BP-4W head on Astina

[Cosmo Dude]

A long shot but has anyone seen this tried?
The BP-4W head is from the 1999-2000 Mx-5 has better porting, better valve angles and solid lifters (buckets and shims).
It does have a hole at the rear for the thermostat housing and the hole at the front but that can be blanked off easily with a welsh plug the same way the BP-05 and BP-26 heads are.
The big difference that could cause grief is the inlet ports are higher so the bolt arrangement could be different causing problems attaching the inlet manifold.
I have to change the head gasket anyway so it would be the ideal time to play.

[project.r.racing]

Originally Posted by Cosmo Dude

The big difference that could cause grief is the inlet ports are higher so the bolt arrangement could be different causing problems attaching the inlet manifold.

The bolt arrangement is different for the BP-07 head, (or is it BP-06). The outside 2 bolts sit 5mm wider and 2mm higher than the BP-05 head. So getting a flange welded up will = $$$. On top of all the other crap that needs changing over.

I don't see the point in it as the gains vs dollars spent out way the bonus.

Better off polishing and porting the BP-05 head, getting some agro cams and swapping the HLA for shims. That way you aren't f-ing with you intake manifold and water/coolent system/s.

Or find a worked NA8C MX5 head/engine and doing a swapover.

Are you gonna build a engine that revs past 7,500rpm? If not, then the shims won't be required either.

[Cosmo Dude]

I want to get rid of the HLAs for more than just top end stability and I'm not sure porting (I don't feel that polishing delivers the bang for buck) would be cheaper than moding the intake manifold.
Oh yeah I do have the B-Spec cams just waiting to be put to good use.

[project.r.racing]

Will you be getting a aftermarket ecu and coil packs also?

As the NB8 motors do not have the dissy/hall sensor keyway on the end of the exhaust cam, as the NB8s have 2 sensors, 1 on the intake cam gear and 1 above the oil pump.

So if you are planning to use the original Astina dissy, issues will arrise when trying to mate it the BP-4W and BP-Z3/VE engines, as I've been told that the exhaust camshaft is shorter due to it not have the keyway thingo. But it is only speculation as I haven't visually seen it to confirm it.

Something for you to test / play with while the engine/head is out.

[Cosmo Dude]

I'm planing on using my B-Spec cams per previous post. Not to worry BP-4W exhaust cam has the keyway thingo in the 1999-2000. Only the later turbo engines may or may not have the keyway thingo.

[project.r.racing]

Should be no problem then. I see you love my technical terms huh?

[project.r.racing]

http://mx5cartalk.com/forum/viewtopi...2ff2cc812d72cc

i found this. it should help a little.

interesting as they say using the intake manifold from a na8 on a nb8 head will limit the gains of the wider ports. guessing cause the nb8 intake and head are port matched to each other.

[project.r.racing]

update?