DrFishbone Engine Build Thread 2017

Why not just a simple PCV catch can that several of us have used for years without issues?

I’m not sure what everybody else uses...all I seem to recall seeing / reading is a catch can between the PCV and intake to keepsome of the junk out of the intake tract. I’m looking at reducing crankcase pressure primarily....seems to me that the small 1/4”(?) tube out of the drivers valve cover is a restriction under WOT...for a higher-boost SC, there HAS to be enough blow-by to at least add a little pressure in the crankcase when using that small line. There will be oil mist too...maybe not enough to matter? I don’t know. I’ve seen oil accumulate in that crossover tube though.

By upsizing the PCV side and eliminating the valve, it would be a second way to relieve the pressure, in addition to pulling fumes out during idle/cruising. It may be better to leave it in place though. Unless I’m just off on an imaginary train of thought, all the PCV does is control when crankcase vapors are pulled from the valvecover.

If understand correctly, the PCV is closed during high-vacuum AND when the crankcase sees pressure, but open between the two (slight vacuum). Otherwise, wouldn’t it just be a check valve?

Anyways - I’m just wondering if we can’t improve the crankcase evacuation IN ADDITION to cleaning up the PCV air.
 
I remember the first time my PS rack failed, I replaced it with an aftermarket one and I had hard steering and stalling, I had to replace it again with another unit. Try raising the idle to test if the pump will do the job better, with a large cam I had stalling issues when loading the engine with steering as well. You might need to try a rebuilt rack. It was a painful job with the stock Kmember, another great thing about the tubular one I have.

Jacob had the same thing go on with his Cobra (bad rebuilt rack possibly)...it IS a pain - that’s why I did this with the engine out....lol...should have just left it alone I guess!
 
If understand correctly, the PCV is closed during high-vacuum AND when the crankcase sees pressure, but open between the two (slight vacuum). Otherwise, wouldn’t it just be a check valve?

In my experience, not all PCVs do that the same, meaning some don't close/seal as well as others under all conditions. If you're trying to eliminate backflow during boost, as an example, see - see http://www.sccoa.com/forums/showthr...-an-after-market-pcv-valve-leak&highlight=PCV

If you're looking for examples, check out the systems on newer supercharged mustangs.
 
Is it? :confused:

During high vacuum or idle a normal pvc almost shuts itsellf closed. During wot high vac it opens to allow the gases to get burned in the combustion process.

The way you have it has a vac leak at idle cause there is nothing restricting airflow from the intake tube to the inlet which is under vac at idle. Basically creating a vacuum leak.

Under boost it will work but you will now gunk up the throttle body on both sides from the remaining oil mist the catch can let’s through.
 
I’m not sure what everybody else uses...all I seem to recall seeing / reading is a catch can between the PCV and intake to keepsome of the junk out of the intake tract. I’m looking at reducing crankcase pressure primarily....seems to me that the small 1/4”(?) tube out of the drivers valve cover is a restriction under WOT...for a higher-boost SC, there HAS to be enough blow-by to at least add a little pressure in the crankcase when using that small line. There will be oil mist too...maybe not enough to matter? I don’t know. I’ve seen oil accumulate in that crossover tube though.

By upsizing the PCV side and eliminating the valve, it would be a second way to relieve the pressure, in addition to pulling fumes out during idle/cruising. It may be better to leave it in place though. Unless I’m just off on an imaginary train of thought, all the PCV does is control when crankcase vapors are pulled from the valvecover.

If understand correctly, the PCV is closed during high-vacuum AND when the crankcase sees pressure, but open between the two (slight vacuum). Otherwise, wouldn’t it just be a check valve?

Anyways - I’m just wondering if we can’t improve the crankcase evacuation IN ADDITION to cleaning up the PCV air.

I have ran the same AMW catch can that I did 3 group buys on for years at over 20psi boost. Works great, catches stuff, and my intake is clean.
 
In my experience, not all PCVs do that the same, meaning some don't close/seal as well as others under all conditions. If you're trying to eliminate backflow during boost, as an example, see - see http://www.sccoa.com/forums/showthr...-an-after-market-pcv-valve-leak&highlight=PCV

If you're looking for examples, check out the systems on newer supercharged mustangs.

I guess my ponderings are twofold -
1) if you have a catchcan....do you really need a PCV, given it is plumbed into a non-boost (vacuum only) part of the intake system? I think this can needs to be packed tight, but seems like there;'s no harm constatly cirulating air through the crankcase, rather than just when the PCV opens.
2) are we losing any power (at all) by venting the WOT crankcase gases only through the little crossover tube from the driver valve cover?
 
The way you have it has a vac leak at idle cause there is nothing restricting airflow from the intake tube to the inlet which is under vac at idle. Basically creating a vacuum leak.

I see what you're saying now....but that's not a vacuum leak...it's just additonal METERED air going around the TB plate...right? Same concept as the IAC function, bypass screws and having the TB plate cracked slightly, correct?

There will need to be enough restriction in the former PCV path to keep the idle within range without the IAC having to go crazy...hard to say what hose size, etc. would be okay....maybe a PCV or constant restriction would need to be added.
 
Last edited:
1) I would avoid any scenario that involves feeding additional unmetered air of any type into the crankcase. Also remember that the PCV shunt action involves closing/restricting flow in two directions, not just one. It might help to review PCV basics:

http://www.agcoauto.com/content/news/p2_articleid/197

If you delete the PCV, you should at least incorporate some sort of restriction, such as a simple baffle with a small hole...I've heard that some manufs. are doing this on cheaper cars in an effort to reduce costs, etc. But by the time you go to that amount of DIY, you could just retain the OE PCV system and be done. Wasn't there a recent thread where someone found out the factory baffles were somehow missing/removed when they inspected the valve covers?

2) Along with moisture reduction, the idea is to reduce crankcase pressure (neutralize, actually) so the pistons see as little resistance as possible going both up and down. Before it became an emissions issue, manuf's used to vent down into the air stream under the car (for both moisture vapor and pressure evac). Track cars still do this in many examples, but they also have to be able to catch/control spills, etc. on the fly, which is another topic. Notice that the driver's side vent feeds into the intake tube, upstream of the TB, so I don't see power loss as a factor....it is basically re-circulation that hopes to burn off condensation and balance crankcase pressure. Power loss might be a factor if that balance is out of whack, I think.

Ken
 
1) I would avoid any scenario that involves feeding additional unmetered air of any type into the crankcase.

Agreed - I don't think what I have in mind is doing so though.

When the inlet is under partial vacuum with the stock arrangement (when PCV is open), air is being PULLED from the intake pipe through the crossover tube, into the drivers valve cover (crankcase), out the passenger valve cover (crankcase) and into the inlet...this all happens as a closed system, AFTER the air has been metered. Under boost, PCV will be closed and half of the system acts as a crankcase vent path only (through the crossover tube)...so, the way I'm seeing it, blowby / crankcase pressure is unmetered even with the stock setup. I'm just wondering if 1) it's nearly negligible (I'm doubting it) or 2) the factory (and our custom WOT tunes) account for the additional blow-by air.

Maybe I'm over-imagining the amount of blowby we see at 20psi+, 7000rpm....but watching David Clark's dyno session in Illinois and seeing the amount of oil mist blown out of the catch can vent (before he changed back to a closed system) really got me thinking.

If you delete the PCV, you should at least incorporate some sort of restriction, such as a simple baffle with a small hole...I've heard that some manufs. are doing this on cheaper cars in an effort to reduce costs, etc. But by the time you go to that amount of DIY, you could just retain the OE PCV system and be done. Wasn't there a recent thread where someone found out the factory baffles were somehow missing/removed when they inspected the valve covers?

I agree - some restriction may be required. That should be easy and cheap to add though. Didn't see the thread you're referring to, but I do know that some of the rocker stud / rocker arm custom setups require modification or removal of the baffles for clearance - I don't have the factory internal baffles in mine right now - I will be putting the modified ones in when i take the covers off again.

2) Along with moisture reduction, the idea is to reduce crankcase pressure (neutralize, actually) so the pistons see as little resistance as possible going both up and down. Before it became an emissions issue, manuf's used to vent down into the air stream under the car (for both moisture vapor and pressure evac). Track cars still do this in many examples, but they also have to be able to catch/control spills, etc. on the fly, which is another topic. Notice that the driver's side vent feeds into the intake tube, upstream of the TB, so I don't see power loss as a factor....it is basically re-circulation that hopes to burn off condensation and balance crankcase pressure. Power loss might be a factor if that balance is out of whack, I think.

Right...so the question I am posing: Is increasing the boost from ~12psi to 20psi+, increasing the static CR, advancing the timing further (sometimes), increasing the redline RPM on our motors also increasing the blow-by to a point where we SHOULD be looking at increasing the flow path that the blowby (crankcase evac) takes?
 
I feel you are still missing the closed at high vac and closed and low to no vac function of the valve. It already acts as a restrictor when under boost cause the inlet should be near zero when boosting unless you are cavitating the blower. Yes some is venting but it’s not fully open, if the engine has excessive blow by then that’s a problem but you have a brand new engine and hopefully the rings seated as they Should.

You can test it out by running a hose to the windshield or near the cabin so you see what’s happening under boost, part throttle or full vac. That might put your fears to rest, you run alky things get cleaned with that as well.
 
increasing the static CR, advancing the timing further (sometimes), increasing the redline RPM on our motors also increasing the blow-by to a point where we SHOULD be looking at increasing the flow path that the blowby (crankcase evac) takes?

Like I said...in certain 'race type' conditions, the choice is to keep it simple and generously vent the crankcase directly to the atmosphere.
 
I decided (or more accurate: realized) last night that I'm pretty much out of time to work on my car for the Shootout, so now it's down to getting some seat time in it, changing oil and tuning it. So, here's what I'm running for the Shootout, since I had all these things on-hand from last year's TBU Box-O-Crap auction. :D

shootout whipup.PNG

I don't like the idea of much street driving without PCV, but this will do. Hopefully later in Oct. I can find time to play with it some more.

Now it's time to put some love into my wife's Anny as time permits...looks like we'll be bringing both (and racing both) this year!
 
What you just posted is what I'm going to be running on my new motor. I kinda feel the same as you about the PVC, but I think that's the tree hugger brainwashing that we have all been exposed to for the last 30 years coming out. Cars ran fine without them before the hippies took over!
 
I don't like the idea of much street driving without PCV, but this will do.

Not bad, but...

This appears to be an even simpler, also boost compatible, check-ball solution: http://www.uprproducts.com/billet-one-way-crankcase-breather-kit.html

As our oil filler is already a stack off the valve cover, $70 for billet isn't that bad a deal. Not sure it would be a direct fit...might need to swap the cap socket/neck for something late model, perhaps easy to find via PnP/eBay etc.

They also sell this if you need to vent to a catch can: http://www.uprproducts.com/mustang-billet-oil-fill-neck-adapter-plug-n-play-straight.html
 
Last edited:
I decided (or more accurate: realized) last night that I'm pretty much out of time to work on my car for the Shootout, so now it's down to getting some seat time in it, changing oil and tuning it. So, here's what I'm running for the Shootout, since I had all these things on-hand from last year's TBU Box-O-Crap auction. :D

View attachment 68929

I don't like the idea of much street driving without PCV, but this will do. Hopefully later in Oct. I can find time to play with it some more.

Now it's time to put some love into my wife's Anny as time permits...looks like we'll be bringing both (and racing both) this year!

This will work getting the blowby at wot out but will not evacuate moisture and gases at part throttle. But it should work for your application.

What would work best is those oil cap breathers with the checkball and baffles used in MAF applications. That way you will make the pcv work under normal use, but also relief pressure under WOT vía the breather. A sealed catch can should still be used to keep the intake semi clean.
 
Not bad, but...

This appears to be an even simpler, also boost compatible, check-ball solution: http://www.uprproducts.com/billet-one-way-crankcase-breather-kit.html

As our oil filler is already a stack off the valve cover, $70 for billet isn't that bad a deal. Not sure it would be a direct fit...might need to swap the cap socket/neck for something late model, perhaps easy to find via PnP/eBay etc.

Those are nice products. The filter / vent might make a mess, but should work without too many parts / clutter. Adding that to my existing vented can and leaving the PCV system in place was the first direction I was heading to minimize parts/costs....just couldn't find a nice-looking check valve for it.

I'm sure it's not a direct fit...but it never has to be anyway.

Thanks for linking, Ken.
 
This will work getting the blowby at wot out but will not evacuate moisture and gases at part throttle. But it should work for your application.

What would work best is those oil cap breathers with the checkball and baffles used in MAF applications. That way you will make the pcv work under normal use, but also relief pressure under WOT vía the breather. A sealed catch can should still be used to keep the intake semi clean.

Right - I'll do some more heading-scratching this fall/winter. Priority #1 is to be ready to race in less than two weeks right now! :eek:
 
What you just posted is what I'm going to be running on my new motor. I kinda feel the same as you about the PVC, but I think that's the tree hugger brainwashing that we have all been exposed to for the last 30 years coming out. Cars ran fine without them before the hippies took over!

I kinda started at that...I'd like to get the moisture/oil mist/combustion gas leaks out of the crankcase though.....I just don't care as much where they end up. Don't want them on the road or caked-up in my engine though.
 
Back
Top