Mopar Muscle Association UK

I changed my cast iron inlet manifold earlier in the year for an Edelbrock RPM Air gap and since doing so the ball in the PCV valve rattles up and down like a loud rattly thing! I dont recall this being the case before (may be wrong) and it doesn't bother me (untill someone tells me it should ) but what I have noticed since the change over is a puff of smokeafter the following: Hard acceleration - let off say round a corner - normal acceleration - smoke. It's not the tyres After showing MattH he wondered if oil/oil vapuor is being sucked into the carb (Edelbrock Performer) through the front PCV and we thought does the valve even need to be there as I already have a vent in the rocker cover. The carb does seem oilier than before but very marginal, I suppose my question is, do I ned to be sucking gases and oil out of the rocker cover and will it affect the fuel/air mixture in the carb? (if I ever learn how to tune it correctly )

The PCV valve should be getting a constant vacuum from the carb so it shouldn't rattle up and down in operation. With the engine not running it should rattle when you shake it.

If you put a vacuum gauge on the carb to measure manifold vacuum does that show a constant reading or is that all over the place too?

I would always use a PCV valve myself because I suspect a slightly negative pressure in the crankcase frees up more power than the exhaust fumes going into the car loose.

There is a slight effect on the carb tune but not enough to worry about unless the engine is in desperate need of a re-bore.

If you don't use a valve and just breathers the fumes will collect under the hood and in the car. OK on a drag car but rather smelly and probably not good for you in any other kind of driving.

Cheers Dave, I'll try and track down a vacuum gauge and check. I presume I need to keep the foam filled breather on the other end of the rocker cover in order not to create too much vacuum ?

Hang on. Is your breather on the SAME rocker as the PCV valve???

The system will not work like that. You need the valve on a sealed drivers side rocker and one breather (with its own filter or plummed to the air filter base) on the passenger side rocker.

That way air is drawn into the breather, through the crankcase, and out through the valve to the carb where it is burned with the mixture and blown out the exhaust.

Like this.

You are a legend Dave I did swap the covers over when I did the manifold change because the PCV valve was in the way of a plug lead rail I made, I'll put a photo up whe I get home. I kept the breather to the back left where it was originally but the PCV valve ended up front left with the filler cap front right. As the PCV Valve used to be directly opposite the breather (both at the back) I presume it will be ok if I put them opposite again but at the front ? newbe error

I dunno mate. You have me totally lost now.

I went cross eyed myself as I was typing Basicaly I can see from your diagram that I'm not doing what I should after I mucked about with the rocker covers. Bet ya cant wait till I get home to put pics up now eh? That will explain all, thanks for your help. I might even slope off early to swap it all back

Dave I think you are spot on. Jim has the breather and the PCV valve on the same rocker cover, so he needs to move it back so they are on opposite sides.
I always thought the breather let fumes out, not suck air in, so your diagram makes a load of sense and (as always) I learn something new every day!

I thought we could do away with the PCV but then I looked at my Charger and that has one sending crank case fumes to the same place on the bottom of the carb.

I think this is problem solved when Jim can switch the PCV or breather to the other side.

MattH wrote: I learn something new every day!

me to

great dave

autofetish wrote:

MattH wrote: I learn something new every day!

me to

great dave

Its like being back a school, but for grown up blokes !! I didnt know that either

Done last night Both at the front now but on opposite sides

This home made plug leads rail is why I ended up moving the PCV Valve to the front (need a few more grommets to finish ) I could have made the bracket futher forward or back but it would hold the leads wrong so I moved the valve & thank the Lord I did cos we now know a bit more about crank case ventilation I have a transmission question on the tranny section if anyone can help some more

Jimfish wrote: Done last night Both at the front now but on opposite sides

Are they still not the wrong way round ?

I just thought they had to be oppposite each other, does it matter if it sucks right to left instead of left to right?