Oil inside the intake, why?
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Teching In
Joined: Aug 2008
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From: Braidwood, Il. USA
Oil inside the intake, why? I just pulled the carbs (2 edelbrock 600 carbs) off my rebuilt 4oo sbc engine and see oil inside of the intake manifold, could it be that I don't have a pcv valve on the engine?
Also when idling and you rev the engine between 1400- 2000 rpm the inside of the car vibrates so bad you can't read the gauges, at idle its VERY smooth.
The engine was just rebuilt, new rings, a small roller cam and new heads and valves. Please help because I'm lost and don't know what to do.
Also when idling and you rev the engine between 1400- 2000 rpm the inside of the car vibrates so bad you can't read the gauges, at idle its VERY smooth.
The engine was just rebuilt, new rings, a small roller cam and new heads and valves. Please help because I'm lost and don't know what to do.
Last edited by sunnyd 95; Feb 18, 2010 at 07:17 PM.
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Joined: May 2009
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From: over dere
I just pulled the carbs (2 edelbrock 600 carbs) off my rebuilt 4oo sbc engine and see oil inside of the intake manifold, could it be that I don't have a pcv valve on the engine?
Also when idling and you rev the engine between 1400- 2000 rpm the inside of the car vibrates so bad you can't read the gauges, at idle its VERY smooth.
The engine was just rebuilt, new rings, a small roller cam and new heads and valves. Please help because I'm lost and don't know what to do.
Also when idling and you rev the engine between 1400- 2000 rpm the inside of the car vibrates so bad you can't read the gauges, at idle its VERY smooth.
The engine was just rebuilt, new rings, a small roller cam and new heads and valves. Please help because I'm lost and don't know what to do.
a 400 sb is an externally balanced engine. the balancer shouldhave a groove cut half way around it,
and the flywheel should have a weight welded on it if it's an auto, or holes drilled in it if it's a manual. if you dont have either of these it will cause the vibration you are experiencing. this will kill either your crank or trans pump quite quickly.
the pcv valve can hurt you either way,
if you have a pcv valve then oil/oil vapor can get past it and load up the intake. It can especially happen if there are no baffles around the vent port in the valve cover- so i would check your valve covers and if there's just a hole for the pcv valve or breather then that will most likely be a problem regardless- either plug that vent hole and don't use it or get a valve cover that properly baffles the pcv hole.
if you don't have a pcv valve then the next question is do you have the crankcase vented properly? If not then you will have pressure building up in the crankcase, the worst thing happening is blowing out the front and/or rear main crankshaft seals causing massive oil leakage, but the first and most likely problem is oil/oil vapor getting pushed up through any vent hose going to the carb or intake, and also oil pushing past the intake valvestem seal and guide into the combustion chamber but you would not see this in the intake. Because you say you can see oil in the intake tells me it's not so much an intake gasket because where oil would get in because of that you wouldn't see by looking down the top of the intake from where the carb mounts.
And what you can also do is rig up a fuel pressure / vacuum gauge, you need one that has resolution to a 1/4 or 1/2 psi, and measure crankcase pressure. You should have at most 1 psi pressure at any rpm in neutral no load, and ideally have slightly negative pressure which means the pcv system is working. If you get > 1 psi then you're crankcase is building up too much pressure which is bad, if it goes too negative then the inlet breather or vent is blocked or not big enough.
if you have a pcv valve then oil/oil vapor can get past it and load up the intake. It can especially happen if there are no baffles around the vent port in the valve cover- so i would check your valve covers and if there's just a hole for the pcv valve or breather then that will most likely be a problem regardless- either plug that vent hole and don't use it or get a valve cover that properly baffles the pcv hole.
if you don't have a pcv valve then the next question is do you have the crankcase vented properly? If not then you will have pressure building up in the crankcase, the worst thing happening is blowing out the front and/or rear main crankshaft seals causing massive oil leakage, but the first and most likely problem is oil/oil vapor getting pushed up through any vent hose going to the carb or intake, and also oil pushing past the intake valvestem seal and guide into the combustion chamber but you would not see this in the intake. Because you say you can see oil in the intake tells me it's not so much an intake gasket because where oil would get in because of that you wouldn't see by looking down the top of the intake from where the carb mounts.
And what you can also do is rig up a fuel pressure / vacuum gauge, you need one that has resolution to a 1/4 or 1/2 psi, and measure crankcase pressure. You should have at most 1 psi pressure at any rpm in neutral no load, and ideally have slightly negative pressure which means the pcv system is working. If you get > 1 psi then you're crankcase is building up too much pressure which is bad, if it goes too negative then the inlet breather or vent is blocked or not big enough.
