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Anyone Try 2 Barrel Carbs on a 454?

N

Natchamp

New member
Gents,

I did a search on the forum and didn't see anything. I'm trying to find out if anyone has tried running a 2 barrel carb on the 454's to help increase fuel mileage. My boat is a 33' express cruiser @ 16,500lbs with twin Crusader 454's mid 80's vintage. I currently have Q-Jets.

I've read about the Edlebrock 1409, 1410's providing good results but am also wondering how a good 2 barrel would work. I'm not after the top speed of the boat but would love to increase the fuel economy, as I'm sure everyone can relate to.

Anyone try it?
 
I can't imagine a single marine 2 barrel capable of delivering a rich enough mixture to keep your engine from leaning out and melting pistons under load, on plane. You would need a 700 cfm 2 barrel at least. If that even exists, it would not be efficient trying to dribble fuel to your engine at idle/no wake speeds....
number of barrels in carb doesn't determine fuel economy. All the energy that keeps your boat up on plane and moving through the water comes from the gasoline. The efficiency of your engine comes from every aspect of its design and the hull's design/weight - not just the carb.

Bottom line, HP= gasoline.
MPI fuel injection is the only way to seriously increase economy, in my opinion. And on plane, it would be slight gains...

Where MPI can really save fuel is at slow speed I suspect. I'd be looking for some used MPI 7.4's to swap or at least rob all the MPI parts off if that were my boat.
 
Actually, deliverying a reasonable air-fuel mix under load (on plane) would be much easier than getting up on plane, for a 2-BBL.

If you research the issue, you will find that the Q-jet's primary system is one of the most efficient ever designed....You can only exploit it by optimizing the carb's tuning to satisfy the engine-hull combination...it is time consuming to do properly and parts can be a challenge to obtain.
 
You can make YOUR 4 barrel into a two barrel by locking out the secondaries with some wire. If your boat planes easily and is NOT underpowered, you might see a mpg improvement.

Jeff

PS The secondaries on my engines never have to open--it planes effortlessly at half throttle on the primaries.
 
Thanks guys for the information.

If I were to lock out the secondaries, wouldn't I run the same risk of leaning out the engine?

Here's the real question I guess: If I were to install a pair of new edelbrock 1409/10's approximately how much fuel economy are we talking about?
 
Unless the present carbs are flooding, NO significant difference. No reason the motor would be leaned out by locking out the secondaries. The carb is designed to run that way until the choke opens.

Jeff
 
I know I can plane my boat without getting into the secondaries on my Rochesters. Once I get close to 3000 rpm's, that's when they open up and I watch my fuel gauges go down.
 
Just for fun, open up an online CFM calculator.
Plug in your engine displacement, and the RPM that you'll be most likey cruising at.
You'll be surprised at how low the typical CFM requirement is for a Marine engine operating at lets say 3,800 - 4,000 rpm.

For example;
a 454 cu in engine @ 4k rpm requires only 525 cfm @ 100% VE
same engine @ 3.8k rpm, this drops to 499 cfm.

a 350 cu in engine @ 4k rpm requires only 405 cfm @ 100% VE
 
..."Once I get close to 3000 rpm's, that's when they open up and I watch my fuel gauges go down. "

Oh yeah!

I did a throttle position check on my boat (32 Marinette) to see how far the butterflies were open at cruising speed (about 20 mph @ 2,500 rpms). I was stunned to discover I could not slip a pencil between the butterflies and the carb body--they were barely open! Still burns 16 gph (both) at that speed.

Jeff
 
To answer your question abt how much better economy the 1409 gives. None. I have a qjet on 1 engine and 1409 on the other and both tanks run dry at the same rate.
 
And another fuel line...there have been a few detailed posts on this forum covering this particular mod in detail. You may wanna search for them and exploit the lessons learned that have been shared.
 
Thanks guys,

I was aware of the adapter plate.

I searched and didn't find anything on adding another fuel line. Can't imagine what you are referring to or how that would help anything but I'm always ready to learn something new.

One thing I do plan on doing when I install the 1409's is to add a fuel pressure regulator on each engine. One engine has a mechanical pump while the other has an electric pump. I should have put regulators on in the first place but I didn't. For the 1409's, I know the pressure should be set to below 6 but anyone have a more specific number like 4 or something?
 
You will need a new fuel line if you are still running the original steel line as the inlet in the edelbrock is not in the same place. Seirra sells a replacement flexible line with the fittingsalready installed. It is also easy to cut so that you can put an inline filter on because the edelbrock does not have the filter a qjet has.
 
If you're handy, and have the tools, the stock Edelbrock fuel inlet can be tapped for pipe threads. You can then adapt it to whatever you wnat: a barbed fitting to a CG approved hose, or a tubing fitting.

On mine--with the boost pump set up--I use a Tee and check valve, One small electric pump fills the carbs after the boat has been sitting a while, then the mechanical pump takes over.

Jeff
 

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I've heard that before, but here's why I use it.

Flared copper fittings are famous for fatigue cracking at the flare. You don't see that--ever--with a compression fiting. Finally, this is a tiny, 1/8 " copper tube. They seal fine.

Jeff
 
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