76 l82
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 28
Likes: 0
From: Clarksville Iowa
76 l82
I just bought this vette and put a tune up in it New 8mm msd wires, the ac delco plugs r45ts gapped at 45 thous. MSD diis.cap rotor, module, coil, but when done it seems to run rough, when just sitting at an idle doesnt sound to bad but when I put it in gear with brakes on runs rough. All plugs are firing. I put old cap and coil on and does same thing. I rechecked firing order and its right. checked vaccume lines all seem ok. checked vacumme advanced pulled it off and ran real rough so im guessing it works. any help is greatly appreciated... wanted to do all my own work on this and hate to take it in.....
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Were the wires custom-fit or did you have to crimp them yourself?
I agree that a timing order check is job #1.
You noted that you checked vacuum advance - what timing are you running?
I agree that a timing order check is job #1.
You noted that you checked vacuum advance - what timing are you running?
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 28
Likes: 0
From: Clarksville Iowa
76 vette
Wires were custom fit I looked and I have fireing order correct I did buy a chiltons book on vette. Today I pulled 1 plug and replaced it with new one and took old plug and hooked it up to plug wire and started car to see if its fireing then pulled next plug and replace it with the one I just checked and went through them all to make sure they are all fireing and they were..
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Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Timing first, then carb - always.
The changes came from the ignition changes...so assuming that the firing order is correct and the wires are on the same towers...timing is the next thing to check.
Borrow a light...but don't do anything else until you check the timing.
The changes came from the ignition changes...so assuming that the firing order is correct and the wires are on the same towers...timing is the next thing to check.
Borrow a light...but don't do anything else until you check the timing.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
There's any number of possible ways timing could have changed.
HEI modules pretty much work or they don't - so that's likely not the issue if it runs at all.
If it's dark there, you can open the hood while it's running and see if possibly there are any breaks in the wires or plugs...you'll see them glowing with the spark.
But...last time....you need a timing light. The pickup can tell you if every plug is firing and firing evenly, and it will tell you if the timing has changed.
HEI modules pretty much work or they don't - so that's likely not the issue if it runs at all.
If it's dark there, you can open the hood while it's running and see if possibly there are any breaks in the wires or plugs...you'll see them glowing with the spark.
But...last time....you need a timing light. The pickup can tell you if every plug is firing and firing evenly, and it will tell you if the timing has changed.