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Block decking???

Discussion in 'The Garage' started by Diesel Dan, Oct 17, 2005.

  1. Diesel Dan

    Diesel Dan 1/2 ton status

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    Any machine shop gurus out there? :D

    Here's what I'm working on. About 3 years ago put together a '96-00 L31 Vortec crate motor for a blazer repower. Was a new GM crate motor, installed the "hot cam" kit, .525/525 lift with 1.6:1 self-aligning roller rockers with duration in the 218/220 range @.050 lift. R&R heads and had the spring pockets opened up and towers turned down for seal clearance. Installed Performer RPM intake and performer 750carb. With about 9.5:1 compression and proper tune it should have been in the 400HP range.

    Now up to current speed, truck was rolled and burned.
    Redoing engine and owner wants closer to 500hp :doah: .
    So in fire carb melted, MSD billet dist, gear drive starter and all accesories toast.
    Going with Edelbrock Etech 200 heads, flow better than GM fast burns. RPM air gap intake, maybe a 1460 series holley 750 that GM uses on the 430hp/350. Also looking at the Edelbrock RPM roller cam, .560/.580 range and CompCams chromemoly 1.5 rockers.

    Now machining question.
    Looking at decking the block. All pistons measure .026-.030" below deck height. How much can a stock block reliably be decked? Don't want to, at this point, get into offset bushing the piston pins to raise them to the top of the deck.
     
  2. Beast388

    Beast388 1/2 ton status

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    When I built my 388, all of the pistons were down 0.011 to 0.019". I had the block square decked so they were all down 0.004".

    Taking 0.025" off the deck of block should be ok but I would check with the machine shop. They usually know what works and what they would feel comfortable with. :D
     
  3. neverendingproject

    neverendingproject 1/2 ton status

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    Ive heard of people using zero deck hieght and using the head gaskets for proper quench.
     
  4. Beast388

    Beast388 1/2 ton status

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    That is basically what I did, except for the zero deck. With the piston down 0.004 and a compressed gasket thickness of 0.041", I get the ideal quench thickness of 0.045". :D
     
  5. Diesel Dan

    Diesel Dan 1/2 ton status

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    Called the machine shop and the guy that does the decking wasn't in today. IIRC distance from the crank centerline to deck height spec is 9.800 +/-??? So it will also depend if I'm above or below the mean dimension of 9.800" and if I go the whole .022" I'll need to check pushrod length.

    Now I'm trying to find out what the limits are on the powdered metal (PM) connecting rods.
     

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