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Thread: Big port cams in a small port motor

  1. #1
    Junior Member Backyard Mechanic Evan's Avatar
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    Default Big port cams in a small port motor

    Hey i am about to swap a 96kw rwd bigport motor out of an ae86 to a ae92 small port one.
    I was wondering if there is a gain in performance if u swap to the big port cams?
    I couldn't find any info on it.

    cheers
    1986 JDM AE86 GT Apex panda coupe
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  2. #2
    Chookhouse Chooning Automotive Encyclopaedia Hen's Avatar
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    Default Re: Big port cams in a small port motor

    Just quoting internet "knowledge" here, but it seems that they do improve things (as you'd expect from the specs) but wouldn't be worth paying someone to fit and reshim.

    So if you can do it yourself go for it. If you are paying for the work anyway, save up a little more for some bigger aftermarket cams.

    Hen
    I need a working 4AGE bottom end. Pref smallport GZE, but all others considered. Also complete motors.
    Drift Volvo. Was fun. 2JZ next time.

  3. #3
    tilting at windmills Carport Converter Ben Wilson's Avatar
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    Default Re: Big port cams in a small port motor

    FWIW, I compared the cams from a smallport ZE to a bigport AE82 and are as far as I could tell, they were idnetical. The old AE86 cams may have been bigger, I haven't had a chance to check them.
    Strange things are afoot at the circle K

  4. #4
    Olde mechanic Carport Converter oldeskewltoy's Avatar
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    Default Re: Big port cams in a small port motor

    the differences are there(when new) but are not substantial. From memory they provide a marginal lift increase with no duration change. All and all, I agree with Hen

    Quote Originally Posted by Hen
    Just quoting internet "knowledge" here, but it seems that they do improve things (as you'd expect from the specs) but wouldn't be worth paying someone to fit and reshim.

    So if you can do it yourself go for it. If you are paying for the work anyway, save up a little more for some bigger aftermarket cams.

    Hen
    Information is POWER... learn the facts!!

  5. #5
    Junior Member Automotive Encyclopaedia
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    Default Re: Big port cams in a small port motor

    they seem to help with 4agzes. but i have seen dyno results that loose power on n/a
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  6. #6
    Forum Member 1st year Apprentice
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    Default Re: Big port cams in a small port motor

    From memory they are 30thou lift difference.
    As mentioned before its not worth paying someone to do it.
    Ivan

  7. #7
    tilting at windmills Carport Converter Ben Wilson's Avatar
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    Default Re: Big port cams in a small port motor

    According to my digital calipers (accurate to 0.01mm), there was zero difference in lift.
    Strange things are afoot at the circle K

  8. #8
    Chookhouse Chooning Automotive Encyclopaedia Hen's Avatar
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    Default Re: Big port cams in a small port motor

    I've heard that the change in cams wasn't bigport vs smallport. The change occured earlier than the port change. So some bigports have the "smallport" cams from factory.

    Unsure of exact details of the change though.

    Also the exact cam specs are around, search if interested.

    Hen
    I need a working 4AGE bottom end. Pref smallport GZE, but all others considered. Also complete motors.
    Drift Volvo. Was fun. 2JZ next time.

  9. #9
    Junior Member Automotive Encyclopaedia
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    Default Re: Big port cams in a small port motor

    the bluetop has one cam, all other 16vs have another type. which is the same
    ie theres the bluetop cam
    then theres the cam for all other 16v engines.
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  10. #10
    Building Corollas Chief Engine Builder Cuzzo's Avatar
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    Default Re: Big port cams in a small port motor

    As Hen suggests, smallport cams where used in some late bigports and also some bigport cams are different.(internet knowledge not actual venier checked by myself)

    It has been done and dynoed creating a few kw's more, however id doubt its worth doing. Better off doing a major clean and service. To know when you flog her she should handle it alright.
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  11. #11
    Forum Member 1st year Apprentice
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    Exclamation Re: Big port cams in a small port motor

    16v 4AGE heads specifications
    • Valve included angle (angle between the inlet and exhaust valves) - 45°
    • Minimum valve spring seat pressure to allow for 7,700rpm - 35lbs, or 16kgs
    • Inlet valve diameter - 29.5mm
    • Exhaust valve diameter - 25.5mm
    • Both valves have 6mm diameter stems.
    • Cam bucket diameter 28mm, shim diameter 25mm

    Cam Specs
    Big Port
    Inlet Cam
    IVO BTDC - 9°
    IVC ABDC - 51°
    Duration - 240°
    Lift (mm) - 7.56
    Exhaust Cam
    IVO BTDC - 51°
    IVC ABDC - 9 °
    Duration - 240°
    Lift (mm) - 7.56

    Small Port
    Inlet Cam
    IVO BTDC - 8°
    IVC ABDC - 44°
    Duration - 232°
    Lift (mm) - 7.1
    Exhaust Cam
    IVO BTDC - 44°
    IVC ABDC - 8°
    Duration - 232°
    Lift (mm) - 7.1

    4AGZE
    Inlet Cam
    IVO BTDC - 8°
    IVC ABDC - 44°
    Duration - 232°
    Lift (mm) - 7.1
    Exhaust Cam
    IVO BTDC - 44°
    IVC ABDC - 8°
    Duration - 232°
    Lift (mm) - 7.1

    20v 4AGE head specifications
    • Valve included angle (angle between the inlet and exhaust valves) - 35° (I think ...)
    • Inlet valve diameter - 26.5mm
    • Exhaust valve diameter - 26mm
    • Both valves have 5mm diameter stems
    • Cam bucket diameter 23mm, with very small shims between the valve stem top & bucket


    Cam Timings - (AE101) VVT <4400rpm & >~7000rpm
    Inlet Cam
    IVO BTDC - 0°
    IVC ABDC - 70°
    Duration - 250°
    Lift (mm) - 7.97
    Exhaust Cam
    IVO BTDC - 54°
    IVC ABDC - 16°
    Duration - 250°
    Lift (mm) - 7.6

    Cam Timings - (AE101) VVT >4400rpm
    Inlet Cam
    IVO BTDC - 30°
    IVC ABDC - 40°
    Duration - 250°
    Lift (mm) - 7.97
    Exhaust Cam
    IVO BTDC - 54°
    IVC ABDC - 16°
    Duration - 250°
    Lift (mm) - 7.6

    Cam Timings - (AE111) VVT <4400rpm & > ~7000rpm
    Inlet Cam
    IVO BTDC - 5°
    IVC ABDC - 65°
    Duration - 250°
    Lift (mm) - 8.2
    Exhaust Cam
    IVO BTDC - 54°
    IVC ABDC - 16°
    Duration - 250°
    Lift (mm) - 7.6

    Cam Timings - (AE111) VVT >4400rpm
    Inlet Cam
    IVO BTDC - 35°
    IVC ABDC - 35°
    Duration - 250°
    Lift (mm) - 8.2
    Exhaust Cam
    IVO BTDC - 54°
    IVC ABDC - 16°
    Duration - 250°
    Lift (mm) - 7.6

    Information found here.
    Accuracy is unknown but it looks about right.

    Hope it helps,
    Ivan

  12. #12
    Junior Member Automotive Encyclopaedia
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    Default Re: Big port cams in a small port motor

    Quote Originally Posted by cuzzo
    As Hen suggests, smallport cams where used in some late bigports and also some bigport cams are different.(internet knowledge not actual venier checked by myself) .
    by late bigport you must mean redtops, ie all 4ages with the 42mm crank.

    there is 2 types of cam..... the bluetop ones.. then the rest. EPC p/ns
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  13. #13
    tilting at windmills Carport Converter Ben Wilson's Avatar
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    Default Re: Big port cams in a small port motor

    Quote Originally Posted by ivan
    16v 4AGE heads specifications
    Big Port
    Inlet Cam
    IVO BTDC - 9°
    IVC ABDC - 51°
    Duration - 240°
    Lift (mm) - 7.56
    Exhaust Cam
    IVO BTDC - 51°
    IVC ABDC - 9 °
    Duration - 240°
    Lift (mm) - 7.56
    Perhaps somebody had stuck some big port cams in the ZE head I bought, just looked at the data I recorded and I measured around 300though (7.5mm) on all of them..
    Strange things are afoot at the circle K

  14. #14
    Oh What a Feeling! Backyard Mechanic c2888's Avatar
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    Default Re: Big port cams in a small port motor

    According to the EPC, the change over period was during 1987, it doesn't seem to be ruled by any sort of logic.
    AW11 NA got both sets of cams, changeover being Sept 1987, BUT 4AGZE got the updated smaller cams from the start of their production in Aug 1986

    The confusion lies in that australia was behind when corolla production started, so our ae82s got bigsnorts with small cams, where in japan, the cam change coincided with the model change to ae92.

    Probably why the 88 build date AE82s don't feel like they go as hard as the earlier cars, smaller cams, combined with the fatter 42mm crankshafts.

    The only way to know for sure what you have is to pull it apart and measure them.

    Dan

    it made sense when i was typing, sorry if i confuse
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  15. #15
    Junior Member Automotive Encyclopaedia
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    Default Re: Big port cams in a small port motor

    42mm crank in an ae82?
    are you sure?

    aw11 got both cams, cause they also got the first 42mm crank engines
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