Torque specs carbs to manifolds | FerrariChat

Torque specs carbs to manifolds

Discussion in '308/328' started by rcraig, Feb 15, 2025.

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  1. rcraig

    rcraig F1 Rookie

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    I noticed a few bolts pretty loose when taking off one of my carbs.
    Is there a torque spec other than for standard spec for bolting carbs onto manifolds with two gaskets and bare insulator.

    Thanks in advance
     
  2. yelcab

    yelcab F1 World Champ Consultant

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    Yes, there is a torque spec. But those 16 nuts are exceedingly difficult to get to and impossible to put a torque wrench on it. All I ever do is use a open wrench and tighten it ... good and tight.
     
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  3. johnk...

    johnk... F1 World Champ Owner

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    Not familiar with the carbed 308s, but for hard to get to nuts, that what they make these for.

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  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ Lifetime Rossa

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    Not too tight -- you don't want to warp the carb baseplate.
     
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  5. rcraig

    rcraig F1 Rookie

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    Yeah that’s what I was afraid of.
     
  6. yelcab

    yelcab F1 World Champ Consultant

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    Well, you use a 6-inch long wrench, how much torque are you going to be able to put on that nut while contorting your hand/wrist to do that job?
     
  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ Lifetime Rossa

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    True, but, IMO, this is a good example of where if you just looked up the "typical" (steel-on-steel) torque spec online based on the stud's thread size, and used that torque value = you'd probably pull the stud out of the Aluminum manifold ;).
     
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  8. rcraig

    rcraig F1 Rookie

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    thanks Steve. That was my big worry. It would be a bit of a major disaster for me to strip it out.Thanks guys.
     
  9. sltillim

    sltillim Formula 3 Silver Subscribed

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    so 20 - 25 ft lbs?
     
  10. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Will not fit. As already explained it requires an open end wrench.
     
  11. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Way too much for any standard 8mm fastener and assures destruction of Weber carbs.

    Just how are you planning to torque them with an open end wrench?
     
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  12. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Not to mention irreparably bending the carb housings.
     
  13. johnk...

    johnk... F1 World Champ Owner

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  14. Rifledriver

    Rifledriver Three Time F1 World Champ

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    I guess you have never removed/installed a set of Ferrari carbs.
    You need an open end wrench.
     
  15. bitsobrits

    bitsobrits Formula Junior Rossa Subscribed Silver Subscribed

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    Sooo much easier to get a wrench on them if you replace the factory nuts with reduced hex flange type, which take a 10mm wrench. That allows you to use the box end of the wrench on most nuts (I would suggest a 12 point box wrench). I also added a stubby 10mm combination wrench to my toolbox which also helps. But I've never felt the need to use a torque wrench on any carb nut on any vehicle. Maybe if I was doing vintage aircraft engine work I would feel differently.

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    Last edited: Feb 19, 2025
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  16. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Some things its advisable to use a torque wrench. Everything else we just tighten. Been working for hundreds of years.

    I fail to understand the fetish for torque wrenches especially when (as in this case) we would have to guess and make up a number to set it to.

    The other day I was told by someone here he used a torque wrench on trim screws. My God, get a life.
     
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  17. mike996

    mike996 F1 Veteran

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    Old story is that the first time torques specs were ever published by Ford, they handed their experienced mech a (newly invented) torque wrench and told him to assemble an engine. He did so by feel, as all mechs did, and the boffins noted the individual torque reading that resulted for each fitting. Those were then published as the "torque specs." ;)

    Doubt that it's a true story but it's a good one!
     
  18. sltillim

    sltillim Formula 3 Silver Subscribed

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    I believe it and I know the real pro's can do it by senses. At the same time I try to live by some guidelines. I'm sort of a big guy and strong and sometimes my version of tight is different than someone else. BUT I also break things so I know a have to be careful and think about how I assemble. So for something like this and the oil pan(s), it would be good to say a number or just a even a range like somewhere between 10-15 ft lbs.
     
  19. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Its pretty well established more things are damaged or broken by over tightening than by being too loose. You car retighten things. You cannot undamage threads or warped carb bodies. I have seen far too many Webers so distorted by over tightening that the throttle shafts siezed. . Pierce used to offer a service to straighten them.
     
  20. sltillim

    sltillim Formula 3 Silver Subscribed

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    Super helpful info!
     

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