Engine failure - swap compatibility?

[hks_kansei]

I'd really suggest trying to source another BP4W

swapping like for like will be a heap easier in troubleshooting and actually installing.

Plus, BP4Ws are usually a little cheaper than the VVT.


Do MX5 plus have any in stock? from memory they have decent pricing (granted, i;ve never bought from them since they're at the opposite end of the country)

[StanTheMan]

one way to find out if you have VVT controll is have a look. You need tuner studio.Its a free download if you don't have it. It will also tell you what MS version you have once you are connected.

[manga_blue]

I'd really suggest trying to source another BP4W

This. x2

[1600Dave]

I’d pull the head off & check before you remove the whole engine

My only qualm is the time and effort (I've never taken a head off myself) involved in doing this versus the likelihood I know that the BPs are pretty solid and like you said, aren't known for this sort of thing and I concur. I also have to consider the fact that my engine has been running hot for a year or so... god only knows what components I've worn out by doing this.

You'd have the head off in 2 hours. I doubt very much that its a dropped valve, based on you driving it 35k's to work and back after it started making the noise, from my experience of dropping a valve (admittedly in a vintage bike), you'd be lucky to go 35 metres afterwards.

[hks_kansei]

the head off in 2 hours. I doubt very much that its a dropped valve, based on you driving it 35k's to work and back after it started making the noise, from my experience of dropping a valve (admittedly in a vintage bike), you'd be lucky to go 35 metres afterwards.

Depends on luck really.

my gf's old workplace had a car come in with the complaint that it was down on power and running a bit rough, and had been for a few years.

The valve was embedded into the piston, and had been for those few years.
It was just pure luck that it didnt touch the bore, and only left a single dent in the head where it got slammed into the piston face.



But in relation to the OP, if you're not 100% what it is, at the very least borrow/buy a bore scope to have a peek inside.

[manga_blue]

But in relation to the OP, if you're not 100% what it is, at the very least borrow/buy a bore scope to have a peek inside.

Also could be worthwhile to disconnect the drive belts for the A/C pump, steering pump, water pump and alternator just to make sure that one of those is not making all the noise. Then make sure the harmonic balancer hasn't disintegrated.

[ManiacLachy]

You can run a VVT head without a functioning VVT actuator. So if you're pressed for time, don't worry about the VVT tuner right now. You won't get the gains from VVT, but you'll have a running working engine.

[Skifey]

Update for everyone and another quick question.

I didn't end up rushing and buying the BP-Z3. It's since sold and the car is as it was. 2 Days from now I'm putting an endoscope/borescope down the spark plug wells to see if I can get a confirmation of the damage. I'll put some lovely pictures up here should I find the time! If that all goes as expected then the engine will be out and pulled apart shortly after.

In the meantime; I've sourced a BP Engine from a local wrecker. Wants $550 for it. It's from a 1997 Mazda Astina and has ~163,000kms on it. The intention is to buy it, give it a quick pull apart and inspection. If it all looks clean I'll give it a major service and throw it in the car.

FUN FACT that I only realised today! The 'BP' engine is different from the 'BP-4W'.... I thought it was just the full engine code.... whoops!

Now, all of my research leads me to believe that regardless of what car the 'BP' engine was put into, the internals, block, head and EVERYTHING is the exact same. i.e. this engine from a 97 Astina will be the same as the engine from a 1994-1997 NA8. Am I correct or is there differences that I'm missing and need to watch out for?

[hks_kansei]

Am I correct or is there differences that I'm missing and need to watch out for?

Pretty much.

From memory the main differences are just little things like compression ratio and cams may be a little different, but that's not an issue sicne you have a standalone ECU.

Other little bits like rocker cover having the PCV vents in different locations, the head will have the thermostat on the back of it rather than the front like an MX5.
Maybe a few other bits i'm forgetting.

Overall though, most of the stuff is easy to change by using parts from your existing motor (rocker cover, coolant neck)

[93_Clubman]

sourced a BP Engine ... It's from a 1997 Mazda Astina

If you've not already seen them might be worth taking a look at the following:
-Making a FWD BP work in RWD configuration: https://forum.miata.net/vb/showthread.php?t=127747
-Which FWD BP into '91?: https://forum.miata.net/vb/showthread.php?t=351282
-Reverse of your project, but some useful info by PRR: BP RWD to FWD?: http://www.astinagt.com/forums/showthread.php?t=13069
-Mazda 4 cylinder Engine History and Interchangability Guide: http://fixjunk.com/solomiata/solomiata/MX5Engine.html

[shirtz]

interested to see how this turns out. you ever pulled an engine out or torn one down before?

*subscribed*

[StanTheMan]

interested to see how this turns out. you ever pulled an engine out or torn one down before?

*subscribed*

are you getting some pop corn?

[shirtz]

interested to see how this turns out. you ever pulled an engine out or torn one down before?

*subscribed*

are you getting some pop corn?

no E-popcorn here. maybe a carrot and some hummus.

[project.r.racing]

Am I correct or is there differences that I'm missing and need to watch out for?

Pretty much.

From memory the main differences are just little things like compression ratio and cams may be a little different, but that's not an issue sicne you have a standalone ECU.

Other little bits like rocker cover having the PCV vents in different locations, the head will have the thermostat on the back of it rather than the front like an MX5.
Maybe a few other bits i'm forgetting.

Overall though, most of the stuff is easy to change by using parts from your existing motor (rocker cover, coolant neck)

The main difference is HLA vs SOB, and the water inlet/outlet locations. And the cams are different durations and overlap as the Astina was designed for more mid torque and less peak power.

Astinas went solids mid 96, MX5s went solids for the NB.

PCV locations wont be an issue, as when changing over all the timing belt covers, the cam covers gets changed over as well.

But even the cams and lifters can be easily swapped over without too much issue. But with a MS, said changes can be overcome.

[Skifey]

Alrighty! Major update! I'll try to keep this interesting shirtz But before I start to answer your question... No... No I have never pulled an engine out or torn one down before. Until now!! HAZAHH!!

I decided I ought to take this opportunity to learn and so sourced an endoscope to have a look down the plug wells. That was a bit unproductive and didn't really tell me anything as I couldn't see anything other than carbon build up on top of the pistons. So I decided rather than blow $1k on an engine without even knowing for sure if mines cooked, I'll confirm it 110%. Many youtube tutorials, google guides, drinks and hours later... I removed the head. I finished it just ~30minutes ago in fact and what I found has me absolutely baffled.

None of the valves appear to be broken. I can't see any damage to the cylinder walls (haven't rotated the crank obviously - should I do that?). There's a lot of carbon build on the piston tops but otherwise... it looks completely normal. WHAT. THE. HELL. Engine overheats for a year and nothing I do fixes it. Engine stalls and fails and there's nothing wrong with it. Am I cursed or just daft honestly?

Also, that coolant and oil on top of cylinder 4 : I saw none of it with the endoscope before taking the head off so I'm guessing it's a spill from my sloppy handling during the head removal. My bad.

Lastly and just quickly; thanks for all the useful info and links from the posts previous to this one. Greatly appreciated guys!

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