70 Z28 engine

Discussion in 'Engine Topic' started by Antonio Duarte, Jul 7, 2017.

  1. Antonio Duarte

    Antonio Duarte New Member

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    Hello everybody,

    My name is Antonio and I am from Portugal.
    I am restoring a Group 1 FIA Z28 Camaro racecar and could really use some help.
    The car raced back in the day here in Portugal for some years. When we got it it was missing the engine.
    The body restoration is almost finished and I am now in the process of getting an engine for the car.
    I need to build an engine as period correct as possible.
    The dates on the parts (i.e. on the engine block) are completely irrelevant to me. I just need them to have the same specs as the original engine.

    Alsa, as an example, the rods don't have to the pink ones. As long as they have the same size, it'll be fine)

    After spending hours browsing the intenet I've seen so much information that got me completely confused (I have no experience in American engines).

    What do you guys think I should do? Do you know the part compatibilities for these engines?

    I can upload a copy of the FIA papers, if you guys don't already have them :)

    Thank you for your help.

    Cheers,

    Antonio
     
  2. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    If dates are irrelevant, than it should be easy depending on how much you want to spend. If you want it to be at least cosmetically correct, than double hump heads and a late 60's, early 70's gen block would be best. Casting number 3970010 is the correct one and was used in millions of cars and trucks in the late 60's to mid 70's.Most were 2 bolt main, but that is an easy conversion to the LT-1's 4 bolt main. The internal pieces can all be purchased new. Heads can be correct 186 castings which are getting rare (RE:expensive) or the over-the-counter replacement 492 large (correct looking) spark plug (or small "peanut" plug version) which are a bit easier (and less expensive) to find. I would go with a SCAT crank and rods and pick a piston like the original TRW (now Sealed Power) L2304F forging or similar from several suppliers. This will require "race gas" of at least 97 octane (USA rating). The original spec 3972178-3972182 cam is available from Crane in their "Blueprint" series as pn 110951. Be aware that it is an old school flat tappet cam of which there are many horror stories relating to oil and lack of zinc in the new oils. It all depends on how "period correct" you want it to be. The old solid lifter, flat tappet cams had a very distinct clatter to them and most folks can tell when they hear one running. The 3972110 intake is getting VERY hard to find in nice shape, but GM made an over-the-counter replacement 3972116 that is close in appearance. Don't let anyone tell you that it was installed originally on the LT-1's. It wasn't. They are even getting a bit pricey. Ebay has several listed at any given time. Again, it depends on how close you want it to look. Experts can tell the small differences a mile away on these things, but most normal people (of which I am not) won't be able to tell. Valve covers are readily available depending on the condition and exactness required.
     
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  3. Antonio Duarte

    Antonio Duarte New Member

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    Hi Dave,

    Thanks for your help :)

    My goal is to comply with the FIA papers in order to pass the scrutineering in case they decide to open up the engine.

    FIA papers here: http://ge.tt/2Zdnehl2

    There are a lot of limitations as you can see. In my case, only the first 13 pages are of interest.

    One issue I have come across is the CR ratio. I read everywhere that the 70 Z28 has a 11:1 CR but the papers talk about a 10,71:1 CR. Does this make any sense to you?

    When I say period correct, I mean complying with the FIA documentation.
    I am considering having the engine assembled in the US because it'll be more expensive for me to do it here. Our machine shops are seriously good working with inline 4 a 6 cyl engines. V8's are no so common here so the lead time and the price will go a bit up. Do you have any clue on who I should talk to for this?
     
  4. Antonio Duarte

    Antonio Duarte New Member

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    Almost forgot.. Our commercial fuel is 95 octane (regular) and 98 (premium) so I would assume that if I use the 98 premium gas I won't have a detonation problem.
     
  5. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Don't know. I know the USA system is an average of Research and Motor Octane according to this formula:

    (R+M)/2 = Octane stated on the pump. This is what needs to be around 97+ octane. Research is usually greater than Motor so if in Europe the octane is only stated as Research, you may still experience knocking-detonation.. I don't know.

    Your link comes back as "Share not Found"

    The difference between 11:1 and 10.71 could come down to a combination of things such as piston height in the bore, head gasket thickness, combustion chamber volume in CC (nominal for these heads is 64 cc's). There are calculators such as this:
    http://www.csgnetwork.com/compcalc.html

    That you can put all the variables in and it will determine the static compression ratio.
     
    Last edited: Jul 7, 2017
  6. Antonio Duarte

    Antonio Duarte New Member

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    Please try the link again... I forgot to click on the verification link on the sharing website :/
     
  7. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Still the same thing on the link....Share not found
     
  8. Antonio Duarte

    Antonio Duarte New Member

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    It is working on my side... Just in case I hosted on a different provider: http://jmp.sh/GI2oyM3
    Does this one work for you?
     
  9. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    I can see it from the new link. I've never really looked at an FIA document like this before. Kind of interesting. A few superficial mistakes. Not sure when the document was actually put together. It has a photo of a 1971 in Photo B and a 1st gen engine compartment in Photo O.

    The 10.71 is interesting. Might have been calculated using some extremes of tolerances. Hard to tell as there is not much detail there. Just the head volume of 64 cc's. The calculations for the camshaft specs show it is the LT-1 3972182 cam. They have an incorrect alternator amperage of 61. Stock was 37. Horsepower and torque was wrong. Perhaps due to being SAE net instead of gross.
     
  10. Antonio Duarte

    Antonio Duarte New Member

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    It was put together in feb. 1970 the first 13 pages. That was the initial homologation sheet GM got approved. From the 14th and beyond you have the appendixes that were submitted to the FIA as Gm produced upgrades/modifications to the car.
    One thing about the tech specs.. those days manufacturers falsified/manipulated the information they gave to the FIA in order to gain competitive advantages. Not sure if this is the case.

    These are the specifications I have to follow building the engine.

    EDIT: the production numbers were reached on Feb. 1970 but the FIA papers were submitted on a later date (still not sure when)
     
    Last edited: Jul 7, 2017

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