OK, I was reading up on our Street Demon 625 and I quote directly from the Demon box "625 CFM-Perfect for stock to mildly modified small block V8 and 6 cylinder engines" and I quote "750 CFM-Perfect for highly modified small block V8 and stock to mildly modified big block V8 engines". Now what I would like to know is what constitutes "mildly" and "highly" modified in regards to the small block V8? Thanks in advance
mild could be like a fairly stock rebuild maybe a 306 and I would say wild would be 347 or 363 but on some motors 750 wont be enough so it all depends on what youre doing with the motor. if youre just building something for the street to drive around and get on every now and then the 625 would be fine..
The cam would make a huge difference, then have the heads to support what the cam needs, then that would lead to having a matched intake....
When they say "smallblock", they're most likely referring to a 350, not a 289 or 302. A 750 is too big for a 302 unless it's a full-race engine. The 302 Boss came with a 780 Holley double-pumper, but it had huge valves & ports, lots of cam duration, and 11:1 compression. It was made to rev to at least 7500 RPM. It also had very little low RPM torque and got terrible fuel economy. 600 to 650 ( or 670 if it's a Holley Street Avenger) is plenty for a mildly modified smallblock Ford. Heck, the Hi-perf 289 came with a 470 carb, and was a little monster. But I guarantee that someone here will tell you that "bigger is better".
But I guarantee that someone here will tell you that "bigger is better". I'll be the one. It actually depends on what you are doing with your maverick. My car has always been a race car first, then streetcar second. With that being said, I always ran at least a 750 double pumper carb. It ran low 12's with a stock 302 w/ hipo 289 heads and a decent hyd. cam, and ran slower with a friends 650 carb. SBF's love big carbs and loose converters. I never had a problem driving on the street with that combo or my pump gas 347 with a 980 cfm carb. Now if you like to cruise the car more, I would use a 600-650 carb.
I said "unless it's a full-race engine". And there is no way in hell any "stock 302 w/ hipo 289 heads and a decent hyd. cam" is gonna run in the 12s (much less low 12s). There's also no way a 347 is gonna flow anywhere near 980cfm. You're obviously one of those who loves to tell tall tales, like those guys I always run into at the cruise nights.
Yo man, not trying to start up anything, but I'm just going off my experience. no b.s. here. I can tell you exactly what I ran. Back when I first got my car together, I bolted on a set of ported hipo heads, comp 240 hyd cam, single plane intake, 4:11 gears, and a 5K stall 8" converter, and yes it ran low 12's. I would disagree with you on a 347 not needing such a large carb. My 347 ran 10.40's on pump gas and turning 8k through the traps. When Joe Sherman did the custom cam, he said himself, put the biggest carb you can on it. It was a simple engine, Dart Block, AFR 205's, Joe Sherman solid roller 690 lift, duration 273/280 @ .050, 6k stall, and 4.56 gears. I'm just trying to help others in picking what's best for their combo.
Not everyone sizes carbs for street cruising and there are TONS of smallblocks running small dominators and huge HP series race carbs on the streets too. And as Ray already eluded to.. gears and stall speed can make the boosters of a "bigger than recommended" carb come alive. Peaky cams also love big carbs on the top end. This is one of my favorite cars with a small motor that surprises many people with stroker motors. Knocking on 10's with such a small "street type" 289 inch motor is no small feat. It runs 4.56 gears and huffs through a 950 HP series carb.
I don't know who you're fooling with that claim, but it ain't me. If you ran those times with that setup, it wasn't in a Maverick/Comet. Maybe if you installed that in a Yugo. Or, unless that is 1/8th mile time. It ain't quarter mile. "Comp 240 hyd cam"?? Yeah right. That cam runs out of steam at 4500 RPM.
The Boss came with a 780 vacuum sec ....Holley 4511 (1969) and a 4653 (1970, different pri metering block). I run a 750 DP on my 289 Comet BUT it saw track time as well. On the street, it behaves really well. My mild 84 Cougar has a 700 DP that I've tuned to the point of 26MPG and excellent street manners. I've also tried and tuned a 725 VS that came on the little 68, 289 GT-350 on my Cougar and although it runs good, it is no where near the DP for mileage and performance. As far as the combo that ray-g151 had running in the 12s, I can back that up. My stock 302 with a cast 4bbl manifold, 600 Holley,headers,Crane Fireball cam 4-sp top loader and 4.10s ran 12.90s all day and still got me to college and back and forth to the track. Getting back to the topic, the Demon 625 will work. It wouldn't be my choice since I'm a Holley man and there are better carbs out there.
Really? So you can launch at 4k to 5k running a hydraulic cam that runs out at 4500, and run a "low 12" in a Maverick/Comet?? I have a bridge in the Bay area that I am selling if anyone is interested.
.....26" tire, 4.10s @ 100mph= 5300 RPM.....OUCH. I'm talking MY combo with a stick and a tiny .460" cam. This was way back in 1985 before the way the car is now.
Lets get back on the subject. I never told you what cam I was running, when I speak of cams I always refer to the duration at .050. , the lift was in the low 500's. I can pull up my records later and let you know the exact specs. The answer to the op's question is, the carb company will put general terms to classify and market their item. The cfm needed is dependent on the use of the engine.
