mtomlin1

Guys

I'm getting some blue smoke on high rpm decel, could it be caused by a catchcan??

Heads/msd/cai/arh headers no cats and btr 3 cam, we recently installed the catch can and didn't notice the smoke before

Any help appreciated

Cheers

Matt

lucxy

I think it is related to PCV. I don't think it is a catch can, but how it is routed. Maybe something is clogged?

I have a catch can and don't have this problem. Have your shop inspect the PCV and make sure catch can is routed properly. Check for clogs.

AzDave47

Frequently something like this would be attributed to piston rings, but lets hope it is an issue with the new catch can. I did not have any issues like that when I installed the catch can on my 09Z several years ago, and many performance events since that time.

My catch can gets noting on highway/city driving and about 4 oz. in a HPDE day running in the 4-7K rpm range, but no blue smoke. Now with HCI I do get black smoke due to the rich tune.

l98tpi

Make sure the catch can does not route back into your intake. When you catch can gets full it will route back into the intake when you excel and the vaccum pressure increases.

Undy

Guides and seals can cause it, big time. I'd do a wiggle test just to be sure. You're liable to be blowing chunks of pistons out the tail pipe instead of blue smoke in the future.

Bad piston rings typically smoke on accel, not decel.

AzDave47

Sorry I got the wrong symptom, OP. Thanks, Undy.

mtomlin1

Ok so i have just checked

My catch Can was set up as follows

Left side pipe was from valve covers and he right side went to valley cover

Both my intake and throttle body were plugged so I have no pcv valve

stefuel

"excel and the vaccum pressure increases."

Not. Vac drops under a load.

l98tpi

Supposed to be increase Vac on decel; these smart phones can be stupid sometimes🙈

mtomlin1

Well I just plugged the catch can as below and it's still smoking on decel

Not sure what to do now really , maybe I'll just leave it

mtomlin1

David@MMS

trying to follow up here;

if you do not have a crankcase connection to the intake manifold (through a catch can or not) then it is impossible for the oil to be crankcase ventilation / pcv related.

on ls7's it is often down from the valves however it could certainly be coming up from around the pistons. both situations would be exaggerated by engine braking. let your brakes do the braking and let your engine do the pushing

if you think the catch can caused it, why not try putting it back the way it was before and look for a difference (sorry if this was covered) the catch can certainly has the possibility of altering pcv flow, especially if it is not installed per the mfg. routing.

mtomlin1

Thanks mate.

I have run it with / without and on a new set up which is basically as per the drawing above. It smokes slightly on all.

I have just done a compression test and all were 220/230

AzDave47

If supercharged, install per CC manufacturer; if not:

The diagram you show (blue lines) and the way I installed my EE catch can is the CC inlet was from the valley cover and the outlet was to the intake manifold. You just remove the OEM U-shaped hose from the PCV system and replace it with the hoses in/out of the catch can.

AzDave47

That is the way the EE catch can is designed to be installed, it just uses the U-hose PCV connections.

It is the operator's responsibility to empty the can before it gets full. I get essentially nothing on the highway and just have to empty it after each track day, never overflowed yet.