AJ4

I'm trying to think of useful ways to increase my rod/crank ratio by spacing the head off a bit ( 2.4 litre SR20DET ).

I have Darton sleeves with a 5mm thick lip all the way around the top of the sleeve that would normally need seating into the cylinder so it lies flush with the top of the block. Would this work though - fitting the sleever so it sits with the lip on top of the block and using a copper spacer/gasket of the same thickness as the lip ?

I thought maybe if the liners were installed and the liner / spacer machined as one, the softer copper would spring back up slightly proud of the liners. When the head is torqued down, most of the compression force is on the face of the liners but a small amount would act on the copper as well. The copper wouldn't have to seal that well as its only containing water and oil lines, not any combustive forces.

Am I going about this in entirely the wrong way or does it sound like something worth investigating ? I've seen head spacers before that are fitted almost permanently to the head and milled through to fit the liners, but with this idea the spacer could be lifted on and off easily and doesn't have to be a perfect fit to the liner ( the liner is permanently fitted to the block and is prevented from dropping by the lip ). This would also minimise milling the recess for the lip into the head as its a bit of a headache...

Any thought, comments, suggestions are appreciated, or any alternate ideas or methods to space the head off most welcome. One final thought, the piston pins are fitted as high up in the piston as possible, so no room for improvement there unfortunately

Cheers,

Ross.

 

bigtom

it is a difficulty with regard tot the chain. i added 1 inch spacer once and that was the most difficulty. there are 2 companies in japan doing a similar thing but the use a 4mm aluminum spacer and 2 gaskets above the liner. they do this for the RB26 and one of the companies is OS Giken. they just run the piston up intot he gasket space and the crown thickness is a minimum of 6mm to make it work so the rings dont fall out of the liner into the gasket. the RB uses a belt which makes it easier. 5mm spacer would add about .5in chain length. it is easier and cheaper to gain up to 6-8mm with longer rod and adjusted pinheight on a custom piston.

__________________
http://www.bigtomsgarage.com

JimmyNX2000

is that the RB30 package from OS Giken you are referring to?

__________________
1993 NX2000

AJ4

I did think about raising the pin but its near impossible on the piston design I have ( CP's ). The pin is almost cutting into the oil control ring as it is, and I don't see how they could drop the ring land width any more and put the rings closer together. The only option would be to lose the second ring altogether but the engine is designed for low rpm torque and having only two rings total wouldn't work too well until high rpm.

I think theres probably enough adjustment in our chains to get a 0.5 inch increase in length, especially if I use an older one that been stretched a bit already.

bigtom

i have done it reliable running the pin 6.85mm higher and still running the .866 pin. if you rebush the rod you can gain a little more. NA this setup has worked fine. this used a 6.85 mm longer rod and still has 3 rings. this is the max i would do. you can go more making the pin even smaller and using an oil rail support where the pin is in the oil ring then max is about 8mm.

if you want a set of these rods/pistons let me know. the rods are reasonable but the pistons are expensive and weigh around 240g with pin and even less with Ti pins.

if you already have the pistons i guess your stuck there, but if its just a design maybe you should redesign it.

if you must go your spacer way i dont recommend the copper if you want it to last. go with the proven AL spacer 2 gasket system OSG has for the RB30 kit.

hope the info helps. good luck to you.

AJ4

Unfortunately I already have the pistons and really want to keep them. Thanks for the suggestions about the 2 gasket system, I'll look into it