Mechanical Fuel Pump for Drag Race

[skinny z]

BYPASS regulator.
It's a game changer with respect to heat soak.
Of course proper fuel line management is important but keeping the fuel circulating is the way to go IMO.

[F-BIRD'88]

True but you don't even need a bypass regulator.
Just a small orifice bleed after the carb on the carb fuel line splitter.. A simple small say .030"- .040" bleed to the fuel return line ensures some fuel is always recirculating back to the fuel tank when ever the engine is running.

Back in the day the OEM factory fuel filters had this built in simple bleed orifice with ¼" or 5/16" return line to the tank "fuel vapour return line" Again people would remove these OEM fuel filters with return line not understanding the function or too cheap to buy a OEM replacement from the GM dealer parts counter..
It burps out any excessive fuel pressure and vapour in a hot fuel line near the carb. If you look around you can still buy these OEM replacement fuel filters with the extra lil fitting on them.. Thats the return line.

[F-BIRD'88]

On those Holley carb fuel line splitter that lil ¼" fuel fitting is not just for a fuel pressure guage. Its real purpose is adding a simple small bleed orifice fuel return line to the fuel tank. When you plumb the fuel system correctly yiu do not need a fuel pressure gauge.
A simple low cost reliable narrow band O2Senor AFR guage tell you SO MUCH MORE about you fuel system dynamic performance. If the carb is being starved for fuel at WOT at any point running down the track it WILL clearly show up on that N/B AFR guage way before you can detect it.

[amc fan]

3/8" tubing has a diameter of 5/16"if it is 1/32" wall thickness. Flow velocity through pipe/Hose varies inversely as the square of the inside diameter. Doubling the inside diameter increases the area 4 times. You want a good size diameter at least 1/2" inside diameter. Fuel/fluid is pushed not drawn into a pump. Atmospheric pressure equals 14.7PSIA at sea level. A pump does not pump pressure; its purpose is to create flow. Pressure is caused by resistance to flow. There must be a pressure drop (pressure difference) across an orifice or restriction to cause flow through it. Conversely, if there is no flow, there will be no pressure drop. Thanks to my Industrial Hydraulics instructor Rich Yanza from Applied Motion Technologies for the information. I hope it sheds some light into addressing your problem.

[1980RS]

I have a old NASCAR mechanical fuel pump I should show you. I guess this thing moves the fuel volume pretty good. I will get a picture of it.

[Tom68]

I have a old NASCAR mechanical fuel pump I should show you. I guess this thing moves the fuel volume pretty good. I will get a picture of it.

Here ya go
Carter with the higher pressure spring, late 90's -10 in - 8 out. This is an earlier one -8 in. We could eventually get them with big enough ports so we didn't have to weld the fittings on. There was no tricks inside, and no need for a regulator. Last car I was involved with was 666hp unleaded 9.5:1. We were making more earlier with Unocal Nascar fuel and no comp limit.

20220830_064709.jpg

Edit, still got a couple, when we switched to unleaded the pumps got unreliable, Goss gave me some replacement valves to try but I never got around to it.

Fuel Pumps.JPG

[skinny z]

What kind of service life would get out of the pump pushrod?
Or the cam lobe? See the picture above for the results of the 110 Edelbrock on my cam pump eccentric.
This was a street/strip deal with average mileage.
But past the days of engine oil with high pressure additives.

[Tom68]

What kind of service life would get out of the pump pushrod?
Or the cam lobe? See the picture above for the results of the 110 Edelbrock on my cam pump eccentric.
This was a street/strip deal with average mileage.
But past the days of engine oil with high pressure additives.

No problems with the race motors, we were flat tappet limited for about 6 years then roller cam 9.5:1 for the next 6 years. Pushrods were tipped hollow tube. CV Products supplied all the reliable stuff back then.

[skinny z]

For the record, I'm not disputing the effectiveness of a return-less mechanical pump doing the job.
I ran one successfully but that was in the days of flat tappet cams from the OEMs and better oil.

But I'm thinking this conversation is more about the fuel boiling in the lines. Especially when hanging out at the drag strip waiting in the lanes. The NASCAR boys don't have that hassle. And I can imagine the amount of fuel that went through that pump posted above would do a pretty good job of pulling away any heat.

[skinny z]

What kind of service life would get out of the pump pushrod?
Or the cam lobe? See the picture above for the results of the 110 Edelbrock on my cam pump eccentric.
This was a street/strip deal with average mileage.
But past the days of engine oil with high pressure additives.

No problems with the race motors, we were flat tappet limited for about 6 years then roller cam 9.5:1 for the next 6 years. Pushrods were tipped hollow tube. CV Products supplied all the reliable stuff back then.

That's the luxury of a racing engine. Frequent inspections and top quality parts.

[F-BIRD'88]

Another method of purging the HEAT Soaked hot fuel from the fuel lines and fuel pump is to install a fuel solenoid (nitrous system part) to the fuel bypass return line. Fire the engine up. Raise the idle rpm and open the fuel purge bypass solenoid. Now most all of the fuel will run thru the fuel system and pump and back to the gas tank carrying excess HEAT with it. That will cool off the heat soaked fuel pump and the fuel lines on the whole csr.
When done close the fuel purge bypass solenoid and you are ready to race without the hot soak fuel delivery issues.

[1980RS]

I have a old NASCAR mechanical fuel pump I should show you. I guess this thing moves the fuel volume pretty good. I will get a picture of it.

Here ya go
Carter with the higher pressure spring, late 90's -10 in - 8 out. This is an earlier one -8 in. We could eventually get them with big enough ports so we didn't have to weld the fittings on. There was no tricks inside, and no need for a regulator. Last car I was involved with was 666hp unleaded 9.5:1. We were making more earlier with Unocal Nascar fuel and no comp limit.

20220830_064709.jpg


Edit, still got a couple, when we switched to unleaded the pumps got unreliable, Goss gave me some replacement valves to try but I never got around to it.

Fuel Pumps.JPG

This is the one I have,

20200228_124710.jpg

[Monza355]

I have a old NASCAR mechanical fuel pump I should show you. I guess this thing moves the fuel volume pretty good. I will get a picture of it.

Here ya go
Carter with the higher pressure spring, late 90's -10 in - 8 out. This is an earlier one -8 in. We could eventually get them with big enough ports so we didn't have to weld the fittings on. There was no tricks inside, and no need for a regulator. Last car I was involved with was 666hp unleaded 9.5:1. We were making more earlier with Unocal Nascar fuel and no comp limit.

20220830_064709.jpg


Edit, still got a couple, when we switched to unleaded the pumps got unreliable, Goss gave me some replacement valves to try but I never got around to it.

Fuel Pumps.JPG

This is the one I have,
20200228_124710.jpg

Weren’t these called race pumps or something like that. Claimed to pump 450 gph or something like that !

[prairiehotrodder]

My first thought is that you don't need that regulator at all. And a true 3/8 ID fuel line with no restrictions should be enough at the mid 12 second level.
Brian

[F-BIRD'88]

The combined flow area of TWO standard .110" holley needle seats is equal to a ID of 5/32". Why would you need much more fuel line/fuel fitting ID minimun size than ¼"…? A 3/8" ID fuel line is a 7/16" diameter tube OD.
The in/out fittings on that pump is ⅜ NPT.
Will only take so big a fitting. The ID of such a ⅜" NPT fitting will be ¼" (.25") tops. The ID of ⅜" fuel line is 5/16". Its plenty big.

A .25" ¼" ID is 2.50 times the combined flow AREA of two holley .110" needle seats.