Jump to content
SAU Community

Recommended Posts

there is no such thing as an HKS 2.7 litre crank. and as for the '2.7 litre pistons' in what way are they 2.7 litre pistons? pistons size doesn't equal capacity. it's bore X stroke which is the deciding factor in the CCs (yes obviously head combustion chamber size makes a difference but we are not changing heads). HKS use the same pistons in 2.6 litre kits and their 2.8 litre kits.

if you want an 2.8 litre then you will need new crank and new rods. your current pistons should be fine (just make sure you match the pin size - ie don't get 22mm rods if you don't currently have 22mm pins which is unlikely).

there is no such thing as an HKS 2.7 litre crank. and as for the '2.7 litre pistons' in what way are they 2.7 litre pistons? pistons size doesn't equal capacity. it's bore X stroke which is the deciding factor in the CCs (yes obviously head combustion chamber size makes a difference but we are not changing heads). HKS use the same pistons in 2.6 litre kits and their 2.8 litre kits.

if you want an 2.8 litre then you will need new crank and new rods. your current pistons should be fine (just make sure you match the pin size - ie don't get 22mm rods if you don't currently have 22mm pins which is unlikely).

I know piston size dont = capacity. Interesting info though, the owner of the motor/car asures me it has "oversized HKS pistons". quote "it's now 2.7lt" :laugh: Maybe i'll get the sump taken off and have someone look in there before I exchange cash :D

Edited by Nismo_Boy

Well how much oversize are they? Oversize pistons can make a bit of a difference to the engine capacity.

Remember stock GT-R

Bore: 86mm

Stroke: 73.7

Capacity: 2.568 litres

If you overbore the thing by 1mm (Not that you would necessarily want to straight up)

Bore: 87mm

Stroke: 73.7mm

Capacity: 2.629 litres.

So a 1mm overbore doesn't make it a 2.7 litre motor - you need a longer throw crank.

If you go to 2mm

Bore:88mm

Stroke: 73.7mm

Capacity: 2.689 litres.

Which can be claimed as 2.7 litres.

Remember though, if you bore the block out to its limit (2mm or whatever it is) it will be a throw away item the next time you need to rebuild it. All that for 60cc's?

Edited by djr81
I know piston size dont = capacity. Interesting info though, the owner of the motor/car asures me it has "oversized HKS pistons". quote "it's now 2.7lt" :laugh: Maybe i'll get the sump taken off and have someone look in there before I exchange cash :D

yes! definately get the sump off before handing over any decen cash for it. 88mm bore is not a positive selling point, it's a negative. and off the top of my head the largest pistons HKS make atm is 87.5mm I can check later as I have the 2007 goods master at home.

increasing the bore but leaving the stroke does not get the same result as the stroker kits. sure they may both be 2.7 litre or 2.8 litre but the capacity does not tell the whole story. further increasing the bore whilst leaving the stroke the same will reduce some of the low down punchiness of the engine but yes it should make more power high in the rev range. this is why when you want more capacity in an RB26 you go longer stroke.

also 88mm bore is the absolute limit of what you can bore a 26 to safely and at 88mm bore the engine is no longer really suitable for big revs or big power as the cylinders are now quite thin (weak). for big power you want to be using 86 or 86.5mm.

Well, back in the day people used to overbore motors in increments of 10 thousands of an inch ie 0.25mm. If you had (for example) a Cleveland V8 you binned it after 40 thou. Which is why you have to be careful with going too much over size too quickly. Like the Baron says a block out to 88mm is on its last rebuild - so why pay extra coin for something in that condition?

Anyway, to anyone looking for a stroker crank & larger capacity from their RB26 - be careful about which size pistons you order.

Oh, and by the way. Combustion chamber volume has nothing to do with motor capacity. But piston diameter certainly does!

Overboring will always increase low down torque, not as much as a stroker, but still will none the less. I wouldnt discount the car if its been bored that much, as if the motor does need rebuilding in the future, you can always get a second hand block, they are around, and worth bugger all($2-300). I doubt taking the sump off is really an option in a gtr just to check the bore size, it would be a $1000 job. How do you know its only got an r33 crank. I would be buying the car more based on the rest of the car, and its bolt ons. Preten it doesn't have the pistons and look at the rest of the car on its merits.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • To follow up a question from earlier too since I had the front bar off again (fking!) This is what is between the bumper and the drivers side wheel And this is the navigator side, only one thing but its a biggy! So basically....no putting coolers in the wheel arches without a lot of moving other stuff. Assuming I move to properly race prepping this car I'll take that job on and see how the computers respond to removing a whole bunch of ADAS modules
    • So I prepped the car for another track day on Wednesday (will be interesting to see coolant temps post flushing out and the larger reservoir, with a forecast of 3-14 being 20o cooler than last time I took it out). Couple of things to mention; since I am just driving the car and not taking a support vehicle, I took the rear seats out and just loaded the back up Team Trackday style. Look at all that space! To cover off removing the rear seat....it is weird (note the hybrid is probably different because it wouldn't have folding rear seats) Basically, you remove the lower seat base, very similar to a r series but it is a clip that pulls forward to release the base rather than it being bolted down. Easy Then, you need to remove the side section of the rear seat on each side. There is a 14mm head nut at the bottom of the side piece, the it slides upwards off a hook at the top to release; you also need to unhook the seatbelt from the loop at the top. Then the centre piece is weird. You need to release/fold the seats forward with the tab in the boot on each side From there, there are 2,x12mm headed bolts holding the rear of each seat to the folding bracket, under the trim between the rear seat and the boot (4x christmas tree clips there, they suck). The seat is out but you can see where the bolts attach to the bracket
    • As discussed in the previous post, the bushes in the 110 needed replacing. I took this opportunity to replace the castor bushes, the front lower control arm, lower the car and get the alignment dialled in with new tyres. I took it down to Alignment Motorsports on the GC to get this work done and also get more out of the Shockworks as I felt like I wasn't getting the full use out of them.  To cut a very long story short, it ended up being the case the passenger side castor arm wouldn't accept the brand new bush as the sleeve had worn badly enough to the point you could push the new bush in by hand and completely through. Trying a pair of TRD bushes didn't fix the issue either (I had originally gone with Hardrace bushes). We needed to urgently source another castor arm, and thankfully this was sourced and the guys at the shop worked on my car until 7pm on a Saturday to get everything done. The car rides a lot nicer now with the suspension dialled in properly. Lowered the car a little as well to suit the lower profile front tyres, and just bring the car down generally. Eternally thankful for the guys down at the shop to get the car sorted, we both pulled big favours from our contacts to get it done on the Saturday.  Also plugged in the new Stedi foglights into the S15, and even from a quick test in the garage I'm keen to see how they look out on the road. I had some concerns about the length of the LED body and whether it'd fit in the foglight housing but it's fine.  I've got a small window coming up next month where I'll likely get a little paint work done on the 110 to remove the rear wing, add a boot wing and roof wing, get the side skirt fixed up and colour match the little panel on the tail lights so that I can install some badges that I've kept in storage. I'm also tempted to put in a new pair of headlights on the 110.  Until then, here's some more pictures from Easter this year. 
    • I would put a fuel pressure gauge between the filter and the fuel rail, see if it's maintaining good fuel pressure at idle going up to the point when it stalls. Do you see any strange behavior in commanded fuel leading up to the point when it stalls? You might have to start going through the service manual and doing a long list of sensor tests if it's not the fuel system for whatever reason.
×
×
  • Create New...