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Thread: Bigport or smallport?

  1. #1
    Senior Member dunga70's Avatar
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    Default Bigport or smallport?

    Just had a quick look at FAQ and coulnt find it.
    How do you tell the difference between bigport and smallport engines without pulling it apart? Does the ecu say anything on it?
    Pretty dumb question but I got no idea.
    Cheers
    olympic gold keto

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    Senior Member squish_m8's Avatar
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    bigport has 8 holes on the inlet side, smallport has 4

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    Senior Member dunga70's Avatar
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    Is there anyway of telling without taking the manifold off? It's got a jdm rwd manifold are they all smallport or something?
    olympic gold keto

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    Senior Member 86coupe's Avatar
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    Does it still have TVIS? If there's a little linkage and vacuum tank under the intake manifold, its bigport. Smallport can also use the rwd manifold, but will have an adaptor plate there instead of the TVIS one.

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    smallport:

    -oil drain out the back of the head (sorta on the side, on the intake side im pretty sure)
    -no tvis between the inlet manifold and the head (set of butterflies to add more torques, aprox 20mm thick)
    -no "tvis" sticker on the inlet manifold.
    -inlet manifold usually has lines or groves running down it.
    -the spark plug lead from the coil to the dizzy is the smaller type, from my limited experience anyway.
    -if the smallport is in RWD the mainfold has prolly been cut and welded.
    -funky plastic cover thing to cover the spark plug leads

    bigport

    -tvis between the intake manifold and head
    -tvis sticker on the intake manifold (or at least provision for it)
    -all the plugs on the dizzy cap are the same size
    -inlet manifold is generally pretty flat on the top
    -if engine in RWD it may be a genuine RWD intake manifold, or manifold has been cut and shut.
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    Default

    The easiest way to tell is with a ruler.

    If the injectors are all exactly the same distance apart, it's a smallport. There's 2cm extra gap with a bigport fuel rail between injector 2 and 3, it's fairly noticeable.

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    Senior Member dunga70's Avatar
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    Cheers guys with all that info should be able to work it out.. Pretty sure it doesn't have tvis or at least not anymore..

    Thanks!
    olympic gold keto

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    sorry to hijack it a little bit, but if it has a bigport manifold on a smallport, will you have to remove the TVIS butterflies?

    joe
    Quote Originally Posted by Jdm-Mcc View Post
    quit hatin get bakin!

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    Senior Member 86coupe's Avatar
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    Yeah, you replace the entire thing with a plate that matches the ports. Such as this

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    Default

    big top small bottom

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