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Flathead Valve size your opion needed.

Discussion in 'The Hokey Ass Message Board' started by big jungle jim, Nov 17, 2004.

  1. big jungle jim
    Joined: Jun 29, 2004
    Posts: 240

    big jungle jim
    Member

    Just starting to build the new motor to replace the detonated one. Can't decide what valve size to use. The new motor will be 313ci still blown like the old one. What do you reckon will be best. Been stratching my head so long think ive now got a bold patch.
     
  2. Kilroy
    Joined: Aug 2, 2001
    Posts: 3,227

    Kilroy
    Member
    from Orange, Ca

    1.6 untake and exhaust is what most folks say.

    Barney Navarro has a motor with about 1.8 valves intake and exhaust that looked mighty impressive. Overkill!

    I have been thinking 1.7 intake and 1.5 exhaust lately. I think that with flatty exhaust being what it is, there isn't much point going over that for most motors but the larger intake might air things out a little. I dunno...

    1.6 would work just fine.
     
  3. Smokin Joe
    Joined: Mar 19, 2002
    Posts: 3,770

    Smokin Joe
    Member

    1.6 chevy valves, They're WAY better than stock, swirl cut and cheaper than the stock 1.5's to boot.
     
  4. delaware george
    Joined: Dec 5, 2002
    Posts: 1,246

    delaware george
    Member
    from camden, de

    what is involved in running the chevy valves?...can you use the same adjustable lifters?...how about the seats?
     

  5. big jungle jim
    Joined: Jun 29, 2004
    Posts: 240

    big jungle jim
    Member

    Used the chevy valves in the old block worked good thought i might try something different but cant decide. They work with the adjustable lifters just need to get the seats re cut. You also needed to put a shim on the valve spring to get the correct spring rate. They do work good. Was thinking about flathead jacks pro-flow valves which are under cut on the valve stem for better flow. But havent heard if they are any good.
     
  6. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Jim,

    Talk to Joe Abbin - he's flowed it & the 1.72 doesn't gain much over the 1.6 intakes, but I assume you'll be running the blower again, so double-check with him.

    My personal guess is 1.6/1.6, but with the size engine yer runnin, ya never know!

    [​IMG]
     
  7. big jungle jim
    Joined: Jun 29, 2004
    Posts: 240

    big jungle jim
    Member

    Good thinking Ernie i'll give Joe a call.
     
  8. Flatdog
    Joined: Jan 31, 2003
    Posts: 1,285

    Flatdog
    Member Emeritus

    Jim ,I running with !.6 intakes 1.5 ex.My 313 cracked very early in it life 30 mim. unless you have a aftermarket block 3 3/8 not the way to go for me .I like 3 5/16.Went 12.91 sunday 3200lb
     

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