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Venting SBC fuel pump area

General engine tech -- Drag Racing to Circle Track

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tenxal
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Venting SBC fuel pump area

Post by tenxal » Sun Nov 10, 2019 8:50 am

Couple of questions re: venting the fuel pump area on a SBC to an external vent can.

- Is the drain back to the crankcase enough to allow a flow volume that could be helpful in reducing pumping losses ?

- Would it be better to plug the fuel pump push rod bore to stop the oil draining into this area or leave it open?

Application is a mild drag race SBC, real world experience and pro/cons appreciated.

Thanks! :)

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Re: Venting SBC fuel pump area

Post by Coloradoracer » Sun Nov 10, 2019 10:07 am

Put a block off plate on it and be done with it. Some guys will run a hose from the fuel pump boss to a valve cover to "balance" the crankcase pressure. There is too much oil down there to use it as a vent. Just go off a valve cover breather hole if your covers have them, or add in one if they don't. Then you can run either evac tubes to the headers or a vac pump. Just have to make sure the engine is SEALED or there isn't any benefit.....
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tenxal
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Re: Venting SBC fuel pump area

Post by tenxal » Sun Nov 10, 2019 11:28 am

Coloradoracer wrote:
Sun Nov 10, 2019 10:07 am
Put a block off plate on it and be done with it. Some guys will run a hose from the fuel pump boss to a valve cover to "balance" the crankcase pressure. There is too much oil down there to use it as a vent. Just go off a valve cover breather hole if your covers have them, or add in one if they don't. Then you can run either evac tubes to the headers or a vac pump. Just have to make sure the engine is SEALED or there isn't any benefit.....
Can't run an evac system per rule. Any experience with blocking the fuel pump push rod hole to minimize the oil accumulation in there?

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Re: Venting SBC fuel pump area

Post by Coloradoracer » Sun Nov 10, 2019 12:03 pm

tenxal wrote:
Sun Nov 10, 2019 11:28 am
Can't run an evac system per rule. Any experience with blocking the fuel pump push rod hole to minimize the oil accumulation in there?
Can't run an evac system, but can run breathers? If so, just go off valve covers. The pushrod hole is not where the oil comes from.....the pump boss is open to the crankcase, and there is a TON of oil being slung around there....

What exactly can you run per the rules?
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Re: Venting SBC fuel pump area

Post by tenxal » Sun Nov 10, 2019 12:39 pm

Coloradoracer wrote:
Sun Nov 10, 2019 12:03 pm
tenxal wrote:
Sun Nov 10, 2019 11:28 am
Can't run an evac system per rule. Any experience with blocking the fuel pump push rod hole to minimize the oil accumulation in there?
Can't run an evac system, but can run breathers? If so, just go off valve covers. The pushrod hole is not where the oil comes from.....the pump boss is open to the crankcase, and there is a TON of oil being slung around there....

What exactly can you run per the rules?
Can't run an evac system or a vacuum pump. On the engine stand, there is a bunch of oil that comes down the fuel pump push rod hole when running the oil pump. Blocking the hole with a shortened fuel pump push rod showed minimal oil into the area.

Thoughts?

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Re: Venting SBC fuel pump area

Post by Kevin Johnson » Sun Nov 10, 2019 1:31 pm

If you are set on using that opening (with blocked pushrod hole as you mentioned) you should fabricate some sort of baffle to shield the opening from the direct blast of windage flow.

Four years ago: viewtopic.php?f=1&t=43244#p549831

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Re: Venting SBC fuel pump area

Post by BOOT » Sun Nov 10, 2019 5:02 pm

If you loop it to the head then you could always add another breather to that valvecover.
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Re: Venting SBC fuel pump area

Post by vortecpro » Sun Nov 10, 2019 6:05 pm

Nyhus got you thinking LOL :D
Racing a NA NHRA stocker should be mandatory before any posting.

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Re: Venting SBC fuel pump area

Post by Coloradoracer » Sun Nov 10, 2019 7:35 pm

To the best of my knowledge, breathers on valve covers are not considered crankcase evacuation. What class are you running in?? What sanctioning body? Still think you're wasting your time connecting anything to the fuel pump boss but that's just me. If you can have a breather tank there and meet the rules you can have one on the valve covers and not have to deal with the oil flow that present there.
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Re: Venting SBC fuel pump area

Post by tenxal » Mon Nov 11, 2019 8:06 am

Coloradoracer wrote:
Sun Nov 10, 2019 7:35 pm
To the best of my knowledge, breathers on valve covers are not considered crankcase evacuation. What class are you running in?? What sanctioning body? Still think you're wasting your time connecting anything to the fuel pump boss but that's just me. If you can have a breather tank there and meet the rules you can have one on the valve covers and not have to deal with the oil flow that present there.
The engine is already well vented. Class rules (NHRA Stock Eliminator) prohibit any sort of pan evac. system. After blocking the push rod hole, the oil flow to the fuel pump area is markedly reduced so that leaves the oil control to be about what the windage tosses up there. I've got a rudimentary baffle designed that should suffice for that.

Since this class is restricted to using a stock or accepted replacement pan, could the added volume of a breather system serve as a way to 'increase' oil pan volume, giving the crank case windage extra volume to expand into and reduce pumping losses? Or is the volume of a breather can system not enough to markedly change anything? Directly venting the pan is a possibility, though less preferable.

I did some work in this area a while back with mixed results and shelved the project to concentrate on other areas. The small, oval shaped drain back to the crank case does act as a significant venturi and the pressure is pretty significant. One thing is for sure...what's going on in those oil pans is impressive, to say the least! :shock:

Thoughts?

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Re: Venting SBC fuel pump area

Post by tenxal » Mon Nov 11, 2019 8:09 am

vortecpro wrote:
Sun Nov 10, 2019 6:05 pm
Nyhus got you thinking LOL :D
Was good to catch up with you. Thinking is the best part of racing this class! :wink:

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