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Old 06-29-2009   #1
mcfly's Avatar
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Default DIY RB26 Rebuild

Credit for this DIY goes to T.P.S

Part 1

after buying a R32GTR the engine blew after 2 days on the way to the mechanics....i had a "det" noise and then lost a lot of compression on no:2 cylinder

i was fully aware of a tapping noise and i understand that this is a signature noise of detonation but this was soo loud i thought it was a gearbox mount..the car has a shortshifter on it but the seal had not been fitted allowing the noise to come from the gearbox area so even though i was on the way to a friends garage to have a look when it was on the lift i gave it about 3/4 throttle for a few secs and it dropped a cylinder

when i got to the garage we didn't bother checking the gearbox mounts lol but we did stand around shaking heads under the bonnet, we noticed that the fuel regulator hose had come away from the regulator.....this is a serious failure on a turbo car as the fuel regulator needs to increase the fuel pressure as boost rises, if it does not then the engine will run lean and detonation occurs

it may have been knocked off by one of us just before we noticed it so its not a definitive cause of this failure but its a good theory for the moment

upon checking the compression was 165-170psi across the board on the tester apart from no:2 which was 40psi down:apoke:

i haven't the cash to pay for a rebuild and not many want to help on a project like this so i have done 99% of it own

here's a pic of the car in my back garden awaiting rebuild

another as the dismantle process starts...chassis looks nice and stiff (jacked up on passenger front only)

now for those that don't know me ive been fecking with cars for a long time now and in my previous cars i had honed down the engine strip down or removal process time to less than 3 hours but this car has a lot more stuff attached to it and after careful consideration it may prove easier to remove the engine and gearbox as a complete unit rather than remove the inlet and exhaust manifolds in the car!, and really i need to remove the cylinder head to find out what i need to replace

some of the nuts on the inlet side seem so far away from access it may be impossible with conventional spanners and sockets and the exhaust side isn't much better, the odd pre-rounded off bolt here and there always being in the most inaccessible of areas.....

the clutch is a real nasty paddle type so maybe it makes sense to change it during this engine work period anyway eh (well thats my excuse lol)

here's the exhaust side with the heat shields, inlet pipes and other stuff removed

i don't intend this to be a quick the mo is about 10 degrees outside and ill be doing all of the work my myself this time so most of the heavy stuff may just have to wait until warmer weather, i have spent around 15 hours on the car and it feels like i have got no-where with it yet...

had some time off work this week to get this engine out, done 99% of it own my own and TBH that was prob the best way, don't normally disagree with myself lol

as mentioned before its a pig of a car to work on but i tackled it like this

remove the inlet hoses from the bonnet area, remove rad and fan to get a bit of room to work in

the down pipe nuts, easier then they look to remove from under the car with a 14mm and extension

obviously it also needs to be disconnected from the cat also

i found a load of excess exhaust paste that had gone hard in the i know what that dam noise was lol

the clutch control arm needs to be removed on the pull type arrangement that i have on mine, you need to remove the slave cylinder and then pry a pin and circlip off from the end of the clutch arm inside the box, you gain access through the hole the arm travels through

after the pin and circlip have been removed pull it away from the thrust bearing

the bottom bellhousing bolts are easy to get to but the top six bolts look almost impossible...if you remove the top and bottom driver side engine mount bolts and the bottom passenger side mount bolt you can jack the engine and then remove the driver side engine mount, the passenger side mount does not need to be removed to get the engine out of the bay

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Part 2

when you drop the engine down onto the subframe you can get those bolts with a normal 14mm spanner from the bonnet side

the driveshafts are held in by circlips and in theory they just need a jolt and they will come free if you have removed the hub to allow movement, i couldn't do this on the driver side though even after about an hour of abuse, tried to release it from inside the diff housing to no avail so i split the shaft from the engine side joint, it didn't make engine removal any harder with it still attached

the passenger side has a very long driveshaft and it also needs to be unbolted from the engine before removal, the driveshaft castlenuts are a 36mm BTW

i left it to almost last to remove the power steering hoses..

the engine should come free as soon as you try to "wiggle" it off the input shaft, i didn't put a jack under the gearbox as it seemed very secure by itself

once thats all done just lift the engine as much as you can whilst keeping an eye on any wires still attached, the higher the engine is at this point the easier it is to remove the knock sensors etc

sounds straightforward but that took me the best part of 20 hours in a typical English February 5 degree weather

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Part 3

the strip down process is pretty normal really, i wont go into that as this guide is for the experienced mechanic (although a beginners guide to skyline engine overhaul process)

upon removal of the head the valves in cylinder two showed no signs of damage...i filled it with water but none seeped through (water may not be thin enough for some but its thin enough for 40psi drop i believe eh)

the head gasket seemed ok too

upon removal of the piston it also seemed i started to clean it i saw det marks on the "flats" of the piston

cleaning a bit more on the ringlands gave a nasty surprise!!, a lump of no:2 ringland came off in my hand and i then saw two cracks in the ringland above it!

just sitting there waiting to jump out eh lol,the detonation couldn't break the top of the piston but the shockwave the detonation made traveled through the piston and cracked it where it was weakest....a bit like the "din mak" that jean-claude van damme done in the film bloodsport lol!

the others have tiny cracks here and there..wouldn't have thought they were cracks until i saw no:2 piston so if you are doing a rebuild yourself changing the pistons or having them xrayed would be a very good idea if you have any signs of detonation on the flats

so...a set of forged pistons is on the cards and this is where the skyline tuning parts prices come into can easy pay 1200 for HKS pistons and near that price for most makes that uk tuners stock

some uk tuners charge 3-5000 for a basic rebuild compared to 700-1200 for your average 6 cylinder engine

the prices of OE parts isn't too bad...50 for bearings, 260 for a slightly uprated clutch, gasket kit 140 so why the massive prices?

apart from the "hassle" involved with a GTR rebuild there seems to be a serious lack of information on the net (or anywhere else!) about the cars/engines, and from what ive read most rebuilds end in engine failure even when done by some tuning company's...

in fact my engine had 6/6/05 on the sump and rocker indicating that the engine had just been replaced....i presume due to engine failure?....this engine only lasted a few hundred miles before it blew for one reason or another so the chances of this "poverty" rebuild going smoothly is low to nil maybe

so anyway..the first and longest job of the rebuild should be the clean down, if you take the bits off and get them as clean as possible before starting any engine work the whole rebuild will be a far less messy operation

here's the inlet and exhaust manifolds as they were

i just gave them a degrease with some gunk, jetted them off and then put them in a friends sandblaster

i done that to pretty much all of the parts i could as the engine was very corroded, even the turbos

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Part 4

to clean the head i used oven cleaner as per instructions on the carbonized parts of the head and jetted off, i then used fine grade wet and dry (wet) followed by fine wire wool to get a polish...this isn't just done from a cleaning point of view, it makes sure there is no sharp edges/hotspots on the combustion surface and will reduce the chances of detonation in future, the flat part of the combustion face (the bits that stop the head part of the cylinder being round) should also be rounded off slightly to avoid det...the inlet side is more prone to det than the exhaust side

so before clean down we have something like this

combustion face, oven cleaner first then jetter should get something like this

same bit but rubbed with fine grade wet and dry (wet) for about 45mins..maybe less

same bit, polished with fine wire wool for about 30mins

i cleaned the mating surface in the same way...didn't take too much time doing this as i have not yet checked the volume of the combustion areas on the head so it may need a skim if its off but we will come to that shortly, make sure you use a straight edge on top of your cleaning medium to make sure you are removing any material in a uniform manner

doing this polishing is a long process but it really does have great results

now here's an exhaust port as stock

here is one with the bump removed

i used a dremmel with a sandpaper end, then wet and dry followed by wire wool

the inlet side just wanted smoothing off really

now we can check the volume of the cylinder part of the head, i used some perspex, some sealant and a 100ml syringe

you will need to drill two holes for each so you can fill the void with water and one to let the air escape

put perspex onto head, mark out two holes for each cylinder and then drill the holes

then apply sealant to the perspex/head and weight it down for 45mins or so, after that fill a 100ml syringe up and fill each cylinder with paraffin, you can use water but if it does get past the valve it can corrode the valve seat..

you may want to check for leaks as one of mine was letting by at the sparkplug which gave some very confusing results lol

remember to keep a record of the volumes...

i got 66ml across the board so no problems there (34ml left in the syringe)

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Part 5

with the head now prepped and ready for lapping the parts have arrived to start the block

as mentioned previously the pistons were all either damaged or had suspected fractures on the replace these with stock items would cost 70 each from Nissan but TBH they are not great pistons so i have gone with a larger bore with a set of JE forged items i bought from the American eBay site, worked out about 470 with shipping and customs tax

going 1mm oversize works out to be 2628cc (stock being 2568cc), this will not increase power by any noticeable margin

the engine needs a good jetting out after any work like this, making sure no swarf has found a corner to hide in, all of the oilways and water ports blown through with the coreplugs removed for 30mins or so followed by some compressed air to dry it off is a must, dont want to allow any corrosion to get into the oilways, finish off with some WD40 on the oilports, journals and mating surfaces

i gave it a coat of silver high temp paint whilst it was outside and dry

moving on to the pistons....i weighed and bagged every piston and recorded the weight, i done the same with the pins and the rods with the old bearings removed

i found about 1 gram difference on the new JE's and about 4 gram on the rods, i am not going to balance the rods or pistons but i did do some basic blueprinting which is setting the heaviest piston with the lightest rod and so on

i took a record of the stock piston weight vs the new ones for no other reason than curiosity..

nice set of scales eh and perfect for this application....i got hold of this during the time i was made redundant from a closing down sugar factory

the stock rods averaged out at about 640g IIRC

there are some sharp edges on the pistons that id prefer removed, i used some fine wet and dry to round off all of the sharp edges on the face of the piston, basically its minimizing the amount of hotspots which will go some way to deter detonation

i went with the recommended 4 thou bore clearance and ring clearances for "street car turbo/nitrous", the clearances have to be worked out by inch of bore, in this case its 87mm so thats 3.4 inches roughly, this does not apply to the oil control ring cluster though!

TBH i would prefer to see a more reasonable description of the application, there are too many variables on a turbo/nitrous engine to just throw it all into one part of the scale IMHO

on a previous engine i used the max clearance for turbo/nitrous on the bore and also on the rings........that was an engine that was designed to last ten thousand miles and no more so remember that if you want bigger clearances, lifespan will decrease at an unbelievable rate the bigger your clearances are as they only allow good sealing of the rings at very high temps (which is what you would want on a 10 second drag car but this is a road car...)

so i have gone with a clearance of 17-18 thou on the top ring, 23 thou on the middle ring and the stock gaping on the oil ring which is ok provided its over 15 thou
the rings are file fit so its just a matter of filing gently on one side of the ring until you can fit the feeler gauge through the gap in the ring with just a tiny bit of resistance when it is installed in the bore for your desired clearance

i always chase the ring up and down the bore checking the clearance after i have finished filing the ring, if the clearance on your ring increases or decreases as you do this the bore has a "taper" to it

the JE pistons seem to have a lot of failures where the pin (or circlip) jumps ship and allows the gudgeon pin to slide out, there isn't any info supplied with the piston set as to how to fit them but after looking at their site and speaking to people on forums the general method is to place the open ends into the groove facing away from the face of the piston and push in with your fingers, it shouldn't be hard to push them in if you are using the right technique...they just slide in real easy and hopefully make a nice click when they seat to let you know they are home, i still rotate them a few times just to make sure though as you really don't want to make a mistake here

with any rod/gudgeon pin there should be roughly 1 thou clearance...its not easy to measure this without specialized mics but if you oil and then place the gudgeon pin into the rod it should slowly glide through *slowly under gravity alone

although there was no crank failure on my engine i still wanted to get the crank checked over, it came back "all ok" but i had the journals polished up whilst it was there

the bearings are a bit tricky on these engines...normally its just a case of ordering a new stock set but these are all graded

there is a bearing grade stamped into the sump face for each main bearing and another for the cranks mains journals, these numbers are listed on the flywheel end of the crank

top-mains journals
bottom-rod journals

left to right nos 1-7/1-6

you add the numbers on the block to the numbers on the crank and thats the grade of bearing you need

same thing with the rods and the pistons (obviously the piston grade does not apply if you have a rebore)

also remember that cylinder 4 mains has the thrust bearing bit on it and you will need to mention that when you order

these bearing grades should still only be used as a guide, the bearings will still require checking with "plastigauge" if we are to be sure that clearances are correct and that the crank journals are not elliptical, it was given the "ok" by the rebore company but ill trust my own measurements only!, the crank is SO important you cant just take it for granted......double checking here will prevent the engine coming back out again in a few weeks time

after installing the mains bearings (prior to checking) we started to install the oil squirters..pretty cool items by all accounts and its a wonder why they are not fitted to all engines, they have an oilway and valve inside the bolt so make sure you fit the right ones in lol, the piston is also supplied with oil by the rod

one of mine had been damaged somehow, it wasn't until it was positioned along with the others that we noticed the bend...and then the crack on the shaft

cant be too careful eh:nonono:

i doubt it would have led to an immediate engine failure as the squirter is pressure dependent....if oil pressure drops under 3 bar (guess) the oil squirters are shut down, it may have led to failure at full throttle with lots of heat in the piston though

also from the above picture you should be able to see the block "cast lines"...these are basically stress points that we could removed if we wished....this would be a very useful mod on a block that is on the brink of its power level but on this engine 500bhp would take you nowhere near that stage so i have mostly left them alone but i did take the sharp edge off them....just a tickle with the dremmel to radius the stress point

there is more information on this subject on under "advanced"

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Part 6

the coreplugs should be renewed at this point..they are cheap and can only really be all renewed when the engine is out...just knock the sideways in their bore, remove with pliers and then use the least bent old coreplug as a drift to insert the new ones with

the bearing grades on the mains, crank and rods have been noted and ordered to spec, i had the crank checked whilst i was having the block bored but i would still like to check it with plastigauge

the bearings are fitted to the block, mains and rods but without oil!

you want to cut a slither of the stuff so its slightly shorter than the journal itself, do this to all of the mains journals on the crank with the crank placed in the engine awaiting the girdle

now fit the girdle with the plastigauge in suit being careful not to knock it off, torque up the bolts in the correct fashion and then dis-assemble it all again to measure and then remove the plastigauge

measurement is real easy with the bit of card they supply, you just match the size of the "splat" it makes on the crank with a splat on the card lol

the stock clearance is just under 2 thou, max clearance is 3.5 thou, all of mine came up at around 2.0-2.1 so well within clearance

mains bearings cleaned and oiled ready for the crank to be finally fitted

mains offered up to block just prior to crank install

crank and mains fitted

top view

__________________________________________________ _________
Part 7

all coming together now!, the piston rings have already been cut to spec and they have been fitted to the rods already too so its just a case of taking them with their piston and oiling them up to help slide them in to the cylinder

before we fitted the rod/piston we placed duck tape on the studs to prevent assembly marks to the crank journal

bolt up the rod to the crank to the correct torque and repeat 6 times

fit the splash plates, oil pickup, oil pump and the flywheel side crank cover before fitting the sump

heat the timing pulley up in a saucepan of water before fitting to help it go on and make sure the washers are round the right way!, round one to block, then timing pulley with groove to block, then curved washer with the bowl facing away from the engine before fitting the pulley

pump and timing pulley fitted

bottom end rebuild complete

the head is now back on the agenda for the next stage

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Part 8

so the last time we saw the head it was clean and measured, the next stage is to "cut" the valves in and replace the seals

if you have not done this before you will need these

the idea is to clamp the valve spring down and remove the "collets" from the top of the valve

with the collets removed the spring and cap will come out as the valve tool is released and the valve can be pulled out with the plunger

keep all of the valves/springs/caps/collets/spring seating washers from each port in one bag labeled with the number of that port, i normally write the numbers next to one or two of the ports too as you can see in some pics...just to make sure they go back in the same place

here is one of the exhaust valves as it came out

when the valve and spring/cap is removed you can see the valve seal

these can be removed *carefully* with a pair of pliers...must be careful not to score the wall of the head

when everything is removed you can give all the parts a clean with fuel inc the parts of the exhaust ports that you cant get to with the valve in place....i wouldn't clean around the valve seat/valve sealing surface with anything other than cutting paste but you can clean the backs of the valves with a dremmel type wire brush end on a slow setting

with any dirt/grit out of the way the valves can be recut

to cut the valves you apply three small dabs of coarse paste onto the sealing surface at the back of the valve, you then insert it with the plunger and rotate the plunger like you are making fire on one of those discovery channels lol (you will need to then repeat with fine paste at least two more times or until you are satisfied that the paste is being pushed out of the sides of the valve in a uniform manner indicating that the valve seat has been matched)

you also need to lift up every few seconds and rotate the valve about 90 degrees before placing back down to make more "fire"

you can feel after only a few moments of rotation that the paste has been pushed out so you wipe up and repeat a couple more times with fine paste.....some valves/heads will need more cutting than others but in this game less is more.....if you remove lots of material you will at least affect the height of the shim (we will come to those later)

you can get marks on the valve mating surface but some of these will not come out no matter how much fire you make

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Part 9

here is a valve in the process of being cut, paste applied to the back of the valve

after you have cut 24 valves the seals are next on the list, if you don't have a press to fit these you can do it with a socket, extension and a small hammer, not a job for the ham fisted!

oil seal then place seal onto "stem" and tap in, i removed all of the seal springs first to avoid damage and refitted them after

oil the valve and push it gently through the new seal into its home then install the washer/spring/cap and compress with the valve tool

getting the collets back on is a hell of a lot easier with some grease applied to them first

one they are home just release the tool and everything should fit snug, it takes some time to do them all

well the block is already prepped we just gave it a turn or two so the pistons were on average half way down their bores (to avoid any piston/valve contact when the cams are fitted later on), and fitted the gasket

a bit of oil over the tops of the new pistons before we lock them away

thanks must be given to "JohnB" for the practical and theory input on this thread and on this engine, a pleasure to work with
also thanks to "JohnA" for putting up with persistent questions lol

the shims and buckets are yet to be measured and fitted before the cams go on to have the tolerances on them checked but i will come back to this...for now i am more interested in fitting the engine

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Part 10

the engine has a lot of stuff that needs to be connected before the engine is fitted, because they were all cleaned beforehand it only takes a couple of hours to refit and TBH if i wasn't too sure where something went i just checked the earlier pics i took on its way out

i did have a rather noisy nismo paddle clutch fitted, its being replaced by a single plate exedy uprated version

here's a set of shots of the engine dressed

an input shaft from an old skyline gearbox is the best tool to line the clutch up with as you clamp it down but they are not easy to come by...this one was lent to me by tony of abbey motorsport

rigging the engine to the crane is pretty important with a fully loaded RB26DETT, the engine is very heavy and it will snap chains as i found out shortly after taking the three pics above

the rigging broke and the rebuilt engine fell approx 1 meter into paving slabs and into the front of the car, i expected serious engine damage but the block was came down on one of the bottom corners and just took a hole out of one of the slabs before resting itself on the front bumper, scary stuff really

the 250kg engine stand we used during the rebuild was also bent by the weight of the block when the head and sump, turbos and inlet etc were careful out there lol
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mcfly is offline   Reply With Quote
Old 03-09-2010   #2
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Default Re: DIY RB26 Rebuild

All the clearances scare me from doing this on my own...
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Old 03-10-2010   #3
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Default Re: DIY RB26 Rebuild

i just lost hope DIYing my gtr after reading this thread
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Old 09-13-2010   #4
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Default Re: DIY RB26 Rebuild

Really nice DIY guide, a lot of effort put in there! Definitely will be a help when I go to do mine.
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Old 02-19-2011   #5
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Default Re: DIY RB26 Rebuild

Very nice DIY! This is kinda off do I know which valves to buy, OEM size or +1mm.
RB25DET OS Giken STR clutch.
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Old 07-20-2011   #6
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Default Re: DIY RB26 Rebuild

Nice write-up, but where's "the parts we'll come to later" posts??
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Old 07-24-2011   #7
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Default Re: DIY RB26 Rebuild

My GTR used to blow the vacuum hose off the FPR all the time. The pipe was just so worn and rigid that it couldnt seal down anymore even with super glue, so I replaced it. However, I ran it many times with it popping off so im not sure if that could cause the damage you say, as my engine is ok. So what Im really saying here is that the pipe had probably come off from age
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