### CARB/EFI for 521

sspano01 · #1 (**permalink**) 02-07-2012, 06:17 PM

Hi Folks,

I am running the Commander 950 TBI on my 521 inch BBF. Its a 'mild' 521 build, 9:1 compression, ford super cobra jet heads, and a flat tapped hydraulic (non roller) cam. I forget the specs right now. Modeled at around 500hp.

I mostly have the 950 TBI dialed in, but it still has some hesitation or a soft-spot or two.

I am going to simplify my Cobra setup, removing the MSD 6AL box and a few other small items I put on.

That got me thinking about the TBI. I have recently completed a restoration on a 66 mustang with a 289 and am using an edelbrock carb. The edelbrock seems to work very well and the 289 runs great.

So I was thinking of getting an edelbrock 750 or holley 850 (750 may be on the light side for the 521) and trying it out to see how it responds and maybe ditch the TBI all together?

Any thoughts on a good carb if I want to try this?

fordracing65 · #2 (**permalink**) 02-07-2012, 06:38 PM

Quick fuel carb

sspano01 · #3 (**permalink**) 02-07-2012, 07:49 PM

quick fuel - i'll give them a call and see what they think.
thanks for the idea

akfish · #4 (**permalink**) 02-07-2012, 08:01 PM

Paging bykins....mr blykins to the front desk...thank you.

STL Mark · #5 (**permalink**) 02-07-2012, 09:10 PM

I run a Quickfuel 850 on my 588 BBF. Not a radical cam - makes an easy going 680HP and 750 TQ. No crazy jetting either. Actually left some HP on the table to make a SAFE A/F ratio.

I dumped the Mighty Demon 850 a couple of years ago. Keep the MSD box. Make sure you dizzy is correct, or replace it. Make sure up have 1/2" fuel lines back to front and are feeding the beast properly with a top of the line electric fuel pump and pressure regulator.

x10 votes for the Quickfuel.

blykins · #6 (**permalink**) 02-08-2012, 04:14 AM

Quick Fuel without a doubt.

A Q-850 would be my weapon of choice. I would be happy to give you a quote on a custom carb if you wish, and I can provide a list of customer references from fellow Cobra owners as well. I work very closely with an ex-Quick Fuel carb builder and you will not find a better carburetor out of the box anywhere....

sspano01 · #7 (**permalink**) 02-08-2012, 07:42 PM

hi folks. i was checking out the quick-fuel website, looks pretty nice.
Brent - if you can set me up with a carb, maybe i will give it a try.

i like the efi setup....but after running that edelbrock on my 289 mustang, it really got me thinking about running a carb on my cobra.

thanks for the advice folks!

sspano01 · #8 (**permalink**) 02-08-2012, 07:52 PM

and STL - 680 HP!! Wow! I need to get mine to a chassis dyno this summer.
I was hoping for 500-550 range. whatever my 521 is putting out, i'm happy with. it seems very well behaved and very fast

blykins · #9 (**permalink**) 02-09-2012, 01:44 AM

I can hook you up like a tow truck....

If you decide to go that route, just shoot me an email or call me and we can talk about your setup.

mdross1 · #10 (**permalink**) 02-09-2012, 03:26 AM

Always used the Holley HP never liked the rich idle.Had Dan davinci build me a 1000cfm dbl pmp for my 460 could not be happier.Instant throttle response and much leaner idle FYI.

sspano01 · #11 (**permalink**) 02-20-2012, 06:14 PM

ok, so I moved the oxygen sensor much closer to the engine. its in the #8 tube now on the header. that seems to make the holley much happier the base "502max" profile seems to run much better than it did before. I also removed my MSD 6AL box and the timing seems much more stable now as does the pulsing on the injectors. This isn't just by eyeball...I used my oscilloscope from my engineering company. I could see the timing moving on the scope. Without the MSD, the timing is rock solid. I suspect some kind of ground/interference issue.

Still working on other upgrades so I have not driven it yet though,

sspano01 · #12 (**permalink**) 03-07-2012, 04:21 PM

To follow up on this in case someone else searches this topic....

It was 60 degrees in Upstate NY today so I got to take the cobra out a bit and test my changes.

Much Better!

I have the ignition timing set to 18 degrees at idle, with about 20 degrees of mechanical advance by 3000 rpm. The oxygen sensor is about 8 inches away from the engine on the #7 tube only. the MSD 6AL has been removed and my timing at idle is rock solid now.

No more slog/bog when I press the gas in any gear! It just picks up speed nice and smooth. From a dead stop, in first gear, no more bog down either. It will light the tires up and speed away :P

Perfect !

Until I find something else I want to change