In a previous thread you said the above. What are your reasons? I see a lot of LT1 guys using them. I am curious.

------------------
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

Kevin,

I've got two LT1s and neither gets the breather cap. TPI V-8 and MPFI V-6 engines with MAF sensors shouldn't get them either. If you study the PCV system, you'll note that the PCV air gets drawn into the intake with the rest of the air charge. Air that is allowed to enter the engine through a breather cap is not metered by the MAF, thereby causing a potnetially lean mixture. The O2 sensors SHOULD detect this and the PCM SHOULD correct for this, but the fuel tables will always be skewed toward the lean end. The factory PCV air supply is from a hose connection at the throttle body, so that the PCV make-up air is drawn through the MAF with all other intake air, as it should be.

OTher than that, I can't think of a reason not to use a breather cap, other than the oil mist blowing onto the rocker covers and staining a nice, clean engine bay.

------------------
Later,
Vader
------------------
"Fear is how I fall, Confusing what is real..."
Adobe Acrobat Reader

 

It would be all right to use on a SD TPI setup and a TBI since both run on a map sensor that measures the amount of air once it has already passed into the plenum (or TB in a TBI case) past the PVC air supply hose, right?

 

Right. I've had a red Moroso breather cap for almost 2 years now with no "adverse" effects.

------------------
92 Z28 5.7
------------------
Trick Flow 23° heads, Comp Cams XR270HR-10 cam, Accel intake base + ported TPI,
TES headers, Flowmaster catback, MSD ignition, #24 SVO injectors, 1LE aluminum driveshaft.
[b]
Click here to see pics of my car !

 

I used one open breather on my old car (85 TPI T/A) and it worked fine. I plugged the vacuum port on the TB and removed that hardened pipe that runs along the valve cover on the passenger side from the hole in the valve cover at the rear of the engine up to the TB. I kept the PCV on the driver side however. I did not notice any problems with this setup but I didn't put a scan tool on it and see what the Block Learn and Integrator were at either. From a SOTP reaction I would say it revved a little better (unloaded - not noticeable under load ). My reason for doing this is I put on some aftermarket taller valve covers for rocker clearance and that hardened pipe dealy just looked like crap and didn't fit very well after the V/C swap.

Theory: As long as you plug the vacuum port that the PCV (or just CV in this case) is routed to, I do not see the problem. The engine will have great crankcase breathing with the open element breather (I agree with the oil misting thing but ...eh) and as long as you block off the unused vacuum ports, the engine should not notice the difference. Vader, I guess I am not following your description of the problem with doing this. The mass air flow sensor meters the air on its way to the TB/plenum/runners/intake but as long as the PCV valve itself is still used it should not notice the difference. The PCV valve itself regulates the intake of the crankcase gases to the engine and therefore is factored into the idle speed in the EPROM I assume so it must be retained. It was my understanding that PCV was nothing more than an attempt to stop the HC's and other 'greenhouse' (cough cough.....ak ak)gases that are produced in the crankcase from going directly into the atmosphere.

Maybe I'm way off here................dunno

Laterzzzzzzzzzzzzzzzzz

------------------
Matt

1987 GTA L98 MD8 GW6

"Stop Lights timed for 35Mph are also timed for 70Mph"