What is the GPH on stock 74 mech. pump?

With a warmed up motor (350-370 hp) is an upgrade required? If so, what GPH is recommended?

 

I have ran a stock replacement pump on a 400 hp 350 in my 73 with no fuel starve in the qtr mile. I think for anything under 400 hp you should be fine with a stock pump.

 

How would I know if it's starving unless there is a fuel pressure gauge (which I don't)?

 

A pressure gauge will not tell you if you have fuel starve, the eng will cut out on you like it is missing since it will be running lean. With an EFI system you can tell with a gauge since you need a certain amount of pressure for the injectors to spray right but with a carb once the floats open up your gauge will not show the diff between 1/4 bowl and 0 bowl of fuel.

You can take it to a dyno shop also and your a/f ratio will show if you are leaning out, prolly a safer way of telling then 1/4 mile passes.

 

Thanks. I plan to take it to dyno once all mods are done. Main reason is to tune the carb on the dyno for proper a/f ratio.

 

Any stock fuel pump with 3/8`s lines is adequate for nearly everything except supercharged engines.

 

no way dude! anything over 400 horse, i would recommend at least a aftermarket mechanical pump! its a big no brainer and its cheap insurance.over 500 horse its strictly electric pumps either alone or in tandem, with the stock pump. at that level id even rip out the small lines!

 

Beg to differ Dude, you have been bench racing too long. Try the real world. Chevy 427 L88`s, ZL1`s 454 LS7`s and the A990 Race Hemi all of which produce a conservative 550+ HP run stock pumps with 3/8`s lines. And the Hemi even has dual 4 bore Holleys on a cross ram manifold.

 

I'm also interested in the stock fuel pressure. I've heard Demons and Holleys run best on 6-7 psi and I'd like to make sure I'm in this range with the stocker if this is important.

Thanks.

 

Most pumps by AC or Carter as OEM performance Vette applications are in the correct range of 6-7 lbs, anything over will possibly blow the needle and seat off the carbs.

 

ok ill agree to a point. while these ultra rare engines youve listed used STOCK pumps, they are not the same as what you would find on a 70's something 350. what youve listed no dought was supplied with suffecient pumps and lines for the job. and while YOUR bench racing my friend, dont forget hp ratings in those days were based on an over all gross output, and seldom met their ratings. todays cars use a net based system. thats why youve got a 400 hp 2004 vette that can stomp a mudhole in your L88, ZL1, AND THE LS6. NOT 7.

 

Wrong again Dude, the L88, ZL1, LS6 and the LS7 uses the same stock performance pump as the L71,L72,and L78. And when your stock 400 hp 2004 starts running in the low 11`s then you can start comparing the new stuff with the old 60`s stock engines otherwise you will be in a mud hole. One other point, you have obviously never heard of the 454 LS7 over the counter crate engine. Look it up, it`s actually a little better in some aspects except for the iron heads. And if you think a L88 is only a 430 HP engine, by any HP standards your incorrect. Also i`m not a bench racer either, see for yourself about me and some of my friends and the toys we play with at, http://www.nitroalley.net But hell, is only great fun.

 

 

ok well agree to disagree. no i never heard of ls7 crate engine, but we were talking stock cars were we not? and i have no dought the factory race engines you listed had at the minimum better springs in the pump. and thats one item im sure any racer ripped off instanly! and you show me stock anything that could do an 11 from the 60's and ill eat my hat. i dont think even the cobra could do that, could it? truth is the hp ratings were funky back then. the c6 zo6 is gonna have 500 hp. at it is and will be fastest vette ever! so lets do some math, shall we? you claim 550+ and ALL those cars were slower than the new vette. stock anyway.and yes i understand that given modern tire tech, the old iron would catch up easily. i only wanted to say an aftermarket pump was the way for my man to go. it is cheap insurance, and can only help not hurt! so dont throw the insult so quick next time ( bench racer ). i grew up in the south, and you get a oily wrench as a chew toy when your born. been doing this stuff for a little while.

 

Coinsidence but i'm building a warmed-up 350" also in a '74. I spent a lot of time to build a recirc line for my carb since the Carter hi-po street pump i chose didn't use a vapor return. Drilled into the carb inlet to mount a tee for elect press sensor and recirc orifice. I didn't need this but i enjoy installing instruments and bending tubing - but it took serveral days to build and install. Now the recirc provides some constant flow to limit a static head when carb inlet needle shut/fuel bowl full. And constant flow prevents vapor lock when cruising around the desert hwys. But that stock pump had a vapor return to the tank and thats what i used for my recirc line to tank. Take a look at my set-up @ http://members.cardomain.com/cardo0.
But all this really overkill and ur stock pump and vapor recirc should be fine for ur (or my) mild 350" mtr. Stock pumps are designed to control press for ur carb (by internal bypass/regualtion). I was trying to improve the sys for future mtr upgrades - kinda WIAI since i wanted to use a hi-po pump with fuel press reg. But now i realize that mech fuel pumps are self reg and an inline fuel press reg just ads flow restriction to a mechanical pump. Press regs are really for hi-press/hi-flow electric pumps that would push fuel past the carb inlet needle & seat. In fact i now see fuel press regs for recirc line too - but lets not go there.
As far as fuel press goes i installed an electric gauge sensor (Holley for $70 @ Summit) into the carb inlet. That about as accurate as it gets but still can be fooled. If carb uses fuel faster than needle and seat can pass fuel (very big hp) then gauge can read press while carb is lean/empty. Stay away from those liquid filled gauges as they become erroneous when the engine compartment heats up. Best just to use a dry mecnanical gauge close to inlet and average the needle fluxuations/bounce.
So unless ur car stumbles at the end of 1/4 mi or that dyno says ur too lean even with big jets - don't bother. Unless u suffer from cronic WIAI itice like me. Ur time & effort won't improve much on what the General designed as stock. Hope this helps. Hey desi u still there?
Good night. cardo0

 

gET A DYNO printout, showing not only HP and torque thru the power curve, but also A/F ratio. If it goes lean above 4500 RPM then either you're out of fuel from low float level, or insufficient fuel pump.