Curious is any of you experience cold start piston "slap" in your Oldsmobile engines. I had 493000 miles on this '74 350 when I had it freshened up in 2013. It has another 30000 miles on it now. I remember the engine had a bit of that before with the very high mileage, but it was pretty clean inside for the amount of mileage, and never gave me any trouble. About 3 months ago, I went on a 600 mile (1200 mile round trip with it). It had a noise when I got there that turned out to be a loose ps pulley. Since then, I think I have become more conscious about any noises. This noise, is of course, more noticable now in cold weather. My question is, should I even be concerned?? If any of you have experienced this, has a different weight oil made any difference? I run Driven 10w30 non synthetic. It has cast pistons. In hindsight, I should have went forged. I have retired this car from Daily driver duty since 2014. But I do love to take it in long trips. It is a '74 Cutlass Supreme. Pretty quiet exhaust too. Best way I can describe the noise is it sounds like an LS engine does when cold. (But not as loud as those). It only seems to happen at or near idle, and in gear under a load..Thanks for any input.

 

I've used 20W50 to mask valve train noise. Using heavier oil is a catch 22 because you'll still have excessive wear.

You can always do a compression test to see the health of your engine. When you redid the engine at 400k+ miles did it get new oversized pistons? 30k miles seems a pretty short time to develop bottom end noise.

 

.040 over pistons. Has great oil pressure (40-65) never goes below 40 hot and idling, uses no oil. Has me a bit stumped. I cut apart the oil filter and there was no metal in it.

 

What piston did you put in it?

 

Badger cast pistons I believe

 

OEM pistons typically have the wrist pin offset to mitagate this kind of noise. No idea if the pistons you put in have that or not. OEM's have the same problem and they take timing out when cold to make this noise go away. Now, this is not to be confused with cold start spark retard to help light the cat off. This is a speed load table, that retards timing, to mitagate piston slap noise. CSSR is mainly at idle.

jerry

 

I may try switching my vacuum advance from manifold to ported vacuum and see how that does. Good suggestion.

 

Ding! Ding!! I found to answer. Thanks so much for the suggestion by JerryW. I switched my timing from manifold to ported. Then I checked the timing and found the centrifugal weights had become stuck halfway advanced. I cleaned the weights and no more cold start noise. Hard to believe the super advanced timing made that much of a difference, and the car drives better than it has in months. Thanks again Jerry. I used to figure this stuff out on my own but I seem to be slipping a bit as I get older

 

No problem. I'm here to help. It's surprising how the OEM background fixes a problem on a 50 year old vehicle......

jerry