Another misfire thread
August 12th, 2022, 07:45 PM
#1
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Thread Starter
Join Date: Sep 2018
Posts: 122
Another misfire thread
I'm chasing the same problem with my fresh 455, but it's simply a misfire, not a timing skip.
I'm down to changing the ignition to an MSD ready to run points-style dizzy with a simple 6A box. Added a Blaster 2 coil.
Does my car (72 wagon) have a resistance-wire in the ignition circuit? Does it matter, except for starting?
I've been a bit under the weather (it's been awhile), but here's what I remember from my install:
Gray wire from bulkhead connector (I assume) to coil positive.
Yellow wire from starter solenoid to horn relay.
Power wire from alternator and starter also to horn relay.
On a side note, the car had an HEI before with a working tik-toc tach. It is no longer inoperative although wired to the negative side of the coil.
Engine to chassis, engine to body grounds are good.
I'm down to changing the ignition to an MSD ready to run points-style dizzy with a simple 6A box. Added a Blaster 2 coil.
Does my car (72 wagon) have a resistance-wire in the ignition circuit? Does it matter, except for starting?
I've been a bit under the weather (it's been awhile), but here's what I remember from my install:
Gray wire from bulkhead connector (I assume) to coil positive.
Yellow wire from starter solenoid to horn relay.
Power wire from alternator and starter also to horn relay.
On a side note, the car had an HEI before with a working tik-toc tach. It is no longer inoperative although wired to the negative side of the coil.
Engine to chassis, engine to body grounds are good.
Last edited by oletrux; August 12th, 2022 at 07:49 PM.
August 13th, 2022, 05:27 AM
#2
Running On Empty
Join Date: Jul 2018
Location: Earth
Posts: 18,068
I'm chasing the same problem with my fresh 455, but it's simply a misfire, not a timing skip.
I'm down to changing the ignition to an MSD ready to run points-style dizzy with a simple 6A box. Added a Blaster 2 coil.
Does my car (72 wagon) have a resistance-wire in the ignition circuit? Does it matter, except for starting?
I've been a bit under the weather (it's been awhile), but here's what I remember from my install:
Gray wire from bulkhead connector (I assume) to coil positive.
Yellow wire from starter solenoid to horn relay.
Power wire from alternator and starter also to horn relay.
On a side note, the car had an HEI before with a working tik-toc tach. It is no longer inoperative although wired to the negative side of the coil.
Engine to chassis, engine to body grounds are good.
I'm down to changing the ignition to an MSD ready to run points-style dizzy with a simple 6A box. Added a Blaster 2 coil.
Does my car (72 wagon) have a resistance-wire in the ignition circuit? Does it matter, except for starting?
I've been a bit under the weather (it's been awhile), but here's what I remember from my install:
Gray wire from bulkhead connector (I assume) to coil positive.
Yellow wire from starter solenoid to horn relay.
Power wire from alternator and starter also to horn relay.
On a side note, the car had an HEI before with a working tik-toc tach. It is no longer inoperative although wired to the negative side of the coil.
Engine to chassis, engine to body grounds are good.
https://classicoldsmobile.com/forums.../#&gid=1&pid=1
EDIT: Wiring Diagram Image
Last edited by Vintage Chief; August 13th, 2022 at 05:33 AM.
August 13th, 2022, 10:04 AM
#3
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Join Date: Oct 2009
Location: Poteau, Ok
Posts: 40,570
I moved your post to it's own thread.
If your tach is inop, it may be the cause of your misfire. Try disconnecting it.
I'm chasing the same problem with my fresh 455, but it's simply a misfire, not a timing skip.
I'm down to changing the ignition to an MSD ready to run points-style dizzy with a simple 6A box. Added a Blaster 2 coil.
Does my car (72 wagon) have a resistance-wire in the ignition circuit? Does it matter, except for starting?
If there was an HEI installed, it should not have been using the stock resistance wire. Yes it matters.
I've been a bit under the weather (it's been awhile), but here's what I remember from my install:
Gray wire from bulkhead connector (I assume) to coil positive.
Gray wire needs to be a 12/14ga and from a 12v keyed source.
Yellow wire from starter solenoid to horn relay.
The yellow wire was the original resistance bypass wire that ran from the starter R terminal to the coil+ terminal. It can be removed.
Power wire from alternator and starter also to horn relay.
On a side note, the car had an HEI before with a working tik-toc tach. It is no longer inoperative although wired to the negative side of the coil.
Engine to chassis, engine to body grounds are good.
I'm down to changing the ignition to an MSD ready to run points-style dizzy with a simple 6A box. Added a Blaster 2 coil.
Does my car (72 wagon) have a resistance-wire in the ignition circuit? Does it matter, except for starting?
If there was an HEI installed, it should not have been using the stock resistance wire. Yes it matters.
I've been a bit under the weather (it's been awhile), but here's what I remember from my install:
Gray wire from bulkhead connector (I assume) to coil positive.
Gray wire needs to be a 12/14ga and from a 12v keyed source.
Yellow wire from starter solenoid to horn relay.
The yellow wire was the original resistance bypass wire that ran from the starter R terminal to the coil+ terminal. It can be removed.
Power wire from alternator and starter also to horn relay.
On a side note, the car had an HEI before with a working tik-toc tach. It is no longer inoperative although wired to the negative side of the coil.
Engine to chassis, engine to body grounds are good.
August 13th, 2022, 11:49 AM
#4
Registered User
Thread Starter
Join Date: Sep 2018
Posts: 122
Thanks.
Some more info for you.....
the existing gray wire looks only to be about an 18 gauge wire.
This intermittent misfire has been in the car since I bought it.
Well, I took the plunge and removed the engine harness. Sure enough, the gray wire was open somewhere. Finally found continuity about a foot from the bulkhead connector. I am now waiting on the terminal I need to reinstall an ignition wire back out to the coil.
My bet is that was the problem all along.
Thanks for the tip on the tach.
Think I might just sick with the Pertronix for now.
Thx guys.
Some more info for you.....
the existing gray wire looks only to be about an 18 gauge wire.
This intermittent misfire has been in the car since I bought it.
Well, I took the plunge and removed the engine harness. Sure enough, the gray wire was open somewhere. Finally found continuity about a foot from the bulkhead connector. I am now waiting on the terminal I need to reinstall an ignition wire back out to the coil.
My bet is that was the problem all along.
Thanks for the tip on the tach.
Think I might just sick with the Pertronix for now.
Thx guys.
Last edited by oletrux; August 13th, 2022 at 06:08 PM.
August 20th, 2022, 07:58 PM
#5
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Thread Starter
Join Date: Sep 2018
Posts: 122
Nope, still got the misfire. Seems worse when the engine is not working hard. Solid during acceleration, but cruising about 40 in 4th gear will beat you to death.
What do you guys use for initial timing? I'm at 14° with the vacuum advance blocked off. Total timing at 3,000 rpm is about 31 or 32°.
What do you guys use for initial timing? I'm at 14° with the vacuum advance blocked off. Total timing at 3,000 rpm is about 31 or 32°.
September 21st, 2022, 07:54 PM
#7
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Thread Starter
Join Date: Sep 2018
Posts: 122
Still screwing with it.
Replaced the ignition resistor wire with a 10ga braided wire.
No change.
Installed the MSD components.
No change.
Reinstalled the old GM HEI.
No change. Plan to return to the mechanical only MSD distributor.
Carb is running pig-rich......and the car will get some professional tuning Monday. I'm sure this is a contributing factor but.....
Meanwhile, I'm wondering if the ignition switch (not the key switch) could be the problem. Any experience with that? The car has had a low-speed misfire with two different engines, three different ignition systems, and two different carburetors.
As always, thanks guys.
Replaced the ignition resistor wire with a 10ga braided wire.
No change.
Installed the MSD components.
No change.
Reinstalled the old GM HEI.
No change. Plan to return to the mechanical only MSD distributor.
Carb is running pig-rich......and the car will get some professional tuning Monday. I'm sure this is a contributing factor but.....
Meanwhile, I'm wondering if the ignition switch (not the key switch) could be the problem. Any experience with that? The car has had a low-speed misfire with two different engines, three different ignition systems, and two different carburetors.
As always, thanks guys.
Last edited by oletrux; September 21st, 2022 at 08:30 PM.
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