Oil Additives?

[Rampro]

I have a 2001 tiffin allegro with a 454 engine. Very soon the engine developed a knock type noise at start up and goes away after a few minutes. I've been to red bay, had a 454 specialist , have sent oil sample to gm. No one can say for sure what the knock is.it is coming up to 100,000.has anyone had good results with using a additive.
Thanks..........bob

[Bahamaniac]

Usually a knock is a bad rod or main bearing. Adding an additive will thicken the oil and quiet it down. But eventually the excessive bearing play will rear it's ugly head. It will cost a lot less to rebearing the engine now than to wait for total failure!

[Arch Hoagland]

I had a exhaust manifold go bad and the sound it made was just like a lack of oil with the engine knocking.

First mechanic that looked at it thought the engine would have to be rebuilt. Cooler heads prevailed and discovered the exhaust manifold was leaking.

[Kraken]

Sounds to me like piston slap which does affect the high mileage 454's. Piston slap goes away, but rod or crank bearings will usually get worse when warm and won't go away. How's the oil pressure at startup ? Make sure your oil filter has a good anti-drainback valve.

[MinntoMich]

Originally Posted by Kraken

Sounds to me like piston slap which does affect the high mileage 454's. Piston slap goes away, but rod or crank bearings will usually get worse when warm and won't go away. How's the oil pressure at startup ? Make sure your oil filter has a good anti-drainback valve.

X2
Have the same noise on startup on a 2000 S10 Vortec 4.3. Gone after 15 seconds or so, bit longer in the winter, not the couple of minutes that you stated. Heard it at 128,000, now 160,000.

Could it be a lifter bleeding down?

[Finance]

I had GM work truck with piston slap from new. Last time I saw it it was closing in on 200k hard miles and had never been opened up.

What's the history, have you owned it long? Has the noise recently developed?

A real mechanic will be able to give some decent diagnosis of where the noise is from.

[VanDiemen23]

X3. Sure it's not a 8.1/496? Forged hypereutctic pistons will slap until quite warm. Had that problem on a 86 VW Golf and they told me to stop worrying about it. Sold the car with more than a quarter-million miles on it, still slapped, still ran fine.

My 2001 8.1, same thing.

[nvs4602]

Watch this video. I did this to my daughters jeep an it really made the engine a lot quiter. I didn't use the Lucas oil treatment. He also has a follow-up video. I also used seafoam in a portable gas generator that would only run on full choke and after about half an hour running it cleaned out the carb and ran fine. https://youtu.be/agAWXnT4-EQ
This works in diesel engines too.

I would also agree with others on the piston slap issue my 2003 available does the same thing when first started then stops once it starts to warm up.

[vettenuts]

Originally Posted by Rampro

I have a 2001 tiffin allegro with a 454 engine. Very soon the engine developed a knock type noise at start up and goes away after a few minutes. I've been to red bay, had a 454 specialist , have sent oil sample to gm. No one can say for sure what the knock is.it is coming up to 100,000.has anyone had good results with using a additive.
Thanks..........bob

I know my 8.1 is a bit noisy for the first few minutes so I just let it idle until it quiets down.


However, one other thing that can cause this if its a recent development is carbon built up on the piston. It will cause the piston to rock when cold. Had this happen on my other car with a different motor. However, I would think that there would be little carbon on an RV motor since they are always working hard.

[Kodiakan]

10 bucks at NAPA will get you a stethoscope. Place it on the top of each valve cover. If you hear the clatter close it is hydraulic lifters (tappets) pumping up. If not go to the side of the engine lower. That is where other problems will sound off. Best of Luck.......