Well as per my post in the new members section, I have been using my '97 monza for a few months and really have been enjoying myself - thought it would perhaps fail its MOT so havent been planning any upgrades / tinkering however… it passed! Living in Aberdeenshire, when the salty roads come, they are here to stay so I am sorting my winter “to do jobs”. Reading some posts on other forums, people seem to have had a good bit of sucess changing the 90bhp cams for the 115bhp cams and getting a little more umph. Having all winter, I thought I would play at this as well!
So when I found a set of 115bhp cams on ebay for £33 delivered… well, they should be in the post! Having only done a cam belt change on a Fiat Barchetta before, I thought it best to see if anyone has any advice before I do the swap? I cant find any guides on line for this job so will just be removing bits until I can take the cams out and change them. Plan to change the cover gasket and the cam shaft seals - anything else I should be looking at (cam belt and tensioner is less than a year and 5k miles old)?
Over the winter I will also be
changing the thermostat engine temp needle doesnt seem to be as high now its cold and heaters are cooler so think it may be stuck
changing the coolant
changing the diff oil
new plugs, leads and engine oil / filter
possibly new clutch if I grow a pair (only axle stands and ramps at home so not sure I want to tackle it)
I thought it was a lot more complex than changing the cams, and it was basically not possible to turn the post-1994 1.6 into the pre-1994 1.6.
Most people who have the 90bhp (or 88bhp, depending whom you believe) don’t think it’s that slow. The important thing is the difference in torque at usable revs. The NC 1.8 is a similar case; the 2.0 only has 12% more torque, but a higher red line and gets the rest of its 32% power increase from that. Whether that’s usable power in normal driving is another question.
UPDATED - Sorry Geoff, I didnt see your comments in the quoted text!
Thanks for the welcome Geoff, I look forward to asking silly questions and pulling on some knowledge, but hopefully I may be able to pass the learning on to someone else in the future! THe local garage is asking £300 to change the clutch which may be reasonable (guessing £120 for a clutch kit plus 3-4 hrs labour) but is more than 50% of the value fo the car! It is slipping but not horendously bad so I may try put it off until next winter!
On the differences between the engines, Rogerzilla, THanks for your comments as wel, on one of the other forums there are some dyno print outs of someone else taking a 90bhp, changing the cams and getting more top end power - although I believe there are other differences (compression ratio, ECU, non-batch ignition)- I was still going to give it a go if I wont destroy anything as a tinkering excercise. I am not really looking for maximum performance but for £33 I thought its worth a try, even if it gives a little more! Does sequential ingition affect performance? I guess you would get a stronger spark if only firing one plug rather than 2?
A stronger spark will make no difference, although having the largest permissible gap sometimes improves things slightly. Platinum plugs (Denso ones are not too expensive) might make a tiny improvement but that’s for more obscure reasons, not because the spark is any different.
If you change the cams it won’t be £33 - you’ll probably need a new cam cover gasket and bearing shells (even assuming the replacement shafts have unworn journals). Then you probably ought to do the cambelt and the camshaft oil seals while you’re at it. And then a piggyback ECU to make use of the new cams, or the fuelling and ignition map will be wrong.
Where are you in Aberdeenshire, I would be more than happy to make sure you do the cam change without causing problems. Not doing it for you!
Let’s get one thing sorted, a slipping clutch with 88 bhp will be worse with say 105 bhp so that needs sorted first and what you are doing by driving it with a slipping clutch is probably adding £100 to the cost of the clutch change as you will also need the flywheel removed and skimmed if you do not change it PDQ.
The problem with cheap Mk1 cars is people rightly get confused between value and worth and you just have to accept that you need a clutch change to keep it going and in reality a reasonably Mk1 is actually worth at least £1,000 even if they cost less than that at the moment.
Hope to see you out on a run with the Grampian section when your clutch is sorted. Log on to http://www.mx5scotland.co.uk
Thanks for the replies. The car really was a song and to be honest I expected to run it for a few months and if it had to be broken… so be it… and then it passed the mot so everything else is a bonus, now its time to get dirty!!! I like tinkering, kids go to bed at 730, wife watches naff american crime series from 730 to 10 so I think i can have at least an hour a night in the garage over the winter! So I have a set of daisy alloys to refurb - never tried so why not, then the cams to change and some general servicing work! More of a learning experience than for out and out power!
Drumtochty, I am in Kintore, a few runs out would be good, I had a 1965 MG B roadster for a few years and loved the trips out, now I know the car has more life in it then a trip out will happen at somepoint! I know that the clutch is an issue but it does bite when accelerating up the dual carriage way, its only of the line it slips … the wear on the flywheel is something I was concerned about but didnt really worry about as I was only hoping to get a few months running from it! I was thinking about changing it over the winter but need to find a more cost effective way than paying full labour rates - or get some tall ramps at home! Any help changing the cams is appreciated, I am just gearing up for it at the moment, and was just looking to ensure I didnt miss something obvious but I have a new cam cover, new cam shaft seals in my head, it seems quite straight forward (are they famous last words!)
Roadster Robbie - I dont understand your comment - could you explain? if the fuel injection is simultaneous, wouldnt you be putting fuel into a cylinder on its exhaust stroke?
The engines are manifold injection, not direct injection.
Injectors 1 & 3 and 2 & 4 are simultaneous.
When 1 & 3 squirt, cylinder one will be going down on induction while number 3 is coming up on exhaust. The intake valves on cylinder 3 are closed so the fuel “waits” behind the valve until they open for cylinder three’s induction stroke (remember, we’re talking fractions of a second here).
I’m not sure but I think only half the required amount of fuel is injected on each injector pulse so half the fuel is waiting behind the valve then when it opens the other half of the fuel is injected. (I’m interested to check that theory with a scope now, anyone in the Ely area got a high power B6 that I could use? I sold mine 2 years ago )
Modern engines use sequential injection, but still only inject half the required amount of fuel initially. This allows the engine ECU to re-evaluate the engine conditions again, before the intake valve shuts so it can inject, a different amount of fuel to ensure a perfect mixture. In effect fine tuning the amount of fuel that is burnt. It does all this in the time it takes the piston to start it’s induction stroke to when it ends it…
Modern engine managment amazes me!!!
Thinking about it, I wonder if changing the cam timing does not bode well with simultaneous injection, is that one of the reasons Mazda changed it to sequential…
Thanks Robbie, thats a really good explanation! Looking at the list of things that changed, it seems cams, compression and the simultaneous injection are the main changes - is that correct? THe others dont appear to make any significant change to the performance? I dont know if you can post links to other forums so I wont but did read one where someone simply changed the cams and got increased top end power - although there is a suggestion the car should ahve had the 115bhp engine in the first place so that car may have already had the different ecu etc. However in the same thread someone else posted that the fuel maps for both the ECUs was the same?
Anyway, I still think its worth a try for a little more umph on the dual carriageway. I live pretty much on the A96 and its the fastest road in the uk - if you arent doing 80mph you are holding traffic up! there are also two hills and its these where the MX5 struggles, it just needs more at the top end in third!
Also, the manifold gasket was changed when the cam belt was done a few thousand miles ago - are these a one time only item or can they normally be re-used a few times? - same question for the cam shaft seals?
I think you ment to say the cam cover gasket was changed at the last cam belt change, no need to do the manifold gasket if it was not leaking and most people advise a new cam cover gasket is required each time the cover is removed.
The front cam oil seals are held in by the front bearing caps so both need changed they are quite cheap.
As far as I know you cannot get the timing belt tensioner undone and then reset without doing a full cam belt change procedure but I may be wrong. Therefore this is not a two minute job. If the tensioner and idler are recently changed then they can be re used but even if the cam belt is recently changed the general opinion seems to be that it should not be re used!
Are you seeing an oil leak from below the engine just where it meets the gearbox!
Would you be happy to re use a cambelt that has done a small mileage. I have only done it once with a 60k mileage belt on a VW that the owner was to tight to change and as you can guess it did not work.
I assume that the user will be able to set up the timing and tensioning marks without the bottom cover being removed. Never tried it but on my Mk2 crankshaft outer pully there are no timing marks.
There are no leaks anywhere at the moment (may be different when I play!), I was expecting to have to do a full cam belt change “proceedure” just not actually change the belt as it is so new. I am not going to start the job in the next month so can still keep researching.
Weather this weekend has been great! Shame wife is away and the mazda doesnt have room for the 2 kids!