Ignition system problem in 72 T top

[L88 crazy]

I have engine misses when Iaccelerate. It's ignition for sure because the misses have a burpy poppy sound to them. I just installed a new rotor yesterday as well as a fresh tune up on the carb. I have triple checked to make sure I properly tuned the car up and I did. The Vette runs AS PERFECT AS EFI! The vacuum hoses are all properly hooked up and working. I have a Unilite breakless distributor with tach drive as well as Accel 8mm ignition wires. I am using to what appears to be the stock ignition coil. Is the coil causing my problem?

 

[The73vetteman]

Have you checked that all the vac hoses are connected?

 

[Hib Halverson]

I have an engine misses at 2500 rpm to 3500 rpms when it shifts into 2nd gear. It's ignition for sure because the misses are loud. I just installed a new rotor yesterday as well as a fresh tune up on the carb. I have triple checked to make sure I properly tuned the car up and I did. The Vette runs AS PERFECT AS EFI! I have a Unilite breakless distributor with tach drive as well as Accel 8mm ignition wires. I am using to what appears to be the stock ignition coil. Is the coil causing my problem?

After the shift, what happens in the next gear? Also, how does the engine run abovbe 3500?

 

[The73vetteman]

The vacuum hoses are all properly hooked up and working.

OK, I admit it, I don't read very well. You already checked this.

Any progress to report or still looking for ideas?

 

[L88 crazy]

Nothing yet

Nothing yet. I gotta act quick 'cause my Vettes off the road till the problem is fixed.

 

[RodsnRides]

Ignition miss?

Nothing yet. I gotta act quick 'cause my Vettes off the road till the problem is fixed.

Are you using ported or direct vacuum advance? How old is the distributor? It may be possible that as the advance comes in, the plate is shifting. This is more of an issue with points, though-because the dwell will change. When you replaced the rotor, did you lube and check the mechanical advance springs and weights? If you have an ohmeter, check the wires. Resistance should be less than 1,000 ohms per inch of wire. I know it's hard to check them off the car, but sometimes just twisting the wire will give you different readings. Obviously, start with the coil wire. Recheck your timing-sometimes the base clamp loosens over time. I hope this helps.

Rick

 

[bobmo]

I just went through the HEI version of hell on a 72 400CID with a 78 HEI distributor.
I found a link in one of the CAC forums to
www.chevelles.com/techref/tecref5.html.
This is a great trouble shooting guide.
In it he mentions the capacitor will give you hi end problems.
I am not familiar with your set up but it may be a cheap check.

Good luck
Bob mo

 

[L88 crazy]

Engine info on 72 T top

The engine uses direct vacuum from the carb to operate the advance and the engine was rebuilt in 1988. I believe I had the Unilite put in at the time it was rebuilt, so the distributor is about 15 to 16 years old and has never given me any trouble. I think the coil is the stock GM coil because it doesn't has a label, it is flat black in color.

 

[RodsnRides]

Try changing the coil

The engine uses direct vacuum from the carb to operate the advance and the engine was rebuilt in 1988. I believe I had the Unilite put in at the time it was rebuilt, so the distributor is about 15 to 16 years old and has never given me any trouble. I think the coil is the stock GM coil because it doesn't has a label, it is flat black in color.

Personally, I prefer to run ported advance. But it seems like a coil swap may be the thing to try-it's been in there a while. Look for oil where the coil wire goes in-that's also a sign of breaking down. Again, check your mechanical advance weights as well-they may be sticking. I usually set timing at 12-15 degrees BTDC. Having a degree timing light is helpful. I like to see about 25 degrees with the mechanical kicking in, then hook up the vacuum line to get about 35-38 degrees total at 2800-3000 rpm. If you switch to ported vacuum, you'll need to turn up the idle speed as it'll change.

Rick

 

[Vettehead Mikey]

I believe I had the Unilite put in at the time it was rebuilt, so the distributor is about 15 to 16 years old and has never given me any trouble.

Aha ha! The magic word. I missed it your first post.

Ditch it. Go back to good old points and condenser.

 

[vetteboy86]

I have been thinking about going to HEI on my TA. It has the old style points and condenser. People tell me that I should do this, it is a no brainer. Mikey why do you say use the points? My car will do the same thing as L88's, but I figure it is a points related problem. I just haven't gotten around to fiixing it yet.


Craig