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65Mm Pistons - Ie Stock Bore For An New Rb26 Block

djr81

By djr81,
in Engines & Forced Induction

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djr81
djr81

After a great deal of messing about - the ACL piston is a no go. I actually had the things but for whatever reason the top piston ring came with far too much end gap. ACL no longer make the rings an

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BuuBox Enthusiast

BuuBox

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Posted

Good to see your build is progressing.

It's a bit of a shame that you didn't end up trying a 1.5mm top ring. The results would have been interesting. I can't help but think there's a reason Nissan specified a 1.5mm top ring for the factory engine.

  • 1 month later...
djr81 Grand Master

djr81

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Motor is back together and working. Some random thoughts.

1. Removed the back of head oil drain.

2. The oil cooler/warmer standard on an RB26 has got some weight to it. Removed that and replaced it with an RB20 unit (Thanks Troy). Running a filter with an oil relief in it now.

3. Drilling out the oil returns in the head is actually harder than people make it sound on the interweb. They are quite lengthy and the top is a little difficult to get to.

4. What I was told about the ring gaps in the old engine was a pack of lies - they were bigger than quoted.

r33_racer Grand Master

r33_racer

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I can relate with number 3. Cast is never very nice to drill, especially over great lengths. I think from memory I had to use long series 9mm drill bits. Then slightly blunten off the cutting edge so it was not so 'bitey' and want to pull itself through so aggressively.

What were the old ring gaps?

  • 2 months later...
djr81 Grand Master

djr81

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Well the thing is back together and on the dyno. Problem now is it wont run more than 16lb for 410 horsepowers. Will run to 22 with the wastegate shut but the boost controller wont allow over 16lb. Bov's are fine. Actuators are HKS on -5 Garretts. Boost controller is a Blitz dual solenoid type. Any one with any clues?

Tonba Rising Star

Tonba

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Yes.

Tomei were my start point but I couldn't find a reference to an 86mm piston, only oversize ones.

Didnt look at ACL or Nitto (Not that the NItto list has an 86mm size anyway) because I didnt want to use them.

Have CP pistons currently and given the issues I have dont want to go back there either.

Nitto pistons are actually made by JE Pistons. Great bit of kit. They make custom items, so IMO, they are the best bet. If you know the size of your combustion chambers, deck height, and what head gasket you intend on running, you can order these with a custom crown / dish cc, thus giving you a custom and a lot more suitable compression ratio.

djr81 Grand Master

djr81

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More info?

Does the power go up when you disconnect the WG and let it overboost or is it stuck on 410?

AFAIK it goes harder than 410 with more boost but I didnt ask for a number as I was short of time.

It was described to me as a boost control issue so the question is:

A set up issue with the controller - something stupid like hoses the wrong way about?

A component failure with the controller eg a stuffed solenoid of the twin solenoid controller?

Please note: I dont doubt the workshop those are just simplistic examples by way of um, examples

  • 1 month later...
djr81 Grand Master

djr81

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Went to Collie on the weekend. For those who arent from WA it is a small country circuit which takes 50 seconds to get around. It is anticlockwise and if your engine is having oiling problems then Collie will show them up. Anyway the bottom line is there was no more than three drops out of the breather all day. So I am claiming victory and moving on.

Need to find a workshop now to sort the boost controller.

Jazzadub Enthusiast

Jazzadub

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Good news! Do you think the tighter ring gaps was the main factor in reducing oil entering the catch can?

How about deleting the rear head drain? Do you think that had any bearing?

djr81 Grand Master

djr81

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Good news! Do you think the tighter ring gaps was the main factor in reducing oil entering the catch can?

How about deleting the rear head drain? Do you think that had any bearing?

Honestly, no I dont any more. I did fixate on it for quite a while but the gaps in the piston rings I have arent at the low end of what people use and they work fine. I reckon its a combination of the Pacific Engine Parts rings and the CRC bore lube on start up followed by driving the thing immediately on engine start.

As for the drain, yes I pissed it off. Used the return in the sump as an extra vent for the blowby. Probably doesnt make a huge difference if your blowby is under control. Probably helps if it isnt.

SimonR32 Grand Master

SimonR32

Posted
Posted

Honestly, no I dont any more. I did fixate on it for quite a while but the gaps in the piston rings I have arent at the low end of what people use and they work fine. I reckon its a combination of the Pacific Engine Parts rings and the CRC bore lube on start up followed by driving the thing immediately on engine start.

As for the drain, yes I pissed it off. Used the return in the sump as an extra vent for the blowby. Probably doesnt make a huge difference if your blowby is under control. Probably helps if it isnt.

Glad to hear you have it under control!

I'll be interested to see how mine goes if/when I get down to Collie, venting the sump seems to make all the difference

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