Holley types vs. Q-jet types..

[Flip]

Just wondering the major differences regarding power and efficiency (fuel mileage) are between the Holley types (Holley/Demon) vs. the Q-Jets (Rochester,Edelbrock, Carter)??

[Foggerjet]

Well, they both atomize fuel and introduce the mixture to a common manifold. That's about the only similarity between the two. The Holley platform carbs are relatively cheap, super easy to tune, easy to work on, and plain simple. The Q-jets require metering rod changes along with jets and you have to dissasemble the whole damn thing to do it. With a holley you just drop a bowl for a jetting change. Look at the price of a brand new Edelbrock Q-jet, and a brand new DP. The Q-jet costs more. Now, the AFB platform witch is the "other" carb. is a good one, but it also has the assorted metering rods and stuff. A properly tuned Q-jet is a great carb that will provide years and years of reliable service. But, getting just right may(will) take a bit longer. IMO. I run an 800 CFM Edelbrock (AFB), manufactured by Weber. I was lucky, that was good out of the box. Now as for fuel economy, if the boat has a pump poking out the back, it'll probly get shitty fuel economy regardless of the carb(s). But who cares. If we can't afford gas, we need to sell our boats.
fog

[Flip]

Ok, that kinda goes along the lines of what I've been hearing from other people. Like, Holley's are great for performance but can be a bit less reliable (maybe due to the power valves?) and tend to eat more gas. On the other hand, Q-jets are really realiable and tend to be more efficient (cause of the spread bore setup?) but not as big on making power....
I dunno... I'm just trying to get a feel for what might more truth that myth and vice-versa.
Now as for fuel economy, if the boat has a pump poking out the back, it'll probly get shitty fuel economy regardless of the carb(s). But who cares. If we can't afford gas, we need to sell our boats.
Man, if thats the case, there's gonna be alot of boats for sale here in Cali. :frown:

[Sleek-Jet]

Q-Jets get awesome gas mileage for a carburator... They have dinky little primary's. I have a BB chevy in my 85 3/4 ton GMC and I used to regularly see 15-16 mpg when I had the Q-jet on there. When the old carb gave up the ghost (the throttle shaft bushing wore completly out and the thing leaked more gas than went down the manifold) and I put the AFB on, my gas mileage immediately took a dump to the 9-10 mpg range.
AFB's are just as easy to tune as Holley's in my opinion, and you don't have to get gas all over when you change jets.

[Ken F]

Hey Sleek, you can take it to a machine shop and have the shafts re-bushed.
I've got about 7 or 8 ol Q-jets.
Ken F

[Foggerjet]

I agree that Q-jets get good mileage when you are only into the primaries. If you were to put it on a jetboat, you would rarely be on the primaries. When you hear that distinctive Q-jet "honk", gas is dissapearing rapidly. My old truck has a Q-jet and I wouldn't have it any other way, It's all in relation to how far you stuff your foot in it. That's generally pretty far in a boat.
fog

[HOSS]

A quadra-bog is an excellent carb. It does enable you to get better mileage because (as stated) the primaries are small. But thats why it gets better fuel mileage. Most of your driving is with just the primaries. A 4bbl quadrabog will get better fuel mileage than a 2bbl quadrabog just for that reason. Holley`s are easy to work on (power valves suck) and make consistent power because of the venturi sizes. Quadra-bog got the name from the loud bogging sound when fully openned. There are however a lot of tricks that you can do to a quadrabog without taking the carb aprt or even off the intake. You just have to know what the hell your doing. For this reason I use a Holley. I know this information from reading alot at my bench.

[steve d]

dont get rid of the quadra jet. took mine to c&j santa fe springs 10yrs ago.they rebushed and went thru it. pricey but havent touched it since.

[HOSS]

Hence the most common problem with the quadra-bog, finding someone capable of fixing it. See if the place is even still open. I`m willing to bet that a new one from Summit or the Zone is 1/2 the price.

[Sleek-Jet]

Hey Sleek, you can take it to a machine shop and have the shafts re-bushed.
I've got about 7 or 8 ol Q-jets.
Ken F
I know that there are people that still rebuild them. The problem with mine was that the shafts were also worn. I ended up giving it to a guy I knew that rebuilds Q-jets as a hobby (go figure) as a parts carb.
With the way gas prices are going, I'm thinking about buy a Q-jet for my Cutlass.... :hammerhea