Bronze or Powdered metal valve guides

Discussion in '96-04 - 2V Specific' started by Notthenow, Oct 30, 2020.

  1. Notthenow

    Notthenow New Member

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    I am working through my set of 2v PI heads and will be removing the guides to do some mild porting. I know all the head porting shops replace guides with bronze, but the PM does wear well. What really is the reason for switching to bronze? This engine will get the Comp 262ah cams and sit on a 98 npi shortblock. Nothing crazy and will be a daily driver with long tubes, some suspension mods and 3.73 gears and T45.
    Any insight is appreciated,
    Mike
     
  2. Werecow

    Werecow Well-Known Member

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    I'm not sure about the wear, but I do know that bronze is self-lubricating. That being said you should be able to run tighter clearances between the valve guide and valve stems and not have as much wear this longer life as you would with the powered iron ones as they would wear out sooner and allow for leaking of oil and vacuum. This is just my thoughts on the subject, as I'm not experienced with using them, just observations from what I've learned and seen by using bronze for this type of application..
     
  3. Notthenow

    Notthenow New Member

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    Hey Werecow, thanks for passing that on. Its everything I have always heard as well until a few days ago as I was getting ready to start the process. I read an article on one of the professional engine builder sires and they said the oems used powdered metal guides and chromed valve stems to produce long lasting valve trains. The heads I have I removed from a 2007 Crown Vic with 250k on the odometer. The valves stems have no wear I could measure and the guides are worn, but still have about another 1/2 thousandth before being out of spec. That got me thinking. I also read that the powdered metal had other metals added like zinc to add lubricative properties. That is why I thought I'd see what guys here know. I mean we have dudes running 18-1 to experiment...
     
  4. Werecow

    Werecow Well-Known Member

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    That's just my $0.02 worth we've got several 2V experts here that may be able to chime in with some better info, @96blak54 is one of the first ones I can think of who might chime in on this.. I'm sure he knows a few other experts that might wanna pipe up??
     
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  5. Notthenow

    Notthenow New Member

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    Thanks, yeah I was hoping the same. I know for an extreme motor its bronze, but they seem to do fine in 4v higher revving, higher horse stock motors.
     
  6. Werecow

    Werecow Well-Known Member

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    I'm a pushrod guy, so not much help with the overhead cam stuff but a valve guide is a valve guide... They both perform the same function in either one, so that where I was getting my info from.. Still hoping one of our 2V or 4V gurus will pop in for ya's.. maybe do an intro in the new member section or start a build thread? We're always open to anything like that. And pics!! We do love lots of pics!!
     
  7. Notthenow

    Notthenow New Member

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    I will give that a try, thanks.
     
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  8. 96blak54

    96blak54 Legend

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    Thanks for the kind words Werecow. I also want to say, im learning everyday just like everyone else. Any info i know is info you will know.

    Bronze is oil impregnated and doesnt really secrete unless its properties are compromised....or something like that. With that said its another reason for the use is bronze ability to wick heat from the valve stem and transfer to the aluminum head.

    Funny thing about powdered metal, its heat expansion is minimal compared to the material the valve stem is made of. Meaning the stem will expand them clearances smaller.

    Also, i dont know of any modular head that had in tolerance valve guides. Whoever set the tolerance must have been looking at manufacturing blueprint cause any head ive ever checked, the tolerance was either borderline out of spec or just simply out of spec. And the heads came from perfectly good running engines. None ive ever checked were considered acceptable by any builder, but they all run good.

    Also the valve side play is exactly the same any direction when checked. Where as the guides get worn typically from stress pressures from the rocker/follower.
     
  9. Notthenow

    Notthenow New Member

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    Blak, funny they all run well when out of spec. I was surprised at 250k these guides were still just barely in spec. Super clean engine, old police car I think.
     
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  10. 96blak54

    96blak54 Legend

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    When porting, keep them surfaces rough and stay clear of the valve seat area. There is a ton of technology in that area. When inspecting while porting youll think "wow, this sharp edge from the valve seat could be ground out to the port" when in reality its there for a reason. Air doesnt like to make bends and curves but can be manipulated through tumble and vortices

    Ill also note, in the nmra their is a guy running pi heads. Rules state that no porting can be done. Only cams and valve train work. This guy is running 10.2 quarters naturally aspirated at the set car weight by the rules.
     
  11. 96blak54

    96blak54 Legend

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    Ill also note that the fastest 2v car had npi intake ports
     
  12. Notthenow

    Notthenow New Member

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    I have heard the pi's are very sensitive. I was going to follow a write up by Sneaky98GT over on Corral. I used to follow posts by Jonny and Nick ( RIP) and had thought about staying npi....
     
  13. 96blak54

    96blak54 Legend

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    Each style head has there strengths and weaknesses but the pi heads are an animal all of their own. Im not steering you away from them, cause they strong heads but dont settle for the pi heads are better hype. Either style head can be made to run and the pi heads in stock state are the simplest.
     
  14. Notthenow

    Notthenow New Member

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    Yeah, I really debated which head to go with. I almost went with the +.60 springs retainers on the npi so I could use the comp 262ah, but I wanted the compression gain and I had already done the Livernois pi manifold conversion.