Catch can smoke - normal?

[kbmb02]

On 6/22/2018 at 1:06 PM, Preyupy said:

Ken,

I have seen a number of engines that acted exactly like this,  The only thing we could figure out is the rings were just a bit loose in the grooves and when they are being forced at high speed to seat on one side or the other in the groove they seal better.  You might also have some valve guides that are getting a bit loose and at low speeds the valve does not always seat it's self square when it's closed.  When I slams shut at 7000 rpm it seats better.  I have seen huge differences in Leak down numbers by just putting a screw driver on the rocker or spring retainer and thumping it with your hand with the tester hooked up, the valve just re-seats it's self and the number goes down. 

 

It does not mean they don't need to be freshened up it just means it's not costing you HP.   

 

Thanks, Byron - good info. For now, we just told the driver to keep the RPM's up. -KB

[Preyupy]

3 hours ago, kbmb02 said:

 

Thanks, Byron - good info. For now, we just told the driver to keep the RPM's up. -KB

That's always a good recommendation! LOL

[TobyB]

On 6/22/2018 at 1:06 PM, Preyupy said:

Ken,

I have seen a number of engines that acted exactly like this,  The only thing we could figure out is the rings were just a bit loose in the grooves and when they are being forced at high speed to seat on one side or the other in the groove they seal better.  You might also have some valve guides that are getting a bit loose and at low speeds the valve does not always seat it's self square when it's closed.  When I slams shut at 7000 rpm it seats better.  I have seen huge differences in Leak down numbers by just putting a screw driver on the rocker or spring retainer and thumping it with your hand with the tester hooked up, the valve just re-seats it's self and the number goes down. 

 

It does not mean they don't need to be freshened up it just means it's not costing you HP.   

 

Yup, I've seen this on my older engines, too- 

I also think that pressure on the backs of the rings is different

when you statically pressure the engine versus dynamic (and higher) running pressures-

even to the point where a leakdown at 50 psi is 20%, but at 80 or higher psi it drops to 5% or lower.  Sometimes

with an almost- audible 'pop'.

And Total Seal gapless rings leak down great, but don't seem to make that much dynamic difference...

 

giving away useless secrets,

 

t