4 bbl to 2 bbl

[fendersfender]

Just a question to get a few thoughts....i have a '85 25' searay with twin chevy 3.8L v6's in front of OMC 800 series drives...i know, i know..scrap the omc garbage....but anyway...these have 4 barrel quadrajets on them and i had carbs rebuilt 2 years ago and they are harder and harder to fine tune...they are 25 years old and worn out...so new carbs it is!! but i'm really thinking of going to 2 barrel carbs...what do you most knowledgeable guys think??? other than changing intakes its a simple thing....will i lose any power, if so, how much? Omc rated these engines with a 4 barrel at 185hp each....its not a raceboat by anymeans. but a drop in horsepower may require prop changes...i currently run about 4300rpm top end...and i get that rpm before full throttle....at full throttle i can hear that secondaries are open, but doesnt give me ant noticeable gain in speed or rpm....im guessing that im just pouring more fuel for no results....thoughts, opinions??? thanks

 

[JCF350]

Re: 4 bbl to 2 bbl

Double check a service manual, but I believe your gonna end up with 155hp or 165hp engines or there abouts.
Cost is going to figure in. 2V seem to be about half the cost of 4V then you have manifold (or maybe just adapter plate) costs, plus getting the cables mounted right.

Has far as the prop goes?
Do the job
Run it
Change props

 

[fixb52s]

Re: 4 bbl to 2 bbl

There is not much difference with going to the 2 barrel, other than decreased performance. The only time those secondaries open is under WOT when the demand of the engine needs the extra fuel. Oher than that, they stay closed, and the carb is acting as a 2 barrel. Normal cruising around would not call for the secondaries, but it is nice to have if you need to punch it. You might not notice it when they open now, but you sure would miss them if they were not there. Want proof? Wire them closed and take it out. You will notice it.

I would not go through the extra expense and work of replacing the manifolds, end links, and possibly cables. Like you stated, you might be changing the props, just more money as props are not cheap. 2 4 barrel quads are cheaper than the sum of all the parts to downgrade to a 2 barrel.​

 

[xltier]

Re: 4 bbl to 2 bbl

you can send the carbs off to be professionaly rebuilt and they will come back like new ones.painted and all.i think i paid $150.00 for a 2 barrel.

 

[John_S]

Re: 4 bbl to 2 bbl

The primary barrels on the Q-jet are the most fuel efficient for a carb. They have triple venturies and smaller diameter barrels for higher air velocity than that of a two barrel. If you stay out of the secondaries, should have better gas milage. My vote would be to rebuild what you have.

 

[JCF350]

Re: 4 bbl to 2 bbl

Got to thinking and did some looking. Don't see a 185hp V6 listed anywhere only V8.
Your gonna be way down in power swapping over.

 

[paulrfrancisco]

Re: 4 bbl to 2 bbl

you can send the carbs off to be professionaly rebuilt and they will come back like new ones.painted and all.i think i paid $150.00 for a 2 barrel.

$228.00 each at MarineCarburetor.com for rebuilding your own or replacing them with an exact match Quadrajet....