Interchangeable heads

[93_Clubman]

Some reliable info on the differences of the BP4W head:
http://www.solomiata.com/Mx5Engine.html

[project.r.racing]

Some reliable info on the differences of the BP4W head:
http://www.solomiata.com/Mx5Engine.html

good for the head info, but ignore the camshaft info. incorrect info and a few inconsistencies.

[wazman]

^^^ In that thread the guy goes from a BP5w to a BP26 !!! The 96 protege i pulled the head off had a 5w head ! this is what im trying to clear up for Aussie info.
What year and model car to get the particular head you are after.

that thread is a bp-05 head to bp-26. surprized he had pulled a 26 off a non turbo LX. it must have had a head swap sometime in its life.

what aussie info are you trying to clear up? head switching between mx5s/323s/lasers has been done before. what info are extactly are you trying to find?

I'm just trying to find the cheapest head swap that yields the most performance... Maybe I have to use my 4w cams in a 5w
Or something like that.
I also want to list specifically the year and model of the car I get it from.

I don't want to do a chop shop manifold because not everyone has Tig access or budget to pay someone to do it .

[sailaholic]

I think mx5 plus was working on a bolt on adapter, but i forget if was for late manifold to early head out vice versa.

You can get heads straightened with correct heat application in the right spots, had a tour through a head reconditioning shop a couple of years ago and they said it was quite common to do. The problem was if the whole head had gone soft, it needed a full heat treatment. Possible but more expensive then a new (used) head on most common cars they said.

Sent from my GT-I9100 using Tapatalk 2

[project.r.racing]

^^^ In that thread the guy goes from a BP5w to a BP26 !!! The 96 protege i pulled the head off had a 5w head ! this is what im trying to clear up for Aussie info.
What year and model car to get the particular head you are after.

that thread is a bp-05 head to bp-26. surprized he had pulled a 26 off a non turbo LX. it must have had a head swap sometime in its life.

what aussie info are you trying to clear up? head switching between mx5s/323s/lasers has been done before. what info are extactly are you trying to find?

I'm just trying to find the cheapest head swap that yields the most performance... Maybe I have to use my 4w cams in a 5w
Or something like that.
I also want to list specifically the year and model of the car I get it from.

I don't want to do a chop shop manifold because not everyone has Tig access or budget to pay someone to do it .

there was brackets around years ago to put na8 intakes on nb8 heads. but not the other way around.

camshafts between -05 and -4W heads are interchangable, you will just need to use your the lifters that came with the camshafts. the oem hla tappets (hydraulic lash adjusters) use camshafts with a base circle of 35.94, and the oem solid lifters (SOBs - Shim Over Bucket) use camshafts with a 36.00mm base circle. ramps are different blah blah blah.

bp-05 head w/ hla
90-94 mazda bg 323 astina SP
90-94 ford kf/kh laser TX3 (FWD varient)
94-96 mazda ba/bh 323/323 astina
94-96 ford kj laser glxi/laser lynx
94-97 mazda na8 mx5

bp-05 w/ sob
96-98 mazda ba/bh 323/323 astina
96-98 ford kj laser glxi

bp-26 w/ hla
90-94 mazda familia GTX/GTR
90-94 ford laser TX3 (4WD varient)

bp-4w w/ sob
98-00 mazda nb8 mx5

[wazman]

Bit slow on my research but Lightyear was nice enough to let me borrow his NB8b inlet manifold to try on the my NB8a head.
I wanted to see if the inlet runners lined up with the ports in the BP4w head.

Below is NB8b manifold - NB8a head.


mated up.....it is a perfect match for the NB8a head.


So I am getting a NA8 inlet manifold from a forum member in perth. Hopefully this will mate up to the protege/ ford laser heads that are laying around at the wreckers.
The costs-
NA8 inlet manifold delivered - $200
Head gasket (ebay UK) - $54 delivered
inlet manifold to head gasket - $16 delivered
BP5w head from pick-a-part wreckers(bare -no cams or rocker gear) - $42

so hopefully total back on road/to thrashing cost will be - total= $312

[project.r.racing]

So I am getting a NA8 inlet manifold from a forum member in perth. Hopefully this will mate up to the protege/ ford laser heads that are laying around at the wreckers.

It will since it is the same head.

Just remember to put a cap on the heat core feed pipe on the back of the FWD varient.

Also you need to add machining to your costs for the water hole on the front of the head.

[wazman]

Thanks for the info above Project.r.racing ! ..... wait a minute what water hole do i have to machine?

[project.r.racing]

on the front of the head. on a fwd, it isn't drilled out and the driver side engine mount bolt over it. on a rwd the thermostat housing uses the same bolt holes and the engone mount and bolt onto the front of the head.

[wazman]

I have finally had the chance to get back to the wreckers and get another head.

This time from a mazda astina 95 model


I pulled off the oil cap first to do a quick check that it was not messy inside otherwise may as well move onto the next car.... But it seemed nice and clean so onwards i went.

[wazman]

This car proved to be easier than the last as it didnt have a brace that goes from the inlet manifold to the block underneath. Meaning i didnt have to get under the car
The radiator still had to come out so you can get to the heat shield bolts easily enough and exhaust manifold nuts/studs. Also there was no engine mount going to the drivers side of the head like the Protege had! much easier.

Anyway one hour and off it came...took it home and cleaned it with brake cleaner...you can also see the pressed in metal twin water outlet fitting in the back of the head in this shot. im going to delete this


NA8 inlet maniofold fitted to BP4w head....for injector hole/ fuel rail/ injector fit between inlet runner check....


NA8 inlet mani fitted to BP5w head....for injector hole check blah blah blah..


Looked a little tighter and it was.....my ID 1000's needed to rotate a fair bit to get the plugs enough clearance to get on..... i had barely enough length in my injector loom to allow this.

[wazman]

Choppy choppy and weld a bolt in there......(actually left my welding helmet at work so did do this with me eye's closed!)


re-rout and 76deg thermostat in place.....all bolts up no problem.


This head actually did have all the holes in the front to fit up the original mx5 thermostat mount thingy (which i used in the re rout, so is at the back). But the was a welsh plug in the hole that needed to be removed.


Just take a flat blade and tap one spot right on the edge inwards and its should twist enough so you can grab and yank it out with plyers.

[wazman]

NA8 inlet manifold - Astina BP5w head


$6 gasket from ebay -UK


And everything bolted up! no hidden gremlins.....no machining for holes in the front..... (Actually i didnt machine it at all !! i just cleaned and scraped the head to block surface with a razor and slapped it on! )
I did use a new $80 mls (multi layer steal)head gasket from ebay- UK


All back in .... Happy as a pig in mud !

[wazman]

It did 6500 rpm for two days straight!


I did make the mistake of not getting the buckets and shims with the head (they were an extra $15 !! - pirates!) ....but this ment my setup was now a little tappety tap tap sounding PFFFFFFT ! whatever....thrashed it for two days and kept up with 360 rwkw RB25 skyline monsters

I did that because i wanted to fit my cams and buckets.....having read somewhere that the BP5w heads had hydraulic buckets in some of them...... I wasn't sure id spot the difference so i figured use my own.
So yeah my new (second hand) BP5w head has the BP4w cams and buckets/shims from my NB8a fitted in. Obviously i kept the cam saddles that belong to the head.

[davekmoore]

Ooops! Thought this was about politics. I'll look elsewhere now .....