I'm looking at the Holley Track Warrior carbs. I'm looking to ditch my 750 cfm vacuum secondary holley for a double pumper in the name of throttle response and precision tuning. I'm ready to pull the trigger but am struggling with sizing.

Currently in higher gears, say 2k rpm, if I punch it quickly I get a hesitation. It goes lean, but if I go up more in accelerator pump shot size the duration drops and I'll actually get a delayed carb cough. Running 45 shot, 50cc pump. If I go down in size I'll get a carb cough immediately. Everything is setup right, transition circuit, etc. Idles strong, cruise at 13.5afr, WOT 12.7afr. I'm pretty competent.

This is where I'm thinking throttle response from a mechanical secondary may help me. Car is reasonably light, manual, etc. Checks the boxes. I'm not looking for gas milage, as this is just toy.

Setup:
383ci - 11:1 - pump fuel
AFR 195 comp ported heads
AFR titan intake
Cam 236/244 on 111LSA installed 6deg advanced
​125hp shot nitrous, cheater plate
hooker long tubes
​dual 3in to single 3.5in exhaust over rear axle
T56
3.50 gears
Rear wheel numbers, mustang dyno, no juice.
382hp at 5900rpm
373ft-lbs at 5150rpm
Ran 12.7s on street tires, no juice.
12.1s on the bottle 3rd and 4th gear.

Largely this car only gets to the track every other year. The rest of the time I'm just driving it on nice days, to work, kids games, etc. Streetability is important, but also don't want to give up too much.

Street manners tell me go 650cfm and don't look back. With nitrous providing extra O2 for the track why not keep the street manners great without sacrifice? Being a gear head I have to wonder what I would be leaving on the table... 5hp? No issue. 20hp, not willing...

Based on this article with a very similar motor the recommend 750cfm, but the 650 yields almost exactly the same results (1hp.) Why not take the low end throttle response?

https://www.motortrend.com/how-to/148-0403-seven-holley-carbs-test/

Calculations tell me 700cfm... exactly in the middle... take this and multiply by .9 for volumetric efficiency and I'll get to a 650cfm carb. Any opinions or thoughts would be much appreciated.

 

Howdy! I run a 650 Holley 6210 speadbore on a 305 L69 with around 9.75:1 and it eats all of it very well. I would suggest larger than 650 cfm just from what I run.This carb is great though and performs better than my expectations. L69 305 113 heads 240 RWHP 270 RWTQ.
Good luck!

 

I used both a 750 edelbrock 1407 and a street demon 750 on my 383 stroker, xe282hr cam, 195 dart copy heads engine. I always struggled with a lean bog if I whacked the throttle from idle. AFR would shoot up to the 20's and it would bog hard. I was constantly tweaking and messing with the accelerator pump and squirter sizes and could never get it to go away. I must have read every single forum post from every single american v8 based car forum that had the keywords "lean bog" in it. I switched to a 670 street avenger ultra carb a few months ago on a whim because holley was having a sale and it cured my lean bog issue.

I don't want to say the smaller cfm size was the answer because people have been using 750cfm carbs on standard 383 builds without any issue for decades but it certainly seems to be the case for me. I ran the cfm calculators online and they all came in around 650-660cfm for a street car with a 6200rpm redline. I'll rarely ever spin it that high and I'll gladly take the better throttle response and reliability over some power way up top that I may or may not even be missing out on. My car only sees street driving so ymmv

 

This is great info, sounds like you have a very similar setup. I'm still going back and forth by the minute... did you ever dyno it on both setups?

I wish I could dyno both, be really nice to know real world numbers. Can't be spending $750 twice in the name of science...

Anyone else have thoughts?

 

no dyno unfortunately. the car feels just as quick as it always did, more repeatable as well. it’s a lot more enjoyable to drive knowing i won’t bog and potentially stall at a stop light if i gas it too hard.

im definitely interested in seeing other people’s thoughts on this as well.

 

Took a while but good update. I hit the dyno this morning to test out my new intake/carburetor setup.

Replaced the AFR Titan with the AFR Eliminator 4150.

Bigger part of the test is the 650cfm carb killing power compared to my 750 it replaced. I didn't like the 750s street manners.

383hp before (750 carb), put down 401hp today (650 carb.) Same dyno.

So let me say I'm thrilled with the new intake as i feel this is where I gained the power, however the carb being under sized clearly was not an issue.

Not fully apples to apples as the old carburetor was vac secondaries and new is mechanical. That said, if you're not putting down over 500hp I'd say it's safe and arguably better to go 650cfh for your 383!