HP eaten by fuel pump pushrod?

[65dragster]

I searched but didn’t find an answer. In a street driven SBC engine using a mechanical fuel pump and SFT cam, how much horsepower is lost vs using an electric pump? And, if I use a stronger pump, like an Edelbrock instead of a stock replacement pump, will I lose more HP? Anybody know what the HP loss is, at least approximately? Thanks!

[Nut124]

I do not have any test data. One way to estimate would be by using the formula for HP vs fluid pressure/flow:

Fluid HP = (flow rate (gpm) * dP (psig)) / 1714

So, a pump delivering 1gpm at 10spig would require 0.005HP at 100% efficiency to operate.

A similar electric pump often draws 3A at 12VDC = 36W or 0.05HP.

So, I would say, unless there are huge mechanical losses, that the effect of a mech fuel pump on HP is way less than 1HP.

[steve cowan]

Hopefully one of the stocker guys will post some results

[BillK]

What you have to keep in mind is that the electric pump also uses power, it is just taken from a different source, the alternator. There might be some friction loss from the mechanical pump but I would bet there is not that much difference.

[tenxal]

Hopefully one of the stocker guys will post some results

NHRA Stock Eliminator cars haven't had to use a mechanical fuel pump for many years so I doubt you'll find much in the way of A-B-A dyno results.

I've heard from reliable sources of 2-3 hp gains on Cup engines when the mechanical pumps were really well balanced and sorted out.

My guess is probably 4-5 h.p. lost at 7,000 on your average 450-500 hp SBC/BBC deal.

[65dragster]

Good input from everyone, thanks. I am not building a “last horsepower “ setup, so I’ll just run the mechanical pump for now. Do you think the mechanical pump pressure on the cam eccentric is a likely wear issue if I run Brad Penn oil?

[dannobee]

I've heard from reliable sources of 2-3 hp gains on Cup engines when the mechanical pumps were really well balanced and sorted out.

Would you happen to know if that was the old style block mounted fuel pump or the current cable drive pumps?

[tenxal]

This was with the engine mounted pumps.

[steve cowan]

Good input from everyone, thanks. I am not building a “last horsepower “ setup, so I’ll just run the mechanical pump for now. Do you think the mechanical pump pressure on the cam eccentric is a likely wear issue if I run Brad Penn oil?

I have used a Holley 200gph mechanical fuel pump for several years with no issues, I use a composite fuel pump push rod,again no real issues, yes they do wear slightly.
Having a fuel system that does not suffer from under bonnet heat issues is what I would focus on.

[mag2555]

Since Aluminum pump push Rods are offered for better pump arm control, my bet is that if the motor is Carborated then wild fuel pressure cycles on the needle and seat might have more of a effect on the hp seen at high fuel flow rates then the hp loss from the powering a machical pump .

If the need for good pump arm control is needed for more steady fuel volume flow out of the pump then maybe it's time to start making pumps with a Conical spring to maintain better overall control with less total pressure?

[54chevkiwi]

My engine which has since been sold, (512hp at 6000rpm 406sbc, straub roller cam) when dynoed showed no appreciable difference in power between my robbmc mechanical fuel pump with non roller non composite pushrod and the dynos electric fuel pump.
Engine was dynoed complete with alternator, mechanical waterpump and mechanical fuel pump. Only change made for that test was switching the fuel source to see what the mechanical one would do.

[cv67]

I use a Carter 172 mech pump, composite rod...they are so light I dont see how they could lose power. From the spring probably not measurable
Like the reliability of them, one less thing to leave you stranded. They last a long long time. NEver had an eccentric wear out