Excessive oil pressure (80psi +)
Thread Starter
Racer
Joined: Jul 2004
Posts: 441
Likes: 1
From: Windsor Ontario
Excessive oil pressure (80psi +)
I just totally rebuilt my 350 in my 74 vette and when I start it the oil pressure guage pins past the 80 psi mark and blows the dipstick out and oil as well. What could be the problem?
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Thread Starter
Racer
Joined: Jul 2004
Posts: 441
Likes: 1
From: Windsor Ontario
I used a melling high volume oil pump but that shouldn effect the pressure, should it?
I didn't run the engine long to seat the ring, it was blowing oil and the pressure was too high so I shut it down.
I didn't run the engine long to seat the ring, it was blowing oil and the pressure was too high so I shut it down.
Racer
Joined: Aug 2006
Posts: 330
Likes: 3
From: Wellington, New Zealand
I have the same pump and also get 80+ psi, if your blowing the dipstick then the block is pressurising. This could be due to blow by from new rings not yet seated properly or you need more breathing from the rocker covers. Are you running a pcv valve or a large rocker cover breather?
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Racer
Joined: Aug 2006
Posts: 330
Likes: 3
From: Wellington, New Zealand
Well you can't get better breathing than that! The high oil pressure would not be the problem with the popping dip stick, the only thing that can do that is excessive pressure in the block while the engine is running. If this is a brand new start up motor then you must be getting a lot of blow by from the rings. Is it pushing oil out through the dip stick tube?
Burning Brakes
Joined: Feb 2002
Posts: 752
Likes: 31
From: Melbourne Australia
What am I missing???
How can you get enough crankcase pressure to blow the dipstick out if both rocker cover vents are open and the oil drain holes in the heads are open to the crankcase?
I would not have thought that was possible? What do you think?
Could wrong head gaskets seal the crankcase or gaskets incorrectly installed?
Cheers,
Joe
I would not have thought that was possible? What do you think?
Could wrong head gaskets seal the crankcase or gaskets incorrectly installed?
Cheers,
Joe
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Yes it will. When I got my car it also had a melling HV pump on it and it buried the gauge when cold and still had excessive pressure hot. The HV pump is +20% volume and all that extra oil still has to go through the same size passages = more pressure. I switched to a normal melling pump and the pressures were fine, 30 PSI hot idle and 60 PSI at high rpm.
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
It does sound extreme. Maybe the valve covers are baffled and that creates enough of a restriction to build pressure? I know people that break piston ring lands will blow the dipsticks out so it's certainly possible.
Burning Brakes
Joined: Oct 2004
Posts: 904
Likes: 0
From: Murphy NC
How can you get enough crankcase pressure to blow the dipstick out if both rocker cover vents are open and the oil drain holes in the heads are open to the crankcase?
I would not have thought that was possible? What do you think?
Could wrong head gaskets seal the crankcase or gaskets incorrectly installed?
Cheers,
Joe
I would not have thought that was possible? What do you think?
Could wrong head gaskets seal the crankcase or gaskets incorrectly installed?
Cheers,
Joe
Thread Starter
Racer
Joined: Jul 2004
Posts: 441
Likes: 1
From: Windsor Ontario
Thanx everyone for all you help and ideas. I was a fresh rebuild but the only stock part was the block. .030 over, 480 lift comp cam, 64cc dart iron eagle heads, scat crank and rods. it should be about 400-425 hp. The problem was with the dipstick was because the rings weren't seated yet. I have a 7 quart oil pan and took about a quart out and that stopped the blow out. Thanx again for all you helpful advice.....
Happy cruisin'
Happy cruisin'
Drifting
Joined: Nov 2004
Posts: 1,627
Likes: 293
2020 C3 of the Year Finalist - Modified
I'm running a 10% higher volume melling pump on my 383. my gauge read fine on my fresh motor until about 3-4 weeks after driving it......after that, it began to read around 80 and a few starts/drives later it was pegged out all the way.
i pulled the sensor and cleaned up terminal and worked fine for a few days....now it's pegged out again.....
i pulled the sensor and cleaned up terminal and worked fine for a few days....now it's pegged out again.....
Racer
Joined: Dec 2006
Posts: 416
Likes: 40
From: Swansea IL
Oil Pressure
I think that people get fixated on having high oil pressure.
Most pro-racing engine builders will tell you that you need 10 psi for every 1000 rpm on the engine. That is more than enough to keep the SB or BB engines alive.
Going to HV or HP pumps does two things:
Takes more HP do drive
Adds additional heat to the oil
Oil seals have to work harder to keep the engine dry
Unless you have a special application, road racer, serious drag racer, the stock pumps and pans work very well.
Guess that is why the aftermarket is so successful. All of we gearheads think that we can engineer the car and engine better than a multi-million dollar manufacturer.
If it is on the street, stock stuff goes a long way.
RGDS
Bob
Most pro-racing engine builders will tell you that you need 10 psi for every 1000 rpm on the engine. That is more than enough to keep the SB or BB engines alive.
Going to HV or HP pumps does two things:
Takes more HP do drive
Adds additional heat to the oil
Oil seals have to work harder to keep the engine dry
Unless you have a special application, road racer, serious drag racer, the stock pumps and pans work very well.
Guess that is why the aftermarket is so successful. All of we gearheads think that we can engineer the car and engine better than a multi-million dollar manufacturer.
If it is on the street, stock stuff goes a long way.
RGDS
Bob