How to Stretch an FJ20 .

[discopotato03]

Does anyone know any cost effective ways to increase the capacity of the FJ20 . A fellow I know bored and stroked one to 2400cc's years ago for a group G 1600 . This was very expensive at $1200 to weld and offset grind the crank plus god knows what for its Cosworth pistons and rings . This was an NA motor along the lines of the 240RS engine . I once considered using a block spacer plate and liners but costs go out the window . Does anyone make oversize pistons for the FJ20 ? If so what are the results like .

Also FJ20's are bloody heavy lumps . Some of you seem to be using RB's in R30's , how does the weight compare . I like the look of the RB24 conversion but not sure what youd pay for GTR crank/rods let alone the Tomei pistons . I need more cubes and less weight - any ideas ?

[Doctor 30]

Stick with the FJ. It revs to 7500 stock. My RB20DET broke valve springs and that hasn't revved over 6800. The RB is a massive engine too.

You just need a bigger better turbo

[0HR-30T]

Disco-cheapest way I can think of would be to get some 80thou over pistons.I can't remember the bore size off the top of my head,but 80thou each pot would take it out a bit.

[dr30man]

HKS makes a fj21et piston kit, i saw one on importbitz, i dont know how readily avaliable they are though would be interesting to see.

[discopotato03]

For those of you who have not seen FJ24 style pistons , the gudgeon pin is far higher up the skirt and the ring lands close to the pistons crown . Not the ideal thing for a turbo piston wich should have thick strong ring lands . As mentioned above my plan was to use a spacer plate and liners to get the increased stroke with std or at least conventional pistons . From a cost point of view big bore pistons are more practical . I would rather use a factory style cast piston for a road car and not have the rattles and bore clearence dramas that forged pistons have .

[DR30RS]

For those of you who have not seen FJ24 style pistons , the gudgeon pin is far higher up the skirt and the ring lands close to the pistons crown . Not the ideal thing for a turbo piston wich should have thick strong ring lands . As mentioned above my plan was to use a spacer plate and liners to get the increased stroke with std or at least conventional pistons . From a cost point of view big bore pistons are more practical . I would rather use a factory style cast piston for a road car and not have the rattles and bore clearence dramas that forged pistons have .

Im using Arias pistons(80thou over) and are availible from Rocket industries.Forged pistons nowadays(mine anyway) dont rattle cold because of higher silica content,hence some factory built motors can now use them.

Driving my car never ever leaves me wanting for more capacity....

[0HR-30T]

Driving my car never ever leaves me wanting for more capacity....

lol Gold! Pure gold!

I also use 80thou over pistons,which I bought "off the shelf" for my FJ. And Disco,what's so bad about a little noise for 10 min while forgies warm up anyway?

:confused:

[Doctor 30]

And with the amount of money you seem to be spending why not just buy 2 or 3 different engines and try them out

Why the hell did nissan mount the FJ so far forward? Surley the car would be better balanced with the engine set back a few inches....

[discopotato03]

I'd like to know the details about the Aries +2.5mm or 80 thou over pistons . What cost and what compression ratio , how much more torque . Its a lot of expense for 100 cc's more .

Just for the record I'm not spending lots of bucks . All the goodies ie Autronic , GT28RS , R200 LSD Bilsteins etc are bits I gutted from the Bluebird .

Chow A .

[0HR-30T]

Not that you asked about Wiseco's....but I got mine from Rocco's performance in syd.$1200 with rings,at the time....

and just out of interest, "+2.5mm or 80 thou"....isn't 40 thou, 1mm?

[DR30RS]

I'd like to know the details about the Aries +2.5mm or 80 thou over pistons . What cost and what compression ratio , how much more torque . Its a lot of expense for 100 cc's more .

Just for the record I'm not spending lots of bucks . All the goodies ie Autronic , GT28RS , R200 LSD Bilsteins etc are bits I gutted from the Bluebird .  

Chow  A .

I didnt fit the pistons to gain 100cc,it was to gain stronger pistons.As for torque,not many would test the increase from the piston size increase alone,because the boost is usually wound after fitment.The FJ is a torque animal with people fitting RB25 gearboxes behind them.

[discopotato03]

Yeah sorry I was thinking 100 thou and 2.5mm ! It looks like I'll have to call Rocket about the Aries ones . I would be game to bore the FJ20 block to 93mm with a bit of sonic testing . These blocks have really thick cores , its just a shame that its a little short on deck height . Does anybody know off hand what size Rex pistons are and gudgeon pin diameter ?

[V8skylineMAN]

just a thought......dont american 180sx's(240sx) use a ca24 or ka24 or something? i dont know the series of engine but it is definately a 2.4 litre.....try nissansilvia.com they would know....maybe the crank will fit fj's?

[0HR-30T]

just a thought......dont american 180sx's(240sx) use a ca24 or ka24 or something? i dont know the series of engine but it is definately a 2.4 litre.....try nissansilvia.com they would know....maybe the crank will fit fj's?

From what I know,they are not compatable.The Nissan Z24 (pathfinder,etc)cranks are spose to be similar,but that's getting away from the cheap end of the scale to do.

[discopotato03]

US S13/14 used the KA24E (sohc 12 valve) and KA24DE (dohc 16 valve) engines . These have 89 x 96 dimensions with long rods and L Series bore centers . They are a long stroke motor that dosen't like to rev beyond about 6500rpm .

[Boof]

lol Gold! Pure gold!

I also use 80thou over pistons,which I bought "off the shelf" for my FJ. And Disco,what's so bad about a little noise for 10 min while forgies warm up anyway?

:confused:

Ask your bores that and see what they say in response!!!

[0HR-30T]

Boof,I took your advise,and my bore's reply was as follows:

"what's your problem? We're still round.....We like it rough!!! MORE...GIVE US MORE!!!!!!!"

:)

I duely appolijised to my precious bores,and prominsed never to doubt them again

[discopotato03]

To the people using 91mm pistons , what head gaskets are you using . I've never measured the std gasket to see how far they go . I can lay my hands on a Nizmo gasket for 93mm bore but only as a last resort as these are no longer made .

[Boof]

Boof,I took your advise,and my bore's reply was as follows:

"what's your problem? We're still round.....We like it rough!!! MORE...GIVE US MORE!!!!!!!"

I duely appolijised to my precious bores,and prominsed never to doubt them again

Hahaha smart ass What i was trying to say is the whole rattling of the forgies around in the bores can't really be that good for them can it?? Or has the whole fact that there is increased amounts of silica being used now meant that the cold piston to bore tolerances can be decreased meaning less piston rattle when cold????

[discopotato03]

I was just talking to the fellow who had an FJ24 made up . It was rallyd at std capacity then 92mm and finally 93mm . The pistons were made from Cosworth forgings and used Subaru rings . Cosworth pistons usually have thinner walls than most which makes them lighter and expand less when warmed up .