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Thread: MA70 --> JZA70 Conversion

  1. #1
    Toymods Club Member #194 Conversion King Lambolica's Avatar
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    Default MA70 --> JZA70 Conversion

    This will be a trial run to get information on what people want to know to do this conversion as we are documenting and photographing the conversion to hopefully create a FAQ Article for future reference.

    This all started after the 7M-GTE in my brothers MA70 GT Limited Blew the headgasket and after some quotes about rebuilding the 7M and running the numbers on a 1JZ-GTE conversion, in OUR Case the 1JZ conversion came up trumps.

    The aim of this conversion was to get the car on the road as soon as possible and running reliably, there would/could/should be other things that we could have done during the conversion however once again in our case we deamed them un-necesary at this point in time.

    Recipient car:- MA70 GT Limited, Auto, Aero top, Digital Dash.
    Doner Car:- JZA-70 Manual (R154)1/2 cut (appears to be a base spec model - No ABS, Analog Dash, fewer power options) Purchaced from CVAP (forum sponsor) Andrew did a really good job of getting the engine up to Sydney for the long weekend. The engine payment was confirmed Monday morning, the engine was delivered to Melbourne Depot Tuesday, arrived in Sydney Wed morning by 9am, in the garage by Thursday. Andrew also threw in the JZ tailshaft (just in case) plus the exhaust system that origonally came with the car. Pleasure to deal with and Highly recommend him for anything you may need that he deals in.

    My brother Matt (Maphril) is relatively new to the modifying car scene and is generally of the opinion if it is broken send it back to Toyota to get it fixed which is all well and good but isn't in the spirit of modifying, but he is very cluey and currently works as a electronics Technician which was an advantage. My experience in engine swaps is pretty basic (18R-C - 18R-G - 18R-GEU (several times now)) and I looked at this conversion as mearly a step up with more wires hanging off the engine, more accesories hanging off the engine and more gear on the cross member. ie more bolts to strip the heads on
    In general terms we are not Mechanics by trade and Haven't tackled anything like this previously.

    The Conversion:-
    Friday Night:- Prep work.
    We spent friday night getting the cars into position in the garage up on ramps, stands, jacks and pulled the piping off the top of the engine bay of the JZ cut and photographed the vacuum piping and general layout of PS, A/C, intercooler piping for future reference. Pulled the glove box out to get to the computer and pulled the engine loom through the firewall.

    Saturday:- Pulling out the 1J!
    Saturday I went about pulling off all power steering, A/C fuel, and wiring that connected the engine to the car, leaving the plugs connected to the sensors for ease of re-connection, in fact we even left the power steering fluid bottle as part of the engine package. we decided that we would leave all pipes comning out of the engine connected to the engine rather than swapping it in the engine bays later. it was also found that the intercooler on the JZ is much larger than the MA and the JZ only had a hydraulic fan where as the MA had the engine fan + an electric thermo fan + 2 small thermo fans. It appears the 2 small thermos were for the Oil cooler that the MA had which the JZ didn't have. In the spirit of getting the MA bay looking like the JZ bay all the fans were removed from the MA (however we will try to relocate the Big thermo later.
    Whilst I was messing up a perfectly good engine bay Matt was pulling the Interior of the Cut appart to get the pedals and clutch cyl. accel cables and pulling out the gear shifter. (auto - man conversion as well) and pulled the interior out of his car to prepare to install it in. Engine was removed from the cut at about 10pm Saturday night. Then there was beer and big talking.

    Sunday:- Pulling the BHG 7M. + wiring
    Sunday was the same for me as Sat pulling off all engine connections and removing the radiator, intercooler etc. 7M was removed from the engine bay at 6pm. Matt spent the day cutting the Plugs off the 7M loom and cut and shutting them to the 1J loom for all the plugs that feed information to the interior in terms of A/C controls and Dash information with the help of diagrams lifted from the internet. This part doesn’t really need to be done as you could swap the whole dash loom over out of the front cut if the front cut is the same or higher spec. In our case the MA was the higher spec (with digi dash etc) and was easier to cut/shut the looms. He finished the main loom about the same time I had the engine ready to be pulled out.
    The rest of the night was spent comparing empty engine bays and swapping basic stuff over (clutch lines, Accel cables etc) beer and lack off sleep prevented any further productive work.

    Monday ANZAC day P/H:- Cross member Mayhem
    Matt spent most of the day putting his interior back together, now improved with 3 pedals and clutch cylinder! without incident. (note make sure that the rubber sound proofing is removed from under the clutch pedal mounting bracket as it gives just enough movement to make pedal play bad and was a prick to trace * end after thourght* )
    I spent the morning pulling out the crossmember (brakes and all) from the cut after some measurements confirming that the crossmembers were in fact different enough to require them to be changed. (bugger) the brakes from Matts car are to be swapped onto the JZ member as well as some of the PS stuff which was overhauled recently. Time constraints left the project with the JZ crossmember on the floor in front of the MA waiting to drop the MA member. Looking in the empty bays all of the A/C lines are very7 similar between the MA and the JZA however the fittings are different and need to be swapped. the PS lines are similar even thought the filler bottles are on opposite sides of the bay (return lines run under the engine itself) there is a difference in the cooling lines between the two bays further investigation will show if the exrta cooling setup is for the hydraulic fan and the PS cooling lines are the same or if there is a diiference there and require swapping before the intercooler is replaced. was also found that the bonnet release support bracket had to be swapped to fit the 1J intercooler as the MA was smaller and slightly thinner.


    Sunday (weekend 2):- due to work / beer / lack of sleep very little was done bar sitting behind the wheel and dreaming.

    the hole for the gearbox leaver was enlarged to allow the R154 to better fit where the auto leaver was. the front 2 holes were used as factory to fit the boot over, the rears have been bolted down differently as the bolt patterns for the auto and manual are different.

    Saturday (weekend 3) :- With a fresh mind we went about dropping the crossmember out of the MA70 and swapped the brake rotors/calipers over to the JZA member and refitted it back into the car. We were hoping at the outset that we wouldn’t need to pull the nose cone off however this proved to be inaccurate as removing the P/S and hydraulic fan cooling lines from in front of the radiator is impossible with it on so Matt jumped on that whilst I secured the crossmember in and connected the steering and brake lines back up. Due to some electrical sensors in the A/C lines being different we swapped the whole A/C set up over from the cut to the MA (however the piping in the nosecone is very similar except for a release valve) a hole in the radiator support on the drivers side had to be enlarged to cope with the extra pipes that ran through (the MA originally only had 2 pipes (P/S cooling lines) the JZA had 1 P/S line (as it returned to the bottle on the other side) and 2 lines for the hydraulic fan cooling lines. The Intercooler was monted in place and nose cone put back on. From there the engine was lifted into position and sat on the mount whilst we checked over clearances. Then more beer and big talk…

    Sunday (weekend 3):- The gearbox Cross member was bolted in and the engine secured in position all piping was hooked back into place and wiring looms put back in to place. Some fancy (dodgy) wiring was used for the Alternator due to it being on the opposite side of the bay (will be fixed in the future). The exhaust system was bolted under the car (however there was some cracking around the top of the dump pipe that was sorted later at an exhaust shop. We intended to swap the front half of the MA tailshaft for the JZA tail shaft however we couldn’t undo the bolts. The MA auto tailshaft was about an inch shorter than the JZA item and was put in as far as it would go so we could get it to a mechanic to swap it over. All bolted up we cleaned up dropped the car back onto terra firma and went and had a beer whilst we did a final check over things (checking each others work) once satified we closed our eyes and turned the key…. A few turns and Vroooooommmmmm…. She started.
    First impression after letting her idle for a while and the revving …. Wow how revvy is this engine, and oh how sweet a sound comes from the throaty exhaust. A test drive took place around the block (without bonnet) and more beer ensued with talk of boosting the engine in the not too distant future.

    The week after the car was taken to a mechanic for a once over and to swap the Tailshaft. It was given a clean bill of health. And the exhaust leaks fixed. It then went back to the Mech for a power run on the Dyno and turned 172rwkw in stock form…..

    The following are links that we found during our research phase and were used to do most of the wiring. They inclued diagrams of how to convert the JZA70 engine loom to match the MA70 body loom by cutting the MA70 plugs off the MA70 engine loom and splicing them to the JZA70 engine loom. Basically follow the colours.

    Body connector EA2 Mapping
    Body connector 1990+ IG1 Mapping
    Body connector 1990+ IH1
    Body connector 1990+ IH2
    Body connector Pre 89 IG1
    Body connector Pre 89 IH1
    Body connector Pre 89 IH2
    Body connector Pre 89 EWD + Fuse box

    Special thanks to the owner of the site Supra 6 As this single place provided all of the know how needed to make this conversion a breeze.
    Mods this is from a word document that once I put pictures and diagrams to it will be submitted as a Tech article.
    Last edited by Lambolica; 19-09-2005 at 04:18 PM.
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  2. #2
    Former User Conversion King Joshstix's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    Sounds good man. I look forward to seeing the final version with pics etc.

  3. #3
    Toymods Club Member #194 Conversion King Lambolica's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    Top post updated with links to the diagrams for converting the JZA loom to match the MA70 body loom so that your dash works first go!
    Beige.... The new Black!!!

  4. #4
    Junior Member Domestic Engineer urantia's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    hey Lambolica, excellent info! saving me abit of time!
    I'm nearly up to the wiring, i have been working solo for the past 3 days, have the 1jz and manual out of halfcut, the crossmember out, and halfway thru getting the 7m/auto out
    I need to ask tho.

    Does the exuast pipe that is attached to the 1jz engine mate up the old ma70 exuast? (same flange and position? or needs to go to a muffler shop?)

    With those diagrams that you have links too, do you have a copy of them you could mail me (the whole web site has been down for about a week now) just when i need the wiring diagrams too.

    Did you keep the ma70 fuse box in the engine bay? or swap over the jza70 one? I have noticed some of the wiring goes out the side of th engine bay and back to the cabin, i really would not like to have to remove these and transplant them across. (i too have the upspec ma70, and a low spec 1jz halfcut, and want to keep all the nice things like digi dash etc) cheers!

  5. #5
    JZ Powered Too Much Toyota EldarO's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    1990+ MA70 crossmembers are identical to JZA70 crossmembers.

    i will be doing this conversion later on this year, 1990 JDM Auto MA70 - r154 JZA70, this thread is worth berlins weight in gold!

    Eldar.O.

  6. #6
    Junior Member Domestic Engineer urantia's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    your lucky then, my crossmember was an 87 square mounts style, but dropping the crossmember proved to be real easy, 6 nuts 3 on each side and lowering it down with 2 jacks made it a 15 minute job.

    4 days left of holidays before work starts, if i don't have my 1j conversion completed i should start looking for another job as i won't be able to drive anywhere.

  7. #7
    Junior Member Domestic Engineer urantia's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    ah ha! site is workin again i have the files!!
    answered my own questoins regarding the exuast etc.

  8. #8
    Junior Member Domestic Engineer urantia's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    I'm abit confused with the wiring, When i took the 7m, out i relised there were a few plugs that were attached with the body wiring near the fuse box that connected to the 7m, and so i started pulling the complete body wiring harness out, but i'm thinking this might not be needed. Better study the wiring diagrams abit more.

    the mess i'm working with right now is amazing! i am progressing this far on my own with no help in 5 days work so far, i'm pleased but so much to have finished before work starts again. Doing it bush style too.

    Let me tell you moving an engine crane around with a rocky gravel surface is the nineth level of hell!!





    A few more pics if anyone wants to see:
    http://members.iinet.net.au/~urantiacjd/7mout.jpg
    http://members.iinet.net.au/~urantiacjd/fugginheavy.jpg
    http://members.iinet.net.au/~urantiacjd/7magain.jpg
    http://members.iinet.net.au/~urantiacjd/1jzout.jpg
    Last edited by urantia; 28-12-2005 at 10:58 PM.

  9. #9
    HHeLiBeBCNOFNeNaMgAlSiPS Backyard Mechanic
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    Default Re: MA70 --> JZA70 Conversion

    Urantia - well done that man!! I can't believe you are doing it outside as well!

    Don't start pulling the body loom out of the ma70 - and don't cut the connectors off until you are 100% sure of what you are doing. From memory we used the jza70 fusebox - not sure why, perhaps it was because the alterator was on the other side of the engine and we definately wanted to keep it neat and factory spec. I assume you have a copy of the MA70 TSRM with the wiring diags already.

    You have a 1jz with it's engine loom and ecu - this need to be mated with the ma70 body loom. There isn't a lot of wiring that needs to be done from ECU to body loom - mainly stuff for the dash, speed sensor for the progressive power steering, L1, L2 and L3 for the TEMS computer (assuming you have TEMS). we kept all the ma70 body loom connectors attached, and just tapped into the wires required (helps when you're dad is an elctronics tech and sharp with soldering gun and heatshrink). Not sure in hindsight if this was the best idea - it reduces the amount of space to put things in behind the dash - however, if driftspec ever wants to return to stock standard NA 7M it'll plug straight in!

    One little thing to remember is that some (if not all) jza70s don't have an oil pressure gauge, just the low oil idiot light whereas lots of ma70's have a gauge (analouge dashes definately do). The oil pressure sender is in a shitty spot behind the air-con compressor on the 1jz, and while the 7m sender screws in it fouls on the compressor housing. We made up a little adapter from brass fittings to mount the 7m pressure sender parallel to the block, resulting in a good (if tight) fit and a working original oil pressure gauge in the dash. There's other way this can be done (check the old forums) but it's best to sort it out before the 1jz goes in.

    Was your ma70 pre-89 (and thus pre prog power steering?). If so, and you are changing the crossmember and steering rack over don't forget the prog power steering ecu (passeger side footwell)

    And don't forget the hydraulic fan ECU!!! It's a bitch to find (tucked up into the dash on the passenger side) but if not connected the fan won't spin fast enough and you'll have overheating issues. There's an input from the bottom of the jza70 radiator that checks temp and adjusts fan speed accordingly. If that's not connected (but the fan control ECU is), the fan blows full speed all the time - not a problem in most of Aus but maybe a bit cold in tas.
    Last edited by lumpy; 29-12-2005 at 11:35 AM.

  10. #10
    Junior Member Domestic Engineer urantia's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    Lumpy i think you may of saved me alot of trouble!
    I started relising i should be using my exisiting wiring that is already in the engine bay, the thing that had me stuffed was that the 7m's alternator plug and wiring and a few other plugs that go to the 7m engine were still in the engine bay plumbed right in with the body loom. While the 1jz engine has the alt wiring with the engine.

    (i wanted to have all the 7m stuff together as a dude from hobart is buying the motot off me)

    Are you sure the actual plugs have to be cut and reconnected with solder? It seems like all the plugs have a tab in them and you can pull the wire out with the crimped connector attached.

    I was wondering about the oil pressure sender unit!! thanx for that! will save me finding out the hardway! Yep found the hydro fan computer hanging out the side of the halfcut still attached luckily (got a bent to buggery 1jz intercooler tho - dam frieght place).

    How did you go with swapping the fusebox, I noticed alot of the plugs are the same, but some of the fuses are for a few different things like "TEL" i'm not sure what that is.

    Ah i spose i should take it once step at a time, been rushing trying to get it all done so quick, i'll no dount be calling on your expertise tommorow

    cheers, Chris (aka dingaling from old toymods)

  11. #11
    HHeLiBeBCNOFNeNaMgAlSiPS Backyard Mechanic
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    Default Re: MA70 --> JZA70 Conversion

    You certainly should be able to pull the wires out of the plugs - we just tapped/soldered them because the plan was to keep the car until the next century when it may have been nice to return it to stock!!

    It's been years since we did the conversion, and my dad did most of the wiring (back in the days before that cool 1jz-gte site will all the diagrams). We only had a toyota tsrm (hard cover version) and a couple of scanned ecu pinouts with handwritten notes on them. I remember tracing all the wires out in the halfcut trying to figure which one did what!!

    I'm not 100% sure why we used the 1jz fusebox - perhaps we thought it had some extra things that my ma70 (NA 7m) didn't? we definately used the 1j alternator wiring. Anyway if you get really stuck I shake my dad's memory, otherwise there's probably a few other guys on here with more up-to-date info.

    don't forget about enlarging the little hole that the powersteering cooler lines go thru. This is the only bit of cutting you should need to do.

    The main thing is to have a good think about each step - what is the input, what does the ECU need, where does the wire go. Don't rush it or you'll make a mistake that will be a bastard to fix once it's all together. We had the instrument panel out a couple of times becuase we hooked a couple of things up wrong (ie tacho signal to check engine light!!).

    Do you have an analouge dash? there's a good trick to do if you have a jza70 analougue dash and want to get the ma70 tacho working schmick!

  12. #12
    HHeLiBeBCNOFNeNaMgAlSiPS Backyard Mechanic
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    Default Re: MA70 --> JZA70 Conversion

    I should add for anyone doing a conversion - while the crossmember is out you should have a good think about changing control arm bushes, wheel bearings, ball joints, new shocks, new brake disks etc. Most ma70/71s have lived a hard life and are due to replace some of these.

    A lot of these things are much easier to change/replace whilst the engine is out (and possibly the crossmember too if you are swapping them), and since the car is off the road already it's a good time to drop the control arms off to get re-bushed (or do it yourself if you have a hydraulic press that can handle them).

  13. #13
    Junior Member Domestic Engineer urantia's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    Lumpy i can't believe you did the conversion without those wiring diagrams! that is doing it tough. Good thing your dad was a sparky. (i originally tryed to trace each wire to figure out what each one does, but after a few minutes my brain exploded, so glad i got those diagrams!).
    It now makes perfect sense why the 7m alt plug is apart of the body loom and what i have to do with it. (run it into the ea2 jza body connector.)

    Anyhow i decided to take your adive and sort out this oil pressure sender issue, I took the AC compressor off and as you said before the oil pressure sender from the 7m fouls on the block.. But after abit of thinking i think i came up with an excellent solution that anybody can do if they have a halfcut. Take the rubber brake hose off the spare crossmember and use that! same threads! here is a pic to show what i mean:



    Could use a bracket, but it should do the job.

    It must be an automatic supra thing, but the shifter hole where the manual stick will come thru is Alot smaller then the manual shifter hole on the halfcut. I had to cut that out to a larger size as it didn't look big enuf to change into any gears. Also I seemed to be missing a hole for screwing the PS resivour in, so 3 spots that needed cutting to fit parts for my supra.

    I'm pressing ahead trying to retain the digital dash, i know the speedo is going to be out tho, but must keep that retro high tech 80's look

    Yeah i wanted to change my bushings while i had the crossmember out, but didn;t have the right tools to press out the old bushes, so frustrating as i have a new set of poly bushes waiting to go in. i did however take the opportunity to install these bilstein/toyota shocks from a jza70 R which i hope are an improvement.



    I also whent with the halfcuts disc brakes as they looked better then mine, altho very rusty, but should clean up good after using them for abit. (mine needed machining) hopefully the wheel bearings arn't shagged in them. Also had a couple of toyota brake caliper rebuild kits so i rebuilt my front calipers. Should be a nice car when its all finished.

    Just spent the last hour bending my back in unatural ways to put that clutch pedal in, THAT IS HARD! and i still could not get the top bolt in with my dash out for more access. Try again tommorow.

    Thanx again for the advice Lumpy very useful!!!

  14. #14
    Junior Member Domestic Engineer urantia's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    I've hit a snag with the wiring. will post a pic of the problem when i find my camera. (better start looking for another job too)
    Last edited by urantia; 02-01-2006 at 10:43 PM.

  15. #15
    Toymods Club Member #194 Conversion King Lambolica's Avatar
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    Default Re: MA70 --> JZA70 Conversion

    Sorry for no reply, I've been busy braking stuff lately.

    The fues box I'm 90% sure we used the MA70 box and redid some wiring to the alternator based on the JZA70 wiring.

    You will probably also need to enlarge the holes where the hydraulic fan lines run as the MA70 only has the P/S cooling lines there (running through the radiator support panel.)
    Beige.... The new Black!!!

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