Troubles with blow by

L

Linear Six

Well-known member
Hi everyone. I have an issue that has me banging my head and hope someone can help me out.
So I have a 200 with a sniper 2300, paxton super charger (6lbs of boost) and a VI aluminum head.
The last power adder I installed was the blower. Since then I've been having issues with blow by while under boost. Plumes of grey blue smoke out of the exhaust.
All the cylinders have good pressures and all within a couple of PSI difference. I've also performed a leak down test and found all the cylinders are within 7 to 10 %.
I did not install new rings when I installed the blower. So the rings are gapped for NA operation. my last attempt was to install a Wagner PCV valve and catch can inline between the carb vacuum line and valve cover rear port. i've switched back to the factory baffled valve cove and still no difference. Any ideas would be much appreciated.

thanks
 
Did you fix the cam timing that was 12 degrees advanced?
Are you pulling 1 degree of ignition timing for every lb of boost?
 
Linear Six said:
All the cylinders have good pressures and all within a couple of PSI difference. I've also performed a leak down test and found all the cylinders are within 7 to 10 %.
Click to expand...
I like to see less than 5% leak down on a new engine. 7 to 10% seems high.
Is there a way you can remove the PVC line from the carb and plug the carb nipple just for one run under boost to see if the Plumes of grey blue smoke out of the exhaust stops?
 
I have a wagner pvc valve wich has a built in check valve. So under boost there's no opportunity to pressurize the valve cover from the pvc line. I have a breather on the front fill port.
 
Linear Six said:
I have a wagner pvc valve wich has a built in check valve. So under boost there's no opportunity to pressurize the valve cover from the pvc line. I have a breather on the front fill port.
Click to expand...
If the check valve is closed under boost and the front valve cover breather stays open, then the only way for oil to get into the cylinders is past the piston rings.
If I remember correctly, there are only two holes in the lifter gallery to let oil return to the crankcase from the head and to relieve crankcase pressure to the valve cover breathers.
Does all of the above sound correct to you?
 
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you can expect to have to manage the crankcase and head BlowBy situation with the addition of increased CR - cylinder pressures. Increased exhaust contamination is indirectly related. Tolerances in Piston/Ring/Cyl and the Valve Guides contribute to the issue. Assurance testing w/o SC at similar throttle - NA loaded operation for 'without smoke may be indicated.
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Original design crankcase/VC venting is typically not sufficient to eliminate excess blowby. Full crankcase venting and VC venting may help, the catch-can is typically necessary with early engines.
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'old timers would venturi/siphon off oily venting and/or catch can to exhaust plumbing. HI Performance NA BB engines use similar scenarios.
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SC'd 250 Maverick cabin was noticeably stinky under boost with preliminary open engine venting. Boost AFR's are good and exhaust is definitely not blue/grey up thru 1/2 Bar.
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Internal temp differential dual- catch cans help with Fuel Pump blockoff vented and dual VC' vents to cans' , setup 'manages' boost related blowby.
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... also picked up an Audi air injector pump maybe for use as catch-can evacuator under boost .
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knowing probable limits is key to any longevity, the Maverick careful built/ monitored '250 at @ SCR 8.5:1 runs @ 5lbs, occasional 7-10 lbs so far...

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previous Turbo'd version 250 ran nice until an oily mist sprayed windshield as piston ring Lands blew off with little too much enthusiasm .
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hav fun
 
Yes it does, same thought I had. But what is the explanation behind the catch can filling with oil?
When I installed my VI head, I didn't have instructions. Afterwards I found out that the rear oil passage needs to be tapped and plugged when using the new head. Do you think I could be getting excessive oil from this source because I didn't plug it?
 

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Linear Six said:
Yes it does, same thought I had. But what is the explanation behind the catch can filling with oil?
When I installed my VI head, I didn't have instructions. Afterwards I found out that the rear oil passage needs to be tapped and plugged when using the new head. Do you think I could be getting excessive oil from this source because I didn't plug it?
Click to expand...
Do the Yella Terra rocker arm towers cover up the oil hole in the head?
 
Detonation can also appear as blue/gray exhaust smoke as the shockwave blasts oil off the cylinder walls and burns it. I would read your spark plugs for all signs (fuel, timing, det, heat range, etc). Stick an endoscope in each cylinder spark plug hole to check piston and cylinder wall condition (especially scoring from butting rings) and general health. The leak-down does not indicate serious damage, so it's a quick verification of signs and indicators.

Where do you have your fresh air crankcase inlet? Typically, the PCV is to the manifold or spacer, and when it seals from positive boost pressure, crankcase vapor escapes through the fresh air crankcase inlet. While this fresh air is commonly from the air filter housing, it is common to add a catch can on the fresh air line to separate oil blowing at boost pressure to the air filter housing. Preferably, both the air inlet and PCV outlet are baffled in the valve cover for boost apps, to help contain oil mist.

There are other systems and schemes, so if that's not yours, please describe what you have.
 
PSIG said:
Detonation can also appear as blue/gray exhaust smoke as the shockwave blasts oil off the cylinder walls and burns it. I would read your spark plugs for all signs (fuel, timing, det, heat range, etc). Stick an endoscope in each cylinder spark plug hole to check piston and cylinder wall condition (especially scoring from butting rings) and general health. The leak-down does not indicate serious damage, so it's a quick verification of signs and indicators.

Where do you have your fresh air crankcase inlet? Typically, the PCV is to the manifold or spacer, and when it seals from positive boost pressure, crankcase vapor escapes through the fresh air crankcase inlet. While this fresh air is commonly from the air filter housing, it is common to add a catch can on the fresh air line to separate oil blowing at boost pressure to the air filter housing. Preferably, both the air inlet and PCV outlet are baffled in the valve cover for boost apps, to help contain oil mist.

There are other systems and schemes, so if that's not yours, please describe what you have.
Click to expand...
I will post a picture of my plugs. As for my crankcase venting circuit, I have the stock breather cap on the front oil fill port. On the rear port, I have a Wagner pcv valve feeding a catch can which is then connected to the large vacuum port on the base of my holley sniper.1
 
Five &six are abit fouled , originally I had the PCV line attached to intake at ports 5 & 6.
 

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