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Discussion Starter · #1 ·
Hey ya’ll! Looking for input on my build. Justput this build together with a gt40x crate engine. Been fighting a crankcase vacuum problem for a year now. Soon as i fire this thing up it has an excessive amount of vacuum in crankcase. I can unhook the pcv and all vacuum lines and have it immediately. It builds as it’s running and then starts with the humming noise as it pulls through the lower intake gaskets. Have redone these things 8 times and once i put a different upper and lower to make sure its not the intake. The engine was originally brand new amd only had 1100 miles when i wrecked the car…pulled it and it sat for about 5 years and i did all new gaskets and some head studs put it in this car and has not been right ever since. Stumped here and would love some fresh input. Problem is in the heads or in the compression rings maybe?? Sorry for long post but know more info the better…
 

· Dean Scheidt
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Do you have a fresh air inlet that connects to the engine that supplies the fresh air before the throttle blade? This probably isn't the problem since you mentioned you have the problem even with the PCV disconnected.
 

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Discussion Starter · #3 ·
Hey ya’ll! Looking for input on my build. Justput this build together with a gt40x crate engine. Been fighting a crankcase vacuum problem for a year now. Soon as i fire this thing up it has an excessive amount of vacuum in crankcase. I can unhook the pcv and all vacuum lines and have it immediately. It builds as it’s running and then starts with the humming noise as it pulls through the lower intake gaskets. Have redone these things 8 times and once i put a different upper and lower to make sure its not the intake. The engine was originally brand new amd only had 1100 miles when i wrecked the car…pulled it and it sat for about 5 years and i did all new gaskets and some head studs put it in this car and has not been right ever since. Stumped here and would love some fresh input. Problem is in the heads or in the compression rings maybe?? Sorry for long post but know more info the better…
Do you have a fresh air inlet that connects to the engine that supplies the fresh air before the throttle blade? This probably isn't the problem since you mentioned you have the problem even with the PCV disconnected.
i do not have anything hooked before the throttle blade. I have a vac line running off back of intake to the oil fill tube but nothing before
 

· Dean Scheidt
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On my 1989 Mustang, I had a vacuum source line going from the upper intake to the PCV valve. This pulls air from the crankcase.

I also had a fresh air inlet line connected from the engine air intake tube (after the MAF and before the throttle blade) that connected to the oil fill tube on the valve cover. This was for fresh air to enter the crankcase.
 
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· Dean Scheidt
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If you have a PCV valve pulling air out of the crankcase without a fresh air source hooked up to the engine then it will try pulling air into the crankcase from the valve cover gaskets, oil pan gasket, front & rear main seals, front & rear rear lower intake gaskets, etc.
 

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Discussion Starter · #6 ·
On my 1989 Mustang, I had a vacuum source line going from the upper intake to the PCV valve. This pulls air from the crankcase.

I also had a fresh air inlet line connected from the engine air intake tube (after the MAF and before the throttle blade) that connected to the oil fill tube on the valve cover. This was for fresh air to enter the crankcase.
My pcv is hooked to back of intake. On my holley upper it has three ports on the back so i did one to the factory vacuum tree and one to oil fill and other to my fuel regulator? Crazy how many times i have redone these lower gaskets as soon as i fire it to set the timing it is sucking air like a shop vac. Even with all vac lines undone and i can put my hand over the pcv grommet and straight suction. Hope its not in my heads or lower end.
 

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If you have all the vacuum sources removed from the v-covers, etc then the only place a vacuum can get to the crankcase is through an intake port when the piston goes down.

There are two places this occurs: Between the head/intake or through the valve guides/valve seals.

1. Wrong intake gasket is being used..
2. Gasket is slipping out of position when tightening gasket.
3. Distance between the surface of the head and the intake is more than the gasket is thick..milled heads or intake or both can cause this..
4. Worn v-guides thus bad v-seals.

ks
 

· Dean Scheidt
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My pcv is hooked to back of intake. On my holley upper it has three ports on the back so i did one to the factory vacuum tree and one to oil fill and other to my fuel regulator?
Am I reading this correctly that you have your PCV valve and oil fill neck hooked up to a vacuum source?

If so, disconnect the one going to the oil fill neck and see if that takes care of the crankcase vacuum problem. For this test, leave the oil fill tube connection open to atmosphere and plug the line that was going to it since it would be a vacuum leak.

If that takes care of the excessive crankcase vacuum problem, you need to run a hose from the oil filler neck to the intake tract before the throttle blade but after the MAF.

* Edit: I see that you still had the crankcase vacuum even with all vacuum lines disconnected so my experiment above will not help your situation. *
 
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Discussion Starter · #9 ·
If you have all the vacuum sources removed from the v-covers, etc then the only place a vacuum can get to the crankcase is through an intake port when the piston goes down.

There are two places this occurs: Between the head/intake or through the valve guides/valve seals.

1. Wrong intake gasket is being used..
2. Gasket is slipping out of position when tightening gasket.
3. Distance between the surface of the head and the intake is more than the gasket is thick..milled heads or intake or both can cause this..
4. Worn v-guides thus bad v-seals.

ks
So i have have redone these gaskets 6 times with the holley intake and i can see in the ports pretty well to align them as i set it down and torque it. Once i tried a set of cometic gaskets that are thicker because when i would remove the intake I noticed the china wall bead was paper thin. When i tried my gt40 intake set up i could not see down the runners but felt good about the gasket placement still no change though so i felt like i eliminated the intake being the problem. Everything is brand new except for lower end and heads but they only have 1200 miles. The engine did sit for 5ish years and when i went back in i did new head gaskets and studs. Hasnt been right since. Valve seals or guides maybe from sitting? Or am I really just missing something on this gasket install?
 

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Discussion Starter · #10 ·
Am I reading this correctly that you have your PCV valve and oil fill neck hooked up to a vacuum source?

If so, disconnect the one going to the oil fill neck and see if that takes care of the crankcase vacuum problem. For this test, leave the oil fill tube connection open to atmosphere and plug the line that was going to it since it would be a vacuum leak.

If that takes care of the excessive crankcase vacuum problem, you need to run a hose from the oil filler neck to the intake tract before the throttle blade but after the MAF.
I do have them both to a vacuum source. Before i had no line to my oil fill but added it later to try and cure my problem. I will try and move it before the blade. I would have to drill into this Anderson pipe to do it but if that would cure my issue im all about it!
 

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If you are trying to troubleshoot a vacuum to your crankcase then don't add anymore vacuum hoses. Unhook EVERYTHING to the intake. Every single tiny hose that either goes to the valve covers or to the lifter valley on the bottom of the intake, etc..

Once there is no vacuum source to the crankcase then start it up and see if there is a vacuum being pulled by removing the oil fill cover and put your hand over it. If there is still a strong vacuum then it has to be intake or valve guides.

With absolutely no vaccum source there should be a slight amount of pressure developing inside the crankcase that will puff out steam/smoke or ?? out of the oil fill hole.

ks
 

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You mentioned that you felt like the intake gasket was aligned but it's possible that if the heads were angled milled or something weird then the surface angles between the intake and head are not parallel causing the gasket not to sit flat thus not sealing.
I always use a thin film of silicone around all intake and water ports to help with any mis-match but not sure if you have done this.
Also, I never use front/rear intake manifold gaskets, instead I just use about a 3/8' tall bead of silicone to seal the end rails of the intake to the block. This guarantees that the intake doesn't sit too high on those end rail gaskets causing leaks around the intake ports.

ks
 

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Discussion Starter · #13 ·
If you are trying to troubleshoot a vacuum to your crankcase then don't add anymore vacuum hoses. Unhook EVERYTHING to the intake. Every single tiny hose that either goes to the valve covers or to the lifter valley on the bottom of the intake, etc..

Once there is no vacuum source to the crankcase then start it up and see if there is a vacuum being pulled by removing the oil fill cover and put your hand over it. If there is still a strong vacuum then it has to be intake or valve guides.

With absolutely no vaccum source there should be a slight amount of pressure developing inside the crankcase that will puff out steam/smoke or ?? out of the oil fill hole.

ks
Ok. I have eliminated all vacuum over the summer with the holley on there. I will eliminate it all tomorrow and fire it again and check it. Good to hear there is no way its in the lower end it sounds like. Can’t believe this thing has beaten me like this.
 

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A broken bottom end (rings/piston, head gasket, etc) usually produces pressure and blows smoke out the breathers like a choochoo train.
It's definitely topend just need to isolate areas...

ks
 

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Discussion Starter · #15 ·
A broken bottom end (rings/piston, head gasket, etc) usually produces pressure and blows smoke out the breathers like a choochoo train.
It's definitely topend just need to isolate areas...

ks
Awesome! Guess i need to really concentrate on this upper area and find it. I will start by unhooking all vac lines and then do another leak down test to make sure valve seals and guides are good? Maybe blow smoke through the dipstick?
 

· Dean Scheidt
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I will try and move it before the blade. I would have to drill into this Anderson pipe to do it but if that would cure my issue im all about it!
Here is how I routed my fresh air line with the Anderson pipe. I drilled a hole in the rubber elbow and screwed a brass elbow into it. I modified the factory line to connect the oil filler tube to the intake elbow. This worked great for me.
Automotive fuel system Automotive design Motor vehicle Auto part Rim
 
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Here is how I routed my fresh air line with the Anderson pipe. I drilled a hole in the rubber elbow and screwed a brass elbow into it. I modified the factory line to connect the oil filler tube to the intake elbow. This worked great for me.
View attachment 1092727
That’s fine provided you don’t have a centrifugal supercharger or turbo. If you do you can’t put it there.
 

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You need a PCV valve on one valve cover and a VENT on the other valve cover to allow your PCV to work correctly..
I am guessing your PCV is drawing a vacuum with NO source of air INTO the engine... I have seen this before..
 
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