Difference between heads bp4w - bp05

lightyear · Postby **lightyear** » Sun Jun 13, 2010 7:02 pm

We bought a couple of NB motors and noticed a couple of differences. Firstly 1 block has 2 bolts on the side where you tap into for an oil feed line for the turbo, and the other block has none, just 1 flat area that could be drilled and tapped. The other difference was the head numbers, the heads look identical but 1 is BP05-9-2 and the other is BP4W-4-1. I was looking at the NA8 motor i bought and it has BP05-9-1 and looks different to the others, it is very straight up and down on the face of the intake and the others have an angled face. The NA6 head has no numbers.

93_Clubman · Postby **93_Clubman** » Mon Jun 14, 2010 12:29 am

BP05 heads are from NA8 & are a narrow angle port head, whereas BP4W heads are from NB8 & are a wide angled port head for better flow. The BP05 gets a few mentions in the following:
viewtopic.php?f=29&t=38310

'99 Miata BP4W mentioned here:
http://www.solomiata.com/Mx5Engine.html

project.r.racing · Postby **project.r.racing** » Mon Jun 14, 2010 9:33 am

for the earlier BP block, astinas/323s 90-94, familias 89-93, MX5s NA8 94-96 have the provision of oil and water feed from the block. on the non turbo applications/versions, the holes ate filled with bolts as you noticed.

astinas/323s 94-98 and MX5 NB8 do not have the threading or holes in place for those feeds. you could drill as you mentioned, but that wold mean stripping down the bottom end, and at that stage, you might as well pick up and earlier block for less $$$ and save the effort.

the main difference in the earlier and later heads is the port shape as mentioned above. and for this reason the 2 outer exhaust bolts are positoned a further 4-5mm apart from each other.