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inline 6 rebuild

Discussion in 'The Garage' started by bear76, Apr 9, 2007.

  1. bear76

    bear76 1/2 ton status

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    I have a 250 and I want to rebuild it for low end torque. The previous owner said he had the head shaved, but I cant prove it. What would you do?
     
  2. boz42

    boz42 1/2 ton status GMOTM Winner

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    more than likely there will be no problem w/ the head being shaved. they only remove enough material to true it back up. if u are concerned about it u can always have it cc'd(measure the size of the combustion chambers). that would give u a good idea how much a was taken off. & if there would be a compression ratio problem.

    straight sixes make great low end torque anyhow. it is a feature of the design of a straight motor.
     
  3. bear76

    bear76 1/2 ton status

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    How would I "cc" it? In general the I6's have good low end torque, but I'd like to improve it while its out of the truck, i'm just sure how to go about it.
     
  4. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    Are you set on staying with the 6?
     
  5. bear76

    bear76 1/2 ton status

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    I already have it in the garage, so yea, I'm planning sticking with it. BTW, I have m1009 with the 6.2. I'm gonna take it out for a rebuild/freashining up, which might take me awhile to get to it. In the mean time I'll put in the I6 so I can drive it.
     
  6. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    you need a few things for "ccing " the combustion chambers. do a google search for proper technique or, maybe a head specialist could look at the cutter pattern on the surface and tell you.
     
  7. Hossbaby50

    Hossbaby50 3/4 ton status

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    Put a new cam in it for lowend torque. Comp & Crane both make cams for them. Which cylinder head do you have? The integral head or the earlier head? The earlier head is a better choice from what I remember & you can get headers & manifolds for it.

    Someone makes roller rockers for it but I was told that for a 250 that isn't going to see high RPM then they aren't necessary.

    Rebuild it with a new lowend cam, & put a header & maybe a 2brl on it. You can also upgrade to HEI ignition if you still have points. I helped my buddy put an MSD 6a box on his 250 I-6 w/HEI & it worked really well. It gave it some more pep for sure.

    Harley
     
  8. bear76

    bear76 1/2 ton status

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    It is the older seperate head, it came from a 69 camero if it matters. Does anyone know where I could find HP/torque numbers (charts) for differnt cams?
     
  9. kennyw

    kennyw N9PHW Premium Member

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    Vendor websites should give you all the specs.
     
  10. dontoe

    dontoe 3/4 ton status GMOTM Winner

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  11. Thunder

    Thunder 3/4 ton status

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    I have built a few performance Chevy and Ford inlines. I get my parts from:http://www.cliffordperformance.net/ They specilize in American inline 6 and 4cyl engines. They have everything you want to build an inline from mild to wild.
    Good tech support too.

    If the PO had the head decked that is good. it is a common thing to do to them to make more power. Chevy 250s have a swirl problem that slows down the air flow. Either Decking the heads or using flat top pistons stops the swirl and really improves air flow = more power.
     
    Last edited: Apr 10, 2007
  12. u2slow

    u2slow 1/2 ton status

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    Start with a 292 block :D
     
  13. kirkallen143

    kirkallen143 Registered Member

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    When I cc'd the head on my inline 6, all I did was take a piece of plexi-glass big enough to cover the combustion chamber, drill two holes in it (one to fill and one to bleed air out). I put some grease around the outer edges of the plexi-glass to seal, then with a graduated cylinder or syringe, measured how much tranny fluid I could put in the combustion chamber. Of course you will want to now how much in cc's, mine measured 52cc's each (it was a small 200 inline six, ford). There is a formula to figure compression from knowing what cc's your combustion chambers are, and bore, stroke, etc...

    Just to add, not being rude, but it's "mill" the head and "deck" the block, and it is best if you do these together, just don't do one or the other.

    Kirk
     
  14. bear76

    bear76 1/2 ton status

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    I think what I'll do is put a cam in and leave everything else stock and see what happens.
     

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