# 472 Stroker Dip Stick blows out



## jtwoods4 (Dec 22, 2011)

Hey Guys,

I have a 472 stroker with pretty decent power. Under hard acceleratrion, around 5k RPM's, my dip stick will come out about an inch. This is enough to splatter some oil all over the passenger side engine compartment. I just clean it off and put the dip stick back in. What's a good solution to keep that dip stick in its place?


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## BearGFR (Aug 25, 2008)

Do you have both the breather tube and PCV system installed, connected, and functional?

Bear


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## jtwoods4 (Dec 22, 2011)

I think so. I connected a hose from the PCV valve to one of the vacuum ports on the carburator. Is there something other than that I need to check?


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## geeteeohguy (Feb 2, 2008)

The PCV valve should get its vacuum at an intake manifold runner, preferably. Also, as Bear said, make sure your breather(s) are functional. You are blowing the dipstick out due to excessive crankcase pressure build up. This will blow out seals and cause oil leaks all over, eventually. Solution is to stay under 5000 rpm, or to vent the crankcase properly.


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## jtwoods4 (Dec 22, 2011)

There is no connection on my intake to plug in the PCV hose. The only connection on the intake is connected to the power brake booster. And yes, my engine links oil because this is affecting my seals.

How do I test the PCV valve?


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## 05GTO (Oct 6, 2004)

Do you have a vented oil cap?


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## jtwoods4 (Dec 22, 2011)

Not sire I will check when I get back in town next week. I hope that's the problem.


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## BearGFR (Aug 25, 2008)

jtwoods4 said:


> There is no connection on my intake to plug in the PCV hose. The only connection on the intake is connected to the power brake booster. And yes, my engine links oil because this is affecting my seals.


69, right? There should be a long "pipe" coming out from the rear of the carb base with a large fitting and a smaller fitting. The larger of the two is the connection for the power brake booster, the smaller is an unported source to use for "whatever" (originally it was connected to the input side of the thermostatic control on the front of the intake that went from there to vacuum advance). The PCV hose was connected to a large elbow fitting on the front of the intake manifold.



> How do I test the PCV valve?


Pull it out of the rubber grommet and shake it. If you hear it rattling freely, it's probably fine. Also keep in mind that the PCV provide a crankcase vent only during part throttle. At WOT when there's very little or no manifold vacuum, the PCV is going to be closed. There should also be a metal tube that inserts into a grommet in the center of the passenger side valve cover and connects to the air cleaner housing. This tube is the main source for crank case venting, especially under WOT.

Bear


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## 05GTO (Oct 6, 2004)

BearGFR said:


> 69, right? There should be a long "pipe" coming out from the rear of the carb base with a large fitting and a smaller fitting. The larger of the two is the connection for the power brake booster, the smaller is an unported source to use for "whatever" (originally it was connected to the input side of the thermostatic control on the front of the intake that went from there to vacuum advance). The PCV hose was connected to a large elbow fitting on the front of the intake manifold.
> 
> 
> 
> ...


:agree 100%

It doesn't sound as if his car is stock, I assume with a 472 stroker he is not using the stock carb, breather or the tube from the valve cover to the breather. sounds as if, at WOT the only vent is thru the dip stick tube.


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## jtwoods4 (Dec 22, 2011)

I do not have the original intake though, or the original carb. I am using a Holly 850 and an Offenhauser intake. The intake only has one connection on the back and the power brakes are connected to it. 

I also have after market valve covers, there are no hoses attached to the valve cover.

I do not have the connections you are referring to.


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## jtwoods4 (Dec 22, 2011)

05GTO said:


> :agree 100%
> 
> It doesn't sound as if his car is stock, I assume with a 472 stroker he is not using the stock carb, breather or the tube from the valve cover to the breather. sounds as if, at WOT the only vent is thru the dip stick tube.


Yes, thats correct. But this cannot be the correct setup. It doesnt make sense that an aftermarket intake uses the dip stick as a breather hole. There has to be a solution.


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## 05GTO (Oct 6, 2004)

jtwoods4 said:


> There has to be a solution.


There is, A vented oil cap.


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## SDGoat619 (Mar 21, 2011)

I am having the same issue. Oil is burning on my headers from my dipstick. However I have no tube from the valve cover to air cleaner and my dipstick is leaking oil now also. . I just thought that maybe my oil was to high. Going to install a proper breathing valve cover cap and plumb it to the air cleaner and we'll see if that solves the problem. 

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## 05GTO (Oct 6, 2004)

Venting thru the breather was an emission modification to reroute the engine fumes thru the engine to burn before releasing to the atmosphere. The earlier GTOs did not require this and only used the vented oil cap. There may be a small venturi vacuum in the breather at WOT but not enough to make a difference. In addition, I would also replace the PCV valve.


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## lars (Sep 28, 2004)

Any engine, whether it be a street engine or a race-only engine, must have proper crankcase ventilation: The crankcase builds up pressure from combustion gas ring blowby, and this pressure and gas must be allowed to escape efficiently from the crankcase. There are 2 ways to do this:

*1. PCV System*
Prior to 1964, most of the automakers used a ventilation system consisting of a breather in one valve cover, and a "draft tube" that came out of the engine valley area and hung down under the engine around the bellhousing. This "draft tube" would "suck" vapors out of the engine crankcase as you drove down the road, effectively ventilating the crankcase. As the engine grew older and started to generate more blowby, the "draft tube" would smoke like a steam engine. The EPA didn't like that very much.

So a very simple and effective system was put into use by all the automakers: A ventilated breather cap was installed in a valve cover, and a "calibrated leak" (PCV) was installed either in the valley cover or in the opposite valve cover and connected to manifold vacuum - the PCV had a baffle underneath it to assure it could not "suck" up engine oil being splashed around in the crankcase. At idle and under light-throttle cruise conditions, ring blow-by was minimal and manifold vacuum was high, so the system would pull fresh air in through the ventilated valve cover breather, purge the "bad gases" out of the crankcase, and suck the gases up through the PCV and right into the intake manifold to be burned. When the engine was placed under heavy load (wide open throttle - WOT), engine vacuum would go away, ring blowby would be high, and the pressure and flow reversed direction, blowing the crankcase pressure out of the ventilated breather cap in the valve cover. This cap had a mesh screen inside it, and a baffle underneath it, to prevent actual engine oil from being blown out - only "vapors" would normally blow out the cap.

This system works great: it pulls a low pressure on the crankcase, which reduces oil leaks; the low pressure under the pistons actually helps increase engine efficiency; it purges the crankcase of acidic gases; and it has no detrimental effect on power at WOT.

But the EPA still didn't like it, because at WOT, you were blowing crankcase vapors out of the valve cover breather and right into the atmosphere. So the automakers removed the plug-in breather, and ran a tube up the the side of the air cleaner. Now, under normal cruise, the PCV would suck fresh air from inside the air cleaner, down the tube, through the crankcase, up through the PCV and into the intake. At WOT, when the crankcase would get pressurized and the PCV was no longer "sucking," the "bad" gases would simply vent into the air cleaner and be sucked down the carb. As long as you didn't have excessive blow-by, this had little effect on WOT power. Everyone was happy.

For a high performance street-driven car, you want to duplicate the early PCV system: Install a PCV in the valley pan or in a valve cover and plug it right into the manifold plenum under the carb: If you have an aftermarket intake, you can drill and tap a 1/4" pipe hole right into the manifold plenum at the carb base. Install a 3/8" hose barb pipe fitting, and run a rubber hose to the PCV. Then, install a valve cover breather in a valve cover or other suitable place on the engine. This will assure that the crankcase is ventilated under "normal driving," yet allows crankcase over-pressure to escape at WOT. It has no detrimental effect on your WOT power, and really helps cure oil leaks. ...and your dipstick won't blow out.

Here are a couple of shots of a PCV/Breather system I built for a 500-horse street engine (it's a Chevy - forgive me - but the concept is the same for the Pontiacs...). This engine has valve covers with no oil fill or breather holes, so I fabricated valve cover spacers and installed the entire breather system into the spacers at the back of the engine - it's "invisible" from the front of the engine. I drilled holes into the spacers and installed the PCV on one side of the engine and a K&N breather on the other side. There are baffles installed inside the spacers so neither the PCV nor the breather are ever exposed to direct oil splash. This system works perfectly at WOT, preventing any oil splash escape or crankcase pressurization, and idle/cruise performance is perfect:

System overview from the back of the engine: PCV on one side, and breather on the other:











Breather is a generic K&N breather, plumbed into the rocker arm area with a fitting. There is a baffle inside the valve cover spacer to prevent oil from entering the fitting:










The PCV is a screw-in PCV that was used on some 327 Chevy's in the mid '60s. Notice how the intake manifold is simply drilled at the carb base plenum for the 3/8" vacuum hose coming off the PCV:










From the front of the engine, it appears to have no PCV or breather system at all:










*2. Breather-Only System*
You'll hear some "performance" guys knock the PCV system, claiming it "robs power" and is bad for performance: Race cars don't have PCV's.

If you never drive your car on the street, and it's used for race-only where it's either idling or is at WOT whenever the car is in use, the PCV serves no purpose, since the engine is never operating in a range where it's pulling any vacuum. On this type of an application, you just want to ventilate the crankcase as much as possible to prevent pressure buildup under your WOT condition. Engines of this type typically will run a breather in both valve covers, and not use a PCV. Any crankcase blow-by is always vented out of the breathers, and you'll typically get a light "oil film" all over the engine compartment after heavy use. No problem for a racecar - you just clean it up again. You can do this system on a street car, but I can't for the life of me figure out why anyone would want to... Maybe it makes your non-racecar look like a "real" racecar... I wouldn't suggest doing it unless you enjoy wiping oil film off your engine and inner fenders. But it will keep your dipstick from blowing out. You can run tubes from the breathers to your header collectors so that your exhaust system actually "sucks" the gases out of the crankcase area - many racers will do this. Again, not a real good idea on a street car, and certainly not if you intend to pass an emissions test.

Here is our track-only racecar with the dual breather system. The dipstick does not blow out, and we don't worry about how clean the engine is:










Lars


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## jtwoods4 (Dec 22, 2011)

Wow. Thank you everyone. Great posts! Thank you Lars for the details. Looks like I need to install a breathing oil cap on the valve cover. Can I keep the PCV plugged into the carb vacuum or do I have to drill a hole and run it into the intake?


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## lars (Sep 28, 2004)

You can run the PCV to any direct manifold vacuum source, whether it be on the carb or in the manifold. You should run it as a dedicated line, though, and not "T" it into your power brake line or other accessory (since at WOT, you can blow oil vapor up through the PCV line, and you don't want this in your PB booster). Some carbs have a 3/8 line connection on the front and the back of the carb's base throttle plate - the one in the rear for brakes and the one in the front for PCV. If you just have one in the back, and you currently have it hooked up to brakes, you might want to drill a new hole someplace...

Lars


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## 05GTO (Oct 6, 2004)

lars said:


> You can run the PCV to any direct manifold vacuum source, whether it be on the carb or in the manifold. You should run it as a dedicated line, though, and not "T" it into your power brake line or other accessory. Some carbs have a 3/8 line connection on the front and the back of the carb's base throttle plate - the one in the rear for brakes and the one in the front for PCV. If you just have one in the back, and you currently have it hooked up to brakes, you might want to drill a new hole someplace...
> 
> Lars


:agree

You should have a capped manifold port available on the front of your 850 for the PCV;


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## lars (Sep 28, 2004)

The carb shown in the photo has a 3/8 port at the back (right side in photo) - not the front - for PCV or brakes. The small port at the front (left side in photo) is not big enough for PCV. Depending on carb model, some of the upper-end Holleys have no 3/8 port at all.

Lars


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## jtwoods4 (Dec 22, 2011)

Thank you lars. The pcv system is now connected properly. I had no idea that port was on the back of the carburetor. I added a little stop leak to the engine and I have only had a minor drip or 2 since connecting the pcv correctly.

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