adding hp to 1976 truck

Discussion in 'Chevy Truck Forum' started by jimm417, Oct 15, 2013.

  1. jimm417

    jimm417 Full Member

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    i am going to put a thumpr cam and vortec heads on wondering about how much hp it would make and if it would raise the compression enough that i would have to run high octane fuel?
     
  2. gpmorgan

    gpmorgan Auto Banned

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    As long as it has the stock pistons, you shouldn't need high octane fuel. As far as hp, maybe 300 give or take a few ponies. You will need an intake that will accept a carb and fit the vortec heads.
     
  3. gpmorgan

    gpmorgan Auto Banned

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    You will want to get a cam kit. You will need new lifters, valve springs and retainers. All should be in a kit. While you have the springs off, it would be a good time to change the valve stem seals. Measure spring heights and check valve geometry. This will ensure longevity of the cam. Also be sure and read the cam recomendations for things like compression ratio, headers, gearing, stall converter, etc. There is more to it than just installing a cam if you want all the potential out of it. A large lift and duration cam can actually cause an engine to loose power if it doesn't have the right components in the engine. With stock pistons, you probably want to stay under a 450 to 460 lift cam.
     
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  4. Boudin

    Boudin Forum Moderator

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    GP covered it completely as usual. He certainly knows his stuff. About the only thing I can add is maybe if you were to tell us what engine you have now (I'm assuming 350)....at least we can tell you what kind of power you have now. Especially if you give block ID numbers or even RPO code.

    As far as octane....you don't need anything higher than regular unleaded. Anything more is a waste of money simply because you don't need it. It won't do anything other than cost more per gallon. On a similar note....is yours a leaded or unleaded model? Quickest way to tell is either if you have catalytic converters....or if they have long since been removed....if your fuel gauge says nothing or "unleaded fuel only".
     
  5. jimm417

    jimm417 Full Member

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    its a 76 so its unleaded stoped having leaded fuel in early 70s and it is a 350 idk who the engine code is its old work truck really beat up idk anything about it i been trying to find the vin number but cant find one on the door so idk where it is at and it has been so rigged up idk whats all in it as cats idk if it has them or ever had them
     
  6. jimm417

    jimm417 Full Member

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    and i heard putting vortec heads would raise the compression how much would it rise?
     
  7. Boudin

    Boudin Forum Moderator

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    I beg to differ. 76 had some that required leaded fuel. My 84 requires leaded fuel because it was an exempt model due to its GVWR. The unleaded switch started in the 70's....but it wasn't universal.

    If you will look at any Chevy parts catalog (like LMC and such)....you will see that replacement fuel gauges came both with "unleaded fuel only" and ones without.

    VIN is at the base of the windshield on the dash. You have to view it from the outside. The engine ID numbers are behind the alternator and on the rear driver side lip where it meets the tranny.
     
  8. gpmorgan

    gpmorgan Auto Banned

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    Just a guess here. I'd say you are at 8.5 maybe 9 to 1. With the vortec head it might rise to 9.5 to 1 if it starts out at 9 to 1.
     
  9. Boudin

    Boudin Forum Moderator

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    This is one of the reasons I asked you for more details about your motor that you have in there now. I can't tell you how much compression will increase if you were to add Vortec heads if I don't know what the details are for your current motor.

    Regardless of what you have, adding Vortec heads will not increase compression enough to warrant higher octane fuel. If you could provide details like casting numbers for the heads you have now and/or the block casting number....I can surely get you a solid estimate. For example....if you have say....882 76CC heads on there now....and the rest of the motor is stock....you are probably at about 8.3:1. Depending on what you decide to upgrade and with what (besides the L31 vortec heads)....you will be in the low 9's at best. Like I said....still not near enough to warrant higher octane gas.
     
  10. Boudin

    Boudin Forum Moderator

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    Looks like we posted at the same time.....and are of the same mindset.
     

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