Stock mechanical fuel pump output?

[e rock]

How much can I reasonably expect the stock mechanical fuel pump on a '71 350 to put out?

The new motor has considerably more power and will be running a ~700cfm Holley, but I'm told that I should have at least a 750cfm on it. The builder says redline is around 7500rpm, but I'm not racing it and realistically it'll just be serving daily driver duties. I have a Mallory 110 electric pump (and 140 filter) that I can put in, but I'd rather keep it simple if possible. I know there are high-output mechanical pumps as well - are they worth the $$$?

Thanks,
Eric

[72 cheyenne pdx]

Does the 110 mean the PSI? If so, a carburator is only designed to handle from up to about 7 PSI.

[70c10]

I think stock output is around 60-70GPH.
More info on Holley's site:http://www.holley.com/data/Products/...ech%20Info.pdf
I would run a Carter personally.

[RACINJASON22]

110 probably means GPH.

No you won't need that IMO.

I have run nothing but the Carter line of mechanical pumps and, many times stock over the counter fuel pumps on even many of my race (Circle Track) engines. Never a problem.

Also IMO the 700 cfm carb will be more than enough to supply a built 350 SBC. Specialy on a daily driver.

Summit Carter Fuel Pumps LINK

RJ22

[e rock]

Originally Posted by 72 cheyenne pdx

Does the 110 mean the PSI? If so, a carburator is only designed to handle from up to about 7 PSI.

110gph free flow. ~90gph @ 6psi.


Thanks for the link and recommendations. I think I'm settled on keeping the mechanical setup now and if the stock pump gives me problems, I'll order one of those Carters. Even the sub-$40 stuff looks like it would be fine for what I need. That's considerably cheaper than the $100+ ones I'd seen before.

[RACINJASON22]

e rock I have ran the 23 and 24 dollar Carters more than any of the ones listed there with no problems at all.

IMO your stock pump will suit your needs fine and do as you stated if you have problems.

Note the Carter Pumps are rebuildable but who would at the prices they sell for

RJ22

[Billla]

Stock pumps deliver about 60 GPH @ about 6 PSI.

There are typically two types of aftermarket mechanical pumps based on if an external regulator is required (output PSI > 7 PSI)

It's pretty tough to flow 110 GPH unless you're well over 1.4 HP/CID.

[KFreddy]

For a 350 ci. spinning like a Honda at 7500 RPMs that 700 cfm holley should be just fine. At 83% volumetric efficiency your engine needs 631 cfm, same motor at 90% efficiency need 684 cfm. You should be good to go with the carb you have.

For comparison I'm using an old school 3310 Holley/ vacuum secondaries on a ZZ454, top RPM 5800 when I'm killing it, at 83% volumetric efficiency the engine needs 632 cfm, at 90% volumetric efficiency, pipe dream here, I require 686 cfm.

[e rock]

Originally Posted by KFreddy

For a 350 ci. spinning like a Honda at 7500 RPMs that 700 cfm holley should be just fine. At 83% volumetric efficiency your engine needs 631 cfm, same motor at 90% efficiency need 684 cfm. You should be good to go with the carb you have.

For comparison I'm using an old school 3310 Holley/ vacuum secondaries on a ZZ454, top RPM 5800 when I'm killing it, at 83% volumetric efficiency the engine needs 632 cfm, at 90% volumetric efficiency, pipe dream here, I require 686 cfm.

See, I guess I'm fuzzy on estimating volumetric efficiency (or what it really means). I found one online calculator that had options for "stock" "mildly built" "built" and "full-on race" (or something similar), which I assume to be estimations of VE. While I'm definitely not racing with it (and rarely exceeding 5K rpm I'm sure), this motor was originally built to run 1/4s, so I was basing my estimations on that.

It's funny you mentioned that carb - it's the same one that came with the motor. I don't know anything about it... Do you know if it's possible to convert to an electric choke?



Thanks a ton guys. It's always nice to have some confirmation before blindly spending money.

[Billla]

VE is basically the ratio of the maximum physical volume in the engine to the attainable physical volume.

The approach to calculating (ROUGHLY) VE is the formula:

VE = (HP * 792001.6)/(AP * CR * CID * RPM)

AP = Atmospheric pressure in PSI = Pressure in Hg * .49113, or use 14.7 as a good rule of thumb value (standard pressure = 29.92 Hg)

Applying this, a 330 HP 350 turning 6500 RPM will approach 75% VE.

As for the carb, very simple as pointed out:

CFM = ((CI x RPM)/3456) x VE

So in your case 570 CFM...PLENTY of room


This electric choke conversion will work - the 3310 is basically a 4160 with a secondary metering block vs. a metering plate.

http://store.summitracing.com/partde...5&autoview=sku

[Billla]

BTW, there's a great article on estimating fuel needs at the link below:

http://www.chevyhiperformance.com/te...r_fuel_system/

In a nutshell:
Pounds of gasoline/hr = HP x BSFC, BSFC = .55 for a carb engine
GPH = (pounds of gasoline/hr)/6.2

[e rock]

I :heart: this place.

Thanks Billla. BTW - from your avatar - you live in the Farm?

[Billla]

Originally Posted by e rock

Thanks Billla. BTW - from your avatar - you live in the Farm?

Yep :-D I see you're in Monroe too - whereabouts? Come help me with a '74 Blazer HEI install :-D

[e rock]

Originally Posted by Billla

Yep :-D I see you're in Monroe too - whereabouts? Come help me with a '74 Blazer HEI install :-D

I'm in the middle of the Fryelands. Once I get this motor back in the 71 (and my own HEI), I'd definitely be up for lending a hand.

[Billla]

Originally Posted by e rock

I'm in the middle of the Fryelands. Once I get this motor back in the 71 (and my own HEI), I'd definitely be up for lending a hand.

Well, if I can help in any way drop me a line! billla@warbird.org.

Hope to see you at the swap meet!