Carb size or efi

[Gmoney]

I have a 440 in my 69 roadrunner with some head work and mopar purple shaft cam with 248/248 duration at .050 and 108 lobe separation. What carb is the best for this setup? I'm currently running a holley 750 vacuum secondary and it's just not enough. I was looking into the FAST efi or the msd atomic but it seems they won't work with this cam, anyone know any efi setups that would work or have used it with this cam? Thanks

 

[Meep-Meep]

Are you running a single plane intake? If so the 750 should work pretty well. I'm just sayin' people have done a lot more with less. If you have poor performance you might go over the timing curve to make sure it's right. Is your exhaust free flowing? What about compression and cylinder pressure? You didn't give a lot of engine details so I'm just throwing out other possibilities...

 

[Gmoney]

Sorry about that. It's a dual plane intake 10.5 compression with 2 1/2 inch exhaust with 2 chamber flowmasters on it. It's about 500 horsepower. The engine runs great just always seems like it's starving at higher rpms. I was looking into the new self tuning efi kits but none of them will work with my cam setup because of lack of vacuum. So I figured I would put my money into a new carb setup.

 

[RustyRatRod]

Holley 950 HP. Oh and according to Herb McCandless, that camshaft is not 248.5* @.050. It's 242* @ .050. I've noticed a lot of the MP cams come up different than advertised.

 

[Meep-Meep]

Sorry about that. It's a dual plane intake 10.5 compression with 2 1/2 inch exhaust with 2 chamber flowmasters on it. It's about 500 horsepower. The engine runs great just always seems like it's starving at higher rpms. I was looking into the new self tuning efi kits but none of them will work with my cam setup because of lack of vacuum. So I figured I would put my money into a new carb setup.

With that high overlap cam you might try a single plane intake like an old Torker. Unless you have the perf RPM then the gain from the single plane may be small to none, or even loose power. I'm not sure if you should condemn the 750 just yet. The carb may have some issues internally like jetting or float settings. Make sure it's up to snuff and you have adequate fuel pressure/delivery at WOT in high gear. I'm not saying your assessment is wrong; just that there are a lot of engines in your power bracket that make it on 750 CFM.