Piston Slap: Smoothing out the Rocket V-8’s imperfections?

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Ron writes:

I own a 1954 Oldsmobile V-8 and want to know how to make it smoother. You can hear the rods at time when you first start it, knocking. Also the carb hesitates when you come to a stop and start moving.

Sajeev asks:

How old is the motor, and how many miles does it have? Depending on age and condition, both the engine and carb might need to be rebuilt.

Ron answers:

I bought the car in 1983 it had 82,000 it now has 90,000.  I don’t know for sure if it was the original miles since it was 29 years old? I am the third owner. The carb was rebuilt twice recently in 2019. Thank you!

Sajeev concludes:

Okay, this information helps. Assuming your second carburetor rebuild in 2019 was performed correctly (fingers crossed on that) the most likely culprit for the hesitation is also the easiest to fix: set the idle correctly, as it sounds like it might be juuuust a little too low.

For the engine noise, there’s not much you can do aside from ensuring you are using the right weight oil: any repair to the affected parts (rod bearings, main bearings, timing chain, etc.) requires significant disassembly or even engine removal. And then cubic money shall leave your wallet.

So remember that you can (and should) run Diesel oil because this Oldsmobile is pre-1974. A good choice is Shell Rotella T4 15w40 (many WalMarts stock it) but a similar offering from Mobil, Chevron, etc. will be just as good. If the rattle still persists, try a bottle of Lucas oil stabilizer: I had good luck with this product solving an obnoxious bottom end engine rumble with my 1983 Continental Valentino, years before it became Project Valentino.

So anyway, if the oil and oil additive doesn’t work, I recommend living with the noise. It’s probably not worth the cost of tearing into the motor for this problem, unless you have the spare cash lying around for a rebuild, or have the skills and interest to rebuild a Rocket V8 in your spare time. No matter which route you choose, thanks for writing and best of luck!

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! If you need an expedited resolution, make a post on the Hagerty Community!

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