View Full Version : Carburator Question

05-11-2012, 10:51 PM
My 1966 17' Champion needs a carb swap. It sits on a fresh 351w with an Eldebrock air gap manifold. The carb on it now is a Holley 750 Marine and I am tired of it. For one, it is probably too big for the motor as some of you have mentioned. Two, power valves and adjustments are not my bag.
....So I took two of my other carbs into the the shop for rebuilds. The first is a old Carter AFB I have had for years and although on a truck it never failed me. The second a new Eldebrock 1407 600cfm that has been sitting for years. Neither are marine type carbs. The shop rebuilt my AFB saying it was better for my application on a boat.
But, the Carter has the overflow vent coming out the side. The Eldebrock is internally vented. Are either of these adequate or recommended to use? And what precautions or safeguards are needed if I do?
Note* I did install the Carter to get her up and running this year and liked the sound of the swap so far. The motor seemed to run much better, smoother idle and quicker throttle response.
I know I am on the right track, just not sure if I need a new marine carb. What do you think?

05-12-2012, 01:53 AM
I think you definitely need a marine carb for safety. I have heard people say you can convert an automotive carb to marine by adding a j-tube, but I don't know if that's true. Or if there are other important differences. Some folks here almost certainly know--there are guys around with tons of carb experience. I'd think that'd be the cheapest bet for you if it's actually true since you have several lying around.

That said, if you end up hunting for a from-the-ground-up marine carb, I have a 600 cfm Holley 4160, set up from the factory for 350 Chevy/351 Ford, basically new in the box (less than one minute of running time) that I'm selling for way under new. It was a spare for my Nova Marine 24, which I just sold. If you have any interest please PM me. Here's the listing: http://www.donzi.net/forums/showthread.php?67379-New-Holley-4160-600-CFM



05-12-2012, 03:08 AM
I would go with the Edelbrock Performer 1407 .
600 CFM is a better carb size for your 351 application .

Unlike Holley that use special "J" vent tubes on the bowl vents on their marine units.

Marine & standard street Edelbrock units are basically the same with the vents located inside the flame arrestor air horn.
The Marine Edelbrocks do have an anti-corrosion coating~~~But I believe the rest of the carb is basically the same as the standard street auto & truck units.

05-12-2012, 08:15 AM
Champ's are RARE

pic's are required at this point :cool:

Dr. David Fleming
05-12-2012, 02:58 PM

The vent nipple on the side of your float bowl which you talk about on your truck AFB is to attach to a charcoal canister. This is a 1970 era automotive anti pollution addaptation to the AFB. Origianal AFB circa 1957-1967 were just small vents drilled in the carb in the float bowls and somtimes in the sides of the venturi and just vented gasoline vapor into the atmosphere to prevent vapor lock etc.

In 1968 these were all made to close off with a large rubber stopper that shut the external venting when the carb throttle opened. At Idle and with the throttle shut the carb vented externally. As I said in 1970 or so the AFB venting was changed to feed into a charcoal canister. When the throttle was opened all these vents were shut by a rubber stopper and the carb vented through the internal air horn vents which are called "balance vents." In automotive use the "balance vents" which stick up next to the choke - these vent to the float bowls. These "balance vents" were made so that if the air cleaner clogged with dirt the high vacume created inside the air cleaner and carb throat would syphon fuel from the float bowls and the carb and engine would go into rich fuel consumption condition. These air horn vents give the same air pressure over the surface of the fuel in the bowl as is in the air horn.

The external venting was to keep the engine from flooding when it was turned off or at idle and the fuel sat in the carb and overheated this would also push fuel into the engine flooding it. As I said the external vent bled this into a charcoal canister or into the air.

The various marine AFB carbs I have seen from the 1960's just used the automotive drilled vents and vented into the boat engine compartment. More modern marine carbs like CArter and Holley bend the "Balance vents" over into a J shape so the point down into the carb barrels. Any fuel coming out of them would go into the engine.

Marine carbs have all electric choke and other various modifications changed for marine use depending on when they were built.

05-13-2012, 08:38 AM
The crisp throttle response and low end fuel savings of a QJet..just don't let it get dirty...Would be great on a 17' boat with a 351.

05-15-2012, 07:58 AM
Edelbrock. Plug and play, foolproof. Just bolt on and run.

joseph m. hahnl
05-15-2012, 06:15 PM
The fuel pump rupture over flow needs to connect to the carb. Any and all over flows need to flow back into the veturi. That it what makes a marine carb a marine carb.
If you get gas in the bilge it will be one less Champion:wink: