mx5cartalk.com

This is going to be a mini project thread in the style of the old one that I had - which I think now exists in the technical archives. I can't search so I can't say for sure. It's actually a mirror of the continuation of my OCAU project thread. I recently cooked cylinder 3 of my temporary Familia motor - and seeing as the aim the whole time was to have that motor as a temporary solution and rebuild the original motor I pulled out - it's hardly unexpected. It's just sooner than I had anticipated.

-------

I've been doing a fair bit of reading (and asking of questions lately and have decided I will get forged pistons after all. I don't know whether it's the silicon content or what, but apparently forged pistons have gotten better lately. They're running tighter clearances, and when the block is machined properly they won't slap at all. Assuming my block hasn't yet been machined, I'll be going for a +1 oversize. I won't know for sure until I get the verniers on the weekend and measure the original engine's bores.

The pistons I'm more than likely going to get are the Flyin' Miata Wiseco forged pistons - they're custom versions of the Wisecos by Flyin Miata with different wrist pins, better quality rings, different rod bolts and a coating on the skirts of the pistons. They're $US563 without shipping. if I end up ordering those, I'll post a thread and see if anyone wants to split the cost of shipping - but I may end up going through one of a few nice folk who have offered discounted pistons. I'll see what happens there.

As for the rods, I'd say I'll go standard rods. The standard rods are a decent item, and good ones can withstand around 20psi. I just have to make sure I get a good tune done. I'll get them inspected and treated where necessary - though the exact treatments I haven't yet researched.

Also, all of the pics for sabretooth.id.au are dead - I have to find some alternative hosting.

I would have thought that rods AND pistons would be the way to go as The stock rods will be very suspect at any power level that \"requires\" forged pistons.
If you want to keep stock rods as a comprimise then why not just use TX3 turbo pistons??

I would hate to spend all that money on the engine only to have the rod bust out the side of the block.

i have to agree, if you want a long term bulletproof engine sabre, do it right the first time i reckon.........i got caught many years ago when i rebuilt a 351........not with a rod thankfully, but accepted a report that the standard valve springs that were already in the engine were well within \"tolerance\" for the high spec engine i was building......after the initial running in period, i took it in for a dyno tune, then the guy said let's take her for a test spin..............going up a slight incline, i tramped the boot into it, took it nowhere NEAR it's new rev limit & \"POP\"...........a valve spring unloaded, the valve tapped the piston & wallah, the engine had to come back out to be checked, when the heads came off, EVERY valve had marked a piston .......a whole new set of 4V valves AND race spec valve springs ............all for free after i seriously spat the dummy



my new philosophy after that was: do it ONCE, do it RIGHT!

Well normally I'd be inclined to get aftermarket ones - and I was until I read this post by MX5_DriftFury: http://archives.aus-cartalk.com/viewtopic.php?t=9826. Have a read and tell me what you reckon.

i guess the question you have to answer for yourself is \"how hard am i gunna work this new engine & how long do i want it to last???\"...................if it was me, i'd be putting the best money can buy in it.......that's just me tho

Anyway, much work was done over the weekend. I bought some Jaycar digital vernier calipers, a Kinchrome 10-150ft.lb torque wrench, two pairs of axle stands, and some other bits and pieces. I'm still out on the hunt for a few more tools though - a piston ring compressor and DOHC-compatible valve spring compressor.

Work on Saturday was minimal. I did some inspection and cleaning, and also fixed up the wiring to the coil pack - I used a plug that I bought from Jaycar ages ago and soldered/crimped it on. This plug allows me to remove the coil packs as before they were always tethered to the car - but now I am able to just unplug and remove them. It's the small things...

On Sunday, saboteur came around to help take things apart to remove the head from the car and inspect the damage. And in the process to learn a few mechanical tidbits for when he gets his MX-5. With the engine still in the car, off came the turbo, intake, alternator, various hoses, out came the coolant and eventually off came the head. If you've read the rest of the thread then you've already seen all of those before, and so I didn't take any photos. But I did take photos of the important part - the head removal.



Yep, all looks fine doesn't it... but seeing as cylinder 3 is the cause of the problems, lets take a closer look at its valves:


Bam, right on cylinder 3 - cracked exhaust valve. Valves. Again!!


The rest of the valves were fine so I guess there was a bit of a lean condition in cylinder 3.

In light of this - the car's going back together with the Familia engine still in it! I was suspecting the car either holed a valve (again), or had dropped a ring - the former requiring just minor work, and the latter meaning a bottom end rebuild is necessary. After having a look at things it appears that the only damage is to the valve - it would account for both the blowby (and therefore no spark/compression for that cylinder) and the oil consumption when driving. So I'm going to buy a new valve stem seal, headgasket and clean up a valve from the original MX-5 motor. This will allow me to get the car on the road again at minimal cost - and being without a car of your own for 2 months would absolutely suck.

To try and prevent this sort of damage happening again in future (seeing as it is the second motor that's had a valve eaten for lunch), I'm going to have all 8 (4 original, 4 Familia) injectors cleaned and flow tested to see if one of them could be causing a problem. I'll also get the car tuned. Now while there was a mark in the bore, there was no apparent damage - the mark couldn't be felt, and you could still see the cross-hatching. spectral and I couldn't see anything obviously bad looking. The exhaust valves to me look like they'd gotten pretty hot so the cylinder mixtures have to be lean.

But! There's always a but. This also doesn't mean I'm going to be putting off the engine rebuild for a large length of time either. While I plan to slap the Familia engine back toegether, I'll still go ahead and buy what I need for the MX-5 engine's rebuild - but at least now I can buy it over time instead of loading my credit card up instantly like I was expecting I would have to.

Speaking of spectral, :thumbup: to him for dropping around his engine stand, piston ring expander and other bits and pieces. They'll come in very handy soon after the block is machined. And thanks to saboteur for his spanner-twiddling skills.

For the engine rebuild itself - now that I have the vernier calipers, next on the agenda is a bore measurement. After establishing the size of the bores, I'll buy a set of pistons to the next oversize. Once I have them, I'll send the block off for machining at UMR. Then will come the bearings, an oil pump and then I'll take it from there.

For fixing up the Familia engine, the following is on the list:

• Replace the dump pipe bolts
• Purchase a headgasket and valve stem seal from mazda
• Replace a few clamps - small, and medium in size
• Purchase a valve spring compressor
• Clean up an old valve from the MX-5 motor
• Bang it all back together
• Get a tune
• Get a wheel alignment

As for how hard, and how much to spend - well if the car is only going to be off the road for a shorter time - it now might be time to get something aftermarket.

Anyway, much work was done over the weekend. I bought some Jaycar digital vernier calipers, a Kinchrome 10-150ft.lb torque wrench, two pairs of axle stands, and some other bits and pieces. I'm still out on the hunt for a few more tools though - a piston ring compressor and DOHC-compatible valve spring compressor.

Work on Saturday was minimal. I did some inspection and cleaning, and also fixed up the wiring to the coil pack - I used a plug that I bought from Jaycar ages ago and soldered/crimped it on. This plug allows me to remove the coil packs as before they were always tethered to the car - but now I am able to just unplug and remove them. It's the small things...

On Sunday, saboteur came around to help take things apart to remove the head from the car and inspect the damage. And in the process to learn a few mechanical tidbits for when he gets his MX-5. With the engine still in the car, off came the turbo, intake, alternator, various hoses, out came the coolant and eventually off came the head. If you've read the rest of the thread then you've already seen all of those before, and so I didn't take any photos. But I did take photos of the important part - the head removal.



Yep, all looks fine doesn't it... but seeing as cylinder 3 is the cause of the problems, lets take a closer look at its valves:


Bam, right on cylinder 3 - cracked exhaust valve. Valves. Again!!


The rest of the valves were fine so I guess there was a bit of a lean condition in cylinder 3.

In light of this - the car's going back together with the Familia engine still in it! I was suspecting the car either holed a valve (again), or had dropped a ring - the former requiring just minor work, and the latter meaning a bottom end rebuild is necessary. After having a look at things it appears that the only damage is to the valve - it would account for both the blowby (and therefore no spark/compression for that cylinder) and the oil consumption when driving. So I'm going to buy a new valve stem seal, headgasket and clean up a valve from the original MX-5 motor. This will allow me to get the car on the road again at minimal cost - and being without a car of your own for 2 months would absolutely suck.

To try and prevent this sort of damage happening again in future (seeing as it is the second motor that's had a valve eaten for lunch), I'm going to have all 8 (4 original, 4 Familia) injectors cleaned and flow tested to see if one of them could be causing a problem. I'll also get the car tuned. Now while there was a mark in the bore, there was no apparent damage - the mark couldn't be felt, and you could still see the cross-hatching. spectral and I couldn't see anything obviously bad looking. The exhaust valves to me look like they'd gotten pretty hot so the cylinder mixtures have to be lean.

But! There's always a but. This also doesn't mean I'm going to be putting off the engine rebuild for a large length of time either. While I plan to slap the Familia engine back toegether, I'll still go ahead and buy what I need for the MX-5 engine's rebuild - but at least now I can buy it over time instead of loading my credit card up instantly like I was expecting I would have to.

Speaking of spectral, :thumbup: to him for dropping around his engine stand, piston ring expander and other bits and pieces. They'll come in very handy soon after the block is machined. And thanks to saboteur for his spanner-twiddling skills.

For the engine rebuild itself - now that I have the vernier calipers, next on the agenda is a bore measurement. After establishing the size of the bores, I'll buy a set of pistons to the next oversize. Once I have them, I'll send the block off for machining at UMR. Then will come the bearings, an oil pump and then I'll take it from there.

For fixing up the Familia engine, the following is on the list:

• Replace the dump pipe bolts
• Purchase a headgasket and valve stem seal from mazda
• Replace a few clamps - small, and medium in size
• Purchase a valve spring compressor
• Clean up an old valve from the MX-5 motor
• Bang it all back together
• Get a tune
• Get a wheel alignment

As for how hard, and how much to spend - well if the car is only going to be off the road for a shorter time - it now might be time to get something aftermarket.

Sabre,

When you do your major rebuild you may wish to consider getting the valves HPC/JetHot coated. It will reduce the amount of heat absorbed by them and that will make your engine a happier place.

I would do the pistons and head too. Talk long and hard with your engine machinist as many are not all that happy about coating the pistons. Particularly in things like the MX5 where piston sizes are fairly standard. For a V8, you have much choice and can easily order a piston designed to be coated which will then fit the bore without any problems.

Will the beast be ready for a possible club track day next month

So, did you find the piece of valve, or has it gone out the back of the exhaust?


Jules

Surprisingly, the turbo looks fine. I couldn't find any bits in it, so I assume that it disintegrated. I't not in the bore either.

I'm guessing the bit either disintegrated with time, or it's still stuck between the collet and remainder of the face of the valve.

JBT: Maybe. Just maybe.

Anyone got a valve spring compressor that they can loan?

What's your budget Sabre??? In time and dollars?

sabre....
I suggest you invest in a exhaust gas temp probe so you can get a handle on what the engine is doing.... sounds like afr's might be ok but EGT are going way high causing valves to melt/become fragile.

Uncle Arthur wrote:What's your budget Sabre??? In time and dollars?

One isn't set really. I guess it's just equal to the cost of parts. The only labour not done by me will be the machine shop doing the head and block.

4sfed5: That sounds quite feasible to me. I have one I can borrow, so I'll have to slap that in when it's all together again.