mx5cartalk.com

This Thread started to develop here in the classifieds section, in a dead and buried post so vital parts of that thread have been exhumed and recreated here in a way Dr Frankenstein would be proud.

97 MXV wrote:BP05 head from a BPT engine suit NA8.....
This is an NA8 spec head in great condition except corrosion visible around inlet valves from rain water ingress through open injector ports when stored.

project.r.racing wrote:This is a BP-05 head from a 94-98 Astina or Laser. The cam cover that also goes of the cam belt/gears is a giveaway the series is belongs to. It is not a turbo engine head. This did not com from a Famila/BPT. BPT head are BP-26.

If it is a 94-96 engine, then the camshafts will be a exact match to a NA8. If it is from a 96-98, then it will have solid lifters and lower duration but bigger lift camshafts.

97 MXV wrote:Correction ! Read Atmo...not Turbo Cams

cookie wrote:I'm using a series 3 (96-98) head like this and cams in my motor. Reason being it was in an astina. Small differences between them. Cheap though!

So can it be said from this that using these later 96-98 solid lifter heads with such cams "lower duration but bigger lift camshafts" are a worthwhile fit to an NA8 if cheap enough ?

Reason I ask is I am on lookout for good long nose big bolt pulley hub type crank and maybe block.
Now if solid lifter head has higher value, then buying a later FWD engine for part out may be an economic option as such cranks do not come up that often.
So how does one tell by these ebay photos what year this particular head and crank might be ?
The cam cover looks BP not B6.

Its a bp from a BA astina (94/98) , the vics actuator on the inlet manifold being one of the giveaways, along with the cam cover, inlet manifold type, belt covers etc. The crank pulley looks to be from the earlier series 1/2 (94/95) so the crank is fine for what you are chasing ,though the head would likely be the earlier hydraulic lifter type and not the esteemed solid lifter setup that would fetch more pennies on resale.
All BA astinas were bp 1.8 or the larger v6 engine, no b6 engines were fitted.
You really need to see the stamping on the rear of the head to be sure, or look for green injectors...i spy blue in the background

It is impossible from those photos to confirm which which year the engine came from. Certainly as above it is a 94-98 Astina engine. If it was from a laser, it would be the same, just with a Ford cam cover.

The reason it is impossible is all the parts that give the ability to tell if it is pre 96 or post 96 have been removed.

To add to the above into, there are also 2 other thing to look for. The pre 96 engine has the same throttle body as a NA6/NA8. The post 96 engine has a NB8 throttle body.

Also the is a water temp sensor (#10) near the water out for pre 96, this sensor is deleted post 96. Just a regular allen key grub screw is in its place.









The engines from 90-96 are identical inturnally. And the 96-98 only had a change in lifters and cams. The lifters are the same as NB8 lifters. And the cams have a base circle of 36mm, same as a NB8. Below are the difference pre and post 96 for the FWD cams.

Intake cam duration ........ 233° @ 0.003" ........... 233° @ 0.003"
Intake cam opening ......... 5° BTDC ................. 3° BTDC
Intake cam closing .......... 48° ABDC ................ 50° ABDC
Intake cam lobe height ..... 44.094mm (1.7360") ... 44.3mm (1.744")
Intake cam base circle ..... 35.941mm (1.415") ..... 36.0mm (1.418")
Intake valve lift ............. 8.1534mm (0.321") ..... 8.3mm (0.327")
Exhaust cam duration ...... 250° @ 0.003" ........... 241° @ 0.003"
Exhaust cam opening ....... 56° BBDC ................ 51° BBDC
Exhaust cam closing ........ 14° ATDC ................ 10° ATDC
Exhaust cam lobe height ... 44.600mm (1.7560") ... 44.9mm (1.768")
Exhaust cam base circle ... 35.941mm (1.415") ..... 36.0mm (1.418")
Exhaust valve lift ........... 8.6614mm (0.341") ..... 8.890mm (0.350")
Valve overlap ................ 19° ....................... 13°

Hope that helps.

Thanks 3gress and project.r.racing for providing a considerable body of expert research and hard evidence helping greatly to clear things up.

Getting pack to that BP05 head sold to madjak, there is now a chance it is a 96-98 solid lifter as research photos I provided are not nearly as clear as project.r.racing photos.

Despite its donor engine being turbo with B6T rods and low comp dished pistons, block had turbo oil feed and had earlier crank sometime pre 94, it is now proven beyond all doubt that a significant piece of evidence was missed.

Dr Frankenstein's finger prints went unnoticed on that turbo engine.

Next step I guess is to see comparison of these cams with NB8 cams.

97 MXV wrote:Despite its donor engine being turbo with B6T rods and low comp dished pistons, block had turbo oil feed and had earlier crank sometime pre 94, it is now proven beyond all doubt that a significant piece of evidence was missed.

Dr Frankenstein's finger prints went unnoticed on that turbo engine.

Pretty common practice. You find plenty of engine out of Astinas and Lasers like that. The only difference between a BP-ZE and a regular (non GTR) BPT bottom end is the pistons. Both are cast, one has 8.2:1 and the other 9.0:1 comp ratios.

You brought up a good thing I forgot to mention. Somewhere around 1995 for the FWDs, the water and oil feeds from the blocks were removed. they just stopped drilling them at the factory.

97 MXV wrote:Next step I guess is to see comparison of these cams with NB8 cams.

I'll dig up the specs, but from memory, NB cams had more duration but less lift. Really designed for more rpms, where the FWD varients was more lift and less overlap for better and lower rpm point torque. Great for turbo application.

project.r.racing wrote:Thingos ...................... NA8/FWD 90-96 .......... FWD 96-98 ........... NB8 98-00
Intake cam duration ........ 233° @ 0.003" ........... 233° @ 0.003" ........ 237° @ 0.003"
Intake cam opening ......... 5° BTDC ................. 3° BTDC ............... 8° BTDC
Intake cam closing .......... 48° ABDC ................ 50° ABDC .............. 49° ABDC
Intake cam lobe height ..... 44.094mm (1.7360") ... 44.3mm (1.744")
Intake cam base circle ..... 35.941mm (1.415") ..... 36.0mm (1.418") .....
Intake valve lift ............. 8.1534mm (0.321") ..... 8.3mm (0.327") ......
Exhaust cam duration ...... 250° @ 0.003" ........... 241° @ 0.003" ........ 242° @ 0.003"
Exhaust cam opening ....... 56° BBDC ................ 51° BBDC .............. 53° BBDC
Exhaust cam closing ........ 14° ATDC ................ 10° ATDC ............. 9° ATDC
Exhaust cam lobe height ... 44.600mm (1.7560") ... 44.9mm (1.768")
Exhaust cam base circle ... 35.941mm (1.415") ..... 36.0mm (1.418") ..... 36.0mm (1.418")
Exhaust valve lift ........... 8.6614mm (0.341") ..... 8.890mm (0.350") ... 8.890mm (0.350")
Valve overlap ................ 19° ....................... 13° ..................... 17°
Hope that helps.

NB added.

Great info guys... once the head rocks up I'll pop off a cam and solve the mystery if its the later head with solids or not.

Rick

Only downside is that cam selection is limited / different.

Is the cam any different to a standard NA8 head? Shouldn't any NA8 cam fit in (subject to lifter restrictions)?

I know my current NA8 head has been modified to clear the cams... thats just a little grinding though.

Rick

All the standard BP-ZE engines with HLAs had the same cams whether rwd or fwd.

cookie wrote:Only downside is that cam selection is limited / different.

There is just as many camshafts available whether HLA or solid.

Oh I see what you meant. I'd rather the solid lifters as I can run higher lift cams on it if I want to. If this head gets built up it will be for a very high power F/I build, so I doubt I'd run any stock cams anyway.

It's a little exciting having something rock up that may or may not of something cool on it. Keith you should do this with all your sales!

madjak wrote:It's a little exciting having something rock up that may or may not of something cool on it. Keith you should do this with all your sales!

Great Idea ! I was all set to throw in something of worth like Tasmania in the next deal ! But then again I am not Western Australian, I'm a Queenslander.
I'm still serving life from publicly including Rolf, and not Tasmania in the Commonwealth to of all people, the Royals !

Big Thanks to project.r.racing and 3gress for their deep insight into DNA shared with these FWD heads.
"Dr Frankenstein I presume" will be rubbing his hands together imagining the opportunities.

97 MXV wrote:I am on lookout for good long nose big bolt pulley hub type crank and maybe block.
Now if solid lifter head has higher value, then buying a later FWD engine for part out may be an economic option as such cranks do not come up that often.
So how does one tell by these ebay photos what year this particular head and crank might be ?

Mine was the winning bid on ebay for a dodgy condition/spec motor the owner had acquired years ago from an unknown donor car with unknown mileage.

Following strip down, I discovered that I won out on really good block and pistons but lost out on head and the crank.
The head is not the later solid lifter type but the earlier hydraulic valve lifter type BP05-8-2 in what appears good condition despite the blown gasket.

The crank was a total surprise !

The crank (top of the picture) is marked BP02 and looks a the poverty pack lightweight big nose crank seen here compared with later big nose (forged BP MX5 I was expecting) and the early long nose (forged early 323/Laser BP) bottom of picture.
Note that both the big nose cranks shown suit the MX5 BP style pulley boss design. The differing lighter crank design (minus 4 counterweights) begs these brain teaser questions....
- What is the performance capability of this lighter crank ?
- Is it the same cast crank I read was fitted to SOHC engines ?
- If cast is it cast steel or a tough form of cast iron ?
(Toughness coming from spheroidal not flaky graphite inclusions seen in the "quiet" and machinable but brittle grey cast iron of engine blocks)
Undeterred, the outcome from all this discovery will no doubt be a renewed quest for a forged big nose crank from a FWD.

Now another interesting but off topic find is the matching slotted pulley for the lighter crank.
Before coming across this I had assumed slotted pulleys were ADM B6 V belt type and unslotted pulleys were BP multi rib belt type.
But this is an 8 slot pulley to suit a multi rib water pump/alternator belt, not a V belt pulley.


The other interesting thing is the design of the rubber layer and "decoupled inertial mass" part of the pulley is totally different also.
The slotted pulley design has belt drive to the aircon and power steer directly from the hub part of the pulley and has belt drive to the water pump and alternator belt from the decoupled part of the pulley.
On the other hand a typical 1.8 MX5 non slotted pulley has belt drive to both belts from the decoupled part.
There are subtle differences in theory between belts dríven directly and belts dríven off the decoupled part through shear of the bonded rubber layer.
(BTW "bonded" could be friction bonded or adhesive bonded....not sure how Mazda bonds theirs).

Theoretical differences aside, the practical differences seem to be the following:
- the slotted pulley appears to have a lighter decoupled mass
- the slotted pulley appears absolutely fail safe.
The slotted pulley would fully capture the outer decoupled part should the rubber layer fail at high rpm. This seems a more robust way to design it.
A non slotted pulley however does not appear to have this fail safe feature.

This difference in design does beg the question...
What is the rubber layer failure mode of an MX5 BP style pulley ?
Can the outer rim (the decoupled part of an MX5 pulley) detach and spin off at high revs out of control if the rubber ultimately loses retention ?
Therefore something to ponder for a future topic devoted to crank pulley options will be whether MX5 BP style pulleys meet SFI SPECIFICATION 18.1 ?

97 MXV wrote:On the other hand a typical 1.8 MX5 non slotted pulley has belt drive to both belts from the decoupled part.

There are non-slotted/non-ribbed drive belted 1.8L MX5s out there? I must have missed those.

Pretty sure all BP engines post 94 had slotted drive belts. All pre 94 BP/BPTs had V belts like NA6s. Except 92-94 BPD GTR engines had slotted drive belts.

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BP02 crank is 4kg lighter than a BP01 crank. 12 vs 16.