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KZR750R1 2006 OBXT Head Gasket/Motor Refresh


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Replace with two used low-mile heads, if they measure out okay. I do a lot of tunes for a shop that has a large stock of parts, so we can horse trade.
Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Well He said I'm at the 99.55mm mark now and need to go to 99.75mm bore.

Going to drop in on them and confirm the other work to complete since they are ready to roll on this.

 

Writing it down here so I don't forget anything.

Inspect the crank and confirm main bearing size.

Confirm rod bearing size

Confirm wrist pin bore size

Deck heads, will likely be needed

Lap or cut valve seats depending on condition

Clearance the valves to spec lash

See if the block needs decking, do it if needed

Bore and hone to 99.75mm, if I can't get away with the 99.55mm

 

Anything I'm forgetting?

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Reading though these build threads is overwhelming. Just so many small details to keep track of.

 

Thank you for writing it all down. Not sure that I could do it though. Just so many small details.

 

Agreed - I wouldn't have the time nor the courage to attempt it..

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Back on track. Confidence is high on the .25mm bore needed.

Ordering pistons now. Infamous Performance just received my largest parts order to date.

Will pick up standard rod and main bearings and well send the lot over for crank polish and balance.

Head operations are understood. They are nervous about the sodium valves but well cross that bridge when we get there. I'm hoping they can relive the valves a bit and avoid replacing all the buckets.

Edited by kzr750r1
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Yeah, maybe, but I swapped some good heads for tuning services... can't swap welding for tuning, even if it is worth less ;)
Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Remove both banjo filters.

 

You do know that head can be welded, machined and reused.

Passenger side was pulled long ago and drivers side last week. I'd consider both clean... But gone now.

 

I have the V1 Infamous filter kit. Once I get paid will call mike to invoice me for the second hose to replace the old capped hard line.

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****. Just heard back from the machine shop that one of my bores is just enough out of round that my 99.55mm pistons can't be fitted. It's too oval to hone round and there's not enough meat on the large dimension to bore and then hone to the correct diameter.
Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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****. Just heard back from the machine shop that one of my bores is just enough out of round that my 99.55mm pistons can't be fitted. It's too oval to hone round and there's not enough meat on the large dimension to bore and then hone to the correct diameter.

 

Ouch. Are you going to sleeve it or replace it?

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Ouch. Are you going to sleeve it or replace it?

Ouch indeed. I am so pissed. If I'd known this a month back I'd have a new factory shortblock in the car already. As it is, I'm no closer to the car rolling again than I was a month back, but the bill keeps getting bigger.

 

At the moment they are saying it's just the one cylinder and it's just slightly out of spec. They can hone it but it won't be round, and it's far enough out that it can't be bored. They do say it can still be bored to 99.75mm, which is not ideal. It's less meat on the liners than I wanted, but it's better than 100mm and since I can't wait another month to get another shortblock here (shipping) I don't have much choice. Now I'm waiting to find out how long it's going to take to get a set of 99.75mm pistons here.

Edited by fahr_side
Holy run-on sentence Batman!
Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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I'm hoping my 99.75mm pistons are in the first shipment from Infamous... This way I can get them rolling on this. I'm hoping for motor install by the end of October.

 

Just so I am clear. Old engine was too worn to use OEM pistons which is why you went with slightly larger after-market ones?

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Oh I can get OEM oversize pistons but who wants cast pistons if you can go forged. I was glad far_side turned me onto Manley. Initally I was thinking going CP.

 

Manley offer several sizes including A and B variants. Next bore up is a mere .05mm over stock 99.50. I'm at this mark so need to go to 99.75.

 

With Manley there is A/B 99.50, 99.55, 99.75 and 100mm. Plus their all coated skirts.

 

I would likely never trust the wall thickness at 100mm with 15lb of boost.

 

With the 99.75 I may get away with more boost but its probably not going to last long so I'll probably stay at stage one and just keep it running.

 

The transmission isn't going to last forever either.

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I don't think 99.55 or 99.75mm is going to make much difference at normal sort of boost levels. Unless you're running into the 20psi and above range the 0.20mm of meat isn't going to make that much difference. If you look at the guys who have split liners, they are always running well over 20psi.

 

My plan is to carry on running my current 18.5psi tune with meth, and adjust timing as needed to suit the new compression ratio. My powertrain mod list for reference...

 

99.75mm Manley piston kit

ARP L19 head studs

Siruda 1.00mm metal gaskets

ACL rod bearings

Gates timing belt kit

72* OEM thermostat

Tomei Expreme EL header

Invidia catted downpipe

Perrin silicone turbo inlet

Perrin TMIC

Mishimoto aluminum radiator

Snow Performance water/meth injection (#5 nozzle)

BNR VF-40 / TD05H hybrid turbo with proprietary billet 18G compressor

HOA 3-port EBCS

Stock injectors

GRB OEM fuel pump

GRB 6MT

GrpN engine & trans mounts

DCCDPro diff controller

GRB stock clutch & flywheel

GRB prop shaft

3.545 R160 with AP Suretrac diff

Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Rebuild novice here, I've never torn an engine apart. I've been following this thread because engine rebuilds are always interesting to me. Can someone please tell me why the cylinders become worn in an oval way? My logic tells me it's because in a flat engine, maybe gravity takes a toll and the "bottom" of the cylinder wears more because of the weight of the piston? Is this a good guess or am I completely off track? Thanks.
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Oh I can get OEM oversize pistons but who wants cast pistons if you can go forged.

...

With the 99.75 I may get away with more boost but its probably not going to last long so I'll probably stay at stage one and just keep it running.

 

The transmission isn't going to last forever either.

 

:confused: So, it's not going to last forever, and "probably not going to last long", but might as well get forged pistons? Wouldn't OEM oversize be significantly cheaper and last as long as the rest of the car? Not criticizing, just curious.

 

I'm constantly debating about my car - 108K, almost 10 years old. How much longer will she go? I'm hoping another 4-5 years, 40-50k more. I have a few issues, but nothing major at this time. At what point do I just keep driving it until it breaks? I mean, if my block went tomorrow, I'd be really torn between dropping $10K on a full rebuild and transmission rebuild, or selling the carcass for $5K and putting that $15K towards a new car ('15 WRX?)

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