engine rebuild advice


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Gorbash12346

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May 4, 2009
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Hi all right i am planning to rebuild the bottom end of my b18c6

i would like to get a little more capacity if possible so i have been considering how far it would be safe to bore the block out to.

first question is 82mm safe enough would a block guard be a worthwhile investment at this size or can i go further without risking the side-loading becoming too much for the walls??

the plan is to re-use the standard crank fit forged rods (haven't decided on type yet) and run forged high silicon pistons. to bring my compression ratio up to 13:1 or just below.
i plan to use cosworth pistons for this then oem main bearings and arp main studs and a spoon blueprinted oil pump

as far as the rods what type of rods suit high revving n/a applications? I-beam H-beam tapered or not? etc

i will be getting the whole rotating mass balanced to suit.

so the spec should be:
skunk2 high comp valves
skunk2 ti retainers and double valvesprings
toda valve guides
spoon 2 layer head gasket with light tolerance skim
bottom end bored out to 82mm (if this is deemed safe)
cosworth pistons to bring compression to around 13:1
forged rods to be decided on
supertech block guard if required
standard crank
oem shells
spoon oil pump
moroso baffled sump

externals are:
mugen 4-1 2.5"
j's racing decat
mugen twinloop 2.5"
standard intake manifold with port matched 70mm tb
hondata inlet manifold gaskets
closed type oil catch tank

with this kind of setup what sort of camshafts will i be able to use ? i want to keep driveability but plan on having the rev limit around about 9500rpm but also i want to make use of the increased static compression to allow for more overlap if i can make more power

any help on this would be very much appreciated
thanks
 
Hi mate, see my comments below

What cams are you going to run?

skunk2 high comp valves (Not needed)
skunk2 ti retainers and double valvesprings (Supertech are much better)
toda valve guides (Titon vlalve guides are very good and much cheaper)
spoon 2 layer head gasket with light tolerance skim (Use OEM it is far more reliable)
bottom end bored out to 82mm (if this is deemed safe) (Not safe at all 81.5mm is max safe iirc)
cosworth pistons to bring compression to around 13:1 (Weisco hands down)
forged rods to be decided on (A must)
supertech block guard if required (Shouldn't be required)
standard crank (Fine)
oem shells (All bearings and seals OEM)
spoon oil pump (Use OEM don't waste your money also change the water pump)
moroso baffled sump (Very good idea)

Also to consider

A decent full width raditor MINIMUM
Advise and external oil cooler
OIL temp and pressure gauge
Water temp gauge

ECU obviously and a very very very good tune to avoid any det/pinking.

externals are:
mugen 4-1 2.5" (Ok but i recommend heat wrap)
j's racing decat (Ditch fo a custom header back)
mugen twinloop 2.5" (FAR to restrictive to reach even 8000rpm with out the torque curve dropping of. A custom tru 2.5" is a MUST)
standard intake manifold with port matched 70mm tb (Good idea make sure you got a good intake system)
hondata inlet manifold gaskets (Good idea)
closed type oil catch tank (No recirculating)
 
Sorry Viton not Titon

Also

IBspec RODS
Viton stem seals (Inc new guides)
A1Tech headstuds
Bosch Injector Dynamics 725cc ultimate injectors

This is what i've got
 
Gorbash12346 said:
Hi all right i am planning to rebuild the bottom end of my b18c6

i would like to get a little more capacity if possible so i have been considering how far it would be safe to bore the block out to.

first question is 82mm safe enough would a block guard be a worthwhile investment at this size or can i go further without risking the side-loading becoming too much for the walls??

the plan is to re-use the standard crank fit forged rods (haven't decided on type yet) and run forged high silicon pistons. to bring my compression ratio up to 13:1 or just below.
i plan to use cosworth pistons for this then oem main bearings and arp main studs and a spoon blueprinted oil pump

as far as the rods what type of rods suit high revving n/a applications? I-beam H-beam tapered or not? etc

i will be getting the whole rotating mass balanced to suit.

so the spec should be:
skunk2 high comp valves (made by supertech)
skunk2 ti retainers and double valvesprings (made by supertech)
toda valve guides (rip off shite)
spoon 2 layer head gasket with light tolerance skim ( rip off shite)
bottom end bored out to 82mm (need sleeves any bigger than 81.5mm)
cosworth pistons to bring compression to around 13:1(C.P Pistons finest made
forged rods to be decided on ( hell people have seen 400hp on stock blocks)
supertech block guard if required ( no need, you wont make enough cylinder pressure)
standard crank ( sweet)
oem shells (or acl)
spoon oil pump ( oem type r more than good enough)
moroso baffled sump ( do you need a drain back?)

externals are:
mugen 4-1 2.5"
j's racing decat
mugen twinloop 2.5"
standard intake manifold with port matched 70mm tb
hondata inlet manifold gaskets
closed type oil catch tank

with this kind of setup what sort of camshafts will i be able to use ? i want to keep driveability but plan on having the rev limit around about 9500rpm but also i want to make use of the increased static compression to allow for more overlap if i can make more power

any help on this would be very much appreciated
thanks
Click to expand...


Do some research before you go spending lots of money mate, most of that stuff is just smoke and mirrors.
 
I agree with most of that IJW, apart from:

ijwhiteman said:
forged rods to be decided on (A must)
Click to expand...

A must? I don't see it. Boosted yes, NA surely just expensive but ultimately unnecessary (not to mention invisible) bling?

Rs250nut has it spot on IMHO. Most of that stuff isn't needed. You could probably ditch all the blingy aftermarket stuff in favour of an OEM rebuild but with some proper sleeves and 84mm pistons. That would see you some real gains for your money...
 
Last edited:
ok sorry i have a good few of the times i metioned already.

the top end parts are already there as the top end was rebuilt recently
so i've put more info into it sorry should have said.

ijwhiteman said:
Hi mate, see my comments below

What cams are you going to run?

skunk2 high comp valves (Not needed) (already there as oem's where stupid money and i had 3 b3nt valves
skunk2 ti retainers and double valvesprings (already there)
toda valve guides (already there)
spoon 2 layer head gasket with light tolerance skim
bottom end bored out to 82mm (if this is deemed safe) (Not safe at all 81.5mm is max safe iirc) ok was kind of hoping to get closer to an oversquare setup with a little more capacity
cosworth pistons to bring compression to around 13:1 (Weisco hands down) any reason why?
forged rods to be decided on (A must)
supertech block guard if required (Shouldn't be required) ok
standard crank (Fine)
oem shells (All bearings and seals OEM) will do
spoon oil pump (Use OEM don't waste your money also change the water pump) ok fair enough. water pump was done 10k miles ago
moroso baffled sump (Very good idea) already there

Also to consider

A decent full width raditor MINIMUM (i have a fluidyne dual core half width with an import cooling solutions slimline fan)
Advise and external oil cooler (good point i'm guessing a 13 row thermostatic setup should be enough? what make?)
OIL temp and pressure gauge (was planning on running a similare setup to that on my impreza with 3 pro sport gauges oil temp/watertemp and oil pressure)
Water temp gauge

ECU obviously and a very very very good tune to avoid any det/pinking.

still deciding on what to do with this part wether or not hondata s300 will be up to it or if i should go to aem or the like

externals are:
mugen 4-1 2.5" (Ok but i recommend heat wrap) got it ready to go on :)
j's racing decat (Ditch fo a custom header back)
mugen twinloop 2.5" (FAR to restrictive to reach even 8000rpm with out the torque curve dropping of. A custom tru 2.5" is a MUST) i'm trying to keep it usable on the road and therefore i don't want a massively loud exhaust hence i'd have hoped to keep the twinloop
standard intake manifold with port matched 70mm tb (Good idea make sure you got a good intake system) allready there with a j's racing tsuchinoko carbon fibre setup.
hondata inlet manifold gaskets (Good idea) already there
closed type oil catch tank (No recirculating) ?? not quite sure what you mean??
Click to expand...

thanks
 
Kozy said:
I agree with most of that IJW, apart from:



A must? I don't see it. Boosted yes, NA surely just expensive but ultimately unnecessary (not to mention invisible) bling?

Rs250nut has it spot on IMHO. Most of that stuff isn't needed.
Click to expand...

I spose not a MUST. But stronger normal means more reliable and you have to get the stock rods machined which is cost and agro to fit the pistons.
 
Kozy said:
I agree with most of that IJW, apart from:



A must? I don't see it. Boosted yes, NA surely just expensive but ultimately unnecessary (not to mention invisible) bling?

Rs250nut has it spot on IMHO. Most of that stuff isn't needed.
Click to expand...

the rods will practically pay for themselves as by the time you price up rod bolts and bearings and machining your very close to paying for new rods anyway and means i don't need to worry about if there has been any fatigue over the previous 120k miles
 
What do they need machining for? wrist pin? open your horizons and look over the pond.
 
ijwhiteman said:
I spose not a MUST. But stronger normal means more reliable and you have to get the stock rods machined which is cost and agro to fit the pistons.
Click to expand...

I didn't know they need machining? For any aftermarket piston?

Stronger will be more reliable of course, but its a cost/benefit trade off and with the cost of forged rods, I can't see the reliability benefit being worth it until it's pushing some serious boosted power...

Obviously if you want piece of mind with your build then that's cool, but I wouldn't personally splash out £500+ on parts when I would be fairly confident the ones I have are up to the job. Obviously get them checked out by a machine shop though, just to verify they are actually OK!

Gorbash12346 said:
the rods will practically pay for themselves as by the time you price up rod bolts and bearings and machining your very close to paying for new rods anyway and means i don't need to worry about if there has been any fatigue over the previous 120k miles
Click to expand...

You'll need rod bolts and bearings with the new ones though, unless it is all included in the price? But then, you'd be getting the rods for practically nothing?
 
Last edited:
Kozy said:
A must? I don't see it. Boosted yes, NA surely just expensive but ultimately unnecessary (not to mention invisible) bling?
Click to expand...

What about weight savings with lighter rods, there is some value to that.
 
Haha, OK chaps you win. I admit I have no idea what I am talking about.
 
Since you`re on the "more cc`s" route, get yourself an 89mm crank (B20/B18A), forged rods and 84mm pistons (about 11.8 CR is perfect) and sleeve your bottom. Those should bring you around 1970 cc`s. Get OE head gasket, seals and bearings, some toda b`s or pro 1`s, the afore mentioned valvetrain and you have yourself a very reliable sky-high able revving B18.
 
tama666 said:
sorry if I offended you, just inserting something worth thinking about. sheesh.
Click to expand...

Haha, I didn't mean it like that, I'm just admitting there is a lot of reasons 'for' aftermarket rods that I hadn't thought of. :nice:
 
right so revised current plan is:

rebore block to 81.5mm and hone (jem engines £150)
size oem bearings and check if crank requires reground ( Jem engines £50)

Wiseco 81.5mm 12:1 forged pistons (coordsport £418.93)
Arp main studs (coordsport £102.60)
Eagle H-beam rods (race-tech.net £319.95)
Spoon 2 layer head gasket (spoonsports.co.uk £135.99)
Oem oil pump (japservice parts £139.99)
total £1317.46 plus the cost of regrinding the crank if it needs it and the oem bearings to suit

anything i should add/change on this list? or anything i should be aware of? i'd rather have gone for carillo super-A beam rods as they suit high rpm use better but £900 for a set of rods is just being stupid

also i haven't yet been able to decide on what cams to go for. i see stevenek9 has gone for endyn bumpstix but i'm still trying to see what advantage that would bring over the other versions available and also if i'd have valve-piston clearance problems

this engine will be used for trackdays/sprints/hillclimbs but will also need to be usable on the road from time to time to allow work to be done on my impreza if it requires it so i'd rather it was still day to dayable up to a point

the reason i'm getting jem engines to size the bearings etc is i've not used plastigauge before and as i'm unfamiliar with it i'd rather it was done 100% right as i don't want to risk this kind of money
any hints/tips you can give would be very much appreciated
thanks
Lewis
 
good read!

rs250nut said:
After market rods are going to save much weight over stock unless they are aluminium.
Click to expand...

noted...thank you.

same weight, more strength i guess...forged are more dense which I think is why they are stronger...anyone?

There are titanium rods out there for B's, now there are some weight savings for ya! lol extreme I know... however I like knowing there are stronger rods at these revs over stock, insurance of sorts, im running eagle rods.
 
Good call on getting someone to do the build. Whilst I am looking at doing my bottom end build myself, the £200-300 it would cost to have it built by the local specialist seems like incredibly good value for the piece of mind that it will bring. I do not have confidence in myself to get all the clearances spot on, best leave it to someone who does it for a living!
 
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