MK1 project underway - advice needed
Discussion
Hi,
I have an old MK1 Monza ('97 1.6) that had 88hp 4-speed. For the last three years it has deteriorated while the nippers have grown up a bit and it is now or never.
I am fitting a Mk2.5 1.8 VVT and there are some gaps in my knowledge and skills that I could do with some help with. I hope some more experienced peeps on here are willing to help me out!
I had already fitted a set of HSDs prior to starting the project. Now the old motor and gearbox is ready to come out. It's not been easy as the level of corrosion is pretty bad.
So, the questions...
The 4-speed won't do. I might turbo the 1.8 in the future but it is pretty unlikely and I doubt it will ever have more than 200hp; so is the 6-speed from a mk2.5 appropriate? Any other options worth considering?
I managed to get hold of what I was told is a Torsen diff from the same donor as the engine, although I am researching it now. I really think it will need a rebuild, where can I source the necessary parts in the UK, and what should I look out for to determine if its rebuildable or foobar?
The original car had no power steering; can I fit a mk2.5 power steering unit? Should I?
Will I also need to source a mk2.5 prop shaft to match the Torsen diff fitment?
I intend to lighten the flywheel, but by how much I don't have a feel for, any recommendations? It isn't going to be a track car, but it may very well end up driven in the Alps and Pyranees.
Also, the sills seem to be pretty solid having obviously been repaired in the past. I am wondering whether I should be putting time into making sure they are spot on while I am doing this work. Wheel arches down by the sills has some rust but it is solid. I have zero experience with this and the last thing that I want is to put in all this effort only to have it fail MOT on this or even worse turn out to be scrap. I suppose this is rhetorical, it is just on my mind.
I have some other plans too, nothing radical, but I really do need some guidance on these points above to help me with my confidence. The old motor should come out tonight and I have no idea how to properly clean and prep an engine bay.
Need to get hold of a 6 speed pretty sharp, like.
Matt
I have an old MK1 Monza ('97 1.6) that had 88hp 4-speed. For the last three years it has deteriorated while the nippers have grown up a bit and it is now or never.
I am fitting a Mk2.5 1.8 VVT and there are some gaps in my knowledge and skills that I could do with some help with. I hope some more experienced peeps on here are willing to help me out!
I had already fitted a set of HSDs prior to starting the project. Now the old motor and gearbox is ready to come out. It's not been easy as the level of corrosion is pretty bad.
So, the questions...
The 4-speed won't do. I might turbo the 1.8 in the future but it is pretty unlikely and I doubt it will ever have more than 200hp; so is the 6-speed from a mk2.5 appropriate? Any other options worth considering?
I managed to get hold of what I was told is a Torsen diff from the same donor as the engine, although I am researching it now. I really think it will need a rebuild, where can I source the necessary parts in the UK, and what should I look out for to determine if its rebuildable or foobar?
The original car had no power steering; can I fit a mk2.5 power steering unit? Should I?
Will I also need to source a mk2.5 prop shaft to match the Torsen diff fitment?
I intend to lighten the flywheel, but by how much I don't have a feel for, any recommendations? It isn't going to be a track car, but it may very well end up driven in the Alps and Pyranees.
Also, the sills seem to be pretty solid having obviously been repaired in the past. I am wondering whether I should be putting time into making sure they are spot on while I am doing this work. Wheel arches down by the sills has some rust but it is solid. I have zero experience with this and the last thing that I want is to put in all this effort only to have it fail MOT on this or even worse turn out to be scrap. I suppose this is rhetorical, it is just on my mind.
I have some other plans too, nothing radical, but I really do need some guidance on these points above to help me with my confidence. The old motor should come out tonight and I have no idea how to properly clean and prep an engine bay.
Need to get hold of a 6 speed pretty sharp, like.
Matt
mcsellski said:
I have an old MK1 Monza ('97 1.6) that had 88hp 4-speed.
Need to get hold of a 6 speed
didn't think Mazda made a 4 speed except the auto? should be a 5 speed?Need to get hold of a 6 speed
as to strength, the mk2/2.5's 6 speed is supposedly slightly stronger than the 5 speed BUT the top gear ratio is no higher (as they were designed to be combined with a higher ratio diff for motorway cruising but retain the same ratios as the 5 speed)
have a play with FM's ratio calculator
I'm guessing your 1.6 car had the 4.3:1 diff ratio
https://www.flyinmiata.com/tech/gearing.php
for turbo use you'll be wanting 3.9:1 or 3.6:1 diff to use the torque...
you'll find good info on
https://mighty5s.com/
https://www.mx5nutz.com/forum/index.php?act=idx
and
https://www.miataturbo.net/
but beware of MT.net as they can have serious brand loyalty as well as being North American based so have diferent ideas (and fuels!!!)
Rich.
Edited by Zed. on Thursday 9th April 13:10
if you want a laugh, this is my 6speed to 5speed conversion
https://mighty5s.com/post/44074/thread
but I'm using a low ratio final-drive (kia sportage mk1 front diff supplied the 4.778:1 gears built into a mazda diff) and 1.6 na on throttlebodies etc so a diferent 'build'
Rich.
https://mighty5s.com/post/44074/thread
but I'm using a low ratio final-drive (kia sportage mk1 front diff supplied the 4.778:1 gears built into a mazda diff) and 1.6 na on throttlebodies etc so a diferent 'build'
Rich.
I buy and sell MX5s and have done so for many years. As such I've seen many projects and conversions over the years. The one mistake I'd urge you to avoid is the one of carrying out an expensive or complex modification (usually along the lines of a turbo conversion) to a rusty bodyshell.
Its a very common mistake and the car will never be worth the effort as raging corrosion is a real pain to put right and if you have spent lots of time and money on mechanical improvements, you're going to paint your self into a corner where you will either HAVE to repair the bodywork at a later date or transplant the whole lot into a different, more viable bodyshell.
Also remember that an MX5 with a badly corroded shell will never handle as it should either.
Honestly, its best to get the body shell sorted out before anything else.
Its a very common mistake and the car will never be worth the effort as raging corrosion is a real pain to put right and if you have spent lots of time and money on mechanical improvements, you're going to paint your self into a corner where you will either HAVE to repair the bodywork at a later date or transplant the whole lot into a different, more viable bodyshell.
Also remember that an MX5 with a badly corroded shell will never handle as it should either.
Honestly, its best to get the body shell sorted out before anything else.
Sbloxxy,
message received and understood.
The car is up on axle stands, it's not going anywhere for months.
I would really like to find someone local to Dorset that knows bodywork. We're determined to sort this car for better or worse, so if the bodywork needs any attention we will tackle it while the car is stripped and accessible. The sills have been repaired in the past and they feel very solid.
I would like to flare the wheel arches a bit but the main thing is to get the car back on the road first, with the motor fully converted and reliable.
I know what I want, but I don't know entirely what I am doing....
Matt
message received and understood.
The car is up on axle stands, it's not going anywhere for months.
I would really like to find someone local to Dorset that knows bodywork. We're determined to sort this car for better or worse, so if the bodywork needs any attention we will tackle it while the car is stripped and accessible. The sills have been repaired in the past and they feel very solid.
I would like to flare the wheel arches a bit but the main thing is to get the car back on the road first, with the motor fully converted and reliable.
I know what I want, but I don't know entirely what I am doing....
Matt
Couple more questions, if I may....
The old exhaust was junk. The original reason for the project was that the exhaust tip fell off and melted the bumper from the inside. The rest was in pretty bad shape.
1.
I am struggling to find anywhere on the forums where someone has fit a mk2.5 1.8 exhaust into the mk1 chassis. Is it possible? I don't mind doing the work to move the hangers, so long as there aren't bigger issues that I haven't considered.
2.
I seem to recall, but now can't find, that to mate the mk1.6 gearbox to a mk2.5 1.8 motor requires a combination of clutch from one and flywheel from the other. Is this the case and which is it? 1.6 mk1 flywheel and 1.8 mk2.5 clutch? Once I know this I can go get the right flywheel machined. I have two 1.8 flywheels in case this gets messed up!
Matt
The old exhaust was junk. The original reason for the project was that the exhaust tip fell off and melted the bumper from the inside. The rest was in pretty bad shape.
1.
I am struggling to find anywhere on the forums where someone has fit a mk2.5 1.8 exhaust into the mk1 chassis. Is it possible? I don't mind doing the work to move the hangers, so long as there aren't bigger issues that I haven't considered.
2.
I seem to recall, but now can't find, that to mate the mk1.6 gearbox to a mk2.5 1.8 motor requires a combination of clutch from one and flywheel from the other. Is this the case and which is it? 1.6 mk1 flywheel and 1.8 mk2.5 clutch? Once I know this I can go get the right flywheel machined. I have two 1.8 flywheels in case this gets messed up!
Matt
mcsellski said:
I seem to recall, but now can't find, that to mate the mk1.6 gearbox to a mk2.5 1.8 motor requires a combination of clutch from one and flywheel from the other. Is this the case and which is it? 1.6 mk1 flywheel and 1.8 mk2.5 clutch? Once I know this I can go get the right flywheel machined. I have two 1.8 flywheels in case this gets messed up!
f
knose on the exhaust....
as to gearbox, only possible diference is the speedo drive needing swapping and maybe only 2 of the 3 startermotor bolts aligning
1.8 has larger diameter clutch than a 1.6 but gearbox input splines are same for both.
1.8 setup used as an 'upgrade' for high power (although I'm going smaller clutch but thats a diferent story
)Rich.
Edited by Zed. on Wednesday 29th April 21:44
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