Too much carb?

[boyer61]

Hey guys, i got a 84 k10. 305 bored to 311.

It's got a holly 600CFM carb on it. It's running very rich, i'm getting like 8MPG.

I want something that will give me decent gas mileage, some power.

According to Holly's website it says i should be running a 390 CFM carb. Is that too low?

[GreaseDog]

the 390 is definitely too small.

what cam, compression, gears, trans and tire size are you running? you may have a mismatch somewhere in the drivetrain causing the poor fuel economy.

[boyer61]

It's basically stock. 32X11.50 tires, 4sp granny gear. Im not sure what gears are in the truck. It feel's pretty high, around 2500 rpm in 4th gear going 55.

[boyer61]

I've been doing some research, and the edelbrock 1404 carb looks like the best for me. I dont want to spend over 300 dollars.

http://www.jegs.com/i/Edelbrock/350/1404/10002/-1

any suggestions?

[GreaseDog]

I've been doing some research, and the edelbrock 1404 carb looks like the best for me. I dont want to spend over 300 dollars.

http://www.jegs.com/i/Edelbrock/350/1404/10002/-1

any suggestions?

leave that carb on the shelf at Jegs...

http://www.summitracing.com/parts/SUM-210214/

http://www.summitracing.com/parts/SUM-210216/

[boyer61]

Isnt 750 too much?

[RichLockyer]

Quadrajet is a spread-bore

The typical Holley is a square-bore. All 4 barrels are the same size, so a 600 is just like a 300 2bbl when you only have the primaries open.

The Quadrajet, Thermo-Quad, and a few others (I had a Holley spread-bore 650 on my '69 Camaro) have much smaller primaries and "toilet" secondaries.
The total flow capacity of the carb might be 750... but over 75% of that flow is from the secondaries. Keeping your foot out of it give you the fuel economy of a small 2bbl carb!

[boyer61]

Interesting. The PO Said it would need a carb, he said the secondaries stayed open alot. thus the bad mileage.

Would i be better off buying the edelbrock 500cfm? I wouldn't buy it from jegs, i can get it much cheaper locally.

Or would i be better off with a stock replacement?

What would you guys recommend for the best fuel economy.

[RichLockyer]

Edelbrock makes fantastic intake manifolds, good RV cams, and some good looking valve covers and air cleaners.

They do not make good carbs. Actually, they don't make any carbs... they are made for them.

[boyer61]

That you very much for your input. Would something like this be good?

http://www.oreillyauto.com/site/c/detail/HOL0/080457S.oap?year=1984&make=Chevrolet&model=K10&vi=1299696&ck=Search_2431P_1299696_1178&pt=2431P&ppt=C0359

[RichLockyer]

That's a model 4160, looks to possibly be the same as what you have. It's not a spreadbore.

Now, if you have a squarebore, depending on your manifold, you may or may not need an adapter to use a spreadbore.

But seriously, I'd spend the money on the Quadrajet. It was a standard carb for GM vehicles for many, many, many, many years.

[boyer61]

I have the edelbrock RPM manifold.

[RichLockyer]

They do have a couple of RPMs that can take either the square bore or spread bore, but it looks like most of them are square-bore only.

[matt167]

Edlebrock carbs are just Carter AFB's ( Aluminum four barrel ), slightly tweaked, tho they also have the AVS ( Air Valve Secondary ) variation. Webber manufactures them... Quadrajet is what I would run, not only is it what a 305 got from the factory, they only take the air they need. So that 750 CFM could run a 4.3L just the same as it could a 383, with some tuning of course, but that's all GM did with them

[GreaseDog]

whats the number of the manifold you have? and which carb do you have? the numbers are on the choke horn on the top of the carb.

[boyer61]

I have an performer rpm edelbrock manifold. The # on the carb is 1850-2

[boyer61]

http://i484.photobucket.com/albums/rr210/boyer61/IMAG0082.jpg

http://i484.photobucket.com/albums/rr210/boyer61/IMAG0083.jpg
http://i484.photobucket.com/albums/rr210/boyer61/IMAG0085.jpg
http://i484.photobucket.com/albums/rr210/boyer61/IMAG0086.jpg
It's leaking some. been rebuilt 3-4 times by the PO.

[GreaseDog]

from the pics, it looks like you may have a 7104 RPM manifold. if you can find the number on the manifold, it will be 7101 or 7104. if its 7104, you can bolt a QJet right on it. if its not a 7104, buy one of these. http://www.summitracing.com/parts/TRD-2064/

[boyer61]

Is there anyone who could decode the date code on that carb? Everything i've looked at doesnt really make sense.


I know you guys have been suggesting a quadra jet, but im really looking for something thats ready to be used as soon as i get it, and doesnt require much tuning.

I really like that edlebrock i posted. it's smaller than the one i have. Why don't you guys like edlebrock carbs?

[GreaseDog]

i bought a Summit rebuilt QJet, and have had it on 2 different small blocks, a 1980 LM1, and a 1987 L05. minor tuning to the idle mix, and idle speed with the LM1, and i bolted it right onto the L05, and it runs great. you're going to have to do that with any carb you get. as stated before, the QJet may be a 750cfm carb, but its only going to flow what the engine asks for.

the Edelbrock carb isn't especially good at anything, its not great for performance, which is generally Holley territory unless you're really handy with QJet tuning. and they're not great at milage (which is what you stated you were after), that's hands down QJet territory, due to its tiny primaries.

[Jameslleary]

If I ever broke down on the road, in the middle of nowhere, in need of a new carb, and someone stopped and offered me an Edelbrock carb out of the box, I would opt for the tow truck.

[kemble]

Your Carb is in no way to big. It just needs to be gone through and adjusted by a competent person.

[matt167]

Edelbrocks arn't bad carbs by any means, there an older prooven design, just like Holley and Rochester.. However, they are on the harder side to tune, are lesser of a carb from a performance standpoint, and altho there not bad, there not the best choice in a GM vehicle, altho I have seen a Q jet sitting atop a Ford 302 on an adaptor, so it could be said for Mopar and Ford as well. Out of all 3 carbs mentioned, the Q jet will get the best MPG, the Edlebrock second and the Holley last. in perfect tune of course

[GreaseDog]

Edelbrocks arn't bad carbs by any means, there an older prooven design, just like Holley and Rochester.. However, they are on the harder side to tune, are lesser of a carb from a performance standpoint, and altho there not bad, there not the best choice in a GM vehicle, altho I have seen a Q jet sitting atop a Ford 302 on an adaptor, so it could be said for Mopar and Ford as well. Out of all 3 carbs mentioned, the Q jet will get the best MPG, the Edlebrock second and the Holley last. in perfect tune of courseif an AFB carb is hard to tune, you need to not touch a carb ever. that's their only redeeming quality, your grandma can rebuild and tune them. they aren't especially good at anything else.

[matt167]

if an AFB carb is hard to tune, you need to not touch a carb ever. that's their only redeeming quality, your grandma can rebuild and tune them. they aren't especially good at anything else.

I prefer Holley for ease of tuning. I can tune an AFB, and I know many of the Edlebrocks simply run out of the box. They meter fuel a bit better than a Holley from an economy standpoint, but suffer with HP... I'll take a Holley over an Edlebrock, but if I needed a cheap carb to get running again, I wouldn't pass up a good Edlebrock or Carter AFB/AVS if a Holley or Q jet were unavailable..

[boyer61]

I put a 1404 edlebrock carb on it yesterday. My god what a difference. Feels like a new truck.

[CamperSpecial01]

Good info here. I don't need a new carb yet, but its always good to know the good and the bad out there before you buy. I don't know to much about carbs, but I've always heard that edlebrock was a good aftermarker carb, that was easier to tune than a holley. I think now tho, if I ever need to replace id just get a q jet.

[1.721afr]

Yes, a Q-Jet will both out-run, and, get better gas mileage than the Webber/AFB.

[85k5]

the Q-jet will flow enough for most street/trail trucks and will cost you less from the time you buy it to how often you need to fill up. even if you have a mildly built motor a q-jet can handle that too, it will give you good power and the best possible fuel economy, and it will always fire up in the morning

[jimbonice]

Keep the Holley 600 you've got! It's a fine carb for what you are using it for. It has vacuum secondary's, and is more than satisfactory for your vehicle. While I am a big fan of quadrajets, I would not dump the carb you've got to purchase one. A properly tuned 600 on your small block will provide comparable economy and you've got those infinitly adjustable secondaries to play with.

On a side note, I have found when towing with a big block, the larger primaries of a Holley 750 can provide better economy than a quadrajet. More throttle can be utilized on the Holley without opening up those tin can size secondaries that are on the quadrajet. Where you want a bit more throttle to pull a hill, for example, you can ease up over it in the Holley, where the q-jet wants to open up the back barrels. That said, my current truck has the quadrajet on top of the 454, it works like it should, purrs like a kitten and is staying right where it is at, and will be replaced with the same if it needs it one day.

Keep the Holley and fix it.