Technical BLOWN FLATHEAD PCV QUESTION (RETROFIT)

Or a small block Chevy!

 

And there it is.

 

I use an Aero Space Industries unit. I’m sure it will do better than 9” but on a GMC 6 cylinder with such a large crankcase and overhead valve cylinder head there is a lot of volume to suck from. It idles at 2-3”. A NASCAR engine I hear pulls 25-26 inches thru it’s many dry sump stages and I have a wet sump. I have sealed my engine the best I could even the oil dip stick hole in the block is threaded and the hoses and fittings are all AN. There is NO breather on the engine. I have found clear water in the catch can but never any oil. It does have a relief set at 15” recommended by Aero-Space to keep from sucking oil out of the rods.

 

Jimmy, no breather? Could I block both my breathers and run the vacuum off the carb adapter atop the blower? I would definitely suck the vapors from the crankcase. I thought they had to breathe in to replace what was being evacuated? This seems foreign to me, sorry for my confusion, you caught me off guard with that.

 

this is what I did to mine by using an 59ab fuel pump stand modified to accept PCV valve and also act as cold air input

 

If there is no breather, and you don't have enough leaking past the rings, won't you be sucking in gaskets?

 

I was hoping you would reply Carl. I like what you did and I may have to get that involved, BUT if I wanted to avoid the removal of the blower and intake to retrofit an evac system, how would you recommend I do that? Or would you? Do you have a breather in your pan in the truck?

 

actually Billy the breather is also built into the fuel pump stand cold air comes into the valley through the fuel pump stand and if you noticed the 8BA breather pipe is welded shut and a 3/8 fitting braised into it so it will pull from the pan and breath from the valley. The K&N filter is removable by twisting so I can also add oil through there as needed, thats what the keyed adapter braised to the top of fuel pump stand is all about.

 

Here is what your breather looks like. If you want to seal it you don’t need to cut the top off, how about a filler of some sort around the underside and then some JB Weld epoxy.
I’m a bit confused about the statement that you don’t know what the inside of the pan looks like regarding baffling. When you drilled the three 1/4” holes for the breather was the pan on the engine?
I’m not a flathead guy so I don’t know how, or if, the crankcase breathes to the valve chamber but I’m thinking your manifold mounted breather can serve as the fresh air supply and a PCV valve on the Offy breather routed into the carb adapter might be your easiest bet.
If that is the route taken you definitely need more baffling to keep large amounts of oil getting sucked into the intake, like a deflector over the holes to the Offy breather and maybe some copper wool stuffed in the breather too.

 

Front and rear main seals is the most leakage. Racers with modern engines put the lip type seals in backwards. Other tiny leakages , dist, dip stick, etc. I don't remember which way but it will affect oil pressure.

 

These are racing engines and we want to fire the piston into a vacuum. A buddy runs a 600+” Chevrolet with a dry sump and a 4 stage vacuum pump.
Could all this run on the street, yes it could but you would need to do something with the vent on the catch can. Mine goes to atmosphere but I guess you could stick a hose into an air cleaner and have the carb suck it down the engine.

On the same Subject, my 56 Y-Block is an open/ breathing engine. I have a fill cap with a 1/2” hose fitting, it is a Stant. I run a hose to the bottom of my air cleaner in front of my back carb to suck of under hood vapors from the engine. The side stock block crankcase vent is still there with a 45* angle cut in the vent pipe. I’ve had it that way for 6 years to keep the smell down. All engines before 61 PCV systems were this way minus the hose I installed.

 

I went through the pictures on my phone and I cant find one of the inside of the pan after I modified it, but I seem to remember a flat steel piece that prevented oil from having direct access to the holes. Not that it really matters. The pic provided is helpful on the internal design of the pan breather. I just have too much pressure or I am slinging too much oil about.

In your picture the baffle would prevent sloshing oil from coming out the top but what I have is oil vapor or mist blowing out that vent at high RPM.

 

[QUOTE="Bandit Billy, post: 13688025, member: 254716

In your picture the baffle would prevent sloshing oil from coming out the top but what I have is oil vapor or mist blowing out that vent at high RPM.[/QUOTE]

I suggested a way to seal the top of the breather without cutting it off as you had mentioned. If that was sealed and copper wool was put into the Offy pan breather might that keep some of the oil from being drawn into the PCV?
It was said in another thread that Ford used copper wool to aid in oil control for the FE engine PCV adapter.

 

We used to use (a world I have not played in since the '90s) the smog pump off of a Ford on our turbo motors. They were cheap and made to run full time on a street motor. Some race pumps are not made for longevity or so I have been told. Back then a pump off of a ford was 5 bucks at You-Pull-It.

I know that is a little backyard. LOL

 

Well after considerable thought (and cleaning up the underside again after a thrash about the other day) I pulled it apart.

With the upper hose off the motor I think I have ample room to pull that plug out of the draft hole. Worse case I could remove the thermostat housing to get better access.

This is the carb adapter sans 97's, my plan is to drop a 3/8's NPT 90 degree AN -6 fitting in the window between the front and center carbs. Then use some Russel braided nylon hose I have left over and a spare AN hose adapter (never return extra parts, they come in handy sooner or later) to plumb the PCV that showed up in the mail yesterday.

The underside of the adapter though shows a bit of an issue but nothing a mill cant solve. I think the plan is to drill the hole for the fitting about half way into that billet aluminum adapter then use the air file to shape a concave dado in the base.

Anyway that is the initial plan. I'm headed over to the Wizzard (aka @Pist-n-Broke ) after work to get his take. Always best to get a second opinion before destroying expensive parts.
I found this picture of the engine under construction and it shows the tube to the crankcase still in place at assembly so this may just work after all.

This thread sucks, or soon shall.

 

I think a -6 is a little small but it may work for you since a flathead has less volume than your typical overhead valve engine. The 283 Chev threaded PCV valve from a 1965 works great on our 302 GMC 6 and it has a lot of vapor.

 

I thought about that but the issue is the flathead PCV that I bought from a link on the ford barn only has a .30 ID on the input, so larger line isn't going to help. Here is what I purcahsed. It is designed to fit the draft tube hole.

I pulled the brass soft plug out of the intake last night without having to remove the water neck. That is nice since it doesn't leak and probably would if I messed with it.

And the valve assembly installs in the brass plugs stead. The one thing I was disappointed by on the PCV valve was that it came permanently epoxied into the billet adapter so when I change the valve I must repurchase the assembly. Hmmm.

As you can see the valve leaves a nice run under the blower snout for the vacuum hose.

After which I installed the wire looms, power-gen, radiator hose, etc. A proper Manhattan atop the blower appears to indicate the engine has a mighty cant to it but in reality the car is on the 2 post and the front is lifted higher than the rear the way I loaded it the other night.

Prof. Wizzard is milling the carb adapter for the vacuum fitting today. Last night I had an epiphany while enjoying my Manhattan, the vacuum trigger I installed for my BTM-6 box is below the blower so it isn't sending the proper signal at boost hence we are adding that fitting to the carb adapter as well. I had a bit of a flat spot when I lite all three carbs, this may well be the culprit. Chasing bugs, part of building cars from scratch.

 

Just a question about your ignition retard. The setups that I worked with retarded timing as boost increased and would be under the blower reading manifold vac / boost. You have a different control setup?

 

I looked up the instructions and it appears that you are correct and that means I actually read and understood the instructions when I installed it and did it right for once.

If it is indicating that I can tie it into an existing boost line then my below the blower location is correct. Oh well, I now have an additional vacuum source if I need one on the carb adapter. Could come in handy for tuning.

I'm glad you read my post! Not enough experience with superchargers.

 

Update: Done! I appreciate all the advise and more so the knowledge imparted. We tapped the best place for vacuum and fitted it very neatly which is important to me. Show car/driver, this one must be both and that takes some doing and some trial and error.
@Pist-n-Broke threw the adapter on his mill, and provided the PCV vacuum source. It was a simple matter of plugging it all back in tonight. The plug is an additional vacuum source for future use. Perhaps a direct fit vacuum gauge?

And then re-assembling the carbs and firing it back up. Took a little throttle adjustment but it starts and runs nice.

I threw the hood top back on the car and it hides the entire install of this PCV system. I still have the pan breather open for now, I will drive it for a bit and see if I need to close it off.
We have a cruise in tomorrow night in Battle Ground and I wanted to have the 34 ready to attend. Looks like we will make it. Hopefully it will come home with less oil leaks. Thanks to all who helped and especially the Wizzard.
"I love it when a plan comes together!" -Col. John "Hannibal" Smith

 

It is a nice looking engine. I admire / envious of the budget it takes to make it happen. My bet is that before it's a wrap you will be blocking off the pan breather. Enjoy the hell out of it.

 

I have a sneaking suspicion that you are quite correct. Easy enough fix, remove it and stick a full gasket under it and reattach. I am looking forward to losing the oil spray on the underside. I don't care if the flathead marks her turf with a drop or three of Valvoline but the other is just poor manners and I raised her better.

Thanks for your comments!

 

I was going to post a comment but........you have already heard it.

 

I suggested a way to seal the top of the breather without cutting it off as you had mentioned. If that was sealed and copper wool was put into the Offy pan breather might that keep some of the oil from being drawn into the PCV?
It was said in another thread that Ford used copper wool to aid in oil control for the FE engine PCV adapter.[/QUOTE]

This is the way to do it. Use the copper wool and on the inside of the pan you make a Sheetmetal cover over the top holes bored in the pan. space the cover out 3/16 to 1/4" from the holes. In your case you would have to pull your pan, cut the nuts off, weld the spacer to the pan then the nuts to the spacer. You really need the baffle and the copper wool will help a lot.

 

They only got ya for a second unit if you let them. Looks to me like just a little machine work and that plug could be machined for an over the counter P.C.V. rubber grommet and install a new valve in it. You know, the old plug and play kind. Screw epoxy.

 

Well I ran it around Friday night and again last night, stop light to stop light action and there is not even o ne drop of oil on the floor this morning. And yes, I checked the dipstick. I haven't put it in the air to see firsthand but prior to the PCV install it would have 3 or more drips on the floor.

I threw a few more degree timing in it as it felt a bit anemic Friday night. Last night it was running better but I might do a bit more tinkering with the timing and I borrowed a sniffer off a buddy so I can adjust those carb mixtures.

 

looks good Billy................

 

I have been giving some thought on adding a PCV on my blown 8BA. My upstanding on how the valve works is under good vacuum, say at idle, the the vacuum is pulling the valve and stretching the spring cutting down on the flow. At lower vacuum the spring is able to open the valve more by pulling back. Lower vacuum allows the valve to open more. Higher vacuum the valve closes some. Both conditions and everything in between provide good control of evacuation of fumes and provide good engine performance by not drawing too much air.
Both natural aspirated and supercharged motor produce more blow-by at higher load. The blower motor, since it's forcing air in, (boost) is producing more blow-by into the crankcase then carburetor motors.
So my question is, would you use a different pcv? Maybe one with a stronger spring to hold the valve open more to take care of additional blow-by. Perhaps I'm over thinking it.

 

I went looking for this thread for a conversation I am having with a fellow HAMBaholic and I saw your question. I apologize I did not see it earlier but a couple years late beats never right? I have no idea on the PCV and weight of the spring needed. I figured this would be a good starting point and it ended up being just fine. I have no blow by that I can tell, after the year and half of running her around she hasn't dripped and doesn't have any weird odors (that I can blame on the car anyway . @Kim Strobeck rode around with me at a three day beach cruise this last year and he said if his flatty smells or leaks he will follow suit. He is putting an 8BA in a 30 ford and also has a 15,000 mile original 50 ford coupe with the original flathead. I have been in that car and it has "that" odor. It might be a traditional smell but I can think of several aromatic arguments against that one right off.

Many miles and smiles later, this retro fit worked just fine and actually better than I had hoped. Thanks @Pist-n-Broke for yet another successful improvement to the roadster and to the rest of you that responded with helpful tips and insight.

 

Well , I'll probably get a load of crap about this but, I use two PCVs, one installed for normal use and one installed BACKWARDS. During normal driving , vacuum keeps the backwards pcv closed and system works normal . When your foot is in it and crankcase preasure builds the normal pcv will be pushed closed . the backwars pcv will relieve the crankcase presure. It works well on my flatty but I'm using a recirculating valve so it only boosts when my foot is in it and I'm only boosting 4.5 Lbs. "No Breather". Been runnig this for ten years now. No problems.