Carb experts...need recomendation

[Edbert]

Okay, I have a strong yet streetable 351W that I am hoping to fire up pretty soon (after I get electricity and starter). I am expecting 415-420fwhp, but desktop dyno says even more here is the chart:

I bought a vac sec Holley 750 for it but have started to wonder if that is too large. Since then I have also been wondering if I should have picked up a BG Demon carb instead. So based on those performance curves and the breathing patterns based on specs in my sig what is the best carb for my motor?

Here are some more numbers from DD if they help:

 

[ratio411]

I think you have more FWHP than you suppose.
The DD graph is probably closer.

You are thinking too hard about the carb. The 3310 you have is perfect. Just 'super tune' it and you will be happy.

Good luck
Dave

 

[67GTA-FB429]

I agree. The 750 is a good carb, and you can tune it to your needs.

 

[slapper]

Most of the strong street 351s seem to like size 69 primary jets, and the short yellow spring in the secondary vacuum diaphram when using a 4160 750cfm.
I've have very good luck with the above combination

 

[10secgoal]

That carb looks like it'll be just fine. Now depending on the rest of your goodies, I wouldn't worry until you think you want a single plane. Then I would rethink it. Your dual plane will mell out the carb if it's a little too big. Plus it's a vac sec. It's good.

 

[Edbert]

So a 650 would likely be too small then, even if it were a Demon?

 

[Thustlewhumber]

I had a Edelbrock 600 on my 351w that had secondary problems (they wouldnt open...), so my dad let me borrow a 750 doublepumper. I noticed an increase in pickup, but I also noticed an increase in gas smell, trips to the gas station, and days trying to tune it so it would run halfway ok. I attribute all that to the carb being WAY too big for the engine.

For Christmas, my wife got me an Edelbrock Thunder Series 650. The gas smell went away, the fuel economy went up, it requires no maintenance, and now my 66 Mustang smokes the tires at 40mph (and kicks the back end out). I personally think that the 650cfm is perfect for a 351w, or at least mine anyway.

 

[Edbert]

I personally think that the 650cfm is perfect for a 351w, or at least mine anyway.

I've used the calculators, where you take the engine's displacement and multiply it by the max RPM and come up with a cfm number, then round up. That would indicate a 650-700 cfm carb should be right. Problem is that seems too simplistic to me. There have got to be considerations regarding the breathing patters of the head/cam/valve/intake combination that can vary greatly from one 5.8L to another. Then there's the whole issue about intake mixture velocity versus volume.

Based on a number of the posts here I am thinking the 750 vac-sec will be fine. I appreciate all of the opinions here fellas, keep 'em coming

 

[vobraman]

I would go with the 750. depending on the heads on the car and any work done to them you should be fine. I have a 306 w edelb. heads with work done to them and I run a 750. However, I had the car put on the rear wheel dyno and they played with the jets. Worked out fine. Prior to I had a 600 cfm on the car.
good luck
brian

 

[67GTA-FB429]

750 will work good. I have one on my 429 and the only time I have problems is at WOT at 6500 RPMs when it tries to shift into 3rd, then it is a little on the lean side. But for around town stuff, it is fine.

Eventually I want to go to an 800-830 Holley but that is another story.