BP05-?-? head differences

project.r.racing · Postby **project.r.racing** » Fri Sep 04, 2009 1:42 pm

Does anyone know the difference between the BP05 heads. Some have a -7-1 and -9-1 on the end. Also are there different heads with more numbers?

So far I have found BP05-7-1 and BP05-9-1 heads, any others? Different?

Cheers.

93_Clubman · Postby **93_Clubman** » Fri Sep 04, 2009 3:19 pm

project.r.racing wrote:Does anyone know the difference between the BP05 heads. Some have a -7-1 and -9-1 on the end. Also are there different heads with more numbers?

So far I have found BP05-7-1 and BP05-9-1 heads, any others? Different?

Have seen BP05-11-1 & BP05-7-2 off MX5s. Have also seen BP05-4-1k off an Astina. Don't know what differences the numbers designate.

manga_blue · Postby **manga_blue** » Sun Sep 06, 2009 2:02 pm

I had a BP05-6.2 and a BP07 of similar mileage side by side. Mostly I felt the BP07 was better made.

Regarding the BP07:
- as far as I could tell the BP07 used a finer casting sand
- casting appeared to be better done (fewer dags in the ports, but still with some big gaps on the inlet port splitters)
- the metal was harder all over
- it was more accurately machined

Regarding the BP05
- the machining was very bad. Maybe mine was just done on a bad hair day, its manifold stud holes were about 4mm out on both inlet and exhaust)
- BP05 valves had a fatter, squarer profile on the rims and were a better shape for cutting.
- BP05 cams and lifters were in better shape

There were somne trivial diffs in the cosmetic external casting details. Otherwise all the port shapes, valve sizes, springs, seats, etc were pretty much identical. 31 out of 32 valve springs failed to meet minimum OEM specs.

In the end I used the BP07 head because of hardness issues but fitted the BP05 valves, lifters and cams.

It's worth noting that we tested 5 or 6 heads for hardness and all but one failed in the gasket surface area around the exhaust ports.

93_Clubman · Postby **93_Clubman** » Sun Sep 06, 2009 4:29 pm

manga_blue wrote:I had a BP05-6.2 and a BP07 of similar mileage side by side.

manga, do you know what the BP07 was out of?

manga_blue · Postby **manga_blue** » Sun Sep 06, 2009 10:41 pm

Both heads were from NA8s. The BP05 was a 5/95 build, not sure but I think the BP07 was a slightly earlier car.

93_Clubman · Postby **93_Clubman** » Mon Sep 07, 2009 1:02 pm

ta - hadn't heard of the 07!

manga_blue · Postby **manga_blue** » Mon Sep 07, 2009 2:55 pm

I probably wouldn't pay much attention to it. The numbers may just refer to castings. I don't know if Mazda used it for casting batch numbers, or different foundry lines within Mazda or even different supplying foundries. Almost anything in the casting can be cleaned up so long as there's enough the metal and it hasn't gone soft.

93_Clubman · Postby **93_Clubman** » Tue Sep 22, 2009 1:35 pm

also seen a bp05-8-2

93_Clubman · Postby **93_Clubman** » Fri Mar 25, 2011 12:31 pm

Also a BP05-4-2 head on a '93 NA8.

mazdatenfive · Postby **mazdatenfive** » Fri Dec 02, 2011 8:39 am

93_Clubman wrote:also seen a bp05-8-2

Please can you remember what year MX did this come from?

93_Clubman · Postby **93_Clubman** » Sat Dec 03, 2011 2:48 pm

mazdatenfive wrote:
93_Clubman wrote:also seen a bp05-8-2
Please can you remember what year MX did this come from?

MX5 BP05 heads were used on the NA8 from Sep 1993 to 1997, but I can't remember which specific year between those dates that BP05-8-2 belonged to. Indeed, I may not have known any more than it was an NA8. Of course, the BP05 head was used on other models by Mazda & other manufacturers, & even the BP05-8-2 head seems to have done the rounds:
http://www.google.com.au/search?q=%22BP ... rt=10&sa=N