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Thread: Boost Question

  1. #1
    Member JUNIOR BUILDER
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    Boost Question

    I have a 355 with 6-71 roots blower (TBS). 8.25:1 CR, aluminum heads, Cometic MLS head gaskets.

    I run 8 psi boost with pump gas. Can I just change the pullies and run higher octane to run more boost? How much?

    How are guys runing 15, 20, 30 PSI of boost with turbos and cintrifugal super chargers?

    Thanks, Steve

  2. #2
    Senior Member RACING JUNKIE
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    Boost?

    Steve,
    1 Issue?What do ou have for a Lower END?
    If its all Forged and you have Good Head Bolts,Studs.It all depends on the Ammount that you want?
    I Never had any Issues w/a GM Block until I made 26-28lbs of Boost,then the Heads Studs would JUST PLAIN LEAVE there Spots in the Block!
    If you have a Aftermarket Block,then It will Handle More!
    A GOOD Outboard Crank Support is another way of keeping the Snout attached to the Crank!
    If you are looking for 15-18lbs?
    Change the Pullys,Octane and Take some Timing Away!
    If You want to Make More,Then I Need some More INFO on your Motor?
    Later
    G 8)

  3. #3
    Senior Member RACING JUNKIE
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    X2, a stock block 355" can't hold it, case in point 1471 blown alcohol running 30lbs boost, cracked a cylinder burned down a piston and i was running the best parts available including splayed main caps and front crank support.

    JMO

    Zip.

  4. #4
    Member JUNIOR BUILDER
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    Thanks for the help guys. I should have added it is a stock GM 4 bolt block with 4340 forged crank and rods. Forged aluminum pistons.

    Made 615 HP on the engine dyno in January. What can I expect if I go to 12-15 pounds?

    Steve

  5. #5
    Member JUNIOR BUILDER
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    One last thing. ARP head bolts.

  6. #6
    Senior Member RACING JUNKIE fla1976's Avatar
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    I would ditch the head bolts and go with studs. You'll get a better seal and less wear and tear on the bolt holes in the block.

  7. #7
    Senior Member RACING JUNKIE
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    I have run blown sbc on the street for years. I will give you some advice in a bit after i rest!!!! Just got home from a steel erection job for DPS.

    ps i run up to 10-12 lb boost on with 93 octane. Proper jetting and correct timing and a good cooling system. Unless ur blower is a aftermarket it is not going to put out more than 10-14 lbs of boost max. Being in a street car it will put less strain on the engine, since you will get little traction.

    Be back later

  8. #8
    Member JUNIOR BUILDER
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    I look forward to your knowledge.

    My Nova is 80% street and 20% 1/4 mile. As many do, I am chasing the big billboard.

    My blower is from The Blower Shop. Th400 w/TB, Ford 9" with 4-link.

    And no traction with street tires.

  9. #9
    Senior Member RACING JUNKIE
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    ssym: I know nothing about blown stuff, but I wanted to say welcome & that is a beautiful Nova... does not get much better than that... color & all!! Scooter/Rigsby
    "I would walk through hell on Sunday before I fear the enemy"

  10. #10
    Senior Member RACING JUNKIE lively's Avatar
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    a GREAT example of my kind of street machine 8) 8) 8)

    LIVELY


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