curtis84ta

What is the best carb to put on a 305 5L? RIght now i have the 305 low output putting out 150 hp and 240 torque and i would like to boost that up a bit hopefully with a better carb. SO what would you guys reccomend?

IHI

iTrader: (1)

Like always a 600cfm Carter/Edelbrock for daily driver or 600-650Holley DP for all out.

curtis84ta

will the 600-650 dp ruin the engine at all if its bone stock? or doesn't that stuff matter?

IHI

iTrader: (1)

When I first started racing last year I stuck a 600VS Holley on my bone stock 305 w/ 120K on it along with a edelbrock intake, ran like a raped ape to the tune of 14.8 in the 1/4mi. The DP will eat at your fuel economy if daily driven, but you will have more out of the hole than with a VS. If it's gonna be more for racing than daily driven, the DP is the only way to go. I was stuck on a VS at first last year because that's what the magazines said for a heavy, automatic car. When I finally listened to everybody and stuck a DP on, I picked up literally .6 in the 1/4mi. But that was a 750VS on my then new 355 being replaced by a Holley race 830DP. Made a believer out of me and cemented what everbody was telling me.

curtis84ta

whats the diff in fuel economy? is it like 1 or 2 km/tank or is it 5-10 km/tank because its gonna be daily driven (hwy) from now until summer.

IHI

iTrader: (1)

To tell you the truth I personally have no exact data with the differences, hopefully somebody that has experience with this will post. I know when I went from my 750VS to the 830DP I could only drive around town for an hour or 2 at most before I was empty. It won't be that bad with your 305 and a 600/650 but you will drop mpg that will be easily noticable. With gas prices and daily driven I would stick with a VS since you can always install a ighter spring in the secondaries to bring the back venturies in quicker for a simulated DP carb. Keep installing lighter and lighter springs until you hear/feel the back butterflies coming open or feel a slight bog, then go back a spring rate.

sqzbox

DAAAAM! Did you throw that 600 on a stock 305? If U did, I'm going to throw my comp. and TBI as far as I can becuase I hate that dam comp. and all it's little sensor buddies. My 88 is rated at 170hp. so 600 should be quite an improvement. Let's see, carb, manifold, manual hei dist. and shift controler for my 700-R4 Right?

IHI

iTrader: (1)

Alright, truth be told about my stock 305 w/ 120K. I took the car out for it's first maiden voyage after like you said stripped it of all it's computerized BS since I'm not a techno person and seen it more as a pain the the **** to deal with and I like to get at my components easily. So yes, took the stock aluminum factory 4 barrel intake and quadra junk off, installed the edelbrock performer dual plane with Holley 600VS. AND I also installed Headman full tube headers-the cheap bastards $104 I think going into dual 2.5" exhaust with an H pipe-which made an incredible difference over just a dual exhaust with no crossover. When I first picked the car up from my ex-sponsor they did'nt have time that day to get the H pipe in, I drove out of the lot and could'nt spin the tires, next day they installed the H pipe and it was literally like a totally different car, could smoke them in first at will. At the time I had the same 700r4 from the factory with 120K on that as well. Can't remember what timing was set at, 34* total I believe with new parts in the HEI. Open 14" air filter. I was running some new cheap assed 245/60-15 radials all the way around I got from a bud that owns a tire store set at 18psi out back and a 3.42 posi rear end. Was getting 1.95 60' and 14.8's out of it. Believe my shift points with that set-up were around 5K since it seemed to peter out above that. Now since we were all so impressed with what this POS 305 was doing we decided to cam it, so that next day went to my buddies performance shop and got a new cam for a 375hp 350-old school grind just becasue he had it on the shelf, swapped everything over and took for a maiden voyage. Ended up blowing the damn thing about 1 mile from our shop-BUT it got me home knockin like a sum-bitcch. So we never got to see what it would do with the cam swap did for performance. All it all it WAS a strong 305 for awhile till we screwed it up, ended up being a keeper fell into the motor when we were swapping valve springs for the new cam, but oh well. The TBI will get you nowhere, reliable as you could ever want, but not a performance item by any means.

Air_Adam

600-650cfm Double Pumper.

A vacuum secondary carb would be fine for a 'no-frills' boring steet engine (the stock Qjet is VS) but if you wanna go fast, get a carb with mechanical secondaries like a Holley Double Pumper.

nathan2003

i had a tbi setup now all edelbrock, with 600cfm carb.. ,, you will need to get a fuel pressure regulator - stock pump puts out to much. making the switch sounds pretty easy but it was a frustrating thing for me at least.. tons of hidden little extras that you have to do and unexpected crap... also you will have to pull your plugs and gap them to .045 instead of .035... the 600 cfm carb was way to rich for my setup... i have 305 also... the outta the box setting is making it run rich... if this is all you'll do to this 305 like not put a cam in or something or if your not planning on using the carb on another moter get a 500 cfm for the 305 or do as i did get the 600 and but some rods and jets so you can rejet it...

five7kid

iTrader: (14)

Gads, how many times do we have to say this? Not trying to put anyone down, but come on guys, let's get real.

The 150 HP limitation of your engine has absolutely nothing to do with the carb! That is an LG4 - it has a wimpy cam, soda-straw exhaust, soda-straw air cleaner, and small valve heads.

Take care of those things, and the ignition will hold you back a little on the top end - so upgrade the coil and module. The cam will cause a little loss of low-end power, so get a higher stall converter. The intake could be a little better, so a Weiand Action + or GMPP will help a little.

But, the carb that came on the car from the factory will still make as much power as anything you can get from the aftermarket. You may need to tweek the secondaries a little to get the AV to open all the way (see the tech articles), and tune them with rods/hanger - DR/B is a very good combination.

You can improve the bottom end response by going with a double-pumper type carb - really only an issue of you drag race regularly. Gas mileage will take a significant dip with any of those aftermarket carbs. Did anyone mention you'll have to replace the intake manifold to mount one of them, or get an adapter?

Stick with the carb you've got. Fix what's really wrong. If you don't do anything about the exhaust, air cleaner, cam, or heads, putting a different carb on there will make absolutely no difference in power, and will most likely cost you gas mileage.

IHI

iTrader: (1)

Just to keep the record straight, I was making a statement to sqzbox since he'd running the absolute king of realiability TBI, but anyone that thinks these units can make a good performance peice will need to offer whatever is being smoked The HEI's can be fixed/brought up to date relatively cheap as well as new plugs/wires ets...but anytime you up the anty with a better intake, headers for cheap/easy bolt on stuff, ultimately the car will have not choice but to run better/more efficently-more air in more air out than in stock form. A better carb will also spice things up also. Personally have only seen 1 out of 5 Edelbrock carbs even work half way correct out of the box, but we all grew up Holley freaks, hence the favortism, since they take all of 15minutes to set up and go if that. For alot of the folks here a cam swap on a daily driver is out of the question for sake of wrenching ability and/or time,money, so the old tried and true methods of easy bolt ons are still the dominate way to go, since head/cam swaps are pricey by any nature and time consuming for the new mechanic. I can't think of a time I've heard,seen, read of a CC Quadra junk outdoing a modified set-up, but then there's still alot I don't know too.

five7kid

iTrader: (14)

This is one of those cases. A 305 will not out-need what a q-jet can flow. Spending money on replacing it will take money away from what you need to do to improve power.

Oh, for the record, Canadian LG4's didn't have CC in the early years.

sqzbox

The vac. regulator is correct. The pressure from the TBI system fuel pump would have to be cut back some. To much and it will continue to bend the float tangs while trying to shut the inlet valves. Float level would not stay in adj.

five7kid

iTrader: (14)

Squeeze, TBI motors have all of the problems of the carb LG4's (exhaust, cam, heads, air cleaner), plus one more: Unlike the LG4 heads, which can be improved with larger intake valves, porting, and springs, LO3 heads are maxed out at about 200 hp. There's nothing more you can do for them. Improving exhaust will help, putting in a cam will help, converting to carb will help. But, it will always be limited by those heads. They've got to go.

Curtis, back to your original question: If you're looking for power improvement on the daily drive, start with the exhaust - headers, 3" exhaust from the y-pipe on back to the muffler. Then improve the air flow at the air cleaner - dual snorkel is the real way to go. Those two things will make a noticeable difference, and will likely improve fuel economy as well.

If you want to step up to open-your-eyes power, then you've got to improve the flow in the heads and improve the cam. That will probably start costing you economy. But I'll keep on saying this: The carb on the car now will still be your best choice, of all that's out there, for a daily driver.

radiateu2

I am with 57 on this. A 305 could not possibly nee anything more than the quadra-jet it came with, even after fixing the choking exhaust peanut cam and the crappy intake system like small valves but pocket porting and putting in larger intake valves along with upgrading the exhaust will do more for your 305 than aftermarket carb will. These engines cant breath worth a darn stock slapping an aftermarket carb is money that could be spent up grading the choking ailments placed by GM. Tuning the q-jet with rods and hangers would certainly be the best place to start as well as advancing your timing and tweeking the advance curve if your car is equipped with it