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Corvette engines

Discussion in 'The Garage' started by rick88blaze, Oct 9, 2005.

  1. rick88blaze

    rick88blaze 1/2 ton status

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    I was at the local U-Pull-it today and saw an early 70's 'Vette in there with the engine still in it. I was wondering if the heads off of it would be worth putting on my K5? I've got an '88 TBI. I doubt that it would still be there in 2 weeks when I get the cash for them, but I'd still like to know just in case I come across a set down the road. :dunno:

    Rick
     
  2. HarryH3

    HarryH3 1 ton status Author

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    The early 70's were dark days for the Corvette. Some of them were only rated at 160 HP. :( Certainly nothing there worth rescuing.
     
  3. 1979jimmy350

    1979jimmy350 1/2 ton status

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    it depends on how early of the 70's in 1970 there were some of the most powerful small blocks made it was 72 and later that they fell flat because of emissions. The best thing to do would be run the numbers they might have better flow than the stock TBI heads
     
  4. folkenheath

    folkenheath Worthless Trash Premium Member GMOTM Winner

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    They switched from leaded to unleaded between 71 and 72. So if it's older than 71 it won't have hardened seats for unleaded fuel. And you will spend too much money to get them installed in the heads. If they are 71 they could be either. 72 and newer will have hardened seats, but probably aren't worth swapping into your truck anyway.
     
  5. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    GM never used hardened seats until the late 80's or early 90's and not that many heads got them either. GM did start to flame harden the cast iron around the exhaust seat though way early in time. It also happens to be an old wifes tail about needing hardened seats for unleaded fuel. With unleaded fuel you destroy valve guides not seats. Don't get me wrong, hard seats are a good thing if you have a truck that is being subjected to hard use such as heavy loads and pulling hills for long durations of time.
     
  6. folkenheath

    folkenheath Worthless Trash Premium Member GMOTM Winner

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    You'll have to excuse my exorbitantly late response, I don't get on here that often and never really saw this. However, I thought I should clear this up just to save some people some headaches. I am not going to argue with you about how they are hardened or the terminology of what was hardened on the seat. It is a documented fact that the seats are hardened, therefore they have hardened seats (whether they are hardened on the head, or machined and installed after, they are still hardened) for the unleaded fuel starting in mid 1971. And although somone may have told you it is an "old wifes tale" that you don't need hardened seats for unleaded gas, it is not true. I have seen it more than once in my own experience (just not my own personal vehicles) where vehicles driven with pre 72 heads with regular seats pulled a valve up into the head and ruined the head. It happens, it's real, it's not a myth. Feel free to ignore this info if you wish, it's not my problem, I'm just passing it along for those who are listening. Thank you. :)
     
  7. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    If you can get a set of L-82 heads they would be better than L-48 heads.
     
  8. 70GMC

    70GMC Registered Member

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    yeah but all of the manufacturers under rated all of their cars by alot
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Not at that time. EPA regulations came on strong, compression dropped, BUT the way power was measured was changed as well. From net (no accessories, not factory exhaust) to SAE, which was all accessories, factory exhaust. Break from net to SAE was '73 I believe.

    Roughly 20% smaller numbers SAE than net.
     
  10. 70GMC

    70GMC Registered Member

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    okayyyy well if they changed the way horsepower was measured so the numbers would drop, wouldn't that mean the amount of power was technically about the same?
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    No, not totally. There were 375HP 327 Corvette motors in the late 60's, no way a 20% drop in those numbers is equal to the 160HP 350 quoted for later motors. :)

    IIRC compression on the 375HP 327's was 10.5:1 or so, while post '72 was likely 8 or 8.5:1. Compression doesn't make a HUGE difference in power numbers, but adds up with things like carb, cam, exhaust, and head flow.
     
  12. smalltruckbigcid

    smalltruckbigcid 1/2 ton status

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    And don't forget little things like retarding the timing set and others to lower power output
     
  13. Leper

    Leper 1/2 ton status

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    05 threads rule!
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    Retarding the timing is not a technique the manufacturers use to reduce power output. They use configurations that *require* less timing, and without any way to control timing almost infinitely (EFI) there are always going to be compromises.

    More timing is not and never has been the way to more power. You need optimal timing to make the most power, yes, but that is not simply always the most you can get away with.
     
  15. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    The 375 hp 327 (f.i.) was run 1/2 way through 65....then came the 396. for less than 1/2 the price. the 327/365 & 375 hp, had 11.25 c.r.
    In 71 compression dropped on most GM engines, base motors were 8.5 for the 350 corvette engine.
    in 72 the SAE net hp ratings (all engine accessories installed as would be used in the vehicle) were used, replacing the Gross numbers used at the flywheel.
    This resulted in about a 25% decrease in rated hp.
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    My mistake, the carbed 327's could be had up to 350HP up until the late 60's, then replaced by the 350.
     
  17. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    Didn't mean to make it look like a mistake:bow: , just adding what little I know to the equation....I kinda like Vette's:wink1:
     

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