Topic: Flex Plate issues - 67 289 C4

[krelboyne]

What firing order are you using?

[Tiny]

Thanks Midlife, will look into that as well.  Will keep everyone posted as to how it all goes.

[Bob Gaines]

What firing order are you using?

That post got me thinking about a engine that I had where the rebuilder used a 351W cam instead of the 289. The firing order is different between the two. in my case I had to run the sparkplug wires using the 351W firing order. If acted very similar to what you describe except it would run progressively rougher off of idle even with no load.You did say it started after the engine was rebuilt. It is a long shot but you should know real quick if there is a difference plus it only takes a few minutes to check out. 351 W firing order is 1-3-7-2-6-5-4-8. The 289 firing order is 1-5-4-2-6-3-7-8 .

[Bossbill]

Bob has a good point.

I would also see if you can find someone with a spare driveshaft that is known to be good. I chased down a similar issue and finally had my driveshaft retubed and balanced.
Damn -- same thing. No change.
I had it up in the air looking for anything out of whack and found nothing. I even had a scribe very close to the driveshaft and it was not out of concentric.
Out of desperation I swapped driveshafts with a car known to have no issues.
Bingo.

Just because it's new or rebuilt doesn't mean anything.

[Tiny]

Hi all, its been a long time since I posted in regard to the problem I had. Well I finally found the problem which you wont believe. After all of the many months of troubleshooting the problem was that the kickdown accelerator lever was hitting the exhaust when I accelerated hard. The vibration of the engine/exhaust was transmitting through the accelerator lever giving me the vibration. I couldn't believe this was the problem but once I had readjusted the lever, all gone. I was then getting better opening of the 4 barrel and away she went.
The symptoms that the vibration gave me did not in anyway point to the accelerator lever but relayed vibrations elsewhere. I was going to replace the Flex Plate, engine mounts and other things but fortunately I found it in time.
Appreciate everyone's input and I feel a little stupid given the actual fault but 'you live and learn'

Cheers

[OldGuy]

Congratulations! I'm sure that no one would have guessed the fix for this problem.

It really feels great when you find and fix the problem. Persistence pays off.

Frank

[Tiny]

Thanks Frank for your comments

cheers

Mark