everette.

I would be very suspect of the distributor, I am on my third 8360 from MSD, I had one that acted like a rev limiter at 3000 rpm when driving, rev it up in the garage with a timing light on it and it sounded fine but as soon as you put a load on the engine it would fall apart.

Dan, I am VERY suspect of the distributor! I had heard a few bad things about that distributor. How would I get it tested? But this all started happening right after someone worked on my car. Maybe it was a coincidence.

Just Making sure...no egr correct? Crank pully bolts tight correct? Ill get back to ya in the morn. Gary

Correct. No EGR and I will check the bolts today. I am up for trying anything. HAS to be something that is causing this.

What AFR ?
And tried pouring water slowly down the carb while running, dont let stall...old school secarb...then change oil.

That doesnt fix, only think left is the cam timing...was it degreed when put in or just assumed it was correct?

The AFR averages 12.8. And I poured a whole can of Seafoam down the carb and revved it to keep it from cutting off. Smoke was everywhere!!! It didn't make a difference. I am still going to try a can of carb cleaner after I change the plugs again.

 

All in is only 32 degress or so.

That a gess ? what is it and at what rpms?
And what AFR do you have?
Its been on the dyno so they must have those....
And does it ping/detonate at part or WoT or cruise?