Piston Slap: Bubba's Update and the Slapping Audi

Today we will update our last installment with Bubba the 1971 Plymouth Road Runner, as big things are happening to it after our initial assessment . But first, let’s mix it up with an answer to a fresh question about a topic we cover on a regular basis.

Velanesh writes:

Hi, I own a 2003 Audi TT. Recently, when the engine is idling, a type of knocking becomes audible. After comparing it to multiple engine noise problems, it seems to match the sound of piston slap.

The engine oil level seems to be fine, but should I use a different type of oil or like you said, deal with the knock and move on?

Sajeev answers:

There’s one perk to answering the same question several times on a long-running column like Piston Slap , because this gem from last September is probably the best advice:

“If the noise fades away as you 1) rev the engine and 2) listen as the motor settles back down to idle, it’s piston slap.”

If it is piston slap, check with Audi forums and VW-savvy mechanics to see if they recommend a different oil viscosity. You don’t want to switch oils and inadvertently damage another part of the motor in your quest to eliminate this annoying noise.

Now, here’s Bob’s update on Bubba:

Thank you for the response. Bubba’s interior is in very good condition, so I’m going to remove exterior parts for repair and/or replacement. I’ll be doing the work myself, so it won’t be a total repaint. My only concern is the door rust, but luckily a local shop has offered to guide me through the process of repairing.

I can’t justify putting the money into a full restoration, because it would never be worth the investment. Besides, if I make it too nice my buddy would lose our “before and after display” at the car shows!

The Piston Slap inbox lit up a few days later:

See what you made me do today?

I have been wanting to repair Bubba for a couple of years, but always got discouraged by the people who said, “it is better off original.” Thanks again for the motivation, and for giving me a clear conscience that I’m doing the right thing and not ruining it. (My job is done here.—SM)

A full restoration isn’t feasible because of Bubba being outside year round, but I will put in patch panels. I have some that I had made last year and will paint it up so it looks better. But I wish I had better skills. I’m just winging this.

Then the Piston Slap inbox struck gold:

So, I have a question for you and the experts out there. I began the install of the fender patch panel. According to what I’ve read and seen, the weld is made up of a series of small welds to avoid too much heat and causing warpage to the panel.

My question: Do I keep welding and grinding until I have filled in all the spaces between welds, or do you finish off the spaces with Bondo?

I’ve attached a photo of what I’m talking about. I actually did another pass on welds after taking the picture.

Sajeev answers:

I am far from an expert in body repair, but the less body filler (like Bondo) you use, the better. But the patch panel must be fully welded into the fender. From there, grind down the welds for a smooth finish. Having gaps in the metal just invites moisture and rust, especially since Bubba has to sit outside.

Chasing perfection is a noble endeavor, but it can drive you crazy: Flawless finishes use less filler and you’ll spend more time perfecting the sheetmetal with traditional hand tools. I have heard that not using any filler is possible, but that seems like a lot of labor for most classic cars.

Don’t worry, Bubba will be just fine with the effort you are putting into it!

Have a question you’d like answered on Piston Slap? Send your queries to pistonslap@hagerty.com — give us as much detail as possible so we can help! Keep in mind this is a weekly column, so if you need an expedited answer, please tell me in your email.

The post Piston Slap: An Update on Bubba and a Slappin’ Audi appeared first on Hagerty Media .

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