Results 1 to 7 of 7

Thread: Rebuilding a rebuilt 4AGE. . .

  1. #1
    Member
    Join Date
    Aug 2011
    Name
    George
    State
    NSW
    Location
    Sutherland Shire
    Country
    Australia
    Posts
    74

    Default Rebuilding a rebuilt 4AGE. . .

    Hi . . .

    I'm running a Bigport with Quads that was rebuilt ohhh; say 10-15K km ago.

    I'd like to redo the bottom end with higher compression pistons & would like to know if I need to send the block out to be completely redone (i.e. disassembled / hot-tanked / re-honed / crank re-checked & new bearings installed etc or whether I can get away with a DIY hone (or just drop off block to a Machine shop & request a re-hone).

    PS: Haven't rebuilt a block before but have a stand, tools & am prepared to Google . .

    Would also like opinions regarding OEM V Forged pistons. AFAIK car will stay a road-car with occasional track work so I don't see the need for Forged pistons. I am leaning towards late 16V / Small-port units BUT would like to know if there are any other OEM pistons (no larger than 82.0mm) that are compatible with 4AGE with a higher CR.

  2. #2
    Veteran Jimmee1990's Avatar
    Join Date
    Mar 2011
    Name
    James
    State
    VIC
    Location
    Mt Dandenong
    Country
    Australia
    Posts
    1,132

    Default

    With forged pistons your cylinder to bore clearance is a lot more crucial, using a dunny-brush hone and hoping for the best is a patch up job at best. Unless the bore is perfect currently I would personally be looking at boring over-size to get the clearances perfect.

    Bearings is debatable, again I always replace them anyway. As far as I know there's no pistons that will slot straight in as a high comp equivalent, CA18DE or BP Mazda are what I've using in the past at 83mm bore.

  3. #3
    Member
    Join Date
    Aug 2011
    Name
    George
    State
    NSW
    Location
    Sutherland Shire
    Country
    Australia
    Posts
    74

    Default Rebuilding a rebuilt 4AGE. . .

    OK; thanks for that. . .

    In that case I may just rebuild a spare BT 20V block, crank & end-caps I have laying around with 10.3:1 small-port pistons.

  4. #4
    Noooob
    Join Date
    Jun 2010
    Name
    Matt
    State
    NSW
    Location
    Campbelltown
    Country
    Australia
    Posts
    5,246

    Default

    If you have the blacktop pistons you can use them with a 16v head. The motor becomes interference, but keep the belt fresh and it wont be an issue.

    Personally, I'd keep the motor you have complete and build a new one.
    Ae86 Drivingclub - Toyota AE86 Car Club where AE86 | KE70 | Toyota 86 / GT86 | Subaru BRZ | Scion FRS owners

  5. #5
    Member
    Join Date
    Aug 2011
    Name
    George
    State
    NSW
    Location
    Sutherland Shire
    Country
    Australia
    Posts
    74

    Default

    Yeah well I was sort of leaning that way; not by using BT pistons but by rebuilding a complete engine; a tired BT 20V (PSI: 160 160 180 180) I've had sitting in the corner of my garage for the last 4-5 months.

    Reason(s) I haven't gone any further are;
    1. It's way too easy to spend $7-8K on a tuned N/A 4AG & you can basically kiss that $$$ goodbye; no-one ever pays more than 1/3-1/2 your outlay if selling. I have been keeping an eye on various Forums hoping a cheap 4A / 7A build will come up but so far haven't even come across a 7AFE block. . .

    2. A race engine builder I spoke to with some experience building 4As & 7As wasn't all that keen on 20Vs. He says they have a habit of dropping valves when abused & that my Bigpport is a better base for a rebuild.

    FWIW the reason I bought the 20V was that after years of fart-arsing around getting a Cammed 16V 4AG with ITBs to behave itself* on the street w.r.t. a relatively clean idle & acceptable low speed running (and refining my ECU tuning skills in the process ) the option of going to a more advanced engine with Factory ECU (no more $$$ thrown at Tuners) looked quite attractive. . .

    In the event I've come to realise that most of the fuel-smell issues at idle were due to the limitations of the hardware not the ECU; namely a misguided decision to retain the OEM pistons & bump compression by shaving the head & using a thinner HG. Having a Bigport those mods only raised CR to ~ 10: 1 which wasn't enough to make the engine breath in the low / mid range. Past tuners tried to fill the hole below 4000 rpm by increasing the overlap which had some effect but resulted in more unburnt fuel being pushed out the exhaust @ idle.

    It was a flawed build from the start; but I think the character of the 16V suits the car < AE92 FX-GT > better plus it was a one-owner car before I brought it in from Japan so I'd like to keep it matching numbers.

    Since it will remain a road car (with occasional track days) I'd like to stick with OEM type pistons for durability.

    I'm thinking either 10.3:1 Small-port or these >> .

    Having said that I may do an initial build on the spare BT block to minimise the time the car's off the road. That way I don't have to tap holes for oil-squrters or a knock sensor. (original block is a 7 rib Bigport & has same journal sizes as later 4AGs)
    Last edited by GeeEss; 26th September 2016 at 11:33 PM.

  6. #6
    Senior Member Hen may possibly be a nut's Avatar
    Join Date
    Jan 2009
    Name
    Hen
    State
    Victoria
    Location
    Mt Macedon
    Country
    Australia
    Posts
    909

    Default

    Soooo, if you're just going to be using the bottom end of that tired blacktop for a rebuild I'd happily take the head and throttles off your hands. Would hate for them to still be taking up space in the corner of your garage...

  7. #7
    Member
    Join Date
    Aug 2011
    Name
    George
    State
    NSW
    Location
    Sutherland Shire
    Country
    Australia
    Posts
    74

    Default Rebuilding a rebuilt 4AGE. . . Etc. .

    If someone would pay me what it's worth maybe; but I'm not giving it away and I'm not splitting it; I need a 2nd BT block laying around like I need a 3rd earlobe.

    FWIW I paid $1700 for the engine + ECU. Want roughly the same or very close o/wise I'm happy to have it sit there. Who knows; I may still go 20V route if the 16V re-build doesn't light my fire.

    I can't speak for AE86DC but too many guys on other Forums seem to think they "deserve" parts at greatly discounted rates just because they're on the Site.

    I have a set of AE92 FA coil-overs I bought for $1800 that I can't even sell for $1200 ONO. Have only been on car ~ 1000 km.

    PS: I just missed out on a 20V 7AG by a few days recently. A guy with a Hachi spent ~ $8K on it & decided 120 rwkw didn't cut it so decided to flick it & go 3SGE route. He had it on Toymods for 3 weeks before I saw it & was continually low-balled. He ended up selling it for only $3K. . .Because he "needed it gone. . ."

    I'd offered him nearly $1K more than he sold it for. We were both spewing. . . . .

    See what I mean?
    Last edited by GeeEss; 27th September 2016 at 04:58 PM.

Similar Threads

  1. Rebuilt 4age with jap t50 suit rwd
    By gottago in forum Car Parts For Sale
    Replies: 1
    Last Post: 13th February 2011, 09:42 PM
  2. ADM86 4age rebuilt
    By FUTO_GT in forum Cars for Sale (Toyota Only)
    Replies: 7
    Last Post: 6th March 2010, 10:49 AM
  3. RWD rebuilt 4age part out
    By Nikkojoe in forum Car Parts For Sale
    Replies: 49
    Last Post: 10th February 2010, 02:42 PM
  4. Rebuilt Smallport 4age 16v.
    By DAMO46 in forum Car Parts For Sale
    Replies: 2
    Last Post: 9th July 2009, 03:33 AM
  5. Things to Do when rebuilding a 4age
    By r0ck3t in forum Technical - Questions
    Replies: 25
    Last Post: 23rd May 2007, 03:57 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •