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My BP Na8 engine is drinking some oil and i have been toying with the idea of rebuilding it before the year is out.
The car will be a Hillclimb and occasional Supersprint car.
It will also be road registered and dríven on the road but i am not dedicated to having a comfy Limo for a MX5

This is my build list for the bottom end i would love for any contribution or bad ideas pointed out to me.
Save me making more mistakes then i have to.

I have bothered WAZZAH1975 more than enough.
He has been super helpful.


Manley Rods - $350
Supertech 84mm 11:1- $450 (Would go with 85mm but if F/I down the track, more cylinder wall is better)
ACL Race Bearings- $150
OEM Head Gasket- $
ARP Head & Main Studs $200


For the Top End I will be asking Wazzah to provide 4-2-1 Headers and Camshafts.
And am tossing up buying a NB8A Head and intake Manifold or staying with the NA8 Head.

This is the difference between the 2.



Most articles i read state that the NB8A BP4W head flows far better and the intake manifold helps with this also.
Some people i talk to say that in fact is not that big of a difference and that maybe my $$ is better spent on my existing head.
The Solid Lifters may also be of benefit in the BP4W.

Again, i would love to hear any views on my plans.

I will be running most likely a DIYPNP MS2 with RX8 Injectors.

Manga_Blue made some useful observations about the NB8A BP4W head after he tried to source one a while back:
viewtopic.php?f=29&t=48320&p=611433&hilit=head#p611433

viewtopic.php?f=29&t=43856&p=557701

Spoke too two engine builders (woz being one) re the late head. Both said... Eh spend it elsewhere.

1. Stock for stock yes it flow better, but not when ported correctly.
2. Solid lifters are shim on bucket and not full Face, so ok if you have them but not worth trying to change to them.

I believe pham spoke to garry Stewart and got similar response.

To me, you really have to decide if you want fi now. Otherwise run big compression pistons. I would have thought 11 to 1 a bit high for boost? But I don't really know much about turbocharging.

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Also head gasket from USA, about 60 plus shipping.

Head studs and main studs look a bit cheap.

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Dweezle wrote:Manley Rods - $350
Supertech 84mm 11:1- $450 (Would go with 85mm but if F/I down the track, more cylinder wall is better)
ACL Race Bearings- $150
OEM Head Gasket- $
ARP Head & Main Studs $200

i'd add:-
some kind of viton valve stem seals ie supertech
some kind of engine rebuilt seal kit
conrod bearings
water pump
timing belt kit

---

as for 11:1 ratio pistons for FI. not a problem if tuned correctly. use a good hi ron fuel to prevent pre detination. ie E85. not sure about the abilities of a DIYPNP to help with this factor in the future.

and for the lifters, i'm sure warren has been though this with you. the NB8C ones are shim over bucket. really only suitable if the cam you are running are close to the same base circle as nb8C cam ie 36mm. otherwise getting a new thicker shim will add alot of weight to the valvetrain.

i am doing a similar build to yours in my 323. it's a NA8 motor but comes with the NB8C SOB and 36mm BS cams out of the factory. i got Toda 256x9.0 cams, so straight swap. but also took the plunge and brought some MMD solid buckets for $247 posted to my door. that way i can run any cam i want.

Thanks all so far!

Regarding the head, maybe i will just port and polish my BP05 and save the headache.

11:1 compression boosted should be fine with E85 from what i have heard.
I may not go FI but at least the engine will be built and as long as the tune is solid i should be ok.
Happy to be told otherwise though by the experts!!

Regarding the studs that is what Emilio at 949 has quoted me.
Will just get them thrown in with my pistons and rods.




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Ahh ok. Freight them with other stuff helps a lot.

Didn't realise you were happy to run e85...In that case go for it.

Is the pnp micro squirt based on the full deal?

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What are your plans for the intake side ITB's or single throttle body?

Are you looking at other things like oil cooler, radiator, COPs, oil pump, coolant re-route etc?

I plan to run
-Single Throttle body
-Oil cooler & filter relocation.
-ASI radiator.
-Coolant reroute

I guess if i want to run flex fuel i may need lower compression if i go Boosted.
If i am to be sensible


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11:1 is about perfect for a boosted alcohol engine.

Its what I want and what everyone should aspire to.

Dann

My last DIY build ran up almost $1,000 in machining and misc hardware:
- block pressure cleaned, light cylinder honing, light deck skim, end skim (out of square from the factory), general check for line boring/porosity/etc, new brass welsh plugs
- harmonic balancer, front pulley, crank, rods, pistons, flywheel and clutch housing balanced as a unit
- head cleaning, hardness testing, light shave, 5 angle cut on inlets, 3 angle cut on exhaust valves, new seals, valve assembly

Oil pressure relief valve setup needs mods if you're going to go high rpm. I've also heard some tales somewhere about opening out oil lines in the block near/to/from the oil filter mount area, not really sure about that though.

Thanks for the tips mangablue.

Can anyone confirm if a 85mm piston fits on a oem head gasket without modifying?

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Dweezle wrote:Thanks for the tips mangablue.

Can anyone confirm if a 85mm piston fits on a oem head gasket without modifying?

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No, It is too small.

If you're intending on F/I I would stick to an 84mm bore, unless you have the money to invest in someone to accurately sonic test the block. After 84mm they can start to get thin.

Cheers
Woz

84mm it is!!

anyone know a good place in Sydney to get the machining work done?

The last guy i used when we did the 1.6 lost alot of stuff and was really a V8 guy.

Would like someone with 4 banger experience.

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Ship it straight to wozzah.

Dann