Blown head gasket. Which way to go?

[greenMachine]

Great information here, thanks Manga and 93.

It's up to the OP, but I don't think a performance bump is his priority so spending more on the BP4W head may not be where he wants to go. Especially when the bottom end is yet to be proved unharmed.

I am surprised at the availability of heads at the quoted price, and that makes the case for a new head more attractive than I imagined, compared to an engine swap.

Manga, the BP4W will require adapters for both the inlet and exhaust (assuming NA8 manifolds in both cases)? It seems this is getting more expensive and complicated than 'just get a new head', but again, that is a call for the OP to make.

[manga_blue]

Ed, exhaust flanges are the same on BP05 and BP4W. Only the inlets differ. This is the setup that I'm running now.

It can be pretty hard to find an uncooked BP05 head these days. The last one I used was the fourth or fifth head that we tested. They seem to come mostly from poorly maintained 323s.

[Tony]

NB8D SE: BP4W.

While not directly related to the OP's situation, it should be pointed out for future searchers that if I recall correctly, the SE head is actually BP8J.

While the SE head looks like a BP4W head in outward appearance, I believe the cooling port layout of the SE head are the same as the VVT BP6D head, which is a different port layout to the BP4W head.

Needless to say, the SE head uses the same head gasket as BP6D, although many go back to the BP05/BP4W ('94-'00) head gasket (BP26-10-271) when using a coolant reroute.

[Nevyn72]

NB8D SE: BP4W.

While not directly related to the OP's situation, it should be pointed out for future searchers that if I recall correctly, the SE head is actually BP8J.

I just had a look at my SE and cast into the back (firewall end) of the head it says..... BP 4W 4

[Tony]

Completely off topic now - I aplogise to the OP

As it was explained to me some time ago, due to the relatively low numbers of SE/MSM heads produced, the BP4W casting die was used, however a different cooling port configuration was exposed in the head during final machining in an attempt to send more cooling water to No. 3 and 4 cylinders. This is the same configuration as the VVT BP6D head, hence the use of the same later version head gasket. While based initially on a BP4W casting, I have been advised that the SE/MSM head is subsequently referred to as BP8J.

This was confirmed by apparently knowledgeable sources in the US when I was rebuilding my engine a number of years ago and was considering putting an NB8A head on my SE. However, I've not personally had an NB8A's BP4W head sitting next to an SE head to compare cooling passage configuration for myself. Although I did save the following image at the time.

For what it's worth, I hope that helps...

[lonesailor]

I have,with some difficulty, sourced another head. While it is straight and hard it was in a bit of a mess(and cost considerably more than the $100 mentioned on here). It was very dirty with sludge and carbon including a lot of carbon in the inlet ports?? however the valves were OK I have replaced the valve seals and used the best (longest)springs from both heads, they were all a bit shorter than spec but were all fine before.The cams on the new head were non standard (.010" more lift} so have used my old cams.
At this stage I am attempting to source bits and pieces. Can anybody advise me on gaskets? the head gasket I took out was a MLS (3layers of SS shim held together with something), Ebay has MLS gaskets VRS gaskets and graphite gaskets, I would not be happy with graphite on an aluminium head because of the electric mice, but what are the pros and cons between MLS and VRS if any. I plan to replace the waterpump, seals, timing belt and all hoses and gaskets, assuming costs are not prohibitive. I have also made what I hope will be an audible warning device for an overheat situation by mounting a normally open 100*C thermal switch on an unused plug on the waterjacket at the back of the head connected to a piezzo buzzer in the cockpit. Thanks all for your input on here, I now know a lot more about MX5 cylinder heads than I did before( or really wanted to)

[greenMachine]

Please don't ask me how I know this, but a sensor that doesn't have a fluid to sense will not give a reading. No water, no reading. I think the way people handle this is to put a pressure sensor in, which tells you when the cooling system has lost pressure (leak, blown head gasket(?), burst hose ...). It won't tell you have an overheat, but you already have something for that.

Personally, I wouldn't use a random internet seller on the 'bay, but there is one UK outlet that is often quoted on here (MX5parts?) for price and service.

I don't have the knowledge (or opinions ) to comment on the head gasket styles so I will leave that for Manga or 93 or ...

[93_Clubman]

cost considerably more than the $100 mentioned on here

That's what I've paid for bare BP05 heads from recyclers, but not MX5 recyclers. But good to hear you got it so you can get the car going again. manga_blue & StanTheMan know head gaskets better than me.

[StanTheMan]

I usually get them from the UK. For the NA6 I got a German aftermarket one at the recommendation of magna_blue.
For the BP4W they were out of head gaskets over Christmas. I ended up with a total mazda genuine rebuild seal kit which I assume is the factory headgasket....
On the B6 Ive had both Genuine & aftermarket.....both were fine. The Mazda one was more messy though after opening her up later for other reasons

[RS2000]

lonesailer, I think you'll find that VRS is not a type or brand. VRS is an old term & stands for valve regrind set. ie full set of gaskets for head servicing.
Cheers

[manga_blue]

The best sets that I've found, both for quality and price, are the Victor Reinz ones from mx5parts.co.uk

[lonesailor]

Green machine. The unit I am putting on the back of the head is not a sensor as such, but a thermal switch. It works like an overload that is fitted to sealed unit domes in a refrigeration system. It works using a bi-metal diaphram which switches on risr of temperature. I have it mounted on a small square of 3mm aluminium with good thermal conductivity to the head itself. They are cheap from Jaycar. I will try a 70degC switch first,it may give nusance alarms ,if so I will go for 100deg C. Meanwhile while I await parts could anybody identify these hard plastic things 25mm dia with a 9mm hole,They turned up during disassembly & I can't work out where they came from

plastic bits.jpg

[GR124]

spacers between the fuel rail and head, would be my guess

[StanTheMan]

spacers between the fuel rail and head, would be my guess

I can confirm your guess is fact.
Fuel rail spacers.

[greenMachine]

That's interesting! I haven't heard of those before.

I think I would prefer the pressure switch if I wanted a backup to the coolant temperature though, it will (hopefully) give early warning even before the temperature rises. OTOH, if the coolant system integrity is ok, but something like a stuck thermostat or water pump failure occurs, the temperature gauge will/should catch it.

Nevertheless I would be interested to hear how your testing goes.