Results 1 to 10 of 10

Thread: 302 upgrade help needed

  1. #1
    Join Date
    Sep 2009
    Posts
    16
    Rep Power
    0

    302 upgrade help needed

    Hi all, I don't own a Donzi but love this site.
    I have a 16ft Tahiti I/O that has a Volvo 4 cylinder motor with a 270 outdrive. My plan is to change this power plant to a Ford 302 and 280 outdrive. The 302 came out of a Glastron and has log style manifolds with 90 degree risers (which just go straight down).
    I want to turn my Tahiti into a 'Sweet 16' style boat with the 302.
    I am changing to 4bbl intake and carb, center riser manifolds and a thru-hull exhaust. Which should help reduce some weight.
    The 302 currently has '302' heads, would I see much difference if I upgraded to GT40/GT40P heads?
    With the boat weight of less than 2000lbs could I put a mild/wild cam in it and still have a decent hole shot and good top speed?
    With an outdrive ratio of 1.61 what size of prop would best suit this setup?
    All thoughts and opinions are most welcome.
    Thank you
    Pete
    If in doubt, flat out
    Tahiti 16 - Ford 302

  2. #2
    Join Date
    Aug 2000
    Posts
    6,048
    Rep Power
    31
    I personally would not do it, not enough gains.Prop is easy one of my 19 or 21 depending on hp
    Randy owner of Donzis since 1966
    High Performance props 3, 4, and 5 blade. Turbo and Stainless Steel props. Props for old Volvo drives.
    The reason congressmen try so hard to get re-elected is that they would hate to have to make a living under the laws they've passed.

  3. #3
    Join Date
    Sep 2009
    Posts
    16
    Rep Power
    0
    currently it is 190hp, but after 4bbl carb and GT40P heads 'should' bring it up to around 240ish

    BigGrizzly: why not? and what is the price on your props?
    If in doubt, flat out
    Tahiti 16 - Ford 302

  4. #4
    Join Date
    Aug 2000
    Posts
    6,048
    Rep Power
    31
    The heads by them selves with the carb, won't yield that much. My props are in the $400 range
    Randy owner of Donzis since 1966
    High Performance props 3, 4, and 5 blade. Turbo and Stainless Steel props. Props for old Volvo drives.
    The reason congressmen try so hard to get re-elected is that they would hate to have to make a living under the laws they've passed.

  5. #5
    Join Date
    Sep 2002
    Posts
    1,442
    Rep Power
    23
    I have a ported set of GT40P heads FS , double valve springs, and resurfaced, to raise the CR . . The Logs will work fine, until you start adding a big cam . .

    Mario L.

  6. #6
    Join Date
    Nov 2001
    Posts
    870
    Rep Power
    23
    The valves in the back of the motor hate log type manifolds.
    Maddy's Daddy
    L.I.,N.Y.

  7. #7
    Join Date
    Aug 2000
    Posts
    6,048
    Rep Power
    31
    Mario's are a good deal, if he does this like every thing else he does. He is a stickler about every thing he does. Now to answer Maddad's post. He is correct if you use a big cam. There are some center riser manifolds available. PCM and OSCO are some.
    Randy owner of Donzis since 1966
    High Performance props 3, 4, and 5 blade. Turbo and Stainless Steel props. Props for old Volvo drives.
    The reason congressmen try so hard to get re-elected is that they would hate to have to make a living under the laws they've passed.

  8. #8
    Join Date
    Sep 2009
    Posts
    16
    Rep Power
    0
    Mario, PM sent

    BigGrizzly, I plan on the center risers, how big of a cam would you go without having side-effects?
    and
    what type of props do you have?

    Thanks for the advise guys.
    If in doubt, flat out
    Tahiti 16 - Ford 302

  9. #9
    Join Date
    Aug 2000
    Posts
    6,048
    Rep Power
    31
    Actually with a 302, fairly good sized The one thing to be a where of going too big and putting too large a carb on it. Forrest has a great running 302 with only 400+ CFM carb. I believe he ran a Crane 272 cam
    Randy owner of Donzis since 1966
    High Performance props 3, 4, and 5 blade. Turbo and Stainless Steel props. Props for old Volvo drives.
    The reason congressmen try so hard to get re-elected is that they would hate to have to make a living under the laws they've passed.

  10. #10
    Join Date
    Sep 2009
    Posts
    16
    Rep Power
    0
    Quote Originally Posted by BigGrizzly View Post
    Actually with a 302, fairly good sized The one thing to be a where of going too big and putting too large a carb on it. Forrest has a great running 302 with only 400+ CFM carb. I believe he ran a Crane 272 cam
    i just read another post by Forrest about his setup and this is a good plan for me to follow.
    Thanks for your input BigGrizzly
    BTW, the budget 302 that I built for my 70 mph 1972 16 with Mercruiser Alpha SS, puts out about 290 HP. It consists of a 1991 Ford 302 flat-tappet block and cast crank, stock open-chamber 69cc heads (intake gasket matched), KB116 dome pistons (9.4:1 CR), Crane H-272-2, Edelbrock Performer 289 intake, Holley 450 CFM vacuum secondary carb, half-closed cooling-systen w/160-degree thermostat, Kodiak aluminum exhaust and risers.
    __________________
    Forrest
    If in doubt, flat out
    Tahiti 16 - Ford 302

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •