RB25DET Rebuild - Data Inside, Engine Guru's Please see

[HIKARI]

So I purchased this high k's engine practically next to nothing. Yada yada yada too much boost yada yada yada got no compression in cyl 3 and not surprising that it is the ring land. So I've stripped it down to bits and took all measurements. My aim is to purchase new set of rings, replacement piston, arp head studs and new steel HG. The point of this thread is for engine guru's to help me with small advice regarding the condition of the block.

Measuring tool: Inside micrometer and telescopic gauge (no plastigauge)

Block itself, by my judgment, are still true and cylinder walls are in perfect nick, can still see honing pattern and no scoring marks. Please see the data whether if I require to do more than above (i.e. new bottom end bearings etc):

Note: Measuring was at 13*C temperature inside my garage
Note: This engine is for the piggy, I'm more inclined over cost>full reliability. If it can last 3 seasons it's good enough.

http://i52.tinypic.com/fbezah.jpg

http://img803.imageshack.us/img803/374/22521417378916267766110.jpg
http://img849.imageshack.us/img849/9409/24746017453500260307710.jpg
http://img10.imageshack.us/img10/883/22785317378888601102210.jpg
http://img37.imageshack.us/img37/8868/24870417453491260308610.jpg
http://img43.imageshack.us/img43/9096/22579917378900267767710.jpg
http://img813.imageshack.us/img813/1343/23017417453484926975910.jpg
http://img90.imageshack.us/img90/9998/23068117453477926976610.jpg

[MrSparkle]

Personally i would chuck that back together with a new set of pistons like cheapest forgies and new shells and off you go.

Those cylinders still look pretty round to me.

If you are not sure you can choose the new piston size one size up and then just get them to bore the block to suit. I did a 25 rebuild just like yours and we just grabbed a set of pistons a bit bigger gave them and the block and some 26 rods to AA's and they gave them back with pistons fitted to the rods and block bored to suit the new ones for a grand total of $350

We chucked it together with the new shells and off it went to make 490ish for another few years till it got a broken turbo wheel and ruined a piston.


EDIT : Re-reading makes it seem to me like you want to do it cheap cheap so you might be thinking about using another standard 25 piston to replace the broken one.
If that's the case then just do it. I think it needs a light hone to give the new rings something to mate against.(presuming you are using new ones) It wont be a problem if you are not chasing every last hp the engine will be fine.

[HIKARI]

Personally i would chuck that back together with a new set of pistons like cheapest forgies and new shells and off you go.

Those cylinders still look pretty round to me. If you are not sure you can choose the new piston size one size up and then just get them to bore the block to suit. I did a 25 rebuild just like yours and we just grabbed a set of pistons a bit bigger gave them and the block and i used 26 rods to AA's and they gave them back with pistons fitted to the rods and block bored to suit the new ones for a grand total of $350 and chucked it together with the new shells and off it went to make 490ish for another few years till it got a broken turbo wheel and ruined a piston.

If I was baller I would chuck forgies in (cheapest I saw was $1100) + all the machining would add up to two used stock RB25's :(

So what do you reckon sparks, without forgies, replacement piston 3, hone the block and new set of rings standard size?

[HIKARI]

Also might as well bring out the dremel and match the weight of pistons and conrods to each other (blueprinting). Unfortunately, my scale reads to nearest gram....

[duste]

Also might as well bring out the dremel and match the weight of pistons and conrods to each other (blueprinting). Unfortunately, my scale reads to nearest gram....

We've got 2x .00 balances at work - you'd have to use them in the laboratory though as moving them would dodge up their calibration. If you want, I can ask the big boss if he minds?

[HIKARI]

^sweet, thanks for heads up. Let u knoq when im up to it. Ordering parts today

[MrSparkle]

I think with a replacement 25det piston you would be in business.

No worse than any unopened standard 25 to begin with anyway.

Good idea!! Perhaps ppl will follow your thread and see just how simple it can be to repair a dodgy piston or an engine with a bit of a knock. Without going overboard moneywise.

[joshg123]

smash a 2nd hand std bore piston in the hole, fresh set of moly rings and put it back together - if its a piggy

not so piggy - hone the bores and fit std bore forgies....

not at all piggy - bore the block 020 and fit oversize slugs

[HIKARI]

Ordered new oem set rings, cometic 1.3mm headgasket and arp headstuds. $440 delivered.

http://www.lake-link.com/images/forumphotos/The-Simpsons---Mr-Burns-Excellent--C11749617.jpg

[MrSparkle]

Wouldn't have bothered with studs!! When we did mine we just used new bolts from nissan and a new nissan head gasket. Took 24 psi and almost 500 rwhp for years.

You tryin' to be baller after all ? :)

Seriously though it should be fine. Did you check out sau for the rebuilding tips ?
Might need some changes to the oil squirter things in the block from memory. Costs nothing and its a good mod.

[c.rusli]

hey! mr derp is on the photos!

[HIKARI]

Wouldn't have bothered with studs!! When we did mine we just used new bolts from nissan and a new nissan head gasket. Took 24 psi and almost 500 rwhp for years.

You tryin' to be baller after all ? :)

Seriously though it should be fine. Did you check out sau for the rebuilding tips ?
Might need some changes to the oil squirter things in the block from memory. Costs nothing and its a good mod.

Nah head has been taken off many times. So just to make sure.

I've check out on sau soon

[mitcho]

What are these oil squirter mods you speak of?

[mitchy]

probably means oil restrictors in the head.

make sure you do that, cheap and may just save v2.

[mitcho]

Any more info on these restrictors mitchy?

Are they a factory thing?

I havent heard of people mucking around with them before. Not to hijack thread but Im planning on throwing in a billet oil pump gear for safety but if there's other shit I can do Im all ear's...

[mitchy]

yes and no... there is a oil restrictor there, but it's too big.

under high/sustained revs they will pump too much oil into the head, a small restrictor prevents it.

http://www.rawbrokerage.com/Tomei-Oil-Galley-Orifice-Restrictor-RB20-RB25-RB26-RB30-tomei-oilrest.htm

[_oz]

http://www.skylinesaustralia.com/forums/topic/110680-oil-control-in-rbs-for-circuit-drag-or-drift/

[TurboHead]

give the bores a good hone (which is an absolute must if new molly rings are used) and get 1st oversize rings.... then gap the rings to suit each bore and it will be good to go.

[mitcho]

Very interesting read cheers _oz.

Looks like I've got a few things to do next time the motor or head is coming out