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Old 08-02-2008, 12:42 AM   #1
FEM
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Rebuilding N/A BP DOHC

Hey fellas,

Dont really know where to put this post so move it if u want.

My DOHC is needing a new headgasket, I think.. and i dont really want to do it to that motor. So, I have bought lynx's old BP N/A that he has sitting under the house. The plan is to rebuild it.. some new pistons & rings to suit, head clean up and some new gaskets/seals.. nothing to extreeeme.

Few questions..

What is the max bore you want? 60 thou? 40 thou?
What is the best brand on stock, non forged, piston you can get?
What about gaskets and all that? What brand?

I dont want a physco build or anything.. I just want something that runs well and is like NEW!

The reason I am not just doing the head gasket on my one is because i am wanting to open up a engine and fiddle, and my engine is still running atm so when it goes ill take it and put a fresh one in, in a few months.

Thhhanks,

Dan
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Old 08-02-2008, 06:49 AM   #2
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80thou / 85mm bore is the biggest you can go - I wouldn't recommend it as the block will be useless and need to be replaced in 100,000km. but as you are doing a non-performance rebuild, 20thou / 83.5mm bore would be what you require.

I dunno if you can actually buy non-forged pistons for BPs, unless you go buy original from mazda, and I bet they charge more than Arias or Wiseco Pistons do for forged stuff.

Until you open it up, you won't know whether you require newer pistons or not. You may only require new rings...

And if you are doing a rebuild, I'd add things to the list like:- VRS kit (has head gasket in it,) water pump, all belts, sump seal.

Ryan
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Old 08-02-2008, 08:59 AM   #3
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yeah definatley the way to go Mr Ry Ry, thats smart
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Old 08-02-2008, 10:55 AM   #4
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80thou / 85mm bore is the biggest you can go - I wouldn't recommend it as the block will be useless and need to be replaced in 100,000km. but as you are doing a non-performance rebuild, 20thou / 83.5mm bore would be what you require.
I'm not that familiar with this engine, but *generally* you can get bigger overbore, and longer service life if you sleeve the block...this may be an option (essentially, the cylinder walls are completely machined out, and replaced with metal sleeves, which are cemented into place.....when you need another rebuild, the engine builder "simply" replaces the sleeves).

Sleeves can generally live with a greatly reduced space between cylinders, due to the specialised materials that are used.

Cost to sleeve is not *that* much more than an over bore (i think I was quoted $150 extra or something to sleeve over plain jane over boring).

Its certainly worth checking out.



most pistons these days are forged, regardless. OEM or otherwise. not sure about the BP, but the FS pistons certainly are forged from factory.....forged doesn't immediately denote strength - a lot has to do with the types of materials used the form the piston. CP make unreal pistons - with some state of the art chemistry.....i've been told they are some of the quietest after market pistons you can get.

beauty of going to after market pistons is that you can up the compression, which in turn allows you to run a more agressive cam profiles with bigger overlap (i.e. you can afford more dynamic compression loss because your static compression is higher).... slightly higher comp pistons certainly opens a lot of doors in the future, even if you don't open those doors straight away. You can also play with things such as lifting the wrist pin which allows for longer rods. longer rods means better rod:stroke ratio, which is one of the more important factors for lifting the red line (rod:stroke ratio plays an important role with regards to piston acceleration, and to a less important extent, side wall loading due to less rod angularity).
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Old 08-02-2008, 11:20 AM   #5
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My current BP is lacking in torque.. alot.

I am wanting to keep stock exhaust and have a CAI and new induction.
I want to keep same ECU too (stock)

I need something that will last 50-60 thousand k's.. I DONT need this car to last 500 000k's..
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Old 08-02-2008, 01:41 PM   #6
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Quote:
Originally Posted by FEM View Post
I am wanting to keep stock exhaust and have a CAI and new induction.
I want to keep same ECU too (stock)

I need something that will last 50-60 thousand k's.. I DONT need this car to last 500 000k's..
then dont rebuild it. just do the head gasket and move on
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Old 08-02-2008, 01:51 PM   #7
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Quote:
Originally Posted by FEM View Post
My current BP is lacking in torque.. alot.

I am wanting to keep stock exhaust and have a CAI and new induction.
I want to keep same ECU too (stock)

I need something that will last 50-60 thousand k's.. I DONT need this car to last 500 000k's..

OK BP's have low to no torque due to there pistons compression levels (first gen atleast)
also there cam timing/lift/duration isnt worth mentioning . as its not performanced based!

why,..its called "emissions", back in the 80's when the BP was design. it was more about emissions/mileage than all out power

if you want more power, buy some 11.1 compression pistons...but then you'll need cams to get good use of the pistons, but then you'll need a aftermarket ecu. then you need tuning..etc etc

if you have the money for all the above cool..if not...sadly the BP isnt going to do what you asked of it

might have to settle with a BP thats rebuilt back to OEM spec
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Old 08-02-2008, 03:38 PM   #8
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Yeha, i have thought for a while about doing the gasket but as i said, i want to pull it apart and all that..

I might just have to stick with a BP stock then, its all good. I wouldnt mine a 2.2 F2 from the 626 though :P
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Old 08-02-2008, 09:13 PM   #9
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Yeha, i have thought for a while about doing the gasket but as i said, i want to pull it apart and all that..

I might just have to stick with a BP stock then, its all good. I wouldnt mine a 2.2 F2 from the 626 though :P
or a KLZE 2.5L V6? direct bolt in.....(more or less)
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Old 08-02-2008, 09:29 PM   #10
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not into a BG it wouldnt be!
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Old 08-02-2008, 11:08 PM   #11
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I thought it was alot of work? into a BG that is..

Or you mean a Telstar/626 Greggie?
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Old 09-02-2008, 12:07 AM   #12
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think of it this way

ba's come with bp's and v6's and chassis mounts are the same...

i've also seen a v6 in a bg
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Old 09-02-2008, 12:15 AM   #13
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the KLZE doesnt fit in with out lots of modifications though?

so the 2.0L V6 will fit in the bg from the ba/
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Old 09-02-2008, 12:32 AM   #14
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probably. but your engine bay looks to have less room than a BA, so good luck working on one

KL-ZE in BG would = teh sex
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Old 09-02-2008, 06:52 AM   #15
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think of it this way
ba's come with bp's and v6's and chassis mounts are the same...
i've also seen a v6 in a bg
oh but did you also see the radiator mounted? nope cos the front cam bank was were the radiator used to sit.
there is a reason the BA engine bays are 100-150mm deeper than BG engine bays.

i'm not discreditting the idea, but there is a reason why pete gave up on it in the end.

ryan
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Old 10-02-2008, 09:36 PM   #16
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imo, a new radiator is certainly no reason to give up on the idea
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Old 10-02-2008, 09:43 PM   #17
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whos pete and why did he give up on it? "it" being fitting a BA v6 in a BG?
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Old 10-02-2008, 09:46 PM   #18
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whos pete and why did he give up on it? "it" being fitting a BA v6 in a BG?
pete being boostedbatman
"it" being KLZE into a BG.
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Old 10-02-2008, 09:56 PM   #19
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ah yeha, boostedbatmans the PT around this area! yeah he has had that KLZE hanging around for ages.

Whats the go with the V6 in the BG?
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Old 10-02-2008, 10:00 PM   #20
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ah yeha, boostedbatmans the PT around this area! yeah he has had that KLZE hanging around for ages.

Whats the go with the V6 in the BG?
as ryan said, it bolted in (its a direct bolt in, if my understanding is correct) but one of the cylinder banks sat where the radiator should go...

I don't know if this was the only reason pete gave up on the idea.....

edit: KLZE isn't the BA V6, but i'd imagine it would have the same problems the KL does - bolt straight in, other items not so easy......
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