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Old 04-30-2013, 05:52 PM
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Changing carbs..which is best

I have an 83 Camaro with a 350, 882 heads (I know, I know), long tubes, dual 2 1/2" exhaust with Flowmasters, Eddy 1406 600cfm carb with a performer intake, and 4.10 posi. Lopey, solid lift cam ( I didnt build this but got a hell of deal on a nice solid car project), and a TH700R4. Fun car, runs good locked out timing at 36 degrees, I guess I will get to the point now. Rebuilt a 750 Demon for a friend and tossed it on my car while I had it. HOLY S#@T!! did it run! Idled rich and ran a little rich which Im sure its too much carb for my 350 but what a difference in the way it responded! Now I'm looking for a good Holley style carb I guess. Does anyone have any expierence with the new Summit Racing street and strip 600cfm carbs? My choice, I would think, would be the Holley Street Avenger 650. I have to keep the intake manifold because of hood clearance. Any of these combos good or is another better? Just on a tight budget and the Demon would probably be out. I've played with my present carb with metering rods, springs, primary jets, but never got the response like I got out of the Demon in which I understand is a Holley. Maybe I'm missing some tricks with mine?

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Old 04-30-2013, 06:11 PM
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Quote:
Originally Posted by danzigs View Post
I have to keep the intake manifold because of hood clearance.
HOOD? We don't need no stinkin' hood.

Never let sheet metal get in the way of performance. Sling that Performer over the fence and bolt on an RPM.
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Old 04-30-2013, 09:20 PM
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use a 750 HP holley
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Old 04-30-2013, 09:42 PM
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If you stick with the performer intake I would use a Rochester Quadrajet from Jet performance or SMI (Sean Murphy Induction)
You can call them direct and they'll write down your combo and build you a
Quad that's matched to your engines specs.
The small primaries of the Quadrajet makes for really crisp fuel injection like throttle response and the massive secondaries provide all the fuel you need to make maximum power at wide open throttle.
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Old 04-30-2013, 10:00 PM
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Get a 750 cfm carb. A performer rpm fits under the hood when the right air cleaner is used.
Old GM corvette.
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Old 04-30-2013, 11:47 PM
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Originally Posted by F-BIRD'88 View Post
Get a 750 cfm carb. A performer rpm fits under the hood when the right air cleaner is used.
Old GM corvette.
that air cleaner is worth a loss of 2 tenths
yes I try'd it under my 85t/a hood
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Old 04-30-2013, 11:49 PM
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Originally Posted by techinspector1 View Post
HOOD? We don't need no stinkin' hood.

Never let sheet metal get in the way of performance. Sling that Performer over the fence and bolt on an RPM.
this..
a cowl hood is short money and not hard to find used..
you didn't say, but if your camaro has a factory fiber hood, you can fiberglass in the room you need

or use a carb hat and tube to the nose and a cone filter
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Old 05-01-2013, 03:26 AM
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I was afraid you say change the intake too lol. So which 750? Would the Summit brand be ok? Just looking at the funds. I do have the stock fiber Iroc hood.
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Old 05-01-2013, 03:32 AM
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As for the Qjet...how much do you think that would set me back? I have to admit though I was digging the performance look of my buddies carb on my motor. Qjet has that stock look. Just my opinion
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Old 05-01-2013, 06:16 AM
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what carb?

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Originally Posted by vinniekq2 View Post
use a 750 HP holley
use a 750 Holley double pumper with removeable air bleeds.
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Old 05-01-2013, 07:20 AM
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Built Q-Jets work great

Double Vision has the right approach. Save some $$ and get a built Q-Jet. If your thinking of going cheap, remember you get what you pay for. Save up and do it right the first time. Properly built Q-Jets easily flow 750 CFM and they don't perform like the Quadrabog you may be thinking of. Performance, not appearance is where you need to be. Good luck.
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Old 05-01-2013, 09:04 AM
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If your looking to get a carb depending on your cam specs if its over 215 @ 50 then do not get a holley 600 or 670 street avenger as that carb is really not made for bigger cams and the lower vacuum will make tuning a headache as there more for stock or rv type camshaft mild engines.

I just installed a lunati voodoo roller cam in my 350 and is a 219-227 @ 50 and my holley 600 really is not made for this big of a cam and if I had money I would have a holley 750 on it.

If your wanting a vacuum secondary carb a holley 3310 750 should work decent with a little tuning for your engine. If your looking double pumper holley has several options and also check out quick fuel street slayer carbs they have a 750 vacuum secondary one for 300 bucks and will give you a lot of tuning ability over the holley 3310.

It has idle feed restrictions that can be changed in the metering blocks along with power valve restriction changing. Also has changeable air bleeds too and they are really nice carbs. Demons carbs I can't tell you how they are now since holley took them over as before they had some quality control issues but they might be in the past. They have some nice vacuum secondary and double pumper depending what you want for the secondary side of things.

Edelbrock can be made to work too but will have to have mods done to it as there more for street cruising then performance. I had a 350 with a 244@50 hydraulic cam from comp cams and high rise dual plain intake and 10.5 CR and with the edelbrock it did ok and a lot of tuning was done with it but a holley brought it alive even more.

Some will argue with me on some selections but there honestly is not a set rule when it comes to performance stuff as there are many different route to match stuff and tune.

Minus the heads the build sounds nice If your money is tight check out the holley store on ebay as they have the holley 3310 750 refurb carb for around 250.00 and they are as good as new. Good luck.

Last edited by eric32; 05-01-2013 at 09:14 AM.
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Old 05-01-2013, 12:18 PM
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Quote:
Originally Posted by danzigs View Post
I have an 83 Camaro with a 350, 882 heads (I know, I know), long tubes, dual 2 1/2" exhaust with Flowmasters, Eddy 1406 600cfm carb with a performer intake, and 4.10 posi. Lopey, solid lift cam ( I didnt build this but got a hell of deal on a nice solid car project), and a TH700R4. Fun car, runs good locked out timing at 36 degrees, I guess I will get to the point now. Rebuilt a 750 Demon for a friend and tossed it on my car while I had it. HOLY S#@T!! did it run! Idled rich and ran a little rich which Im sure its too much carb for my 350 but what a difference in the way it responded! Now I'm looking for a good Holley style carb I guess. Does anyone have any expierence with the new Summit Racing street and strip 600cfm carbs? My choice, I would think, would be the Holley Street Avenger 650. I have to keep the intake manifold because of hood clearance. Any of these combos good or is another better? Just on a tight budget and the Demon would probably be out. I've played with my present carb with metering rods, springs, primary jets, but never got the response like I got out of the Demon in which I understand is a Holley. Maybe I'm missing some tricks with mine?
600 or 650 cfm is too small no matter whose. I know the formulas commonly found in hot rod magazines and soft cover books say to use a carb with CFM that is equal to half the displacement times the max RPM's you'll turn it divided by 1728 which for a 350 will be about 608 cfm at 6000 rpm. However, except for a moderate street engine this isn't enough to pull the best power out of the motor. David Vizard includes a graph with factors to increase the carb CFM from that basic calculation based on cam timing, but in my experience even that doesn't get the carb big enough. The underlying problem is dealing with reversion, this takes considerable space within the intake passages and back through the venturies, I suspect the problem is not only sizing the carb to accommodate the reversion but to also be large enough to attenuate the signal it presents to the metering system. That simply takes a larger capacity carb to soften this disturbance than the formulas for feeding the displacement indicate. This gets to be a bigger problem with larger cams and or using high ratio rockers where there is more exposure of the exhaust system to the intake during overlap and longer exposure to the effects of the rising piston with late closing intake valve timing. So I'd recommend a carb of 750 to 800 cfm for best performance. 750 for a Holley or clone thereof and 800cfm for a Q-Jet or Edlebrock/Carter.

The Demon is an updated clone of the Holley but is not made by Holley rather by a former Holley engineer. They are very good and like the Holley offer easy tuning and a wide availability of parts where ever you are. I'm less enthusiastic about either the Q-Jet or the Edlebrock/Carter for the average guy. These can be made to work very well but it takes a lot more personal knowledge on the part of the tuner and parts are available only from a small number of sources what adds a lot of time and cost to getting them tuned.

The Performer RPM intake is a world apart from the Performer, if you can fit one, I'd actually start here rather than with replacing the 600 cfm Edlebrock/Carter. That intake will make the carb you have seem bigger to the engine. If you can't get the taller RPM under the hood and don't want to carve up the hood for a scoop, then I'd start with a Holley or one of its many clones. For mostly street with some track I go with the vacuum secondary, for a competition only application then a mechanical secondary model. Match the carb mount of the manifold to the carb being used, I find the Holley or square Edlebrock/Carter really isnít as good as it can be when used on a multiple configuration mount that includes space for a Q-Jet, too much turbulence. If you must use one of those intakes with a universal carb mount then use a spacer with down tubes under the throttle plates to carry the mixture an inch or so into the plenum.

Bigger cams with the Performer intake and a smaller CFM carb like a spacer, but again getting into the bottom of the hood may be a problem. Using a modern remote air cleaner such as found on contemporary fuel injection cars can be used to lower the profile above the carb letting a taller intake or spacer squeeze in without having to modify the hood.

Shop EBay for parts like the intake and carb, you can score some pretty good deals.

Bogie
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Old 05-02-2013, 02:03 AM
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Quote:
Originally Posted by gearheadslife View Post
that air cleaner is worth a loss of 2 tenths
yes I try'd it under my 85t/a hood
You have to remove the choke horn (any of the holley carbs with the straight leg boosters)

my car runs 11's with this air filter. You did something wrong.
I have never seen a loss with this corvette air cleaner on any car or engine in 30+ years.
All you really need is the base.. The lid is the same 14x3" lid.
Its all in the base. and ditch the choke The OEM GM holleys 427-425HP 396-375HP 454LS6 350 Z/28 LT-1 of the day had a lower choke horn height
and down leg boosters like a HP carb.
It fits under a 85 camaro hood with room to spare.

Last edited by F-BIRD'88; 05-02-2013 at 02:12 AM.
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Old 05-02-2013, 02:11 AM
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you can use this base as a start point to fabricate you own custom made ram air cool air system
and pick up even more performance.
Ram Air Box

Some people pick up up to .5 second ET. with a good ram air system.
Cool air is great for high compression ratio engines.


You can still get this from GM muscle car /corvette restoration parts sources.
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