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View Full Version : I need carb help. Please!



sharp67
12-03-2006, 11:01 PM
Im trying to figure out the right carb. but the more I read the more confused I get. So what I m looking for is thoughts on the best choice for a carb. Im thinking 830cfm Holley HP with annular discharge or something from AED. But I just dont know. This is a brand new engine that has yet to be run. I plan on a break in and tune on a engine dyno so I am trying to get close. 383 small block chevy. 3.75 stroke superlight scat crank, 5.7 scat q light rods / splayed 4 bolt / all coated bearings / cam is comp cams 12-432-8 which is retro hydro roller 510, 520 lift 230, 236 dur 110 lsa. intake opens 35 closes 67. exhaust opens 78 closes 30./ Pro magnum hydro lifters / pro magnum 1.5 roller rockers / the new afr195 eliminator heads/ vic jr port matched and reworked from carb flange to intake runner roofs / I believe the combo should be safe to 6500rpm - 6800rpm?/ tko 600 5 speed manual/ lightweight flywheel/ 10 bolt rear/ currently running 3.08 but will be changed to 3.73 or 3.55/ Car is 67 camaro appx 3700 lbs/ it will be used 80% street 10% open road race such as silver state classic etc. bring on the carb combos so I can make a good decision. Im open on cost although would like to keep under $1000.00. Thanks in advance. Jay.

ProdigyCustoms
12-04-2006, 04:45 AM
I would call Quick Fuel. I have used them in the past and heve got good recomendations and service.

68sixspeed
12-04-2006, 04:28 PM
I think your in the right range with a 750-850cfm; if you were running a bigger mech. roller cam I'd say 850-950 for track items, but a good 750 HP series with downleg boosters will probably have the best street manners. I actually end up doing more street driving on my VDL prepped 750 even though the 950 showed another 12hp on the dyno.

6'9"Witha69
12-04-2006, 04:53 PM
If you are 80% street then a 750-780 Holley/Demon would work well all around and have great street manners. Look at the carb comparisons that magazines do. There may be 10-20 extra pek HP, but the smaller ones are usually better on torque, average power and definitely streetability. That is one factor never truly analyzed by the magazines is what type of drivability and mileage are acheived with the different carb setups. In my experience though, bigger is usually not better for a street/strip car. If gettingeverything for low ET and mph is the goal, by all means step it up.

sharp67
12-04-2006, 06:35 PM
so my thought was I could get away with the 830 as long as I ran the annular bosters. I was under the impression that will help with the lack of signal at low rpms yet give me some extra go on the top end, I also thought that with the vic jr the divorced runners would run a little cooler therefore I would want the annular because it would help with creating finer droplets and better mixture because the intake track ran so much cooler. Ive read a few books lately so I probabaly have enough info to think I know what Im doing but am actually dangerous. Im a noob at this stuff so bear with me! Thoughts, Suggestions?

Shaker455
12-04-2006, 08:08 PM
Jay,
I'm a machinist and I build and modify Holley carbs from scratch as that's the best and cost wise way to fit your combo, I can save you a bundle and a headache!

I just finished some mods to a customers Holley 830 annular and it included:
Resizing & relocating the Idle Feed Restriction in the metering blocks as the hole size of the restriction (.039") was too big and the high location made tuning a nightmare...

Added vacuum ports to the baseplate, ported and full as HP's come with no sources.

Replaced the cam track style throttleshaft with the single link style as WOT was not adjustable.

Slabbed the shafts for airflow gain as well as a crisper throttle responce.
Bypass air system
Resize throttle bores to 1-3/4"

CarlC
12-04-2006, 10:07 PM
I run the same cam in a 406 with Fastburn heads. Peak horsepower is at 5300 RPM. Valve float at 6000 with the spring rates as recommended by Comp. Cams but with a lighter valve. Hydraulic rollers don't like high engine speeds.

The 830 annular is a nice carburetor.

Tech @ BG
12-05-2006, 06:06 AM
Jay,

How much compression are you running in this engine?


Technical Support,

Barry Grant, Inc.

www.barrygrant.com

69protour
12-05-2006, 09:18 AM
Hey Jay,
I'm also running a 383, Here's my specs. 9.6 compression, Dart 200's. Eagle 6" rods, eagle crank. 1.5 roller rockers. Solid Cam specs. dur/251 and 256 @.50, 538 and 544 lift. LCC 106./ Victor Jr. and a 650 Mighty Demon carb. I'll tell you what this thing runs awsome. I called Demon Techs and gave them my specs and this is what they recommended. I guess it flows 730 cfm wet? My motor is crisp right off the start,and all the way up to 7 grand. Pulls like a mother too. I'm like you, I wanted to drive it on the street mainly, and boy is it nice on the street cruising around. I also want to run it down the 1/4 mile also, Granted a bigger carb would give me more overall power on the track, but it's mostly going to see street driving. Hope this helps. Talk to the Tech guys, I do like my Demon, despite what others have to say about Demons. All I did was change the powervalve from 6.5 to 3.5. Good luck Trond

sharp67
12-05-2006, 09:32 AM
COMPRESSION IS RIGHT ABOUT 9.75. Im running the new afr heads which use the smaller 7 or 8 mm (cant remember which) LS type valves. Supposedly lighter and therefore more rpms?

CarlC
12-05-2006, 09:43 PM
The Fastburn heads have lightweight sodium filled hollow valve stems. Hydraulic rollers don't like 6000+ RPM. The RPM maximum as listed in the Comp Cams catalog is much lower than your 6500 RPM anticipated.

sharp67
12-06-2006, 02:53 PM
I would consider a demon as well, so what would your recomendations be here? I have purchased a demon before, and I had a couple of problems, I had leaks and delivery issues, I pulled the carb apart and had to clean it up a bit, I removed a big tang where the power valve opening was machined, removed some additional burrs, and had to square up the surface the set screw sits on for the adjustments on top of the bowl as it was leaking. have these types of issues been addressed? again I am willing to consider a demon. just thought I would let you know what I had delt with on my last demon, so you can hold the employees to the level of quality that Im sure you want in every carb you sell. Thanks. looking forward to your recomendations. Jay.

Shaker455
12-06-2006, 03:16 PM
I like Demon carbs as I own three but you may have to go thru the same paces you did with the last one.

That being the case I would not recomend anything bigger than the Mighty 825.

An 830 will not fit your combo well right out of the box and a HP type 750 downleg would cover you bases well.