carb opinion

Im lookin to buy a early 70's Blazer (yeah not a camaro, but im talkin engines here, which are pretty much the same for the two vehicles) and seeing as its already all mechanical, im starting to look at the idea of running a carb instead of EFI to keep from having to do all the custom wiring and such. Problem is, i dont know jack about carbs except for the extream basics. So im wondering, what do yall suggest as the best balanced carb, in regards to performance, economy (gas mileage), and hassle free operation. Im pretty much leaning towards a Quadrajet, but i dont know how Holley and Edelbrock stack up. Or perhaps some other brand i dont know about. Ive got the camaro, so this isnt really a high hp strip engine, but its more for low RPM high torque for towing and off roading, but ill still be driving it on the street putting some highway miles on it. the base for the engine is a 383cid SBC with Vortec heads, dual plane intake manifold, and a cam with somewhere around .430/.450in lift. im lookin to get a carb with between 600-750cfm. but with the quadrajet i could run an 800cfm without worry cuz of how they operate. im just doin some brainstormin here, and open to ideas and input.

Buy a carb, then throw it at someone you dont like..

Then buy yourself a TPI kit and do it the RIGHT WAY!

You said you wanted economy and hassle free operation... And if you know jack about carbs (as I do) than carb is not the way to go..

lol, yeah i know, and the TPI would give awesome low rpm torque, but i dunno, i dont like not knowing about carbs, so having one on the truck would give me the chance to learn. cuz im sure as shit not putting one on the camaro lol

Not trying to call you our Iroc, but being the master sbc design guy you are, 383 for low end torque? Anyway, for that size of a motor just to feed it your going to have to get at least a 700cfm carb. I'd get the holley vaccum advance. But that's if you are dead set on getting a carb. Personaly I would go with TBI, it's more off road freindly than the TPI that you covit over. I think the holley commander 950 would be your best option, plus you can get em from 670 up to over 1000cfm. 950 is just the name. And with that there really isn't any costum wiring you have to worry about, cuz it's a stand alone system. well that's my opinion.

Edelbrock is way to damn sensative man, I've got a Edelbrock 650 CFM on my maro and the thing sux bad. You can smell its running way to rich but if you lean it out it wont run, for 150 bucks I can get it set by a shop but hell man I kinda figured it woulda been set from the factory since it only ran me $300 bucks. If your going to go with a carn get you one of those race demon carbs, I've heard there pretty easy to adjust like holly but there kinda pricy

This depends on what you want out of it. I originally had a 650 Edelbrock on the S10. It was great as far as not having to keep re-adjusting it. The Edelbrock's are very similar to the Quadrajet in design. Once they are set, you really don't have to mess with them that much. Performance is a whole other issue. (Soooo going to get flamed for this...) For performance, Edlebrock's suck ass. I put a 750 Holley dual feed on my truck and it ran a HELL of a lot better, even though that was really way too much carb for the engine. BUT, they can be tempermental. If you're looking at price, you can get a rebuilt Holley for relativly cheap. The Demon carbs are the same setup as the Holley's but they are improved designs (same with the Edelbrock vs. Quadrajet). Personally, I'll only run a Holley.

I would buy the 900 Holley, seen and heard nothing but good. And with you running that cam and a 383 then i wouldnt buy anything below a 750cfm.

oh, hat cam...you know that's a little piss ant cam for that 383 right? your gonna have a starving unhappy engine.

lol, awww common 92RS, i need ya to work with me here, im not building hp. im building torque. the lift of the cam for a 383 can be very low, and make tons of torque so long as you have enough durration. and yes, 383's are known for their torque not their hp, its the long stroke and long connecting rods, taking advantage of the leverage principle.

i cite the GMPP HT 383, tested by CHP magazine, with 1-5/8in full length headers, very similar cam specs to what i have listed above (factory HT 383 cam), with a dual plane intake and carb, made 341hp@4700 and 447lbs/ft@3100 on 9.1:1 compression, vortec heads, 1.5:1 ratio rockers. and 650cfm carb.

http://www.chevyhiperformance.com/techarticles/57841/index.html

dunno if id call that starving boss ;) and on the plus side, with that little cam, i should still be able to get decent cruizing mileage out of it. at least with the right cam. which is also why i was looking at the quadrajet with those tiny little primary bores.

oh sorry, that was with 1.6:1 ratio rocker arms. my mistake, but still, there is even more room there for improovement without messing with the main parts and have a bulletproof, high torque, good mileage engine just begging for a 4x4 to be wrapped up in :evillol:

well next time put the full cam specs on here then.. sheesh. If you have enough duration you'll be alright, but you didn't say that. And still 383's are known for midrange torque more than low end torque, but I guess 3100 is still kinda in the low end. Guess I'm just not used to building a mild engine. Oh speaking of offroad, you should see my buddies 283 he's got in an old CJ7, 400hp 400 and something fpt. It's wicked, he'll spin the motor 8000rpm all day with no problems. I want one.

lol, yeah i knew you were just in the wrong frame of mind, ill let that one slide without an i told ya so ;) oh and your buddy realizes he has an 8000rpm engine, in a JEEP!!!! *shakes head slowly from side to side*

I offered him 2 grand for the engine, he didn't want any part of it.

Edelbrock is way to damn sensative man, I've got a Edelbrock 650 CFM on my maro and the thing sux bad. You can smell its running way to rich but if you lean it out it wont run, for 150 bucks I can get it set by a shop but hell man I kinda figured it woulda been set from the factory since it only ran me $300 bucks. If your going to go with a carn get you one of those race demon carbs, I've heard there pretty easy to adjust like holly but there kinda pricy


Thats odd, when I was messin with the v-8's back in the day, I always found holly to be the touchy one.

well, ive heard bad about both edelbrock and holly, anyone got negative feedback on Q-jets?

The main problem with Q-Jets is the "QuadraJet Bog". This is really what their infamous for. When you stomp on the gas, they will noticeably bog down the engine for a second or two before it kicks in. The lack of response is horrible. You can adjust them all you want but the problem won't go away. Now, not all Q-Jets are like this, but alot of them are. The one's that don't have this problem run great. I've seen a couple that had better response than any Holley I've run. Now if you don't want to keep readjusting your carb, Q-Jet's are the way to go. Set them once and if you roll the truck, you might have to adjust it again. :wink:

I haven't messed wit carbs since back when I owned my 83GT.I think I'll stay out of brands unless you ask specifics of a certain carb, and give you a general outline. First thing is if your Blazer is an automatic I would stay away from any carb with mechanical secondaries. Next if you live in a cold weather area I would higly reccomend an electric choke for those cold winter first start ups. Also are you going to go off-roading in this Blazer and how serious... they make truck based carbs which fuel flow will not be effect when the vehicle is on steep inclines from off-roading. Finally what size to use... well there is the old stand-by formula:

CFM = Engine Size × RPM @ Peak Power × VE ÷ 3456

This forumla is not the end all to be all but it does help give you a general idea.

hmmm, come to mention it, i do remember that bog on my oldsmobile, but seeing as this isnt gonna be a race truck, that bog isnt a really big deal for me, if the carb is low maintanence it seems like a small trade off.

Also with the "seriousness" of the truck, im not gonna be rock crawling or anything like that, just four wheelin in the mud and snow on offroading trails and camping and stuff like that. So i dont think ill be rolling it over, at least i hope not.

hmmm, come to mention it, i do remember that bog on my oldsmobile, but seeing as this isnt gonna be a race truck, that bog isnt a really big deal for me, if the carb is low maintanence it seems like a small trade off.

Also with the "seriousness" of the truck, im not gonna be rock crawling or anything like that, just four wheelin in the mud and snow on offroading trails and camping and stuff like that. So i dont think ill be rolling it over, at least i hope not.

Honestly you'd be surprised how little it takes to get your carb to lean out on you when off-roading. I far from rock crawl or ever came close to flippin my truck. But I have had the fuel cut-out on my while going up bumpy inclines with stock carbs. The combination of an incline and up and down jostling can wreak havoc easily. It's nothing major but it is annoying and when a carb made for off-roading usually is not a lot more it's worth it. If ya not using it for anythign but a winter commuter etc.., then you can save a few bucks.

ill look into that, thanx man.

I know that the Q-jets on the Buick 455 stage one was the biggest q-jet avaible. Not sure of the size though. Also I am pretty sure that the Buick was the only one to get them on

Im lookin to buy a early 70's Blazer (yeah not a camaro, but im talkin engines here, which are pretty much the same for the two vehicles) and seeing as its already all mechanical, im starting to look at the idea of running a carb instead of EFI to keep from having to do all the custom wiring and such. Problem is, i dont know jack about carbs except for the extream basics. So im wondering, what do yall suggest as the best balanced carb, in regards to performance, economy (gas mileage), and hassle free operation. Im pretty much leaning towards a Quadrajet, but i dont know how Holley and Edelbrock stack up. Or perhaps some other brand i dont know about. Ive got the camaro, so this isnt really a high hp strip engine, but its more for low RPM high torque for towing and off roading, but ill still be driving it on the street putting some highway miles on it. the base for the engine is a 383cid SBC with Vortec heads, dual plane intake manifold, and a cam with somewhere around .430/.450in lift. im lookin to get a carb with between 600-750cfm. but with the quadrajet i could run an 800cfm without worry cuz of how they operate. im just doin some brainstormin here, and open to ideas and input.
:smile: Well u helped me so i will try 2 help u if i can . I have tried a lot of carbs,and the best most hasle free carb on the market right now is a Demon, they are made by Barry Grant.For what u r tryin to do u might want to look at a Road Demon jr they get good gas mileage and have vacuum secondaries.ANd if u want a little more bang get the Road Demon, they have many differnt models. The only thing they are a little pricey the better the model.Hope this helps. :) :)

:smile: Well u helped me so i will try 2 help u if i can . I have tried a lot of carbs,and the best most hasle free carb on the market right now is a Demon, they are made by Barry Grant.For what u r tryin to do u might want to look at a Road Demon jr they get good gas mileage and have vacuum secondaries.ANd if u want a little more bang get the Road Demon, they have many differnt models. The only thing they are a little pricey the better the model.Hope this helps. :) :)


I would stay away from Bary Grant carbs for a newbie to carbs. His company is one of my favorite carbs but they are well know and I will agree as the most difficult carbs to tune and get to run properly.

His carbs are Holley copies(he use to work for Holley and his first Demon's he got sued over cause they were so similiar) with a lot more tuning designed in which is why they so much more money. But it's a double-edge sword he gives you all this tuning ability so they expect you to use it.

So I think for what he wants it for it would just be a waste of money. And an exercise in aggrevaition.

yeah the demon carbs are the newest deal on the block, but like GTstang said, im a nooby, so im not ready for something that complex yet. appricate the info though.

yeah the demon carbs are the newest deal on the block, but like GTstang said, im a nooby, so im not ready for something that complex yet. appricate the info though.
Well i guess u r right i forget that i have messed with carbs a long time,and if u don't anybody who knows a little about it it can be a pain.Well I guess a Q-Jet would be best. Just don't turn it upside down.

Nobody that I have ever delt with as far as carbs will even touch a Q-Jet. For what I hear the general rule of thumd for them......expensive paperweight.

Most Quadrajets are junk for hobbyists. If you put it on and it doesn't run right, that's all you get. Drill the caps out, try to adjust... none of this ever helps much. For my '83 carb Camaro, I bought the Edelbrock. As people have said, it usually burns rich. I haven't tried to adjust the mixture yet, but the mixture screws and idle screws are accessible and bring back the feeling of being able to do something. If I get bored, I may get the aftermarket sprinkler to judge the difference.

id go with a 750 and up aftermarket carb if you wanna go that route. thatd be the minimum for that size. tpi would be good since it has the low end torque, but tbi would be alot better. its a carb but 100 times better. you got the power of a carb and efficency of fuel injection. if you go tbi best bet would be a holley 4bbl tbi with 454 injectors. ud still need the computer and all that and probly a custom burnt chip but it would be worth it in the long run. just a thought tho....

well no argument that fuel injection would be the BEST way to go. although ill still give people who think TBI is the best available setup a weird sideways look lol. Im basicly looking to learn carbs this way cuz its an aspect of the automotive realm i dont know anything about. I had a Q-jet on my oldsmobile, and while it did have a little bog now that i think about it, i remember my uncle screwed with it to take power away so i didnt hurt myself, he was kinda a dick like that. Because i didnt know anything about carbs i couldnt fix it. My brothers bronco has an edelbrock carb on it, and it has run like shit since day one, and weve even taken it to the shop and had people work on it. but that was with a POS junkyard engine, now hes got a ford racing 302 to drop in, so well see how it runs on that. but i couldnt get that carb to run for shit, and neither could shops, so ive kinda got a bad taste in my mouth from them. as far as holley, i just dont know anything about em. I appriciate all the input guys, but i think ill just find me a used Q-jet, get the plans, and see what i can get out of her.

for a carb you can't beat a 3310 holley...cheap...easy to tune and a vac sec for that automatic..


i had a 357 with vortec head,cc ee 274h and performer rpm vortec intake....it ran like crap until i put the 750 on it...

To answer your questions: The cheapest, easiest way to go is a 750 CFM Quadrajet, it should meet your needs just fine. Buy one from the junk yard for $10 and pay the 'Carb Shop' or some other reputable carb rebuilder $50 - $75 to rebuild it for you. When selecting a Quad, try to get the non-electronic version '84 and older, but don't worry if you do, it will still run fine. Quads have powered millions of cars over the years and have proven themselves reliable. It will deliver good gas mileage, crisp throttle response, and reliable service. You don't need to know anything about carbs. Worst case scenerio, you pay $100 for a carb and any hack mechanic can install it for $50. Compare this to the $1000's of dollars you're going to spend on EFI. If you want a slight step-up in performance, buy an Edelbrock 700 cfm carb, it won't cost that much and you'll still be 100's of dollars ahead of EFI. A new Edelbrock is basically a bolt-on, it should run great right out of the box. Stay away from fancy, 'stepped up' Holley's, like the demon, they're for racing, and not appropriate for your needs.

Ok, Ok, I know carbs don't start as well, don't run as well, and don't get the same gas mileage as EFI, and don't get me wrong, my cars all have EFI, but if you're on a budget, a carb will work great, with little to no complaints. HP wise, carbs make virtually the same amout of HP as EFI. Take the money you save and invest in other performance parts, or a lift kit.

Note: Forget about a TPI setup, the long runners on the intake will kill both hp and torque generated by a heavy breathing 383. TPI runners would be a huge restriction on a 383, unless you were going for a motor that would never rev above 3500 rpm.

A word on 383's and low-end torque in general: First, the engine combination (cam, heads, intake ... etc) is what determines if an engine makes low-end torque NOT the displacement. Sure, a 383 has a reputation as a torque monster, but that's because it's usually being compared to the pathetic 305 smog motor it just replaced. Having built 100's of hi-po engines, many of them 383's, I can tell you that you can make a 383 spin to 10,000 rpm and make huge hp #'s, but it has so little torque, it can't idle below 3500 rpm! You can also configure the same motor to be a stump-pulling torque monster, just swap the heads, cam and intake.

A word on the long-rod/short-rod, long-stroke, short-stroke controversy. This is years of experience, and engineering skills talking here, not just some BS I heard from my neighbor's dog's, cousin's third nephew. It has been proven time and time again since about 1995 when this first became a hot topic, that long rods or short rods DO NOT make a real life difference in hp. In theory, long-rods should produce more power, however, real world tests reveal that any power difference is negligable. Some tests show long-rods coming out on top, but some show short rods winning. About the only clear advantage that can be demonstrated is that long-rods tend to increase 'dwell' time - that is the time the pistons spends at or near TDC. This reduces the amount of spark advance required, and can make the engine more detonation resistant, which can lead to slightly more hp by allowing for more static compression. In maximum effort racing engines, these minor differences can be worth the added expense of longer-rods, however, on a moderate race, or street driven engine, the hp gains of longer rods are never justified.

Long-stroke engines do tend to make more low-end torque, but this has nothing to do with the stroke. It is because longer-stroke engines tend to have smaller bores, and hence smaller intake and exhaust valves, which promote better volumeteric efficiency at lower engine speeds - more torque lower down. The longer stroke also leads to higher pistons speeds at lower rpm (compared to the same displacement shorter stroke engine) which tends to provide better VE at lower rpm, however this point is debatable, and depends strongly on the engine configuration. Other than that there is no scientific reason why longer-stroke engines would produce more torque then the same displacement, short-stroke motor.

End of Rant ....
If you want to know more, there is a great book published by S-A Design, written by Larry Atherton called DeskTop Dynos, it comes with Desktop Dyno Simulation software. It explains all of what I've said, and much more, in a way that the average guy can understand. Definitely worth the price for someone that wants to learn a little more, and sound a lot more intelligent in gear-head circles.

If you have any questions, feel free to fire them my way: [email protected]

Cyrus Nassiri- Owner - Torque Vendors Racing

Interesting Rant, lots of good information thanks for bringing it up. tech heads are always welcome here to straiten out confusion.

the costs and benifits of different engine components are indeed very debateable, and you can almost never attribute any one variable to a given result. This is why i have spent so many years researching and designing a system that will work together for an end result for both engines i am currently playing with, and in fact use Desktop Dyno 2000 to review different ideas i have.

Im lookin to buy a early 70's Blazer (yeah not a camaro, but im talkin engines here, which are pretty much the same for the two vehicles) and seeing as its already all mechanical, im starting to look at the idea of running a carb instead of EFI to keep from having to do all the custom wiring and such. Problem is, i dont know jack about carbs except for the extream basics. So im wondering, what do yall suggest as the best balanced carb, in regards to performance, economy (gas mileage), and hassle free operation. Im pretty much leaning towards a Quadrajet, but i dont know how Holley and Edelbrock stack up. Or perhaps some other brand i dont know about. Ive got the camaro, so this isnt really a high hp strip engine, but its more for low RPM high torque for towing and off roading, but ill still be driving it on the street putting some highway miles on it. the base for the engine is a 383cid SBC with Vortec heads, dual plane intake manifold, and a cam with somewhere around .430/.450in lift. im lookin to get a carb with between 600-750cfm. but with the quadrajet i could run an 800cfm without worry cuz of how they operate. im just doin some brainstormin here, and open to ideas and input.Just buy a Road Demon,or a Speed Demon,they are easy to tune and work alot better than edelcrap,qudrajunk,and holley.You won't be sorry.

To answer your questions: The cheapest, easiest way to go is a 750 CFM Quadrajet, it should meet your needs just fine. Buy one from the junk yard for $10 and pay the 'Carb Shop' or some other reputable carb rebuilder $50 - $75 to rebuild it for you. When selecting a Quad, try to get the non-electronic version '84 and older, but don't worry if you do, it will still run fine. Quads have powered millions of cars over the years and have proven themselves reliable. It will deliver good gas mileage, crisp throttle response, and reliable service. You don't need to know anything about carbs. Worst case scenerio, you pay $100 for a carb and any hack mechanic can install it for $50. Compare this to the $1000's of dollars you're going to spend on EFI. If you want a slight step-up in performance, buy an Edelbrock 700 cfm carb, it won't cost that much and you'll still be 100's of dollars ahead of EFI. A new Edelbrock is basically a bolt-on, it should run great right out of the box. Stay away from fancy, 'stepped up' Holley's, like the demon, they're for racing, and not appropriate for your needs.

Ok, Ok, I know carbs don't start as well, don't run as well, and don't get the same gas mileage as EFI, and don't get me wrong, my cars all have EFI, but if you're on a budget, a carb will work great, with little to no complaints. HP wise, carbs make virtually the same amout of HP as EFI. Take the money you save and invest in other performance parts, or a lift kit.

Note: Forget about a TPI setup, the long runners on the intake will kill both hp and torque generated by a heavy breathing 383. TPI runners would be a huge restriction on a 383, unless you were going for a motor that would never rev above 3500 rpm.

A word on 383's and low-end torque in general: First, the engine combination (cam, heads, intake ... etc) is what determines if an engine makes low-end torque NOT the displacement. Sure, a 383 has a reputation as a torque monster, but that's because it's usually being compared to the pathetic 305 smog motor it just replaced. Having built 100's of hi-po engines, many of them 383's, I can tell you that you can make a 383 spin to 10,000 rpm and make huge hp #'s, but it has so little torque, it can't idle below 3500 rpm! You can also configure the same motor to be a stump-pulling torque monster, just swap the heads, cam and intake.

A word on the long-rod/short-rod, long-stroke, short-stroke controversy. This is years of experience, and engineering skills talking here, not just some BS I heard from my neighbor's dog's, cousin's third nephew. It has been proven time and time again since about 1995 when this first became a hot topic, that long rods or short rods DO NOT make a real life difference in hp. In theory, long-rods should produce more power, however, real world tests reveal that any power difference is negligable. Some tests show long-rods coming out on top, but some show short rods winning. About the only clear advantage that can be demonstrated is that long-rods tend to increase 'dwell' time - that is the time the pistons spends at or near TDC. This reduces the amount of spark advance required, and can make the engine more detonation resistant, which can lead to slightly more hp by allowing for more static compression. In maximum effort racing engines, these minor differences can be worth the added expense of longer-rods, however, on a moderate race, or street driven engine, the hp gains of longer rods are never justified.

Long-stroke engines do tend to make more low-end torque, but this has nothing to do with the stroke. It is because longer-stroke engines tend to have smaller bores, and hence smaller intake and exhaust valves, which promote better volumeteric efficiency at lower engine speeds - more torque lower down. The longer stroke also leads to higher pistons speeds at lower rpm (compared to the same displacement shorter stroke engine) which tends to provide better VE at lower rpm, however this point is debatable, and depends strongly on the engine configuration. Other than that there is no scientific reason why longer-stroke engines would produce more torque then the same displacement, short-stroke motor.

End of Rant ....
If you want to know more, there is a great book published by S-A Design, written by Larry Atherton called DeskTop Dynos, it comes with Desktop Dyno Simulation software. It explains all of what I've said, and much more, in a way that the average guy can understand. Definitely worth the price for someone that wants to learn a little more, and sound a lot more intelligent in gear-head circles.

If you have any questions, feel free to fire them my way: [email protected]

Cyrus Nassiri- Owner - Torque Vendors RacingThats not completly true Berry Grant has made a few simple to operate modles,like the road demon jr, the road demon. The carbs that take a little know how r the speed demons ,mighty demon, race demon and the all powerful king demon.So for what he is looking for the road demon modles would be a very good buy.