MotorHead

OK this is waht is happening I have an RPM Air Gap manifold and I used to have a 600 CFM Holley. This carb did not interfere with the vacuum hole in maniold directly behind the carb and this is where I hooked up my power brakes etc. and ran the PCV off the carb.

Now I have a 750 Holley DP and I had to block the hole on the manifold behind the carb so it would fit. Now I have been running the power brakes etc. off the carb, fitting at the back. I have not had the PCV valve connected and now I see smoke comiing out of the oil filler cap on the other valve cover. Is this because the PCV is not connected ?

Anyway I teed in another line to back of the carb and hooked the PCV up but today when I went WOT I hit the brakes and no power brakes for a second, then they came back. This is probably due to the fact I have too many things conected to the port on the back of the carb.

My question is where can I connect the PCV and do I really need it ?

Can just put in a small air filter on each side or will I keep seeing smoke out of the valve covers unless I connect the PCV ?

C3 Shark Tank

I'd like to know about this too, I just dropped in a 383 with a Holley 750 and the vacuum hole has to be plugged, I could not find a low profile fitting that would work there at any store.....and having brakes is probably a good thing :D

Vetterodder

Yes, you need to vent the engine. As you already saw, crankcase pressures were enough to overcome the oil filler seal. You could replace the pcv with a filtered breather but the better choice would be to use the pcv system. If you go to an open system with a breather, the amount of smoke you'll see will depend upon how much blowby your engine has.

There have been threads here before about the clearance issue between the manifold with dual feed Holley's. I don't recall any recently but you could check the archives. I do recall that there was a low profile fitting available that cleared but, as you've found, it wasn't available at many places. Have you tried calling Jegs or Summit?

MotorHead

Thanks I do recall a few threads before and if I'm not mistaken one fix was to put spacers under the carb, but I can't do this because I have no room as it is.

427V8

Edlebrock make a low profile fitting just for that porpose...Call Jegs or Summit...

You should not lose your brakes when you get on it, there SHOULD be a check valve that connects the vacuum line to the power brake unit!
Ifit's missing or bad that would cause the problem...

Jvette73

I put a t in the line running to the booster. It hasnt caused me any brake problems. I do have a new booster though. Maybe your booster is ailing. It should hold a vacuum reserve for a long time. Yours may be leaking down. When you get a chance pull the check valve connection from the booster. If youve driven your car in even the last couple of days you should hear the hissing as air rushes back into the booster. If you hear no hissing, your booster is not holding reserve. Boosters fail mainly when brake fluid leaks from the back of the master cylinder and gets into the booster. Or maybe just a bad check valve. thats the plastic part that connects the hose to the booster.

8T1-7T9 BIONIC VETTE

Vetterodder,
I had to remove my PVC and install breathers on both valve covers. Apparently oil was being sucked through the PVC into the manifold and all over the spark plugs...I also had soot all over the back of the car. My valve covers have baffles....and since I installed the breathers on both covers...plugs are clean and no soot......Question....Will this hurt my engine in any way?....I do have some smoke coming out of the breathers, however only after heavy runs.....At idle and normal cruise....nothing. :seeya Cappy

MotorHead

Thanks for the help, gonna look into that low profile fitting and also make sure my booster is functioning properly.

Only thing about the low profile fitting is that is says it's for the Performer and Torker II, no mention of the RPM Air Gap.

Anyone put the low profile fitting ( Edlebrock part # 8096 ) on their Air Gap ?


[Modified by MotorHead, 6:45 PM 4/28/2002]


[Modified by MotorHead, 11:14 AM 4/29/2002]

Vetterodder

Bionic Vette, I don't think it will hurt the engine, other than getting more oil film on it and under the hood. In any case, it's definitely better than sucking oil into the intake. Besides the problems you mentioned, too much oil in the mix will ruin the converter also. You may want to find and fix the original problem with the pcv before your next emissions test (if you have them there).

BeaterShark

Cappy, the other bad thing about using breathers instead of PCV is that the blowby will "hang" around in the crankcase longer than PCV. I've heard this can contaminate the oil causing shorter oil life. I think the 3k oil change should still be okay, though.

Once I verify that my burning problem is completely gone, I'll switch over to Royal Purple street 10w40 oil. It has a total base number (TBN) of 14. For comparison, Mobil 1's TBN is 9. This is a measure of how well the oil neutralizes acids introduced to the oil. The higher the better.

I've just switched this weekend to the two breather setup for the exact same reason as you. It's amazing how easily my car starts in the morning not having to try to burn all of the oil which drips down the manifold overnight.

8T1-7T9 BIONIC VETTE

Chris,
What if I put two PVC's.... one one each valve cover....do you think this will prevent oil entering intake manifold????? :seeya Cappy

nunus79

I got this idea from the Camaro boards..... seems LS1 engines have oil-pcv problems too. One of the remedies they use is an oil trap that is installed in the vacuum line of the pcv valve. The oil trap is made out of a clear plastic fuel filter.

Anyway, doing a take off from this idea, what if you guys who suspect excessive oil coming from the pcv line try temporarily installing a clear fuel filter in for awhile to monitor how much & how fast oil accumulates in the filter. That way you can pin-point if it is a pcv problem or something else.

Cappy, you'll need at least one breather to act as a pressure relief point or else the engine will find its own pressure relief point (not good).

Anybody have any thoughts on this?????

BeaterShark

I'm assuming that if you run 2 PCV valves that this would make it a closed system. This would put your crankcase at the same vacuum as the intake manifold. I'm not sure all of the seals are "built" to operate under these conditions.

The only advantage I can think of running a closed system over a two breather system is that the blowby is being burnt instead of being vented to the atmosphere. Since the intake is at the same vacuum as the crankcase, I don't see how the blowby will be "sucked" out of the crankcase like it would in an open system (fresh air intake on one valve cover and PCV valve on the other).

Jvette73

Many good reasons to run PCV include:

Cleaner enviorment from noxious fumes including the passenger compartment(PU)

Less risk of the gathering of cumbusable fumes in the engine compartment which can ignite at free will from ignition or other electrical sparks.

If you notice on many professional racing engines that dont run a pcv, they do route a hose from the crankcase to other locations to reduce the risks noted above. Some vent the hose to the header collector which creates a drawing effect pulling the fumes out of the crankcase and blowing them out with the exaust. Some monster trucks have thier crankcase vents leading to the tubular chassis and route them out the back of the frame. Even on a street performance engine not using a pcv, it would be safer and more plesant for the driver if the vents were routed away from locations that could cause build up of noxious and cumbustable fumes from the crankcase.

68shark

Agree you definitely need one PCV and either a breather line routed to the air cleaner (later models) or an open breather element (like Mr. Gasket) on cars with the open air filter type unit (mostly older models). Two pcv's would prevent outside air being brought in through the breather (which is the purpose for having one).

I had disconnected my pcv once to test whether it was the source of an oil consumption problem (it wasn't, and since corrected). During that time, I had oil spluttering up the oil fill tube ('68 and prior years had this feature). Fumes were not nice. Suffice to say, having tried it, I don't recommend going without an PCV installed in one bank, with a breather in the opposite bank. :cheers: