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Best carb for dd350 marine engine

Andrew511

Active member
I have a 4 barrel holley 650 on my current engine that falls on its ass when cold. I have a new 350 marine block with 265 hp I’m putting on and want to ditch my current carb. What’s the best one to run? Looking for specific models to order. Thanks
 
That is way too much carb for a direct drive. It falls flat because it’s not flowing enough velocity to pull fuel, making it too lean.

As a pretty simple rule of thumb, at direct drive speeds (2,800 rpm), engine CI = carb CFM. You are looking for a 350 CFM carb. A 2 bbl Holley, varijet etc.
 
Just for a test could you disconnect and wire the secondaries closed and try running just on the primaries.

I would be curious if it still may be a bit to large.
 
SWAMPHUNTER45 said:
Just for a test could you disconnect and wire the secondaries closed and try running just on the primaries.

I would be curious if it still may be a bit to large.


I was told around a 500 2brrl or so would be best . This last reply I got said a 350cfm which I’ve never heard of anyone running one that small. I’m open to whatever works best.
 
Don't judge me, but I'm running a 2bbl motorcraft.... 350cfm I don't know the specifics but I can slide
f o r e v e r on a half tank of fuel/30 gal tank, spin a 72" wispertip at 2900ish and can get outta the water and then back off the banks with a full load, Ford parts or not...might be dumb but it works, runs cheap, I'm happy. Also a new carb, 2100 or 2150 autolite or motorcraft is like $100 bucks new!
 
Dying_breed said:
Don't judge me, but I'm running a 2bbl motorcraft.... 350cfm I don't know the specifics but I can slide
f o r e v e r on a half tank of fuel/30 gal tank, spin a 72" wispertip at 2900ish and can get outta the water and then back off the banks with a full load, Ford parts or not...might be dumb but it works, runs cheap, I'm happy. Also a new carb, 2100 or 2150 autolite or motorcraft is like $100 bucks new!

Na man I’m not judging you I wanna know what’s best I honestly just don’t know. If it works for you then it works. Does anyone have a model number for a eddelbrock or Holley whichever is better that I should use?
 
Andrew511 said:
I was told around a 500 2brrl or so would be best . This last reply I got said a 350cfm which I’ve never heard of anyone running one that small. I’m open to whatever works best.
Many people are misinformed and generically think bigger is better. Very much NOT TRUE in this case.
Gator is giving you good, solid advice. Holley Part # 0-7448 us what you are after.
The 350 Holley you want is the smaller version (CFM wise) of the 500 Holley (#0-4412) that I run on my 472 Caddy.
Both are Model 2300 carbs, among the easiest to tune, and likely have the widest parts availability.

There may well be other places more cost effective than what follows.
Just showing you what you are after. Hope that helps.
https://images.holley.com/2bblstreet_intro.jpg
https://www.holley.com/products/fuel_systems/carburetors/performance_2_barrels/parts/0-7448
 
I've got a Holley 450cfm mechanical secondaries that was run on a sbc 350dd that Jr in Cocoa built for my buddies boat and it did great and was good on fuel..he ran a 72" Woody for a while and then a 72" water walker if you're interested..been on the shelf in a box since he retired that motor and went to a big block
 
670 Holley Street Avenger on my Son's direct drive, no issues at all, turns a 70 Q 2900rpms all day long.
 
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