Tuneup differences between Fat and Fuel heads

Discussion in 'InsideTopAlcohol.com Tech Questions' started by greenracing, Apr 9, 2019.

  1. greenracing

    greenracing Member

    Joined:
    Jul 2, 2008
    Messages:
    65
    Likes Received:
    9
    Has anyone moved between Fuel heads and Fat heads on a blown alcohol setup and has a ballpark difference for timing and fuel? I've got a safe starting point for a Fat head setup and am putting together a Fuel headed motor with the 176cc camber heads. I'm assuming I can use more timing on the Fuel heads - I'm thinking around 30 would be safe, maybe 32 max? Will the Fuel heads use less fuel, or does the big chamber and more timing require similar fuel?

    Thanks!
     
    #1
  2. KENNETH JORDAN

    KENNETH JORDAN New Member

    Joined:
    Nov 28, 2017
    Messages:
    13
    Likes Received:
    1
    subscribed
     
    #2
  3. bruce mullins

    bruce mullins Top Dragster

    Joined:
    Aug 2, 2003
    Messages:
    988
    Likes Received:
    3
    keep your timing under 28.
     
    #3
  4. greenracing

    greenracing Member

    Joined:
    Jul 2, 2008
    Messages:
    65
    Likes Received:
    9
    thanks Bruce!
     
    #4
  5. quickcut

    quickcut Member

    Joined:
    Mar 22, 2016
    Messages:
    30
    Likes Received:
    1
    Anyone else have any input to this ??
     
    #5
  6. turbo69camaro

    turbo69camaro Member

    Joined:
    Nov 26, 2007
    Messages:
    245
    Likes Received:
    9
    Save yourself a ton on money and tail chasing .Get hooked up with Will hanna,Mike @ rage ,Randy Anderson,ETC and get your fuel system set up and flowed they will get you in the ballpark
     
    #6
  7. Soldierboy0098

    Soldierboy0098 Active Member

    Joined:
    Feb 17, 2006
    Messages:
    1,243
    Likes Received:
    14
    On alky Fatheads max of 26 but it depends on your compression ratio for how much you will need to babysit the timing. Fuel heads like more timing because of the big chamber size. I have seen between 32 and 38 on a fuel head but they do not like high rpm's because the pistons weigh a ton.

    Also Turbo is correct for the $800 to flow a fuel system your money way ahead in getting it flowed as they will give you a good starting tuneup, flow your jets, and this usually includes one trip to the local track to help tweak it.

    Hope this helps,
    Trev
     
    #7
  8. John byob

    John byob Member

    Joined:
    Apr 13, 2019
    Messages:
    34
    Likes Received:
    0
    Trevor who mills fuel pistons down to take weight off of them. Met a racer years ago he took 200 grams of each blower piston fr his motor? Thx
     
    #8
  9. Soldierboy0098

    Soldierboy0098 Active Member

    Joined:
    Feb 17, 2006
    Messages:
    1,243
    Likes Received:
    14
    Not sure on that one, I know people who mill the domes to get the compression down but the only people I can think of is the piston company for CP. They do a lot of lightening but not sure on a fuel head deal.

    https://www.cp-carrillo.com/pt-3507-pistons.html

    Hope that helps,
    Trev
     
    #9
  10. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
    Staff Member

    Joined:
    May 6, 2003
    Messages:
    6,565
    Likes Received:
    89
    I have found (was educated is more proper) the timing is relative to the bore size. Bigger bore = more timing. This is comparing fat head to fat head type of deal.

    Now the fuel head has more flame travel, so it needs more timing to start the burn a little earlier.

    You will hear of people running timing numbers well into the 30's with fuel heads. Most (not all) of that comes from the way these motors used to be ran before we got 44 amp mags. With the big chamber and weak ignition, it needed a lot of lead and a hot cylinder head to combust the mixture. Now we have an arc welder, so we don't need to start the burn as early and don't need 200+ head temp to help preignite the burn.
     
    #10
  11. Outlaw Funnycar

    Joined:
    Jun 24, 2018
    Messages:
    48
    Likes Received:
    6
    We run the old dart 96 fuel heads. I put between 34-38° of timing with a 4.5 amp Mallory. 526 with 14-71hh mert. Runs 4.0s no sweat and will run 3.70s-3.60s if I want it to. Shift at 8k launch at 5k
     
    #11
    promodracer and KENNETH JORDAN like this.
  12. John byob

    John byob Member

    Joined:
    Apr 13, 2019
    Messages:
    34
    Likes Received:
    0
    Trevor found a guy who takes 200 grams off each piston. Think he charges 200 t 300. Not sure why piston makers don’t look into this?
     
    #12
  13. John byob

    John byob Member

    Joined:
    Apr 13, 2019
    Messages:
    34
    Likes Received:
    0
    PS if anybody out there has old fuel heads with rockers and valve covers manifold and wants to go to fat heads. I have a set of AJ fat heads with valve covers and stands but no ROCKERS that I would trade if anybody is interested thx
     
    #13
  14. James2

    James2 Member

    Joined:
    Apr 15, 2004
    Messages:
    53
    Likes Received:
    0
    Thinking of going this route instead of building my BBC since I have more hemi stuff. What kind of pump/gallons do I need? Just shooting for a low HP deal to get some seat time in my street car. But gonna use the parts that I have: 170cc heads, 4.187x4.500 with my low compression big pump/mag long block. 14-71 roots.
     
    #14
  15. aj481x

    aj481x Member

    Joined:
    Jan 27, 2004
    Messages:
    953
    Likes Received:
    14
    Still available?
     
    #15
  16. promodracer

    promodracer Member

    Joined:
    Jan 8, 2008
    Messages:
    353
    Likes Received:
    1
    I would say start at 30 degrees, then 32degrees and 5 steps fatter on main jet. if ok another 2 degrees advance to 34 degrees and 5 steps fatter on main jet.
     
    #16

Share This Page