SBC mechanical fuel pump oil seal issues

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Kev7s
Member
Member
Posts: 72
Joined: Wed Oct 24, 2012 9:33 am

SBC mechanical fuel pump oil seal issues

Post by Kev7s » Sun Oct 08, 2017 7:35 pm

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?

pamotorman
Guru
Guru
Posts: 2303
Joined: Thu Mar 06, 2014 11:55 pm

Re: SBC mechanical fuel pump oil seal issues

Post by pamotorman » 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.

User avatar
psychomotors
Pro
Pro
Posts: 252
Joined: Sun Apr 27, 2014 8:20 pm
Location: East Bonne Terre
Contact:

Re: SBC mechanical fuel pump oil seal issues

Post by psychomotors » Sun Oct 08, 2017 8:08 pm

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?
Everyone appreciates your honesty , until you're honest with them , then you're an @$$hole.

Kev7s
Member
Member
Posts: 72
Joined: Wed Oct 24, 2012 9:33 am

Re: SBC mechanical fuel pump oil seal issues

Post by Kev7s » Sun Oct 08, 2017 8:14 pm

Not sure on drain back hole or size I will check tomorrow.

Newold1
Expert
Expert
Posts: 826
Joined: Fri Apr 08, 2016 9:50 am

Re: SBC mechanical fuel pump oil seal issues

Post by Newold1 » Mon Oct 09, 2017 12:15 pm

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.

Kev7s
Member
Member
Posts: 72
Joined: Wed Oct 24, 2012 9:33 am

Re: SBC mechanical fuel pump oil seal issues

Post by Kev7s » Mon Oct 09, 2017 9:03 pm

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.
You do not have the required permissions to view the files attached to this post.

cgarb
Guru
Guru
Posts: 1386
Joined: Wed Jul 09, 2014 11:50 am
Location: Maryland

Re: SBC mechanical fuel pump oil seal issues

Post by cgarb » 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.

Kev7s
Member
Member
Posts: 72
Joined: Wed Oct 24, 2012 9:33 am

Re: SBC mechanical fuel pump oil seal issues

Post by Kev7s » Mon Oct 09, 2017 9:27 pm

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.

cgarb
Guru
Guru
Posts: 1386
Joined: Wed Jul 09, 2014 11:50 am
Location: Maryland

Re: SBC mechanical fuel pump oil seal issues

Post by cgarb » 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.

Kev7s
Member
Member
Posts: 72
Joined: Wed Oct 24, 2012 9:33 am

Re: SBC mechanical fuel pump oil seal issues

Post by Kev7s » Mon Oct 09, 2017 9:48 pm

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
You do not have the required permissions to view the files attached to this post.

cgarb
Guru
Guru
Posts: 1386
Joined: Wed Jul 09, 2014 11:50 am
Location: Maryland

Re: SBC mechanical fuel pump oil seal issues

Post by cgarb » 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.

Kev7s
Member
Member
Posts: 72
Joined: Wed Oct 24, 2012 9:33 am

Re: SBC mechanical fuel pump oil seal issues

Post by Kev7s » Tue Oct 10, 2017 8:15 am

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.

User avatar
Dave Koehler
Guru
Guru
Posts: 3323
Joined: Mon Oct 04, 2004 11:19 pm
Location: Urbana, IL USA
Contact:

Re: SBC mechanical fuel pump oil seal issues

Post by Dave Koehler » 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?
Dave Koehler - Koehler Injection
Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."

User avatar
FC-Pilot
Pro
Pro
Posts: 219
Joined: Tue Mar 17, 2009 2:23 pm
Location: Peoria, AZ
Contact:

Re: SBC mechanical fuel pump oil seal issues

Post by FC-Pilot » Tue Oct 10, 2017 10:13 am

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
"The latest tests prove exactly what my money tells them to prove".

Kev7s
Member
Member
Posts: 72
Joined: Wed Oct 24, 2012 9:33 am

Re: SBC mechanical fuel pump oil seal issues

Post by Kev7s » Tue Oct 10, 2017 10:34 am

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.

Post Reply