mark b

I just changed the oil and filter and put 15/50 mobil in. car runs great, but at slow speeds i hear piston slap...when accelerating hard and at idle it goes away. In fact i dont hear it when Im on the gas or idling at a light. This is unusual because when i drove it in the winter I would only hear it at start up and when the engine warms up its gone...
what could be happenning here? I will be tracking again soon in april.
Has anyone had this happen? could it be the warmer weather? the level of oil is perfect. so that is not it... anyone chime in.

rustyguns

could be a bad oil filter!

Sidney004

Could be, worthwhile eliminating that possibility. I used to work at Purolator Aerospace Filters a long time ago and although manufacturing techniques have improved, an obstruction in the media, which would be noticed at high viscosity/low temp conditions happened. Depending on the location of the pressure sensor, it might not flash as low pressure.

Kubs

Interesting fact!

FASST LN

Why 15w/50 instead of 10w/30 or 5w/30?

froggy47

That oils pretty thick for a part time track car.

Change the oil & filter & check back with us.

Olitho

I agree. There is no need for 15w/50.

How do you know it is piston slap. That is so rare on four-stroke power plants. I am more inclinded to think it is lifter noise as the thicker oil is not circulating fast enough at low RPM.

froggy47

There were some Chevy truck engines that had "piston slap" in late 90's early 2000's.

Was not caused by oil weight.

davidfarmer

The SS454's had the piston noise when cold.....

gkmccready

The 5.3l in my '00 Tahoe has it real bad when cold. :-(

John Shiels

Was it exactly the same before the oil change or is it worse now?

mark b

it was recommended by racers that have seen many blown engines because the oil wasnt thick enough to protect the valve train on these cars, the valve trains are weak, and thicker oil is for more protection at higher temps and driving hard for long periods of time. my car is tracked at least ten times a yr so I feel more secure with the thicker oil..

mark b

thats an interesting possibility, the filter was changed and I even have one of those magnets that wraps around the filter and I havent had this sound happen before

mark b

It is worse after the oil change. In fact i did not hear it at all before the oil change, only at start up. when the engine warmed up it was gone. the oil was kind of dark when it was changed i usaully change it sooner but with all the winter weather did not have time. Im puzzled, and i hope it just goes away.

rustyguns

it is not common but it does happen. my buddy lost an engine on a new filter that was bad

Olitho

I race my car about 20 times per year and it does at least that many other track days. Many of those days are in California desert heat at places like WSIR at temperatures as high as 110 degrees.

The engine if running properly should operate within certain temperature range so going to a heavier weight is not going to help. Even if you have a stock engine without the benefit of the extra coolers like my car, your heavier oil theory is only going to be applicable for when you get your car on track on a 95 degree plus day for the suitable duration that a stock engine without coolers will hit 300 degrees oil temps. Those temps usually won't be achieved until the third 25 minute session in my experience. At some point, I think it is 335 the computer puts the car in limp mode as I recall. The synthetic oils are supposedly good to 355 before they begin to break down.

I did not stay at a Holiday Inn Express last night. I am just expressing my experience and opinions here.

mark b

I spoke to many vette track guys and they recommended the heavier oil..I even have a lingenfelter oil cooler on the car too.. tracks like the glen can starve your engine at some spots because of the elevation changes and down hill turns off camber etc... the thicker oil coats the valve train better at those instances.. I lost an engine because of that happenning and I was using 5/30 on a cool day at the glen.. when the racing mechanic shop guy who installed my new engine asked me what oil i was using and i told them 5/30, they said that that is not enough protection for tracking and i should have 15/50 in it....so thats what i use now just to play it safe..

mark b

thats scary! please dont jinx me.. the car is running fine and its only the valve train noise I hear at coasting speed without hitting the gas...
other than that eveything is fine.

I hope I dont have to change the filter. that means I have to throw away perfectly good oil and start over.

ssdeuce

rustyguns

YOU CAN CHANGE THE FILTER AND NOT LOSE ALL THE OIL