I previously ran an under intake PCV on a blown flathead. While it worked well, it also contaminated/heated the intake charge by routing the fumes thu the intake port and butning them thu the engine as designed. I never liked that from the get go - roots blowers heat up the charge enough without adding heat & vapours and **** to the air/fuel mix. With out the PCV she runs a LOT harder, with the PCV you can FEEL the difference and redcution in efficiency. So what I am contemplating is this. If I block off the breather tube at the rear of the intake and drill/tap its base and fit a 90 deg fitting , run a 1/2" hose to a vac u pan fitting before the header collector, will it create enough vacuum to **** out the fumes from the valley and send em out the exhaust rather than burning the vapours thru the intake as previously set up? I can do this fairly discreetly so it wont look like **** but will hopefully still work well. Im interested to see what you guys think about this? It runs much better w/out the previous under intake PCV but I dont want the vapours exiting the rear ibreather on the intake either - the **** friggin stinks !!! Id appreciate your thoughts ? Rat
I can't imagine why it wouldn't work as long as the tube is properly baffled or if you use an oil separator of some sort between the tube and the exhaust.
I ran a Morso va***e pump on my coupe for a while it cut burning to about 1/4 of what it use to be.I also used the kind of system your thinking of on my altered jury is still out on that one.Put pump on the altered but had trouble getting car considant other problems .Car is considant now but weather is working against us.If you want to talk PM me.
I am looking at the same issue with my blown flathmotor..............haven't made a decision on which way to go yet. Many, many years ago I ran a Moroso Pan Evacuation System on the SS/AI Mustang. It worked well but remember you are pulling a vacuum, and without baffling/check valve you could pull oil out through the exhaust on the exhaust stroke if the motor is completely sealed. Back in the day it was made to give better sealing of the rings and less contamination to the intake charge. http://store.summitracing.com/egnsearch.asp?N=700+115+301022&D=301022 Let me know what you do as I have to get the motor ready for fireup soon. IMHO
A Chopped Coupe - and others; I have been wondering about the same problem. I have a S.C.o.T. blower on my flathead and it troubled me about using the PCV valve under the blower intake. With the manifold under pressure - boost about 5 lbs. - standard PCV valves don't function the way they were intended with a completely sealed crankcase. Now ... unless I'm totally "out to lunch"; doesn't a PCV valve to work right, rely on a "Swept Flow of Air" through the crankcase?? (especially on a flathead) If that's the case; then wouldn't some form of "fresh air inlet" be needed? Even with the "Pan Vac?" (I realize that would destroy some of the "VAC" feature) My thinking was to use the Pan Vac(s) at the rear of the oil pan with the inserts into the exhaust. Then, air inlet breather(s) - with GOOD filters - at the front of the oil pan. I'm running a wide sump 15 quart oil pan that hangs out the side of the block - so the breathers and the Pan Vac's could be positioned vertically. (with appropriate baffles) Could this work???
i actually used to do some of the early development work on vacuum pumps back at Stefs (back when we used GM style smog pumps) and evalutaion of pan evac systems. Two things: 1. Vacuum pumps - are not that durable, the morroso pumps are pretty good but they still aren't made for daily driving. The old GM style pumps **** up as soon as they get oil in em. Plus they are ugly... 2. Pan-evacs do work but they can be tricky to get proper scavenging. The other thing is that they only really work once the motor is wound up (where drag motors live). What we used to often would recommend for blown or turbo daily drivers is to just vent-the hell out of the motor. The best thing i can recommend is venting the motor down low (out of the oil pan). We use to weld 3/8 npt fittings to the oil pan and then run to a puke tank with a really free breathing breather element.. it will definitely help keep your oil clean and will prevent blowing out seals. Blower motors are tough when it comes to this.
Digger Dave I would not try pulling with a pan evac from your oil pan, you are going to pull oil when you put vacuum to it. On a flathead you'd have to go through the valley witha really good baffle. Also note that pan evacs usually do have a pvc or check valve to make sure there is not exhaust reversion into the engine. In most cases you will also vent the motor to let fresh air in and in cases where the pan evac isn't getting enough vac*** the engine can still release pressure. However, some folks actually attempt to pull a vac*** in the crankcase for performance benefits (this is a complicated discussion). In these setups you would typically run a pvc out of the motor to a puke can so that it will be closed as long as you have a vac*** but will open if pressure builds up so the motor will breathe
my un blown flat head is vented out of the back of the intake with two hoses that go to the exhaust , that have pieces of threaded tubing welded in and cut at a angle with check valves they work as a venturi and it draws a va***e . a drag boat guy turned me on to this in the 80`s works good on mine . till I un cap the headers
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