Erratic Rough Running TT

[abcarswell]

I know this topic rises frequently but yet in searching, I’ve not yet came across my exact circumstance. I recently finished the “refresh” on my 1924 TT. Not a full overhaul but more than a heavy service. I am not sure of the exact provenance of the truck as I bought through a local antique car shop that was selling on commission for the owner who had “lost” it for several years after taking it to a less than reputable garage for work. I do know that it was originally restored by a local doctor (now deceased) but no idea what he did although the body work had all the hallmarks of a 1970s-early 80’s type job.

My issue is that after a couple of trouble free sessions, it has now developed a very frustrating rough running scenario, always after it reaches operating temperature. It will suddenly loose power and start backfiring. It has complete new wiring, a new i-timer, Ron Patterson coils, and new Champion X plugs. The coil box wood does not look horrible but I do have a new Fun Projects plastic kit on the way from Langs. Once it starts running rough, it will run rough on both battery and mag. Often, if I pull over and stop for a few minutes, it will stop for a while but will usually restart acting up within 5 minutes. Running a dry compression test yields decent numbers; 1 - 50#, 2 - 48#, 3 - 52#, 4 - 49#. I also swapped out the Holley NH for a fully rebuilt one with no effect.

After talking over possible causes with Ron, I decided to pull the head off which I had not yet done. I was pleased to find no two piece valves and I have aluminum pistons. I was not pleased to find evidence of the #3 exhaust valve running hot and also possible issues with #1. The bores, pistons etc look great and I am pretty sure this engine has had a rebuild not too many hours ago. Do I have sticking valves or leaky manifolds? I have manifold gasket kit on the way in case I need to tear these down. Any observations welcome.

[abcarswell]

Close up of No 3

[Jerry VanOoteghem]

What's an I-Timer?

[Wayfarer]

you need one of these

[HPetrino]

Cory is on the right track. I think you should be looking for an intake leak.

[Wayfarer]

I recently went through a similar issue

viewtopic.php?f=2&t=12187

Mine is not over yet. waiting on parts now.

[abcarswell]

Cory,
I had read your thread with interest and hope you have solved your issue. I’m always up for a new tool so will take a look at the T-Vac. I’m really hoping I’m not in line for a valve job but that would be par for the course at this point.
Thanks,
Bruce

[abcarswell]

Well, some of the parts showed up so I dove in. Unfortunately the T-Vac is backordered so will press forward with out it. Completed the coil box with the Langs/Fun-projects kit. I then pulled the manifolds. It definitely showed signs of exhaust leaks on #3 & #4. It had the dreaded fiber gaskets which were well beyond their life cycle so probably had intake leaks as well. The manifold checks out square so I’m going back with individual copper gaskets and new glands. We willl see where that gets us.