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Rb25 Rebuild

Dasmbo

By Dasmbo,
in Engines & Forced Induction

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Dasmbo

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Hi i am rebuilding my engine its an rb25 std bore and motor has done 110,000kms and there appears to be little if no wear in the bore

i am purchasing a set of CP Pistons and a set of Manley Connecting Rods with arp rod bolts for the rebuild and a set of cometic gaskets.

I havnt built a nissan rb 6 cyl engine before is there anything i should be aware of rebuilding it with forged internals as i want to do it once only

When replacing pistons is it recomended to have engine block rebored with oversize pistons or use std size forged pistons

any info would be great i dont want the engine for high horsepower but i want a bit of overkill for the mods i have and the couple i want currently have 430hp hi flowed nissan turbo hybrid fmic a gtr style intake manifold s/steel exhaust manifold low mount 3 inch turbo back exhaust with 3 inch cat and piggy back ecu on to main ecu

thanks for reading this post

Sam....

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KiwiRS4T Grand Master

KiwiRS4T

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You need to be more specific - what is your power goal? Do you need a rebore? Measurement will determine that - how much oversize and out of round. Also measure crankshaft for wear. If the mileage is genuine it is possible you will be able to use standard pistons bearings etc. Have a read of the oil control thread re restrictors.

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Simon-S14 Grand Master

Simon-S14

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are you capeable of doing the work yourself? do you have the tools to measure clearances etc? if no then just pay someone to do the machining and assembly of the motor. regardless of the bore condition i would certail go for a rebore to the next size up. start fresh to give the rings a chance to bed correctly.

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Dasmbo Collaborator

Dasmbo

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You need to be more specific - what is your power goal? Do you need a rebore? Measurement will determine that - how much oversize and out of round. Also measure crankshaft for wear. If the mileage is genuine it is possible you will be able to use standard pistons bearings etc. Have a read of the oil control thread re restrictors.

Hi thanks for your reply power goal 200-250 rwkw.Taking crank head and block to machine shop tomorrow 2 have them checked i will probably go with a rebore. The reason i want forged bottom end i cracked one of the original pistons and dont want the worry any more. The car will be driven normally 95% of the time and unleash it now and then.

I was also looking at oil pumps and it seems there are as many pros and cons with them not to mention huge cost. Might stick with the K.I.S.S protocol and stick with a standard item.

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KiwiRS4T Grand Master

KiwiRS4T

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After your rebuild the main thing to keep your engine alive is a good tune. Have you got some kind of aftermarket ecu? If not z32 ecu with Nistune chip would be the minimum (and adequate for those power levels) followed by PFC or best a Link/Vipec.

Sorry just reread your post and see you have a piggyback - something like an e-manage would be fine.

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The Mafia Grand Master

The Mafia

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why are you even bothering to rebuild if that is the only power you are after? I ran 300rwkw with a Garrett GT3076 for about 3 years, and when we removed the motor, it still tested perfect in a compression and leak down test.

I wouldn't even bother with a rebuild for your power goal unless the motor is already buggered.

ALso, DEFINITELY get the motor rebored if you are installing new pistons and rings. Forged pistons are sentisive to the right bore size.

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DR 32R Rising Star

DR 32R

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It seems even with a standard oil pump,oil restrictors are advised, 20 bucks a restrictor, there are a couple of billet gear pumps in the parts for sale section. Price of these items will be small fraction at end of build.For your goals, quitting while ahead and buying a used RB25det for $1400 looks good. (price of retail after market oil pump).

Edited by WHITE gtt
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Dasmbo Collaborator

Dasmbo

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After your rebuild the main thing to keep your engine alive is a good tune. Have you got some kind of aftermarket ecu? If not z32 ecu with Nistune chip would be the minimum (and adequate for those power levels) followed by PFC or best a Link/Vipec.

Sorry just reread your post and see you have a piggyback - something like an e-manage would be fine.

Hi bob thanks for the info left head crank and block at machine shop will get the news tomorrow on condition of items

Sam....

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Dasmbo Collaborator

Dasmbo

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why are you even bothering to rebuild if that is the only power you are after? I ran 300rwkw with a Garrett GT3076 for about 3 years, and when we removed the motor, it still tested perfect in a compression and leak down test.

I wouldn't even bother with a rebuild for your power goal unless the motor is already buggered.

ALso, DEFINITELY get the motor rebored if you are installing new pistons and rings. Forged pistons are sentisive to the right bore size.

Hi thanks for your input yes its a low pwr outlook at the moment but like to leave room for the futurei have extra mods id like to do in the future so thats why i want a reasonable bottom end.

I would also like it to run the car on a lower octane fuel somewhere in the future.

The original motor was going great never used oil went well no problems then i accidently filled the car up with regular unleaded in canberra and the car was lucky to make it home. Number 3 piston nearly parted company with itself split around oil ring recess was blowing smoke like no tomorrow.I dont want to change engine block as i like to keep the car,s main components original. You never really know what you are getting buying second hand.

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The Mafia Grand Master

The Mafia

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ok no worries mate, didn't realise that you blew your old one.

Take my advice and experience - When you have the block out, get it acid bathed, decked, bored, hone, and the top of the bores chamfered. Should cost you about $300. And you'll have a peice of mind. Trust me, don't skimp in these areas. Especially if you are looking for bigger power later on.

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DR 32R Rising Star

DR 32R

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Hi thanks for your input yes its a low pwr outlook at the moment but like to leave room for the futurei have extra mods id like to do in the future so thats why i want a reasonable bottom end.

I would also like it to run the car on a lower octane fuel somewhere in the future.

The original motor was going great never used oil went well no problems then i accidently filled the car up with regular unleaded in canberra and the car was lucky to make it home. Number 3 piston nearly parted company with itself split around oil ring recess was blowing smoke like no tomorrow.I dont want to change engine block as i like to keep the car,s main components original. You never really know what you are getting buying second hand.

And when a rebuild gos right, there is a special satisfaction.Oil control mods are a reliability mod, needed just as much as forged parts.

Edited by WHITE gtt
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Dasmbo Collaborator

Dasmbo

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ok no worries mate, didn't realise that you blew your old one.

Take my advice and experience - When you have the block out, get it acid bathed, decked, bored, hone, and the top of the bores chamfered. Should cost you about $300. And you'll have a peice of mind. Trust me, don't skimp in these areas. Especially if you are looking for bigger power later on.

Thanks for your advice has been taken on board just the type of info i was looking for.

I like doing my own rebuilds i have done plenty of engines over the years.

What is your view on oil restrictors to the top of the engine do the lifters suffer ????

thanks Sam....

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DR 32R Rising Star

DR 32R

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Three head oil feeds on an RB25, two block feeds to head, one for VVT. If you restrict two block feeds, you still have three feeds to a hydraulic head. People have adequate cylinder head oil with the VVT feed, one blocked, one restricted.

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The Mafia Grand Master

The Mafia

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I put 2 x 1.3mm restrictors in the block feeds, and welded the head shut on the third feed because I used a RB30 motor. (Doesn't have a third feed for vct). I did the internal pin mod, and robbed 1.5mm worth of feed from the head journal on that side.

Didn't have a single issue with oil what so ever.

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Dasmbo Collaborator

Dasmbo

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I put 2 x 1.3mm restrictors in the block feeds, and welded the head shut on the third feed because I used a RB30 motor. (Doesn't have a third feed for vct). I did the internal pin mod, and robbed 1.5mm worth of feed from the head journal on that side.

Didn't have a single issue with oil what so ever.

Hi is there a thread on here or website that has info on oil restrictors

also would i have to put restrictors on all 3 oil feeds ??

sorry about all the questions just that id like to get it right

first time.

The car wont see any track work maybe occasional day at drags

and normal driving

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DR 32R Rising Star

DR 32R

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http://www.skylinesa...-drag-or-drift/

This is Sydneykids take on oil control. it seems most RB devotees support oil restriction in a rebuild.He advocates blocking an oil feed in the RB25. Mine and the Mafia is restricting the 2 block feeds.

Edited by WHITE gtt
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  • 4 weeks later...
Dasmbo Collaborator

Dasmbo

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Update engine build.

I have most of the parts to do my engine rebuild i have

1 set of CP forged pistons + rings pins clips 8.5:1 compression

1 set of Manley con rods/ARP 2000 rod bolts

Nitto Oil Pump +Crank coller

Cometec Gasket set

ARP Head studs

ARP main studs

New Timing belt + idler and tensioners

Engine block i have left the vvt restrictor alone blocked the middle restrictor and installed a 1.5mm restrictor in the rear

Block Head and Crankshaft now at machine shop for chemical clean head surace decked bored and honed and crank coller installed

Waiting to find out what size bearings will be needed

I hope i have not missed anything looking for more input to my rebuild and looking for any more info on anything i may have missed

thanks

Sam...

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