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SBC mechanical fuel pump oil seal issues
Posted: Sun Oct 08, 2017 7:35 pm
by Kev7s
We run circle track cars will SBC Holley mechanical style fuel pump. Have too because of the rules. The style pump we run has a 1/8" npt. We have a barbed fitting with a hose run up to a small k&n breather filter laying on intake. We get about 4-5 nights out of the pumps (C&S pumps ) before its pushing engine oil out the vent filter. We run a dart little M block but have had same problems with stock blocks but it's worst with dart. Have any pointers?
Re: SBC mechanical fuel pump oil seal issues
Posted: Sun Oct 08, 2017 8:05 pm
by pamotorman
do dart blocks have the oil drain back hole in the bottom of the pump boss cavity ?? any excess oil on the cavity should drain back into the oil pan when the engine is shut down.
Re: SBC mechanical fuel pump oil seal issues
Posted: Sun Oct 08, 2017 8:08 pm
by psychomotors
pamotorman wrote: ↑Sun Oct 08, 2017 8:05 pm
do dart blocks have the oil drain back hole in the bottom of the pump boss cavity ?? any excess oil on the cavity should drain back into the oil pan when the engine is shut down.
This is what I was thinking also , if I understand the problem correctly. If the drain back hole is not present , can it be drilled?
Re: SBC mechanical fuel pump oil seal issues
Posted: Sun Oct 08, 2017 8:14 pm
by Kev7s
Not sure on drain back hole or size I will check tomorrow.
Re: SBC mechanical fuel pump oil seal issues
Posted: Mon Oct 09, 2017 12:15 pm
by Newold1
You really have to have an oil drain back hole to get the mechanical pump seals to live and if your crankcase pressures get to high then you need vacuum if rules allow. You might also try one of Pro/Cams mechanical pumps as I heard they are better than the aftermarket Holley type pumps.
Re: SBC mechanical fuel pump oil seal issues
Posted: Mon Oct 09, 2017 9:03 pm
by Kev7s
image.jpg
there is a oil return hole and it is open to crankcase.
I measured the fuel pump push rod and is within .003". I was rod was worn and letting to much oil passed. Running out of ideas. Thanks for the help.
Re: SBC mechanical fuel pump oil seal issues
Posted: Mon Oct 09, 2017 9:18 pm
by cgarb
There should be an oil seal that the pump diaphragm rod goes up through in the top half of the pump. That is supposed to separate the oil from the crankcase from the diaphragm vent. Last pump I saw that leaked oil that was torn. Do you have to clock the pump to install these on the engines? Maybe you are damaging the seal when removing it somehow? Have you contacted C&S they were decent to deal with when I called them about mine. They have a 1 year warranty he explained to me, they would repair it if it failed within 1 year.
Re: SBC mechanical fuel pump oil seal issues
Posted: Mon Oct 09, 2017 9:27 pm
by Kev7s
cgarb wrote: ↑Mon Oct 09, 2017 9:18 pm
There should be an oil seal that the pump diaphragm rod goes up through in the top half of the pump. That is supposed to separate the oil from the crankcase from the diaphragm vent. Last pump I saw that leaked oil that was torn. Do you have to clock the pump to install these on the engines? Maybe you are damaging the seal when removing it somehow? Have you contacted C&S they were decent to deal with when I called them about mine. They have a 1 year warranty he explained to me, they would repair it if it failed within 1 year.
I have clocked the pumps in the passed but all have been set for a few years. I have new seals, I been replacing them myself there is no signs of being tore and I had c&s do all three pumps we have over the winter. All three same thing ran 3-4 races and it blows oil out vent.
Re: SBC mechanical fuel pump oil seal issues
Posted: Mon Oct 09, 2017 9:36 pm
by cgarb
What type of breathers are on the engine? That seal is just a little grommet, I wouldn't think it would take much crankcase pressure to bypass oil past it.
Re: SBC mechanical fuel pump oil seal issues
Posted: Mon Oct 09, 2017 9:48 pm
by Kev7s
cgarb wrote: ↑Mon Oct 09, 2017 9:36 pm
What type of breathers are on the engine? That seal is just a little grommet, I wouldn't think it would take much crankcase pressure to bypass oil past it.
image.jpg
like this
Re: SBC mechanical fuel pump oil seal issues
Posted: Mon Oct 09, 2017 10:50 pm
by cgarb
You get much oil out of those? Just wondering if the motor has a good amount of blow-by. I saw a guy assemble a motor with the rings in upside down and it created a whole mess of problems. He had oil blowing out of every orifice possible.
Re: SBC mechanical fuel pump oil seal issues
Posted: Tue Oct 10, 2017 8:15 am
by Kev7s
cgarb wrote: ↑Mon Oct 09, 2017 10:50 pm
You get much oil out of those? Just wondering if the motor has a good amount of blow-by. I saw a guy assemble a motor with the rings in upside down and it created a whole mess of problems. He had oil blowing out of every orifice possible.
None, I wash the filters every week, I would think if had blow-by I would see some thing coming out of them.
Re: SBC mechanical fuel pump oil seal issues
Posted: Tue Oct 10, 2017 8:28 am
by Dave Koehler
I am not up on what seals this pump uses but a couple of generic things come to mind.
1:Since it's not blowing out the V covers it is likely not a pressure issue.
If running alky is the seal material compatible?
Same question about the diaphragm.
2: Is it is creating a real big mess that could cause you to lose a race or get a black flag?
If so this leads to...what about mounting a fitting and dump that uncontrollable oil into a catch can with filter vent?
Re: SBC mechanical fuel pump oil seal issues
Posted: Tue Oct 10, 2017 10:13 am
by FC-Pilot
I have used two dart SBC's and on both the drain back from the fuel pump barely broke through into the crankcase. We had to get the grinder out and open it up. Next time you have the engine torn down you may want to check that. That could definitely prevent proper oil drainback.
Paul
Re: SBC mechanical fuel pump oil seal issues
Posted: Tue Oct 10, 2017 10:34 am
by Kev7s
Dave Koehler wrote: ↑Tue Oct 10, 2017 8:28 am
I am not up on what seals this pump uses but a couple of generic things come to mind.
1:Since it's not blowing out the V covers it is likely not a pressure issue.
If running alky is the seal material compatible?
Same question about the diaphragm.
2: Is it is creating a real big mess that could cause you to lose a race or get a black flag?
If so this leads to...what about mounting a fitting and dump that uncontrollable oil into a catch can with filter vent?
We run Sunoco standard 110 race gas,not getting black flagged but its a mess, the real problem is the pump stops pumping because it has to push the oil out the vent, so its is like it hydraulics because oil on the top of diaphragm.