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What size carb should I run.

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10K views 56 replies 10 participants last post by  opie272  
#1 ·
I am referring to my fathers jet boat which has a 460 Ford big block that is approx. 330HP. I am currently using one of the original stock carbs off my Sunsation that sat on the stock 502's. I believe thery are a Carter AFB series and are 750cfm but I am not positive.
I ran a Barry Grant/Holley 750 double pumper that a friend let me borrow and the motor really responded well to it,but I am really wondering if that carb is over kill or will the Carter series that I have will do the job.

What do you think.

Carter series?
 

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#3 ·
If I can find it there is a formula for calculating CFM by determining the max RPM and CID of the engine.

When I find it I will post it.

Calculating mine it hit with 10 CFM of what I showed on the dyno....once I got a big enough carb to flow right. :rolleyes:
 
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#5 ·
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#6 · (Edited)
By my math :rolleyes: I figured (460/2)X(6000/1728)X0.90
230 X 3.4722222 X 0.9=

718 CFM.

So a 750 CFM carb would work. If you are turning less than 6K RPM.

Remember... the smaller the carb the better signal the carb gets from the engine. The better throttle response is.
The larger it is the less throttle response is.

What I have been educated to use is the carb that is just a squeak smaller than you need if you do not run WOT very often.
Just a squeak over if you are like the rest of us and like WFO more than not.
 
#7 ·
Daveboys said:
What carb was on it before? I have never had a BBF run as good with a carter/Edelbrock as they did with a holley. You will find it hard to over fuel that engine, I say the bigger the better. If it had a holley on it to start with I would run it instead of the carter.
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It had a Holley carb on it before but it was only a 600cfm. basicly the same carb that used to come on the early to mid 80's Mustang GT's. I told my dad for years that 600 Holley carb wasn't enough for that motor.

I realize the big Holley is the better way to go but as I said before,I have went WAY over budget on this project and still have to finish the interior and buy a set of headers. So you can probably see where I am coming from.
The lake my father lives on is very small so he doesn't have the room to really stretch this thing out and let her rip. If he tries to do that he will end up on someone's front lawn. :laugher:
 
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#10 · (Edited)
That calculates into 648 in my feeble brain.

I have an Edelbrock Marine 750 carb that you can use to play with and see if you like.

You pay shipping and go for it.

If you like we can figure $$$now or later.

I got $200 for my last one, but they sell new from Jeg's $279.
I'll take 1/2 that so $140 sound fair?
 
#11 ·
opie272 said:
That calculates into 648 in my feeble brain.

I have an Edelbrock Marine 750 carb that you can use to play with and see if you like.

You pay shipping and go for it.

If you like we can figure $$$now or later
Click to expand...
Do you have any pics of it? Isn't it basicly the same as what I am currently running on the boat now? (Refer to 1st pic)

I just might take you up on that offer.
 
#17 ·
DS , don't go by formulas . Holley recommends a 650 for a 460 Ford . A 460 BBF with a jetdrive will not run at its peak with a small carb. The Holley marine 850 CFM vac secondary carb with 88 primaries and 94 secondaries, 6.5 power valve is the best . Check what heads you've got . A CJ head on a 460 will yield 5300-5600 rpm with an "A" impeller , depending on CR. If you have an A2A head , just grind the EGR bumps to
improve exhaust flow. The late 460's came with retarded crank gear for the camshaft . Most experts recommend to go back TDC ;) . I found the retarded setting is best for a jet , since the constant high rpm operation . There's lots of bottom end torque in the BBF already ,and 4 degree retard is better with the power-band moved to the top .
 
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#19 · (Edited)
mirage257 said:
DS , don't go by formulas . Holley recommends a 650 for a 460 Ford .
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The formula was to get him in the ballpark.

Nothing replaces "real world" experience.
I was not trying to give Numbers to live by. Just a ballpark.
That is also why I offered the Edelbrock to use to get "real world" experience.
$20 shipping to try it should not be too much to handle?

Since he said he was OVER budget I figured a couple of different options for minimal $$$ would be helpful
 
#23 ·
DS, the blue boat is a 1991 Carrera .We had Bassett OT headers on it origionally . Doug [ owner ] didn't care much for the excessive noise :winker: and opted for a wet log system . Contrary to many opinions, he didn't loose performance at all . Many jet boaters ignoring the fact that the risers have a step-down reducer to accommodate smaller diameter rubber hoses between the tail pipes and the snails. Cutting this reducer off opens the riser exit quite bit. Big engines with huge cams benefit from headers .
 
#24 ·
mirage257 said:
DS, the blue boat is a 1991 Carrera .We had Bassett OT headers on it origionally . Doug [ owner ] didn't care much for the excessive noise :winker: and opted for a wet log system . Contrary to many opinions, he didn't loose performance at all . Many jet boaters ignoring the fact that the risers have a step-down reducer to accommodate smaller diameter rubber hoses between the tail pipes and the snails. Cutting this reducer off opens the riser exit quite bit. Big engines with huge cams benefit from headers .
Click to expand...
Yeah but the headers just look way cool on these old jet boats.

On another note we took the Sanger out for another run and tried both of the Elderbrock carbs that came off my Sunsation and they both had the same results. THEY SUCKED!!!!!!! :angry1: For some reason it appears that the secondaries aren't dumping any fuel when you stomp on it,and she falls on her face. :angry1:
I pulled the plugs last night and there is no doubt I am running into a lean condition and she will only spin up to 4000RPM's. She runs great as long as she is running on the primaries but the minute the secondaries try to open she just stutters and falls on itself. :confused1
I also checked the in line fuel filter last night and it is clean. So I am gonna try the Holley again so I can verify that it is a carb issue and not something else. :mad:
One other thing. After pulling the carb off last night,I put it on the work bench and opened up the throttle linkage and gas squirted out of the primary squirters but the secondary squirters were dry and nothing came out of them at all. What in the heck would cause this to happen on both these carbs? :confused1 Could it be that since these are set up for a Mercruiser 502 they just won't work on the 460 motor? :confused1 At this point I am just looking at any possibility. :rolleyes:

Could the fuel pump be weak or is this just a carb issue? :confused1
 
#25 ·
Scott,

I would go back to the Holley carb. I would go with either the 700 or the 750. Remember that this is a stock motor. Your old carbs are probably blocked on the secondaries. You may also want to look at the float level or the metering block. I am not sure if those carbs used a PV or not. You may want to buy a rebuild kit for it ( $25-30.00 ) and clean it real good and then retry it. Since you are running over buget, I personally would leave the headers off. Yes they look cool, but remember that your father may not like the noise. I would wait and kind of hint around on his feelings first. Then if this is something that he would be interested in, you can get them for him on his birthday. Maybe even take him out when there are a few other boats out there with the headers on them and see what he thinks.I think you have done a great job with the boat and he will be very surprised with or without the headers. :D
 
#26 ·
Thunderman98 said:
Scott,

I would go back to the Holley carb. I would go with either the 700 or the 750. Remember that this is a stock motor. Your old carbs are probably blocked on the secondaries. You may also want to look at the float level or the metering block. I am not sure if those carbs used a PV or not. You may want to buy a rebuild kit for it ( $25-30.00 ) and clean it real good and then retry it. Since you are running over buget, I personally would leave the headers off. Yes they look cool, but remember that your father may not like the noise. I would wait and kind of hint around on his feelings first. Then if this is something that he would be interested in, you can get them for him on his birthday. Maybe even take him out when there are a few other boats out there with the headers on them and see what he thinks.I think you have done a great job with the boat and he will be very surprised with or without the headers. :D
Click to expand...
Your probably right about the headers. When he first bought it she had the headers on it and he really doesn't care one way or the other. I just wanted to totally blow him away when he see's it by bringing it back to what it was when he first bought it and then some. :winker:
 
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