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help please

Discussion in 'Chevy Trucks' started by mempis, Jun 5, 2005.

  1. mempis

    mempis Junior Member
    from eastern
    Messages: 1

    can someone help hi by the way im new to the forum i just purchased a truck im not sure what block size i have 305 or 350 any tips in finding out thanks all!!!!!!!!!!!!!!!!1 :confused:
  2. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    Probably the easiest to describe in text is this:

    Look behind the alternator. There is a piece of the block that sticks out from under the head (the deck surface) that if you clean it with solvent/wirebrush/etc. should have numbers stamped into it. This is an application code followed by the VIN number. The digits you are looking for will be three letters in a row starting with the letter 'C'. As in...

    CNJ - I believe translates out to a 300hp 350 from a '70 Chevelle, Monte Carlo, Nova or Camaro if memory serves. Others will be similar, but all Chevy engines produced after 1970 will have that three letter code starting with C (for chevy!). Prior to that, they were all two letter codes.

    This assumes that the block has not been decked as that removes the letters. Then we move on to casting #'s etc. but these are easier to see.

    Check the engine code in a Chilton manual etc. and it should tell you what it is... or post it here and I will check my sources.
  3. T-MAN

    T-MAN PlowSite.com Addict
    Messages: 1,363

    Mempis what year and model truck?
    Is there a tag under the hood in liters such as 5.7 ?
    Also is there anything in your glove box that states the specified engine.
  4. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    While a good place to start, that assumes that the engine is untouched original. Anything over ten years old may be likely to have been rebuilt or swapped at one point.
  5. 75gmck25

    75gmck25 Senior Member
    Messages: 119

    The casting number you need to check is on the driver's side of the engine, on a flat space just behind the valve cover. Its hard to see because the power steering booster is above it, so you can't see it from the side of the truck. I had to crawl up into the engine compartment and look straight down with a flashlight.

    Once you get the casting number, go to www.mortec.com and look it up to find out which block you have.

    If you want to know exactly which engine/horsepower combination, you will also have to check the head casting numbers, but there wasn't much variation in some years.

  6. Yaz

    Yaz PlowSite.com Addict
    from NH
    Messages: 1,061

    Just like DerekBroerse stated above the engine numbers are the only way to tell for sure if the motor is not original. And to really be 100% is to check the stroke. 3.5" is 350ci and your not doing that without a head off. Target Master replacement GM engines don't make any sence as to the deck numbering!

    Good Luck I hope your engine is original numbers and you'll be all set.