Stainless

I have a 1972 Duster with a 360 Magnum. I currently have a 750 CFM Edelbrock 1407. Seems to be starving for fuel at high RPM. Changed fuel filter and did some other investigating. My friends say dump the Edelbrock and go with a 750 CFM Holley. They claim it will bring my engine to life. What do you all think?

bremereric

Just preference.

PK1

Both flow the same. The 750 should be ample for that motor even if modded some.

If you are using the stock magnum valve train over 5000 rpm you are floating the valves. the springs are VERY weak. They werent designed to go past 5000rpm. Peak HP with 360 stock mag cam was 4400 approx, most programmed to shift between 4650-4800 rpm.

Install a wideband meter to monitor fuel if you have the valve train updated.

Archer

stainless -

A 750 anything is probably overkill for that motor. Doesn't mean it can't be used, means that much flow just isn't necessary.

Now, I like Holleys, but for a mild street rig, there's nothing wrong with Vic's stuff, and might actually be a better bet. If the engine feels like it's starving at high rpm, you'll have to define "high rpm" and it might take a little more snooping to figure out what's going on.

BTW - it could be a carb adjustment or just a bad carb, or insufficient vac advance / timing or a bad fuel line or etc...

Archer

Stainless

Thanks for the help. It falls off around 5000. I have Manley 1.625 Stainless Exhaust valves, Manley Stainless intake valves 2.020. sealed power lifters, and rebuilt rocker arms. With a Isky 280 Mega cam kit with springs. I am not sure if this will help. I think it is a carb issue. Going to change out the carb to a Holley. I hope it is worth the dollars.

bremereric

Before you blow a wad of money call Holley and tell them the specs on your motor, cam, intake and exhaust. I bet you one of their 670 Street Avengers is what you will need. I had a high lift 340 roller motor and the 770 Street Avenger was way too much carb for it.

Archer

Stainless -

That valve train should be good for at least 6K rpm. Do as Eric suggested call Holley or Edelbrock and ask. Holley has a CFM calculator on their website was well.

Archer

PK1

More specifics?

A 280H non roller cam in a magnum block and magnum heads with rebuilt roller rockers on a non adjustable head.. so chevy guide plate conversion, arp 5/16 thread to 3/8 stud, chevy roller, hardened pushrods.. correct?

What spring are you using and what is your installed height? Did you check the new installed height when the 2.02 valves were cut and installed?

If you want a quick cheap diagnostic, take it to the chassis dyno for a single pull with their AF meter in. Tell the dyno operator you need a pull for tuning. Depending where you are should cost 50-75 bucks.

He will shut it down the second it goes lean on you. He will also shut it down the second HP falls of. And if you have a geometry problem in the VT or spring pressure issue the motor will go flat HP wise but the fuel ratio will stay constant.

SatelliteJosh

Try adjusting the float, my brother has a Quadrajet on his 1971 Monte Carlo, & the float was off by a very minute amount, so it starved for fuel after about 3000rpms or so, but Edlebrock vs Holley, both are great

Mr.Duster

Id do what bremereric said. Give holly or whoever a call it might be to much carb.Id also go back and check the floats out and the jets possibly. i have a 340 and i run a 650 spread bore on it and runs like a raped ape. As for carbs all about preference me i like holly but thats just me.

duster sweden

do you whant power and easy jettin go holley vacuum 750 and go for a kit to adjust secondary you get performance..are you just cruisn around the town go edel..