Vortec 350 Detonation

[Tommy R]

Hey y'all,

 

Over the years I've driven a few Vortec 350 powered trucks. Nearly all of them pinged under acceleration to some degree. Some would ping whenever the throttle was touched while others would only ping under heavier loads. I found this very concerning.

 

Nonetheless, a few years down the road I found myself purchasing one of these motors (in a K2500 Suburban). Normal driving it doesn't ping, but at high RPM under a heavy load it does, though it's not as bad as others I've driven. Is there any kind of fix for this? Is it as common as it appears to me?

 

As a reference, my truck only has an intake (not a true cold air setup) and a cat-back. It also seems to have a t-stat that's too low. I think it's at most a 180 degree. I'm not sure what's stock on these, but I would guess a 190 or 195.

 

It may have some carbon build-up in the combustion chamber, but I'm not so sure that's the real cause of it. I've searched, but was disappointed to find no matches here when I searched for "350" and "detonation". Any suggestions on what to try? Is this issue as common as I think?

 

Thanks,

Tommy

[HawkScot]

I'm not an expert but can share my experiences. Having a lower thermostat without computer changes is asking for trouble. My 92 Suburban with 350 ran better for a short time with the 160 degree performance thermostat but it failed emissions. Turns out that the computer gave it more fuel since it was not completely warmed up. I had to replace O2 sensor and Catalytic Converter. Been running the stock thermostat since. Same thing happened on 84 Ponitac Fiero, had to replace both O2 sensor and Cat.. Now I always run the stock temp thermostat.

 

My '98 Yukon had pinged for more than a year, getting worse as time went on, even when we ran premium fuel. I had to replace the intake gasket (leaking antifreeze) recently and replaced the knock sensor at the same time. I have had zero pinging since, even on regular fuel. Interestingly, the computer did not throw a bunch of codes when it was pinging.

 

As for carbon, seafoam seems to work well. There are some good threads with ways to do it.

[HawkScot]

Forgot to mention, knock sensor on my '98 Yukon 5.7l is on the right side of engine, down low just forward and above the starter. It DOES have antifreeze behind it, not a dry hole...

[Tommy R]

Thanks for the reply. Your experiences mirror my own so that's reassuring. I plan on putting a stock t-stat in it, but don't know what temperature that is for a Vortec motor. I'm also getting cruddy mileage, but I figure that's just 'cause it's a 3 ton Suburban. ;) Nonetheless, any improvement to mileage is a good thing and I plan on replacing the O2 sensors in the near future.

 

And yes, I'm familiar with Sea Foam. I've had pretty good experiences with that stuff!

 

Tommy

[Wingnut]

My '92 was doing that, and it was the knock sensor.

[Tommy R]

My '92 was doing that, and it was the knock sensor.

 

 

Thanks, Mike. I'll look into that, too.

 

Tommy