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66 Posts
I've been reading MX5 forum posts for years now.
These are THE BEST EVER technical postings, both here and the head work postings.

You are so generous and patient with your research and disclosure.
The engines you build are just superb and through your selflessness others can follow.
Please keep the posting coming.
For everyone that contributes to your exemplary work here there will be hundreds more who are just admiring
your work and enjoying your postings. Well done. I really am impressed by you.
Those that know me understand that I very seldom say that.

The wealth of information is just staggering.
I wish I was 25 years younger and still engaged at this level of engine tuning.
Thank you.

Best regards.

596 Posts
Hi Thruxton,

You are never too old to play with engines its your fitness that stops you.( or lack of a suitable playpen )

I am 60 and still playing, I have an Austin Seven Engine on the workbench which will have a billet crank fitted once the hole in the side is welded up,

I am planning a short stroke billet crank mazda engine to bring an 1840cc down to below 1800cc and making it an oversquare screamer.

I already have 169 bhp in a roadgoing eunos with ITBs. I am hoping for more power with a drop into the smaller capacity class for westcountry hillclimbs.

This post and its associated posts are helping us all along the way !

Long may it continue to educate and share information.

Happy New Year to all

spending too much money
1,187 Posts
Hi Thruxton / Dickie,

Thank you for the kind words it is much appreciated :) I do often wonder whether people are reading this so its great to hear the feedback :thumb-up:

So to finish off the last stage of confirming clearances, it was time to set the head onto the engine & get the thing timed up!

First things first more plasticine onto the piston:


I made a bit of a mistake here and that was the exhaust plasticine didn't completely cover the back of the valve pocket. I only realised this after the checks were done but going forward I need to ensure the whole valve pocket is covered. Thankfully I didn't have a radial clearance issue previously so it was unlikely to show itself as an issue in this tests (I'm mainly checking valve pocket depth here).

The next stage is to set the cams at 108 LSA using the lift at TDC method, then move the piston to TDC. finally the belt goes on and is tensioned up (The new tensioner works great btw!).


With the belt tensioned using the new tensioner in place of the old Idle pulley, there is a potential interference fit with the waterpump housing:


I have roughly 5mm clearance when tensioned which should be fine but this area will be closely monitored for interference during high RPM dyno runs incase the belt starts to move around.

So the engine was rotated 2 times by hand, again feeling for any major issues. after this the cams were placed into their maximum valve interference positions which was +6 Advanced on the intake and +6 retarded on the exhaust (102 LSA)


After rotating a further 2 times, dismantle the engine and check the plasticine!


Opps! I didn't use enough WD40 on the valves/plasticine to stop them sticking :lol: Rookie error but some careful peeling and then placed back into the pockets


First off we check the intake side with some small cuts into the plasticine



On the Intak side, the valve to piston depth clearance was borderline at 1.3-1.4mm in some areas (Mainly at the edges of the valve pockets nearest the ring lands which seems to be the biggest issue for me on these pistons!). The valve to piston radial clearance was 1mm minimum.

Here's a side by side picture of the valves at TDC method measurement vs the timed engine clearance checks (TDC method n top / timed method underneath)


So the timed method is definitely better as its exactly what the engine will see and takes into account piston dwell / position in relation to cam events. In my case the difference was approximately 0.1 to 0.2mm less clearance.

The exhaust side showed a good 2.8-3mm clearance within the valve pocket which is exactly what I wanted as I was aiming for a minimum 2.5mm exhaust valve depth clearance. You need more clearance because the piston is chasing the valve and also the additional heat the exhaust valves are subject to causing the valve to expand which can change your clearances.

So armed with the above measurements, I have decided to limit my engine to 103 LSAs for both the intake and exhaust cam. This will ensure the intake valve clearance is maintained at 1.5mm everywhere at all times and the exhaust valves are given a little extra breathing room (I'd rather not bend valves for the sake of 1 degree, I prefer the comfort factor!).

To make my life easier on the dyno, I decided to 'colour in' my cam gears for want of a better term. It something I've always done as I like things to be obvious/visually easy to appreciate when messing with engines. To this effect, the following traffic light colour scheme was used:

Green - 108 to 105 LSA
Amber - 104 LSA
Red - 103 LSA





This will help me ensure this engine stays safe when we start to mess around with cam timing :)

2,640 Posts
I wouldn't worry too much about the cambelt rubbing the waterpump, it's closest on the idler and the belt shouldn't wobble there as it's changing direction (unlike the ocilations that can happen between radius)

if you're realy worried then remove the tensoner's spring (only required for initial belt tensioning) and maybe trim or remove the cambelt-cover threadded boss?


spending too much money
1,187 Posts
Delayed update (as per usual :lol: )

So with the arrival of my son, progress on this project literally halted for a good few weeks but after finally getting to grips with our new lifestyle I'm back on the project!

First step was to get the engine timed up for the final time:


and also just changing some odds & sods gaskets that just needed replacing due to age/use, such as a new oil cap gasket:


Next step was to get the new spark plugs modified and indexed into the engine:





The next problem area was the oil cooler sandwich plate. I went for the mishimoto thermstatic oil plate because it had 2 x NPT ports for my oil pressure/temperature sensors and it has a thermostat built in controlling to 92 degrees which was perfect for my needs.

first problem was the mounting thread for the oil filter was way too long (it was designed to be used with the OEM cooler which is much deeper) so this needed to be shortened via an angle grinder and die to clean up the threads.


after mods:


Next step was to find my SPA combo oil pressure/temp gauge:


find the sensors and fit into the sandwich plate:


Next was a trial fit of the sandwich plate to check for clearances with other bits in place:


Realised due to the length of the pressure sensor I needed to tilt the sandwich plate slightly to clear past the starter motor:


So after all the above was completed, it was time to get the engine off the stand so I could fit the flywheel/clutch:


place engine on a pallet:


Next was to inspect & clean the flywheel ready for install, all was good here and 6 new ARP flywheel bolts used (you can see the balancing holes on the flywheel on this pic)


Next was to inspect & clean the pressure plate/clutch disc and pressure plate bolts. in this case I'm using a 1.6 exedy stage 1 pressure plate and a 6 puck ceramic disc


The pressure plate also has some battle wounds from the balancing process:


The titanium pressure plate bolts needed the threads cleaning of previous loctite blue but otherwise they were ready to go


Finally all the above fitted to the car using the clutch alignment tool as its much easier when joining up to the transmission :)


Next tasks are to order up some AN10 lines for the oil cooler and actually fit the oil cooler into the engine bay, once this is done the engine can go in B)

spending too much money
1,187 Posts
Yeah its definitely better now the engine is on the deck - Its nearly ready to go in I'm just being held up by some AN10 hose (hopefully arriving this week).

To make things easier on myself I fitted the coolant re-route adapter and new 82 degree thermostat before the engine goes in:


The next step was to get the oil cooler trial fitted into position, this is what I started with:


and after some chopping down of the aluminium coolant pipes/new silicone hoses I ended up with:


I have ordered a bracket which will pick up from the car's chassis (next to the brake fluid pots, the little slotted section bottom left of the picture) and will clamp around the aluminium coolant pipe which will give it some lateral support.

Due to waiting on AN10 hose I couldn't mock up the oil cooler hoses so I progressed onto the crankcase breathing system, found a lovely baffled tank with 2 x AN10 fittings online so that was fitted:


after 10-15 minutes:


slowly making progress!

spending too much money
1,187 Posts
Discussion Starter · #169 ·
I purely went laminova for the shorter oil lines / less weight / better oil system protection in a crash

Well whilst I was sorting out the auxiliary parts for the engine I noticed the starter motor was really heavy. Had a quick look/research and found that the mk2.5 starter motor is lighter and same/slightly higher torque.

Old starter:


New starter:


Just over 1kg saved which should help offset the laminova being on the car plus having a new starter is always a good thing with the new high compression motor!

So I removed the ITB setup from the engine as I wanted more room to make up/fit the AN10 oil lines from the filter to the laminova. I thought a quick cheeky look down the new inlet port design at full lift, looks good to me


So I decided to fit my new SPA oil gauge into the car before I fitted the engine, just made sense to plan out the wiring/fit it in the car as it gave me easier access.

As per my usual self I forget to take lots of pictures during the install but here's the end result!


My view from the drivers seat with the steering wheel on:


And finally here's how it looks turned on:


Overall very happy with the gauge, easy to fit and really good quality. Looking forward to setting up my alarm limits (it changes from green to red when it alarms at your set point which is nice). So when I'm next on track, if it stays green it's all good and if it turns red I'll know to back off

Sent from my iPhone using Tapatalk

2,640 Posts
I purely went laminova for the shorter oil lines / less weight / better oil system protection in a crash
Same :driving:

but if you hit as many things as me :wallbash:


spending too much money
1,187 Posts
Discussion Starter · #171 ·
In fairness I've been really lucky with this car, I've only spun it on the tarmac or gravel rash when hurtling into the traps, nothing major just cosmetic & denting my ego

So the Sunday just gone was one of those days I was really looking to, getting the main lump into the car!


Didn't expect the ATI damper being in the way for the install so needed some very delicate turning of the engine in the bay to get it in

After getting the transmission & engine together (forgot how frustrating this can be!), the engine mounts were fitted and I now have a roller once more!

I started on the exhaust side, maybe not because it's less busy and easier! I had previously revisited the exhaust flange and ported it to maximise flow / give me some reversion defence with it being roughly 2mm wider than the exhaust port which should help the mid-range.



I fitted the new starter motor and After messing around with various bolts/wires I decided to leave it for this weekend and grab a victory beer


Next steps is to make and fit the AN10 lines and then get the ITBs fitted!

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spending too much money
1,187 Posts
2 Month delayed update! (getting good at these delayed updates....)

Just when learning the ropes with a new born baby wasn't hard enough I managed to get ill for 3 weeks - not the best idea when there's a pandemic going on but I have made some progress, not much but some!

The first step was to get the AN10 lines made up, this is a nice job to do (just taking your time, measure twice cut once etc).

I forgot to take pictures of the first line being installed but this is how I like to make them.

Put the fittings onto the connection points:


, measure the distance and cut your hose to suit and double check:


install the AN fittings on the hose then assemble the hose onto the car:


Next job was to install the catch can AN10 hoses, in the end I went for push fittings because its only atmospheric pressure (hopefully!) and two AN10 is more than enough crankcase pressure ventilation for this engine so Didn't feel the need for actual threaded fittings here. I bought some Aeroquip hose and its really nice to work with, looks great too


The true test was whether or not the ITB setup would easily fit with the oil lines etc and it does but only just! I had to split the manifold away from the bodies to get access to the bolts


Before I taped up the inlets I did a cold compression test of the cylinders, just to make sure everything is even/good to go for first fire and I got 200psi across all 4 cylinders which is excellent! With the engine not broken in yet & the 2618 pistons needing more clearance I suspect the hot compression test should be in the 240psi region which would be ideal but will have to wait for that test!


So next steps will be:

- fit the jenveys
- fit the air filter backing plate (Might need to cut the bonnet but not 100% yet, would rather not just for the filter at this stage but I hope to make a custom airbox this year which will definitely need the bonnet cutting).
- fit the throttle cable
- fit the vacuum system
- fit the fuel lines/FPR & new guage
- get the old V-power out of the tank
- Fill it with fresh V-power
- Get Dave from Canems to help on initial start-up (injector sizing etc)
- start the break in process

Nearly there!

spending too much money
1,187 Posts
I started at the top of the to do list and started to fit the jenveys & modify my vacuum block so it can mount where I want it to be. All was going pretty steady away until I started to plan the routing for the fuel lines (Due to mounting the jenveys upside down, the fuel rail & associated fuel hoses needed to be modified to suit). This is when I noticed some deterioration of the fuel lines with the outer rubber layer cracking from what I can only assume is ageing & high temperatures.


So I decided to fully investigate the fuel lines from the tank to the engine bay to see if the deterioration was localised. This meant getting the car jacked up / in the air so I can inspect the underside as well.


turns out this was the best move I decided to do this day as the lines were in poor shape



Not the job I wanted to do at this stage of the build, it would have been alot easier when the engine was out of the car but hey ho lessons learned and all that!

So the first step was to remove all the fuel lines from the car:


Then it was time to install the new hoses, I ordered SAE J30 R6 spec hose with a upper working temp of +110c and upper working pressure of 300psi (burst pressure 900psi) - should be more than enough for this build and hopefully it won't crack like the last ones!

Then to fun part of pulling 2 continuous length of fuel hoses through a fully built up car & getting access to all the required clips - it was possible but lets just say my knuckles are pretty worn out :lol:


New list!

- fit the jenveys & Vacuum system (Nearly done)
- fit the air filter backing plate (Might need to cut the bonnet but not 100% yet, would rather not just for the filter at this stage but I hope to make a custom airbox this year which will definitely need the bonnet cutting).
- fit the throttle cable
- fit the fuel lines/FPR & new guage Done!
- get the old V-power out of the tank Done!
- Fill it with fresh V-power (Have 25l of fresh stuff ready)
- Get Dave from Canems to help on initial start-up (injector sizing etc)
- start the break in process

Making slow but steady progress :)

spending too much money
1,187 Posts
Discussion Starter · #174 ·
Well it’s been a productive period for me on this little car!

The car has finally been started and gone through its first warm through cycle

The car was running fairly rich and sounding exceptionally aggressive on throttle during the warm through, I only took it to 3000rpm max as well - this is going to be one hell of a drive!

As ever I forgot to take pictures or videos during the run (I was too focused on the car!). I did have a slight oil leak on the sandwich plate, one of the AN fittings, but that was nipped up just the usual engine commissioning things you have to do.

After the initial warm up process the oil and filter was changed, no issues here and replaced another set of millers run in oil and OEM oil filter.

I also treated myself to a header modelling kit:

Which is the perfect kit for the diameter I need to make this engine work around 7500-8000rpm

Next steps on the list:

  • Get Dave to come and help me get the car’s map driveable
  • book the car in for an MOT
  • Put some running in miles on her then change to fully synth nanodrive oil and hit the dyno!

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spending too much money
1,187 Posts
Discussion Starter · #176 ·
Yet another delayed update! (I'm becoming an expert at these)

I managed to source the kit from Nick at Skuzzle motorsport as he was shutting up his shop, the price was good and I couldn't help myself!

Progress on the car has been amazing these past few weeks, The car has a new MOT and the new engine is fully run in & changed onto fully synthetic oil and ready for the dyno.

The first trip to the MOT station was on a gorgeous day, 29 degrees outside and sunshine all day, the car was looking great in the sun:

It failed on some minor points, so after fixing those I booked in and drove the 17 miles back to the MOT station, this time in torrential rain - I was absolutely soaked but was good fun all the same:

After the MOT was sorted, the engine was run in successfully, following my usual process:

  • millers CRO 10w40 running in oil / OEM filter for first start up, alternating RPM from 1800 to 3000rpm until coolant & oil levels stabilise & Set idle speed to 1800rpm. record engine temp data.
  • Change oil & filter with same as before (Cut open filter to check for bearing material), slowly building up load & rpm (upto 4000rpm / 30% throttle for 25 miles, upto 5000rpm / 40% throttle for 25 miles, upto 6000rpm / 50% throttle for 25 miles, upto 7000rpm / 60% throttle for 40-50 miles) confirm idle speed has increased without adjustment (In my case it rose to 2200rpm). No cruising allowed, either applying throttle or engine breaking under vacuum using gear ratios. record engine temp data.
  • Change oil & filter with fully synthetic oil & OEM filter (Cut open used filter to check for bearing material).
  • Running in completed.

The above process has always given me great results so fingers crossed it has worked well this time.

The engine pulls very hard from 4000rpm, even at only 50-60% throttle its pretty snappy on the throttle response - just how I like it!

So my next steps:

  • Book dyno time with Dave at Canems ECU
  • choose my initial desired intake length
  • Prepare my spares & equipment for the dyno (Extra fuel / fresh modified spark plugs etc)
  • Get driving the car before the weather changes on me!

spending too much money
1,187 Posts
Discussion Starter · #178 ·
The engine temperatures are great, always under control so far (Light/medium street use). I'm using an 82 degree coolant thermostat stat and 92 degree oil thermostat which means the coolant is hopefully always going to be cooler/lower than the oil temp so i still adequate heat transfer, the laminova is situated on the coolant output pipe from the rear of the engine to the radiator so the engine coolant temperature is prioritised.

Pretty impressed with the laminova's performance, in fact it could potentially be overcooling the oil on the street as the oil sits comfortably at 95 degrees with coolant temps around 90 degrees.

I'm expecting my oil temperatures to stabilise even further with the fully synthetic ester based oil in it & reduced frictions from the break in period, I might need to buy a flow restrictor for the laminova - we'll see!

I didn't drain and & inspect the oil cooler because the engine is always protected by the oil filter, although you are correct some bits could remain in it but should they become loose the filter is there to catch it.

After managing to find some time last night for some quick calculations, this is what i came up with for deciding my initial intake length:

Camshaft 'tuned powerband' = 3300-8000rpm (All mechanical or fixed tuning parameters must fall within this powerband)

Fixed tuning options (Cannot change with significant replacement of parts):

Intake runner 'tuned diameter' = 7217rpm
Exhaust primary 'tuned diameter' = 6978rpm
Exhaust primary 'tuned length' = 5750rpm

Flexible tuning options:

Intake runner length - I have the following options available to me and one which is very cheap to implement, these are listed below by length & 3rd/4th harmonic boost range:

365mm = 3rd (6305rpm - 7206rpm) & 4th (4916rpm - 5497rpm)
335mm = 3rd (6790rpm - 7760rpm) & 4th (5294rpm - 5920rpm)
315mm = 3rd (7356rpm - 8407rpm) & 4th (5735rpm - 6413rpm)
290mm = 3rd (8025rpm - 9171rpm) & 4th (6256rpm - 6996rpm) requires purchasing 15mm velocity stacks at £60

After considering the above power boost ranges, I'm going to stick with 335mm for 2 reasons. The first reason being it should ensure by peak torque lands around 6750-7000rpm which would be ideal and the second being I don't think the current exhaust manifold is going to be big enough to break adequately at 7500rpm onwards so no point trying to boost power there!

So this will leave me with the following powerband:

Usable powerband - 3300-8000rpm
tuned powerband - 5750rpm - 7760rpm

This does leave a good amount of torque on the table between roughly 3500-5500rpm but I'm hoping that the higher compression ratio / increased cubic capacity of the engine will help to compensate this area - as ever though, only the dyno will tell me what is actually happening!

I'm hoping I might be pleasantly surprised by the current exhaust manifold and that I may wish to shorten the intake length to 315mm or 290mm to bolster the top end but we'll see.

2,640 Posts
Pretty impressed with the laminova's performance, in fact it could potentially be overcooling the oil on the street as the oil sits comfortably at 95 degrees with coolant temps around 90 degrees.
so it's working properly then:cool:

I might need to buy a flow restrictor for the laminova - we'll see!

the laminova is situated on the coolant output pipe from the rear of the engine to the radiator so the engine coolant temperature is prioritised.
se the 'ah' above, the restrictor could restrict engine coolant flow and prioritise coolant to flow through the Laminova's 'outer' passageways, the opposite of what you're trying to do?

from Laminova Oil to Water Coolers

why I'm fitting mine in the 'heater' circuit - with a partial restrictor....

I think;):unsure:😲


spending too much money
1,187 Posts
Discussion Starter · #180 ·
Your right Rich the ‘restrictors’ they offer only improve heat transfer from oil to coolant, I need to block a few coolant passages of the oil cooler or inside some sort of restrictor ring -

Had a really good session with the car today, did idle adjustments, some road mapping and checking everything over getting ready for the dyno on the 20th August!

First thing that amazed me is the engine is very strong, even at only 1/4 throttle up to 4500rpm it pulls really well - guess that’s the extra cubic capacity helping out.

I tried my first full throttle pull today…. Even though the car is running extremely rich on WOT (10.8-11 AFR), the car will spin the tyres from 35mph in 3rd….. like really unhappy/sideways wheel spin! I genuinely think I may have too much power in this for the road, I’m sure I’ll get used it though.

It really caught me off guard as previously that was the ideal speed in 3rd for it to just pickup and go with the 211bhp engine… gonna have to fit those 205 r888r’s sooner rather than later I think!

From 3500-7000rpm WOT in third then into fourth… I should learned the first time as I went WOT when I clicked fourth and a little wheel spin/chirp again… bonkers. Felt amazing though, sounded glorious and wanted to rev past 7000 very quickly which is good news considering my timing is very conservative at the moment.

The overrun is simply ridiculous due to high AFR’s, It sounds like world war 3! Hopefully that will get tamer when we get the fuelling right, I like the odd crackle but I sounded like an 18yr old kid’s corsa at mcdonalds car park

I’m not going to bother tuning anymore/taking fuel out, I’m just gonna wait for the dyno session!

So time to prep the car for the dyno session, this meant:

- checking spark plugs after run in process:

Yep… very rich indeed!

  • Compression testing the engine, all even and great numbers so happy on the engine front.
  • full tank of fresh V-Power
  • confirm TPS calibration in ECU & confirm throttle
Plates fully open at 100% TPS
- change the trumpet length to 315mm due to desire to shift power up the Rev range rather than down low (another method of calming the wheel spin!)

  • take a fresh set of modified spark plugs to the dyno (do 85-90% mapping on old plugs then change out for new for final WOT tuning & power runs)
  • tightness check all engine bolts
  • order new PX600 air filter

That’s about it I think, usual little things here and there but hopefully it’ll be ready for Friday afternoon’s dyno session. After feeling how hard she pulls around 3500-6000rpm I’m fairly confident it’s above 170ftlb in this area. I still think this current exhaust manifold will restrict my top end, but we’ll see!

The main thing is it starts on the key and idles regardless of coolant temp so feels a lot more usable now, no need to blip the throttle during cold starts (shows I’m getting old when I prefer a nice cold starting engine!)

It would be great to see some torque and horsepower guesses from you lot who read this, post them up and we’ll see who’s the winner

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