Performance carburetor

Im looking to get a new performance carb in the future, whats the best type to go with and not hurt gas mileage but still gain performance???

Stick with the one you have.

That way, your computer system continues to work and you get the most out of your engine while still saving gas.

stick with the q-jet? what im wondering in general will i gain any h/p with a better carb?

No. Carbureting an engine is an artwork - too many people don't do this right and wind up overcarbureting an engine. While a 750-scfm carb would do good on a 350 running at 7K RPM, it is too much for the same engine at driving speeds. Your 305 would do good with no larger than a 600-scfm carb. Now here is the thing - if you demanded high-RPM power from the 305 (being completely hypothetical here - a 305 isn't exactly a powerhouse), that 600 would run out of air at high RPM and engine performance would suffer. If you put a larger carb on it, venturi speeds will be too low and the carburetor will not properly mix the air and fuel - causing other problems.

A Q-jet is, for practical purposes, a variable-venturi carb, providing the proper airflow in all engine RPM ranges - it delivers what your engine needs at any range. If your engine demands 600 SCFM airflow at 2200 RPM, the Q-jet delivers that - but the Q-jet can flow up to 780 SCFM for almost any street-strip need.

If you feel you need to run a 'performance carb', then you will also need to replace the distributor on your engine with one which uses mechanical advance (vacuum and centrifugal). You then lose the power advantage of an aggressive, computer optimized spark curve.

The 350 that is in my car now has about 286k miles on it since its 1993 reuild. 220k of that mileage was spent under the hood of a 1975 Grand Am. The carb I used on it was a Carter AFB 600. It was a great carb for its application, but the E4ME Qjet on the engine now (as well as what you have) is just as good in city driving, giving higher top-end (it's not wheezing at higher RPM like the Carter was), and better economy as well.

ok just wanted to clear that up, i remember hearing that you'd have to rewire a few things too

I agree with silicon, although I did actually have great luck converting my engine to pre-ECM it is a lot of work and in your case may be more trouble than it's worth. Doing so requires a lot of tuning and know how. I did get a nice power gain, but fuel economy suffered a bit. If you still want to get a performance carb while leaving your ECM and fuel economy intact Holley does offer a performace carburetor that has the TPS and Fuel Mixture solenoid exactly as a stock Q-Jet does. It is big $$$ though.

Stay away from Holley for a carburetor,a pain in the butt to set up.Edelbrock makes the best carburetors and are the same as q-jet,are set to put in with no tweeking at all

yeah i had either a edelbrock or holley in mind...

Stay away from Holley for a carburetor,a pain in the butt to set up.Edelbrock makes the best carburetors and are the same as q-jet,are set to put in with no tweeking at all

Edelbrock makes two different carburetor lines. One is the aforementioned Quadrajet - it's not a knockoff either as Edelbrock now owns the licensing and tooling for the Q-jet. The other is a rebadged Carter AFB.

The AFB is an excellent carburetor for non-computer cars - I much prefer them over Holley carbs. Easier to setup, less trouble-prone. In fact, my AFB (Carter/FM and not Edelbrock) didn't need a rebuild until it had piled on about 175,000 miles!

I still think the Q-jet E4MC/E4ME electronic carb is best for a computer car.

One other thing -

If you live in an area where your vehicle is subject to emission/smog inspection, you will have a much easier time with the Q-jet. As great as the engine ran with the AFB, getting it through smog here in Arizona was a beyotch. Same engine with same cam, heads, valves, intake, etc - and it will run on the IM147 test dyno for 15 seconds before the computer passes it (the IM147 is supposed to be 147 seconds on the dyno), first time, with electronic control and the aforementioned E4ME.

We dont have emmissions testing here in fl so im not concerned about that. what if i were to get a 2 barrel edelbrock carb (if they exist) would that be better to gain power but without hurting gas milage as well? btw this car is also my daily driver, hence why its gotta be fair on gas still.

A 2BBL even if you can find one made by Edelbrock will possibly give you better gas mileage, but will also significantly reduce the engine's peak power output. Honestly, you're probably better off sticking with what you've got, like Silicon always tries to say; an ECM will make an engine run at it's peak for both economy and power output. If you want some more power, and keep, if not improve mileage, then TBI or MPI is probably the way to go, however it's pretty involved.

I just figured that since im getting a k & n filter why not get a carb to go with it, i plan on having the exhaust redone too from the headers all the way back. what kind of power gain should i expect from that? i want flowmasters, with the dual pipes out the back.

A two barrel will have lower city performance, and lower highway economy, than the Qjet will.

I agree with sticking with the Q-Jet. If you can get a good deal on a new or remanufactured one, that's the way to go.

The knockoffs are also very good. I had one years back that was made by Carter and it was excellent and provided lots of power to a small block that I has with 202 heads and a mild cam.

Bob

Dual exhaust will give you a little bit in the mid-rpm range, but don't expect a huge power increase. A stock 305 has fairly restrictive heads with small valves which is why they don't always do so well at higher RPMs. An exhaust will only help so much. I'm not saying don't do it, by all means go for it! Just don't expect to jump in the car and start spanking Corvettes on the 1/4 mile strip. Just remember, you do need some back pressure.

so in general whats the best thing to put into a 305 to get noticeable h/p gain?? i'd like to have at least 200 if possible

so in general whats the best thing to put into a 305 to get noticeable h/p gain?? i'd like to have at least 200 if possible

Forgive me but I am getting the strongest, most noticeable sense of deja vu here ...

Do the heads. Locate a set of 461 heads -or- an aftermarket set of World Performance S/R Torquer 305 heads. The latter come with 1.94/1.5 valves and ports/bowls designed for airflow. The heads alone, all else being equal, might be good for 45-50 HP. Throw those, along with a nice bumpstick (don't go overboard), duals and a good dual-plane intake on it and watch the 305 wake up.

However, it might be cheaper to stick a 350 in it, in place of the 305.

ok, i just wanted to get a good comparison, my pontiac grand prix i used to drive had about 230 h/p stock and it was a 3.8 V6, granted it had a factory supercharger as well though.

I don't mean to hijack your thread, but you made a comment of 200+ HP. What exactly is the stock HP on a 305 4BBL caprice? And is my low 0-60 a common thing?

Horsepower and torque of a 305 generally run about 165HP and 240 ftlbs, give or take 5 on both. Low 0-60.... oh yeah, back when I had a 305 in my '84 with no other mods aside from removed AIR pump and A/C compressor, I ran the 1/4 mile at low 18s, very high 17's if I was lucky and launched it right... pathetic, I know.

When I had my '83 with a 305, it was an ok car, but just didn't have the oomph that it needed.

when the water pump bearing siezed up and the engine overheated, I threw in a 350 from a 77 suburban that my uncle gave me for free.

With no tuning or anything other than new plugs, wires, cap, rotor, and a non-leaky exhaust system with a glasspack, the 'ok car' became an awesome fun car. My mother drove it once, and even she said that it was really nice to be able to step on the gas and actually be able to pass someone...

Even with the 350 I was still able to get about 16-19mpg consistently, and I was only able to get about 22 with the 305 on it's best days...


--sarge

Y'know the old saying... "there's no substitute for cubic inches." stock 350s not only have more CI's but also come with better, higher flowing heads in most cases. The combination of the two is a surefire way to power. Mike, if your engine is running fine and you're happy with the power, leave the engine alone, as it is set up right now it's running at it's peak assuming everything is well maintained. If you're really interested in giving that car some get up and go, dropping in a 350 is really the best, easiest and most cost effective way to go. Even if you get a used, stock 350 in good shape mechanically you will be amazed at how the personality of that car changes. May people are intimidated by the thought of an engine swap, but it's really more simple that you'd think, providing you have a cherry picker (engine hoist).

yeah the engine is running fine, i do have access to a engine hoist. a 350 doesnt sound that bad of an idea either. do i need a different tranny for the 350 as well?

Well, you might want to beef it up in the future, but if the tranny bolts to a Chevy 305 it will bolt right up to any small block or big block chevy engine. So yes, to answer your question, your tranny will work.

Ok good to know, i considered doing a 350 swap in the past but i was worried it would be a big task and expensive.

the biggest thing that I've run into when swapping engines in cars this old (finally broken in) are just rusted bolts, particularly on exhaust fittings. If you plan on plenty of time, and make sure you stay organized (keep your wires, hoses and bolts and such labeled and sorted (digital camera pics are great!)) it goes a lot faster than you think.

I was expecting to take a full day to get the 305 out, and another day for the 350 back in, and ended up getting the whole thing done in one day with just my father and I. So I spent the next day putting new cap/rotor/wires/plugs/belts on the 350, and rigging up the exhaust so it fit, and I was actually able to drive it to work on Monday morning! It was a neat change, usually I was the one helping my dad with his projects, but it went smoothly since we'd worked together a lot in the past.

Toward the end of it's life, after having the 350 in it for about 6 years, and upwards of 297,000 miles on the transmission, I finally cracked the flexplate. Otherwise, the tranny held up and shifted great!

Mine was the same color dark brown as yours, but not two-tone, with a vinyl top. I was using S-10 15x7 rims, every time I see your sig, I get cool flashbacks!

--sarge

Getting back to the carb.
What about playing with the jets and metering rods in the secondarys of the stock Q jet for better WOT performance.
I was wondering if this is worth the effort. I was about to do this in my 89 wagon with a stock 307 vin y engine and electronic Q jet.
Also installed a computer chip, not really sure if it made a big difference the car definitely lacks power for passing.
I was told to fatten up the secondarys for added WOT power but have not done it yet. This modification also keeps the car smog legal.

What do you think?

:2cents:

the biggest thing that I've run into when swapping engines in cars this old (finally broken in) are just rusted bolts, particularly on exhaust fittings. If you plan on plenty of time, and make sure you stay organized (keep your wires, hoses and bolts and such labeled and sorted (digital camera pics are great!)) it goes a lot faster than you think.

I was expecting to take a full day to get the 305 out, and another day for the 350 back in, and ended up getting the whole thing done in one day with just my father and I. So I spent the next day putting new cap/rotor/wires/plugs/belts on the 350, and rigging up the exhaust so it fit, and I was actually able to drive it to work on Monday morning! It was a neat change, usually I was the one helping my dad with his projects, but it went smoothly since we'd worked together a lot in the past.

Toward the end of it's life, after having the 350 in it for about 6 years, and upwards of 297,000 miles on the transmission, I finally cracked the flexplate. Otherwise, the tranny held up and shifted great!

Mine was the same color dark brown as yours, but not two-tone, with a vinyl top. I was using S-10 15x7 rims, every time I see your sig, I get cool flashbacks!

--sarge
yeah this is actually my second box caprice so its cool driving around in one again, last one i had was about 2 years ago

yeah this is actually my second box caprice so its cool driving around in one again, last one i had was about 2 years ago

its kinda funny... my first caprice was an 88 LS Brougham, and my second is an 83... i really wish i still had that 88, so many good parts i could have stripped

same here, i actually think the engine on my 88 ran a little better than mine right now, i like the solid bar tailights on that one better too

Now see I think I'm the only one that likes the earlier '80s style lights, with the individual glass headlights, and six separate square chrome framed tail lights. To me it makes the car look a bit classier, a bit more old fashioned. Closer to the cars that I really like such as ones from the '60s and '70s. The way they made the lights after 1985, to me makes the cars look more like the Grand Marquis, and looks newer. Thats just my :2cents:, I'm not saying I don't like the later '80s style, I just like the early '80s better.

Now see I think I'm the only one that likes the earlier '80s style lights, with the individual glass headlights, and six separate square chrome framed tail lights. To me it makes the car look a bit classier, a bit more old fashioned. Closer to the cars that I really like such as ones from the '60s and '70s. The way they made the lights after 1985, to me makes the cars look more like the Grand Marquis, and looks newer. Thats just my :2cents:, I'm not saying I don't like the later '80s style, I just like the early '80s better.

I agree… I do not care for the euro style myself. I just wish I kept my 88 for the driveline minus the trans and interior (leather) the body was shot so it was useless

I agree with that. I absolutely love the body style of my Caprice, and it helps little ricers in their Civics realize that pulling out infront of me isn't a very good idea.

I like the lights on my 83 better than the newer styles also. Looks is secondary for the headlights, I am 100% positive that with 4 separate lights on the front, you have better visibility.

You can aim the Low-beams properly, and you can seperately aim the high-beams properly. No need to compromise the beam pattern, which is necessary when you've got one fixture for both high- and low-beams.

I've got the same setup on my '85 Volvo, and that car has the best headlight visibility I've ever owned, except for a couple friends with Mitsubishi Lancer EVO's. They actually have motorized controllers to raise and lower the aim of the HID lights, VERY handy if you've got a load in the car, and the lights are pointed right into oncoming traffic's eyes because of it.

And plastic lenses, don't get me started. Living in the Salt Belt where i do, you're lucky if you get 5 years of clear lenses, even with a garage-kept car.


--sarge

I like the lights on my 83 better than the newer styles also. Looks is secondary for the headlights, I am 100% positive that with 4 separate lights on the front, you have better visibility.

You can aim the Low-beams properly, and you can seperately aim the high-beams properly. No need to compromise the beam pattern, which is necessary when you've got one fixture for both high- and low-beams.

I've got the same setup on my '85 Volvo, and that car has the best headlight visibility I've ever owned, except for a couple friends with Mitsubishi Lancer EVO's. They actually have motorized controllers to raise and lower the aim of the HID lights, VERY handy if you've got a load in the car, and the lights are pointed right into oncoming traffic's eyes because of it.

And plastic lenses, don't get me started. Living in the Salt Belt where i do, you're lucky if you get 5 years of clear lenses, even with a garage-kept car.


--sarge

There are a few misconceptions that have to do with the composite lamps on the '87-'90 Caprice.

#1- The visibility is better with these than it was with my old '82 Impala (which uses the same 4-lamp setup as any '80-'86 B). Visibility was great with that, but I think I see a little more with my '88.

#2- The aiming of the lamps is not a compromise. The low and high beams aim together, and some people might not agree with that, but think of it this way - the outer lamps in the 4-lamp setup are dual high/low lamps. When you aim those, it's like aiming these - you get the same, legal results. The bonus is that you don't have to reaim the inside highs to match the outside highs on the composite cars.

Personally, I prefer the look of the composite headlamps. It lends a more gracious look to the car IMO.

#2- The aiming of the lamps is not a compromise. The low and high beams aim together, and some people might not agree with that, but think of it this way - the outer lamps in the 4-lamp setup are dual high/low lamps. When you aim those, it's like aiming these - you get the same, legal results. The bonus is that you don't have to reaim the inside highs to match the outside highs on the composite cars.
The low beams true, do also act as high beams, but they work together with the inner beams. Example: When I was aiming my highs and lows I aimed the low beams first, using my garage door X-amount of feet away. I aligned the, and went to do the highs. I flicked on the high beams and saw the level of the highs and saw the light from the low beams where I had just set them. With composite style headlights the highs come on alone instead of with the outer lights so you get your high beam, but darkness closer to the front of the car where with old fashioned glass headlights you get your high beam our in front of you and the low also illuminating the area closer to you. I full spreado of light. I noticed that with my truck as well, although it doesnt have the composite style lights, the outer bulbs do not illuminate when the highs are on. :2cents:Again

PS. I agree with the tendancy for composites (plastic) lights to fog up easily and diminish illumination.

Composite in the regard of headlights mean a lamp assembly that uses a removable bulb, in contrast to a sealed beam lamp where the parabowl is a part of the bulb itself.

The '87-'90 composite lamps are glass and not plastic.

back to the engine talk of this thread, and one last, and maybe dumb question too, would it ever be possible to put a supercharger on an engine like this??

also does anyone know of the max HP acheived on a 305??? (hope this thread isnt too old already to be closed. if so, sorry mods ill start a new one) ANNDDD one last thing, i finally got a video of me doing a pretty good burnout, check it out and let me know what you think! http://www.youtube.com/watch?v=CzIIw1lbXiI

1st off, nice burnout! Secondly, I've seen a 550 HP rebuilt 305 before with a small supercharger.

thanks! yeah i thought there must be some potential for a 305, what would it take to get a supercharger onto my type of engine? just wondering for when i get the $$$ to start putting into the engine.

A supercharger kit generally runs from about $1,500.00 to over $10,000.00. And I wouldn't really say that's great potential. That 305 was heavily built and only achieved a dyno-ed 550 HP (548 point something) while I've seen so many 350s with equal or lesser builds achieving 700+ horsepower (Lester Race Strip, NY). My point is, any engine has potential, even a little 45cc two stroke chain saw engine. Turbo one of them out and see how fast you can cut through a tree! Anyway, I really wouldn't recommend supercharging a stock 350, and even moreso a stock 305. They're good reliable engines, but will not take the beating that boosting forces on an engine well at all. Even engines that come stock with superchargers are built to take more of a beating than engines without boost. The "How to Build Horsepower" series preaches on how all parts need to be "meant" for each other so everything works together in harmony. A 305 does not have heads or valves with sufficient flow to really take a supercharger well. They can't even flow well without a supercharger. A longer duration cam with a slightly higher lift would also be recommended for engine boost. The smart way to do is to build a strong engine that can take a beating first (a foundation so to speak) then give it boost (Supercharger, Turbocharger, Nitrous Oxide).

P.S. Carburetor base injected nitrous is a cheaper and more simple way to go, but will still put a lot of extra strain on the engine. Many kids in my area did it to thier stock cars just to do it, and the results were impressive until one of them over did it.

For a heavy car with lower gearing, it's tough to beat an old TPI system:

http://72.19.213.157/files/1972ChevelleTPI.jpg

The cool thing about converting your Cappy is that most of the wiring you need is already there.

nice engine, what type of car is that on?

oh hey pete, or anyone. in the beginning of my video, whats that little whistling type sound? just wondering cause i noticed its always done that.

oh hey pete, or anyone. in the beginning of my video, whats that little whistling type sound? just wondering cause i noticed its always done that.

The alternator. Normal.

This thread should be pinned. there's alot of useful info that you don't find elsewhere.

Thats true, im def going to refer back to this. i wanted to ask any of the mods here in the caprice section if we could possibly get an "Off topic" thread, just to talk and whatnot.

Mike... I don't know. My Caprice did that all the time before the engine swap. All Caprices I've owned have done it. I don't think the altenator is the cause of the sound... When I swapped engines in my Caprice the new engine didn't whistle even though I used all the same belt accessories on it from the 305. I actually liked the sound an sometimes miss it. It brings me back some good memories believe it or not.

yeah it makes it sound kind of "old fashoned"

It's the alternator. It's a hallmark of the Delco 10SI / 12SI alternators. The newer CS series alternators don't do it so much. It has to do with that little fan on the alternator.

I spent a LOT of time tracking this noise down way back in the 80s - first with my '72 Impala, then my '76 Delta 88 Royale, then my 1975 Caprice Classic 4DHT, then ... well even my Vegas (all three of them) made it. Take the alternator belt off and the noise will go away.

I actually liked the sound an sometimes miss it. It brings me back some good memories believe it or not.

I agree with you. If you like that sound ...

listen to an EMD SD40-2 or GP40-2 (or any 16-645E3 engined) locomotive at idle sometime. The engine driven turbo (these have two stroke engines in them) has almost the exact same pitch whine superimposed over the engine.

In fact, listen to this -

Electro Motive 16-645E3 engine sound (http://www.youtube.com/watch?v=jYn65vidw_8)

yeah i have the delco 12si, looks like this one http://tc.wagoneer.net/sblog/images/alt-12SI4.png

Mine too...
Y'know back about a year and a half ago I dedicated an entire thread to trying to figure out what this sound was and what caused it. I even posted an audio clip of it. Nobody could figure it out. Now in this four page thread one person says "Oh by the way what's that sound?" and a he gets a whole explination as to where it's coming from and what causes it.:rofl:

So how come the sound no longer exists from my caprice even though it has the same altenator from the 305? Different idle maybe?

To tune the secondaries on a Q-Jet, you need to set the secondary AV spring windup tension. Start at the factory suggested ounces of force, and adjust a bit in one direction or the other after test driving until it's right. If the secondary AV also has a vacuum pull-off, you may need to adjust that linkage clearance as well.

Once the AV spring is set, you can adjust the secondary AFR by installing different metering rods and the rod hanger. By removing the air cleaner and only one small screw, you can completely tune the secondaries. If you are feeding an engine with more than 420 cubes or a 350-ish + engine at 7,000 RPM or higher, you may need to adjust the secondary metering well openings (jets). For nearly everything else, the stock size is more than adequate.

Another important question, i wanna get the exhaust redone on the 305, but say down the road i put in the 350, would i be able to use the headers from the 305 on the 350 too?

If you are certain that you're going to a 350 later, get headers with a 1-3/4" primary tube size. They'll bolt up to either engine, but flow more correctly for the 350. A 1-5/8" primary will work for a 350, but not as well at higher RPM.

k ill remember that, just wanted to make sure cause i dont wanna have to resize everything

To tune the secondaries on a Q-Jet, you need to set the secondary AV spring windup tension. Start at the factory suggested ounces of force, and adjust a bit in one direction or the other after test driving until it's right. If the secondary AV also has a vacuum pull-off, you may need to adjust that linkage clearance as well.

Once the AV spring is set, you can adjust the secondary AFR by installing different metering rods and the rod hanger. By removing the air cleaner and only one small screw, you can completely tune the secondaries. If you are feeding an engine with more than 420 cubes or a 350-ish + engine at 7,000 RPM or higher, you may need to adjust the secondary metering well openings (jets). For nearly everything else, the stock size is more than adequate.

Is this also true for the electronically controled Qjet thats in my 89 caprice?

Al

Yes.