What carb for my setup plz?!?!?!?

beaver2489 · Jun 12, 2005

I have a few questions: *not my daily driver*
setup in the sig. my heads flow around 230cfm intake also.

-what carb would you suggest?
-what spark plug gap should I use? I have all MSD ignition
-what should my fuel pressure be set at, 6 or 7?
-what brand of beer do you drink?

maverick0716 · Jun 13, 2005

Probably a 650 dp Holley

I'd set it between .050-.060

I would think 6....what fuel pump are you running?

I actually don't drink much beer at all, but if I had to pick one it'd probably be Corona.

beaver2489 · Jun 13, 2005

right now I have a 750 Holley and it cuts out in 3rd gear around 3grand+. plugs are gapped at .050 right now. I thought maybe the larger carb was causing the spark to "blow out" at higher rpm in 3rd-4th gear. maybe not.

I'll see if I can get ahold of a 650 dp and see if it performs better.

I still have my 255 walbro EFI pump in the tank. with a holley regulator its running at 7-8psi right now. we have the fuel pump wired to run with the key on and turns off with key off. works great. eventually I'll probably put a "blue" fuel pump in for the carb setup, but the 255 walbro still works fine for now. I've seen a few others on here that use EFI pumps with carbs too.

Budweiser for me, treating myself to a coooolld one right now

86bluecobra · Jun 13, 2005

i run a 750 and .050 gap i run autolite plugs(mine are gapped to .40 because of juice) i run 7 psi i have a barry grant fuel pump and regulator it works very nicely mind you the pump is loud. I like canadian beer.

srothfuss · Jun 13, 2005

For a 302 / 306, the 750cfm is too much carb if you are looking for crisp throttle response. A big carb like that will only help you in the Higher RPM ranges... I'd recommend no bigger than 650cfm. Not saying your car won't run with a huge carb on there, but your off the line performance would suffer.

Dark Knight · Jun 13, 2005

whats the fuel pressure when it cuts out? must EFI pumps and fuel lines are designed for high pressure, a carb needs more volumn.. you might be running out of fuel..

crazypete · Jun 13, 2005

Get a mechanical FMS fuel pump and timing cover and eccentric to run it and NEVER have to think about fuel pressure ever again. Ever. Perfect pressure every time year after year. Just my .02 on that issue.

750 cfm is way way way too big. 650 is better, I agree. Maybe even 600 cfm for throttle response if it is not a high revver. 650 if it is. Plus the dp had the potential to bog when throttled too suddenly. Thats why I dont like mechanical secondary carbs. They always seem to run pig rich no matter how well you tune them. A 650 vacuum carb might even give you more throttle response and no 3k lean bog since the vacuum secondaries are inherently load sensing and only pumps as much as the car needs. The dp principle of blasting fuel in there is not always optimal since super rich is detrimental to power production as is super lean.

Point in case, my 40p headed 302 works absoilutely best with a 570 vacuum secondary and not the 670 vacuum secondary or even the 600 dp. You need velocity to suck gas from the boosters and that 750 is killing all your air velocity guaranteed.

69Rcode_Mach1 · Jun 13, 2005

crazypete said:
Get a mechanical FMS fuel pump and timing cover and eccentric to run it and NEVER have to think about fuel pressure ever again. Ever. Perfect pressure every time year after year. Just my .02 on that issue.

750 cfm is way way way too big. 650 is better, I agree. Maybe even 600 cfm for throttle response if it is not a high revver. 650 if it is. Plus the dp had the potential to bog when throttled too suddenly. Thats why I dont like mechanical secondary carbs. They always seem to run pig rich no matter how well you tune them. A 650 vacuum carb might even give you more throttle response and no 3k lean bog since the vacuum secondaries are inherently load sensing and only pumps as much as the car needs. The dp principle of blasting fuel in there is not always optimal since super rich is detrimental to power production as is super lean.

Point in case, my 40p headed 302 works absoilutely best with a 570 vacuum secondary and not the 670 vacuum secondary or even the 600 dp. You need velocity to suck gas from the boosters and that 750 is killing all your air velocity guaranteed.

The reason you are having those issues with a DP is because you are running it on an auto trans. They don't work to well with an auto trans. If you choose to go DP I recommend the Holley HP or the Mighty Demons simply because of their unlimited tuning capabilities will allow you to lean out your charge of fuel at certain rpm ranges and have it be richer where you need it. It all comes down to the tune, on that engine combo I would say a 650DP would work really well on that. Or for a more streetable carb you can go for the street avenger 670cfm carbs by holley.

crazypete · Jun 13, 2005

Yes you are right. But the way I look at it the auto trans just brings to the forefront the issues with a double pumper: issues that can be "covered up" with a manual transmission since it allows you to spin up your motor first. But that does not mean the lack of air velocity is not present on a t-5'ed carbed mustang, you just jump into the situation 1000-1500 rpms later. You still have that inherent bog risk when the clutch hits and pulls the rpms down while both your throttle plates are still wide open.

I love the holley avengers. I've seen a lot of carbs and the avengers have all the bells and whistles a carb could ever want. Wonderful little carbs.

70lightning · Jun 13, 2005

mmmmmmm miller time, Miller Lite for me.

70lightning · Jun 13, 2005

Oh I would try a 670 SA Holley I am going use one some day.

What carb for my setup plz?!?!?!?

beaver2489

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What carb for my setup plz?!?!?!?

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