Fun with Holleys
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Fun with Holleys

  1. #1
    Senior Member Sharkbit's Avatar
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    Default Fun with Holleys

    Thought you guys might find some interest in this.... long sorry

    Last Mohican and I both had carb issues on our boats. His 400 pontiac had to be feathered to not stall and my 454 chevy would only turn 3800 rpm and had bogging issues.

    He bought a used holley 850 dp marine and out of the box it completely fixed his boat. So, we swap it to my boat. Fixes my issues as well, crisp accel and about 4800 r's.

    Then I go buy a brand new holley 850 dp "street" carb. (It was on the shelf instead of waiting on the marine) Out of the box the boat runs like crap and has no power. Check the jetting, the marine has 88's up front and 96's in the back. The street has 80's all around. So I jet the street carb to 88 and 96 and the engine will barely run.

    Getting pissed here, so I decide to exchange the brand new street to a brand new marine version of the same carb. Guess what? Out of the box the boat runs like a raped ape.

    I wouldn't believe it if I wasn't there but.....
    Last edited by Sharkbit; 05-17-2010 at 01:14 PM.

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  3. #2
    "Mad" Member Jet Mad's Avatar
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    Had the same problem with my 850 DP Holley.

    Ran like crap at first.

    I changed the jets to 90 front, 90 rear and also changed the needle and seeds assembley's to offroad/marine.

    Turned my 455 Olds with 7 Cylinders (1 cylinder did not fire ie. Plug was dropped and gap was completely closed) 4600 RPM

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    My guess is that the street version had no or different power valves in it. If one has no power valves and the other one has power valves. Then noway you can run the same jets. Probably different squirters too.

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  6. #4
    AKA OhOneWS6 Last Mohican's Avatar
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    Quote Originally Posted by Wicked Performance Boats View Post
    My guess is that the street version had no or different power valves in it. If one has no power valves and the other one has power valves. Then noway you can run the same jets. Probably different squirters too.
    Checked that. Power valves, squirters, pump cam, pump cam position were all the same on the marine and street carbs. Both had big rear pumps.

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    Senior Member Josh@JBP's Avatar
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    Quote Originally Posted by Last Mohican View Post
    Checked that. Power valves, squirters, pump cam, pump cam position were all the same on the marine and street carbs. Both had big rear pumps.
    I'm betting that the High Speed Air Bleeds are different from the Marine to the Street version.

    I'd double check that carb size also, an off the shelf 850dp (4781) carb should have 80's in all corners with front and rear PV's. A carb with 72's sounds like a 750 DP(4779)

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    Senior Member Sharkbit's Avatar
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    Quote Originally Posted by [email protected] View Post
    I'm betting that the High Speed Air Bleeds are different from the Marine to the Street version.

    I'd double check that carb size also, an off the shelf 850dp (4781) carb should have 80's in all corners with front and rear PV's. A carb with 72's sounds like a 750 DP(4779)
    Yeah you right about that. There were 80 in the street so I'll edit the post. Thanks.

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    Member hollbrow's Avatar
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    Hey Guys- besides the obvious differences (J-tubes, grooved & slabbed throttle shaft) I have often wondered exactly what the difference in calibration of the idle feed restrictions, power valve restrictions and air bleeds was between the marine versions and the street versions of the Holleys- I have several books on Holleys and even they do not go into the details of what Holley calls the "universal marine calibration". I have never ponied up the cash for a 750 or 850 Marine carb or I could identify the differences. I'm just not real enthusiastic with trial and error type stuff like drilling out air bleeds and power valve restrictions- stuff that cannot easily be returned to stock if it doesn't help. If anyone could share their knowledge or experiences it would be great.
    Last edited by hollbrow; 05-18-2010 at 06:44 AM.

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