holley carburetor wondering what to do next

[mxcobra]

I got this bad boy on ebay, its not really what I thought I was getting ad said. Great performing Carb just needs cleaned. When I received it It smelled like very potent bad gas. I cant really find any info on it exept its a 750 cfm Holley. its missing the spacer so it dont fit my manifold. Im not evan sure I want to use this thing on my brand new long block 350??? any ideas on what I have here, and if I should go forth with trying it out on a new motor or not???

 

[Scott Danforth]

Volvo and OMC used holley, and Mercruiser used Rochester and other spread bore carbs. you will need an adapter unless your intake has both bolt patterns or is for a square bore carb.

if the carb smells of bad fuel, you will need to get a carb kit and go thru it (Clean it like the add said). make sure you get the correct kit with the #25 power valve and i would recommend the silicone coated (blue) metering plate and bowl gaskets.

there should be some numbers on the air horn (starting with 8). post them.

 

[flipbro]

I no expert on carbs but I would guess 750cfm holly is over kill 4 a stock 350.

 

[Darrenmb]

I no expert on carbs but I would guess 750cfm holly is over kill 4 a stock 350.

This..

 

[Bondo]

Ayuh,.... Mercruiser never used the Holley carbs, just Qudra-Jets, 'n then 'round the mid-'90s, they went to the Weber/ Carter AFB carbs,...
I like the Rochester some, 'n the AFB Alot, because of the side-bowls, Vs: the Holley's fore, 'n aft bowls,...
Common sense says the aft bowl on a Holley is more apt to over-flow, or the front bowls go lean, considerin' the angle boat motors sit at,....

Also, the 650Cfm carbs are used on the 4.3l, the 5.0l, 'n the 350s,...
The 750Cfm carbs are for Big Blocks,...

Not that a 750Cfm won't work on a small block, but the vacuum signals are less precise,...
hence, the 650Cfm carbs,...

Personally, I'd soak, clean, 'n kit the Holley, then sell it,...
Buy a Edlebrock 650 carb, 'n you can use factory Merc brackets, 'n linkages,...
The Edlebrock is a carbon copy of the Merc/ Weber, the parts all interchange,....

 

[Maclin]

That is a double pumper Holley, usually for explicitly high perf automotive/racing applications. Has the J tubes but other than that thinking not an "everyday" Marine carb. Should be easy to sell to auto racing users though.

 

[achris]

Ayuh,.... Mercruiser never used the Holley carbs,

Err, yeah, they did, until the late 70's.

I like the Rochester some, 'n the AFB Alot, because of the side-bowls, Vs: the Holley's fore, 'n aft bowls,...
Common sense says the aft bowl on a Holley is more apt to over-flow, or the front bowls go lean, considerin' the angle boat motors sit at,....

One of the reasons Merc dropped the Holeys (not misspelled)... And the fact that they couldn't stop 'em from catching fire!

Also, the 650Cfm carbs are used on the 4.3l, the 5.0l, 'n the 350s,...
The 750Cfm carbs are for Big Blocks,...

Not that a 750Cfm won't work on a small block, but the vacuum signals are less precise,...
hence, the 650Cfm carbs,...

Personally, I'd soak, clean, 'n kit the Holley, then sell it,...
Buy a Edlebrock 650 carb, 'n you can use factory Merc brackets, 'n linkages,...
The Edlebrock is a carbon copy of the Merc/ Weber, the parts all interchange,....

Agree, clean up and unload..... And also agree, 750cfm is way too big for a 350 boat engine. The air flow at idle is very slow (large venturis) and it makes getting the idle mixture settings right a PITA.

Chris..........

 

[mxcobra]

well I'm thinking I know what to do now.....I am looking for performance though as opposed to just good running.
R84039-2
3047
are the numbers really not much info I can find on it, id like to know more about what im dealing here on the Holly. I would like a direct fit, that sounds great. there really isn't much room under the hood. I'm not sure the spacer required to use the Holly, would give me the room in the engine bay- its tight.

 

[achris]

A 350 running at 5000rpm only sucks about 420cfm. Even a 650cfm carb isn't being stretched. If you want a direct bolt on, do what Bondo suggested (and most of us agree with), get a Edelbrock 1409.... Even uses the same throttle cable link up. It really is just a straight bolt on, no mods of anything required...

And as far as performance, the Edelbrock will eat the holley and spit the bits....

Chris.......

 

[mxcobra]

I wonder if I used the Holly and got a spacer plate that has the butter fly valves I could tune the cfm that is being used?!?!?!, I did put the thing on craigslist though.... if anyone is interested in the carb let me know I would like to trade it or sell it not looking for much as I didn't pay much.

 

[mxcobra]

Volvo and OMC used holley, and Mercruiser used Rochester and other spread bore carbs. you will need an adapter unless your intake has both bolt patterns or is for a square bore carb.

if the carb smells of bad fuel, you will need to get a carb kit and go thru it (Clean it like the add said). make sure you get the correct kit with the #25 power valve and i would recommend the silicone coated (blue) metering plate and bowl gaskets.

there should be some numbers on the air horn (starting with 8). post them.

I got those numbers Scott, if there is anything else you can tell me about the carb. It will bolt up to my new intake but will need a spacer plate.
R84039-2
3047

 

[Scott Danforth]

Here is the link to the Holley documentation

http://documents.holley.com/techlibrary_carb_numerical_listing.pdf

its a 750cfm mechanical secondary unit. originally it came with #79 jets primary and secondary. it was most likely on a big block, or a really light hull with a built small block. with the mechanical secondaries, you will use a bit more fuel than the vacuum secondary units. It may be a bit big for what you need, especially if your longblock is stock

here is the rebuild kit (Holley 3-1445)

https://www.summitracing.com/search...or-rebuild-kits/carburetor-list-number/r84039

 

[mxcobra]

thanks for the help guys, I really need to start coming here first before I go jumping on, boat parts and such I ordered up the 1409- this will be best....
Im going to have no problem off loading the Holley put it on craigslist and the people are jumping after it. plus it originally came with a nice spark arrester to0 so that's good

 

[Bondo]

Ayuh,.... Wise decision,....

 

[Scott Danforth]

FWIW, Volvo used a 715cfm vac secondary Holley carb on the higher output 350's from the mid 80's on. Its the carb that came on the AQ271's ,AQ310's and the later 571, 572, etc

 

[mxcobra]

FWIW, Volvo used a 715cfm vac secondary Holley carb on the higher output 350's from the mid 80's on. Its the carb that came on the AQ271's ,AQ310's and the later 571, 572, etc

MMMMM my motor is already half volvo, are you saying I should give this carb a shot!

 

[Scott Danforth]

MMMMM my motor is already half volvo, are you saying I should give this carb a shot!

It would depend on what you built the motor with....pistons, cam, intake. Being a mechanical secondary, it may fall on its face as the secondaries open.

 

[mxcobra]

It would depend on what you built the motor with....pistons, cam, intake. Being a mechanical secondary, it may fall on its face as the secondaries open.

Its just a bone stock gm goodwrench 350, I may stick a cam in it. I dont think I wanna put up with the hasshell of using this carb

 

[Maclin]

A Vacuum secondaries carb is variable CFM based on engine demand, ideal for high load duty cycles. A mechanical one like this one is not, and like Scott mentioned if the engine can't use the CFM it will fall on it's face when you stab it. BIG engine in a LIGHT boat is what this carb is for,

 

[jimmbo]

The picture of your carb, may be a double pumper, but is missing the linkage that operates the secondary accelerator pump

Holley makes a real nice marine 650cfm spreadbore. I used it on my 5.7 VP. It increased my top speed by 10%(6 mph), compared to the stock 500cfm Holley 2bbl, and the small primaries helped keep the bottom end even though I had to increase the pitch of the prop by 2" to keep the rpms in check. I did not change the intake, as Volvo used a 4bbl intake and an adapter to mount the 2bbl

https://www.holley.com/products/fuel.../parts/0-80552