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Project Kinder Surprise - engine build


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That and I want low and mid range power with good spool so mild cams should work.

the 1mm oversize should allow more flow with a lower lift and the valve train won’t have harsh profile to deal with. So no valve float at higher rpm. 
it’s all a guess and won’t know how high I can rev it until the tune. With stock valves B cam is good for 600hp.

I can always swap cams and/or turbo out but valves etc need way more work. 

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  • 1 month later...

RCM parts list cos duck it. 

head studs


timing belt guide


timing belt kit



Upper Oil baffle



oil pickup


in the past I just cut a slot in the oem one so it couldn’t even bottom out but this seems more legit

did think of drilling a series of 3mm holes around the bottom of the oem one and threading a 3mm silicone or oil safe rubber tube through it to do the same idea of stopping the pickup hitting the bottom and supporting the weight. 

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  • 1 year later...

Well cos COVID and well all of 2020 since March being out of town, this got nowhere. 

Just as I go to restart it, the car door gets messed up in attempted thief.

Then car got stuck for 2 months with first 2021 lockdown and getting insurance done.

no insurance company issues they took claim in 10 mins.

It got towed day before lockdown and got a bit lost between towing and panel beaters.

Looks mint now though.


So drop in to PBMS to say let’s go and lockdown again… WTF.


Anyway not much left to buy or select.

ECU will Emtron as not much choice with newer canbus car

fuel system bits like cradle and flex fuel. Going to add sensor as why not.

head gaskets depending on need but fire ring if possible

ARP case bolts I’m pretty sure these got ordered but no idea where the ended up.

have those spacers for intake to help drop temp

need intercooler setup and scoop less bonnet 

headers well was going low mount but to much time effort so will fall back to twisted setup

Maybe new radiator as well since it may run slightly warmer 



Edited by Gripless
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Forgot the wide-band 


also torn on pulleys, I like lightweight, but not under drive of alternator. On  the other hand new higher rev limit it might be required.


valve train is super light and cams aren’t aggressive so could pass 9500rpm plus rotating assembly is also way over spec and lightweight.


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14 hours ago, Andy_Mac said:


Skip the lightweight one for sure. Only options on a decent engine should be a factory new one or a proper aftermarket one like ATI or Fluidamper. 

Subaru America said no damper required for boxer in Subaru.

pully is purely to drive the belts, otherwise damper is vital on inline or V motors.

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1 hour ago, Gripless said:

Subaru America said no damper required for boxer in Subaru.

pully is purely to drive the belts, otherwise damper is vital on inline or V motors.


I've yet to see any real engine builder suggesting alloy ones over anything real though. 


I had been tossing back and forth between OEM and Fluidamper for mine but with the timing I just ended up using a new factory one.


Unabomber’s manifesto mentions it isn't needed directly from Subaru America but back to back testing usually shows a very slightly smoother running engine when dyno testing which can't be a bad thing.

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  • 10 months later...
  • 3 months later...
  • 7 months later...


link plug and play G4x

basic tune almost makes same boost at 3000rpm as factory.

no features enabled


Fuel system

radium dual pump cradle

dual detchwerks 300 pumps

radium fuel rail

ethanol sensor 


RCM oil cooler valve

oil cooler front mounted

koyo radiator 

Other parts

twin plate organic sprung clutch
Top mount PW intercooler

AOS self draining

BPV from GFB leaked and couldn’t hold boost so replaced wth turbosmart.

Aircon pump that works with the newer clutch design that does snap as often

stock intake manifold with inside deburred 

stock exhaust headers


Car now runs and drives. few small issues left to sort.

looking at sx-e compressor cover since bpv on intercooler. May also help boost ramp faster

turbosmart bpv makes chuff noises not the Pssssh like GFB which I don’t like.

Exhaust is quieter now with drone mored up rev range so not at 100kph in 6th.

intake makes a s*** tonne of noise.


Edited by Gripless
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After some talks with some Japanese guys who build and deal with American cars the stock nitrided cranks are standing up to daily 1000hp in the 2.5L so the 850hp I was given in NZ was conservative.

so weakest part of motor is now the cylinder walls which a only 0.25 bored to clean them up.

Could be good for 36-40psi given the 14mm in a fully closed deck.


Talked to Kelford again.


idle 1500 rpm is normal especially with 1mm oversized valves

rpm limit is likely 10k but tune until 500rpm past peak power.

So all power is limited by the turbo. Max I can find on a dyno is 550whp or 620whp with sx-e compressor cover.


initial dyno to 8k only has peak power at

8k on e85

Flat from 6-8k on 98 as boost oscillates ~2psi

there is also a dip on 98 from 4-5k5 where turbo is again 2psi lower


Efr turbo is about the same to 21psi boost as stock turbo.


Overall drives and feels very smooth and stock but turbo doesn’t fall off after 5250rpm it keeps boost with no drop.


final peak we will by end of the month.


but tune will be set a lot lower for daily as the aim now is for flat 5500rpm to 9-10k 250-260wkw


Edited by Gripless
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1 hour ago, Gripless said:

Also wish this was around earlier 

I looked initially but there wasn’t any good options before.



Also a range of mount for other turbos too.


I seriously considered putting one of these on mine but due to the layout only just fitting the TS normal one there was no chance of that fitting. 

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  • 2 weeks later...

SX-e compressor cover on the way.


Since a BOV was fitted to intercooler and there is some surge it seems like it is a must.

Under new digital LVVTA cert with photos the cover would show up so needs done before cert.


Hope this will fatten up mid range and reduce intake temps a little for boost in efficiency.

Power and boost is limited by ecu so it’ll still make same peak after.


BW apparently has no stock and they have unfilled back orders from 2021 for parts. They have supply chain and move to china production issues.

Edited by Gripless
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Bonus with cover is its smaller due to no air channel for recycle valve so  looks more ‘stock’

Will refit stock airbox with original top air feed and a secondary cold air from front spotlight grill into the old resonator opening.


Tomorrow likely move the 4 port solenoid from side of engine bay back to stock location on manifold, since it is in way of airbox and also lines bouncing around and hitting pod filter.


The cold air from spotlight grill air feed was enough to get the idle back down under 1000rpm. Before on traffic it was 1500rpm as no heat shielding at all.

Edited by Gripless
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Well that won’t work until get car back to PBMS. 4 port wired to MAF loom so stuck out that side of engine bay for now.


MAF wire can be reused for water spray pattern solenoid.

Have 2 TVG spare outputs, also maybe the front lower o2 sensor wires. 
Depending on what IO they are on ecu can run EGT to heads and another sensor as well.


Engine pulls -0.85 bar vacuum on lift off, compared to -0.8 old motor with 30,000km. Same gauge, pipes and stock manifold.


When done the engine bay other than radium and turbo will look pretty stock. Airbox and boost solenoid cover going back in. 
Need to find or reuse sticker from rad overflow top tank.

Edited by Gripless
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