need help with PCV system on tpi w/moded motor

[Igor]

Hey guys,

I have recently pulled my intake to change the gasket due to a small leak, and found that lower intake/head ports on my superram/trickflows are coated in oil. Not a lot, but enough.

The intake gaskets around the ports were dry, so am assuming the oil was pulled into the intake via a pcv valve. Here is what I have:

408" 10.5:1 motor, xfi 268 cam, tfs as cast 195 heads.
Intake is eddy base/super ram runners/plenum.
TB is 52mm, MAF and air filter assembly are stock 85 corvette with lid mod.

The PCV system is hooked up with a hose running from the throttle body into the pass valvecover with a 90" fitting, no valve or anything. There is no oil in the TB/upper/runners so can't be coming from there.
The lower intake has a hose running from it to a stock style pcv valve into the drivers intake.

The motor is healthy and there is not a lot of pressurization, but its still enough to overcome this system. I am not too sure what to do. I have no emissions concerns, I just want it to run properly and vent good w/o major smells.

Can I cap the pcv valve and run a carb style valvecover breather? What about the other side going into the TB?

Is there a better, aftermarket pcv valve?

Any help would be apricated.

Thanks a lot.

 

[KANE]

Hey guys,

I have recently pulled my intake to change the gasket due to a small leak, and found that lower intake/head ports on my superram/trickflows are coated in oil. Not a lot, but enough...

How about the lower intake? Was there oil lining the intake ports from the heads to where the runners meet the base?

I'm not so sure it was your PCV at this point. If it was, the driver's side breather port should be wet and/or so should the port on the throttle body.

 

[Igor]

How about the lower intake? Was there oil lining the intake ports from the heads to where the runners meet the base?

I'm not so sure it was your PCV at this point. If it was, the driver's side breather port should be wet and/or so should the port on the throttle body.

Yes its coming from the lower intake. Its not the head/to/intake gasket, it is dry.

Tb/upper is dry. PCV valve I have hooked up to a constant vac. port on the lower.

 

[KANE]

Can I cap the pcv valve and run a carb style valvecover breather? What about the other side going into the TB?

Yes- you can run dual breathers. Folks do that all the time.

Below is an EFI equipped BBC with the breathers I'm talking about-

Just out of curiosity... have you had a compression check? I just want to rule out valve seals or blow by.

 

[vetteoz]

What about the other side going into the TB?
.

I have the same problem with my 383; running open breathers at the moment until I can hook up a vac pump through a catch can.
Remember to cap off the port on the TB when you remove the hose to the pass side cover.

 

[Hib Halverson]

The oil film you see coating the the lower half of the intake ports is coming from one of several sources.

1) Intake valve stem-to-guide clearance. Some engine builders put motors together with valve stem sealing that's marginal for street use. Also, this engine may have worn, defective or incorrect valve seals. It might even have no valve seals at all.

2) Oil vapor ingested from the PCV system and it can come from either the "foul" or "fresh" sides of the system because when the engine operates at part throttle, there is flow from the fresh side, through the engine and out through the PCV valve and into the engine. But, at WOT, the flow on the fresh side usually reverses because, at WOT and high rpm, there's high pressure in the crankcase.

3) It wasn't said what the rpm range of the engine is nor was it said how the engine is driven, but extensive high rpm use with a modified engine can exceed the abilities of the stock PCV and other oil control mechanisms to keep oil out of the intake.

4) If this engine has a lot of oil vapor in the intake tract at high rpm, it may have some issues with crankcase windage forcing oil vapor out of the crankcase and through the PVC system.

5) Besides oil consumption, a problem with oil vapor stemming from poor oil control inside the engine is that oil vapor in the intake charge reduces octane so engines which are burning oil are more likely to detonate.

6) Going to "open" breathers is a poor solution for a street engine. It definitely reduces durabiilty in a non-racing duty cycle. It decreases oil drain intevals. On a computer controlled engine with the PCV blocked, you may need to recalibrate if IAC counts go to the limit at ldle.

A properly designed "catch can" system can help, but I'd only go that route after I rule out any problems with valve stem seals or oil rings.

 

[Igor]

The oil film you see coating the the lower half of the intake ports is coming from one of several sources.

1) Intake valve stem-to-guide clearance. Some engine builders put motors together with valve stem sealing that's marginal for street use. Also, this engine may have worn, defective or incorrect valve seals. It might even have no valve seals at all.

2) Oil vapor ingested from the PCV system and it can come from either the "foul" or "fresh" sides of the system because when the engine operates at part throttle, there is flow from the fresh side, through the engine and out through the PCV valve and into the engine. But, at WOT, the flow on the fresh side usually reverses because, at WOT and high rpm, there's high pressure in the crankcase.

3) It wasn't said what the rpm range of the engine is nor was it said how the engine is driven, but extensive high rpm use with a modified engine can exceed the abilities of the stock PCV and other oil control mechanisms to keep oil out of the intake.

4) If this engine has a lot of oil vapor in the intake tract at high rpm, it may have some issues with crankcase windage forcing oil vapor out of the crankcase and through the PVC system.

5) Besides oil consumption, a problem with oil vapor stemming from poor oil control inside the engine is that oil vapor in the intake charge reduces octane so engines which are burning oil are more likely to detonate.

6) Going to "open" breathers is a poor solution for a street engine. It definitely reduces durabiilty in a non-racing duty cycle. It decreases oil drain intevals. On a computer controlled engine with the PCV blocked, you may need to recalibrate if IAC counts go to the limit at ldle.

A properly designed "catch can" system can help, but I'd only go that route after I rule out any problems with valve stem seals or oil rings.

The motor is fresh. I didn't really notice any running issues at all or oil until I RnR'ed the intake.
The motor is mild, but has high compression and is 409". Its def. not stock.

I have not done a compression test yet as i didnt think there was an issues until i pulled the intake. Will after I get it back together. Plugs look good.