RB Rebuild

[flatrate]

I just purchased weisco pistons for my RB, as i was adjusting ring gap i put them into the cylinder to see where i was at... my goal was to have a .017 and .018 gap set and the 2nd ring was .023 out of the box a couple were .024 i swaped them from cylinder to cylinder to see if it was a incorrect hone or something the machine shop had done... it wasnt ever run into this with the weiscos? top ring was .013 out of the box...

 

What do you think of the ACL race bearings... i wasnt able to find anything else for a reasonable price...

[Careless]

my oil support rails and top rings were out of spec on my vg33 using 0.75mm oversized pistons and rings. my machinist bored them "slightly" wider, by like a quarter of a thou (those were his words)... which is very small when you think about it. he did it from his experience in building engines that people push to the limits, i guess.

 

But either way, the 0.75 rings were way too large in the gap... so I got the rings for the 1.00mm pistons and they fit right in, the concentricity looks even, and I had to file the gap for the top rings and the oil support rings.

 

I ended up using the second and expander oil rings from the 0.75mm set.

 

starting it up in the coming days to see how it is.

[jengi]

We’re in the home stretch now. I’m going to skip over the stuff like measuring the rod bearing and piston pin clearances because it’s the same as we did back with the main bearings. Same goes for the piston clearance. Measure the bore, measure the piston or pin, the difference is the clearance.

 

With the new rings from Arias in hand, we can set the end gaps. Generally accepted ROT (rule of thumb) is .004†(.1mm) per inch of bore is the minimum gap. This bore is 3.464†(yea, that's 88mm), so the minimum gap would be .014†or .35mm. It’s not always good to use the minimum gap. Engines that have high thermal loading like forced induction, nitrous oxide, etc., should use more gap. If you were running a fuel like alcohol, you could close up the gap a little. Don’t worry if you accidentally grind a little too much and make the gap too big. You could effectively double the gap and not see a decrease in performance. It’ll affect a leak down test, etc., but won’t really hurt performance, especially in the rpm range where you’re making power. I’ve seen engines with broken rings that you couldn’t even tell something was wrong until they were torn apart. Basically, don’t get too hung up on ring gap. Too much=OK. Too little=Very Bad.

 

On ring expander tools: I hate them.

First, if you have a deft hand, it stretches/tweaks the ring a lot less when it’s twisted on by hand. A ring expander that stretches the ring out enough to completely clear the piston is scary business. I used one once and threw it away. If the ring binds up, just stop and back up. People break rings when installing them in a hurry and using the armstrong method. In 25 years of assembling engines I’ve broken exactly one ring, and that was about 25 years ago.

Second, every pro engine builder I know, including the heavy-hitter mainstream guys, installs the rings by hand.

 

Checking the gap .016â€.

 

 

 

 

Soldiers, ready for battle. Once again, don't bust my chops about the "dirty" bench. It ain't dirty!

 

 

 

 

An army of one. Arias pistons and Carrillo rods.

 

 

 

 

The Carrillo SPS bolt. The best and strongest rod bolts money can buy.

 

 

 

 

These rod bolts torque to 65 lbs. Normally I use a stretch gauge, but it’s impossible to get in there, so for the RB it gets torqued.

 

 

 

 

All masked up and ready for paint.

 

 

 

 

Here’s the almost complete short block. Pistons in, studs in, gasket on. Check that shiny new paint job.

 

 

 

 

A few words on studs. Studs are not necessarily stronger than bolts. The main advantage to a stud is that they use a fine thread at the nut end vs. the course thread in the block. This makes for smoother torquing, and allows you to take the fastener closer to the yield point safely. For instance, say a fastener has a yield strength of 200,000 psi. With a course thread, tightening can be erratic from one fastener to the next, so the manufacturer may set the tightening torque to achieve 60% of the fasteners yield to ensure it never goes over. A fine thread like those from ARP is set at 75% of the fasteners yield. That’s 120,000 psi vs. 150,000 psi of clamp force.

 

You never tighten a stud in the block more than hand-tight, or just barely snug. There should be zero upward pulling or pushing of the block threads before the top nut is tightened. If a stud like those from Tomei, with an extension to bottom in the bolt bore, is tightened into the block, it pushes up on the area of the block around the stud, creating a high spot. These high spots guarantee that the seal around the cylinder is a weak one. There’s nothing wrong with the fastener, per say, but in the wrong hands… The ARP studs have a shoulder machined above the threads as a positive stop. If you were to tighten it, it would only clamp the threads together, but would still pre-stress the block in the area around the fastener. Don’t do it.

 

It’s much easier to lube the threads before the head is on. Lube 100% of the threads. Do not lube the threads in the block. You don’t want those turning. If you use a threadlocker or sealer with studs (only in the block), it needs to be tightened within an hour, or so, before the locker sets up.

 

SR20 studs can not be pre-installed like this. The head can’t slip down on the studs and clear the chain guide.

 

 

 

 

Where the power is made. This is a touge engine. The quench (squish) pads stay in place. Much better mid-range power with the pads. This head is pristine. Perfectly flat, with no imperfections, so it’s not getting cut. It’s a waste to machine things that don’t need it. My thought is that you’re taking away rebuild-ability.

 

 

 

 

The head installed.

 

 

 

 

Another shot.

 

 

 

Here's where people are going to bust my chops...

 

It's info I've been sitting on for about a decade and a half. Well, the cat's out of the bag. I know I've said I never did an extra "oil return" on an RB26, and that's true. But I never said (I don't think) I never added anything for crankcase ventilation to aid oil return through the stock pasages. Semantics...

 

Why do I discourage people from doing this mod? BECAUSE YOU DON'T NEED IT! And, if it's done wrong, you'll end up with more problems than you've solved. Originally, this engine turned around 11,000 rpm, boosted way over 30 pounds, and made hp north of the millennium mark. The new configuration doesn't need it, but because the mod is already done to the pan, the parts are there, etc, it's going on this engine.

 

The following three pictures are of the additional crankcase vent. I first started doing this mod on the 26 in the mid 90’s. It’s a common mod for high rpm engines, so it was a no-brainer for the RB26. Soon thereafter, the Internet got a hold of it and speculation as to its function ran rampant. “Additional oil drain-back†became the consensus, and consensus became fact. Now it’s well known as the additional oil drain back mod… Then it became a fact that all the oil in the engine will pool in the head and the engine will blow if you don’t have it done…

 

Really? Let’s examine some facts. The RB26 has been lapping the Nurburgring starting years before the R32 came out in 1989. Lap after lap at full-boogie. Since then, the R33 and R34 have been lapping the same track. The N1 GT-R that races in the N1 class doesn’t have this mod done. Super Taikyu RB26’s don’t have this mod done. I can assure you that the RB26 does not have an oil drain back problem that warrants modification to implement an additional one.

 

On Youtube you can find some videos of the Porsche Turbo engines in a cradle that simulate a run of the Nurburgring to test the oil system. Nissan has the same thing.

 

 

So what’s the deal??

 

Windage and blow-bye in ultra-performance engines. You get an RB26 up in the 10,000rpm neighborhood and lean on it with 2+ kg of boost and you have a nightmare.

 

See, all but one of the oil drains back into the sump on the RB26 are on the left side of the block. When we examine crank windage, that’s the side of the engine where the crank counterweights, rods, etc., are moving in a downward direction, essentially “pulling†oil back down out of the head. In the right-rear of the engine, there’s another port. This port is on the “pressure†side of the motor, and windage blows up this passage, creating an actual suction on the drain-side of the motor.

 

At high-rpm, high-boost, windage and blow-bye gasses can be so severe, that the single port on the right side isn’t adequate. Gasses are moving up all the ports, sometimes at high velocity. This effectively keeps oil from returning to the sump. What the large hose from the sump to the back of the head does is give the blow-bye gasses another path to the head, and allow the oil to return down the normal returns along the left side of the motor. It needs to be above the oil level in the sump, but below the baffle.

 

In a drag motor, if we accelerate forward at 1g, the oil in the sump will stand up at 45 degrees. It’d be neat to hear an explanation of how the oil in the head overcomes the laws of physics and somehow runs forward to the front of the engine. In a circuit/touge motor like this one, oil will indeed return down the hose to the sump because not all of the acceleration is forward. This is the reason it needs to be lower than the baffles in the pan; on that side of the engine, any oil returning will simply be picked up by the crank and added to the hurricane in the crankcase.

 

 

 

 

 

 

 

 

 

 

 

 

What we found was that under these extreme conditions, we were pumping a quart of oil out of the breathers and into the overflow in a 400m pass. Not only was it not returning, but the blow-bye gasses were pushing it out of the engine. Additional vent was added, and the problem disappeared. It needs to be said that in engines turning 9,000 rpm and boosting 1.7 bar, engines making north of 750hp, this "problem" has never presented itself. That, and the problems you can create if it's not done properly are the reason I've been so against it in more reasonable engines. An example is if you put the tube below the oil level in the pan, not only are you choking any venting action, you're giving the oil another place to go during acceleration. Like I said above, oil will leave the sump through the hose.

 

 

Hate away.

 

 

On 88mm. There's talk on the Internet that it weakens the cylinders too much... I don't know what others have experienced, but I've never had a problem. This engine made BIG power for a long time and had two failures. Dropped a valve both times. I don't recommend going all the way out the first time. I leave the bore stock with a new hone, if I can. Then it's up to 86.5mm, and so on. "Rebuildability" (is that a word?).

 

 

Next I'll write up the race head and put that on an engine like this one, but with Pauter rods, a new N1 block, and 280* high-lift cams.

 

This is a brilliant explanation mate, not to mention one fantastic looking motor

[cheftrd]

Hi there, I know it's been a long time. I've been really, really busy. Still intend to do the write up on the race head, but thought you'd like a small video of the finished product. Only 1.3 bar in this shot. A little wheel spin in second, but pretty solid after that. At 1.6 she's still getting wicked awd wheel spin in third, and at 1.9, you've got to have all your players in the game to keep it straight.

 

http://www.youtube.com/watch?v=D1yFXlJYtI0

 

 

Cheers,

Matt

[cheftrd]

For the record: This is not the engne in the above write up. This engine has been running for a lot of years (like 8 or so...), but it's similar. It uses an N1 block, stock 33 crank, N1 oil pump, 272 cams, stock bore Arias pistons, and Pauter billet rods. Half chamber modification. The engine in the above write up, I sold to another guy with a GT-R, and I'll be tuning it in about a week using the Haltech R32 Platinum Pro. The Haltech Platimum management is incredible, so I bought in and became a dealer since we last talked. I'll shoot some video of that car when we get it trimmed out. Then I'll get to writing up the race head.

 

Cheers,

Matt

[Evan Purple240zt]

Nice video, good to hear you are busy!

[Zim Nismo Boy]

Hello and hello again.

This post has to be one of the most informative, most posts always contain the information but never the direct information and advice.

Its necessary to cover all topics and all aspects to make sure the readers always understand.

I have a problem and have broken two rb26detts sadly the first was a conrod through the block because of a bad build not my fault was done by a engine builder.

My second engine well that ran bearings, crank walked ate the block and now i have no engine, no turbos, no clutch assembly .

So im starting from scratch.....

I need all the advice and help i can get solving why my engine failed.

And also helping me choose the right path forward .

I hope to hear from you all soon and if cheftrd is still around then im in luck and will be over the moon to hear back from him.

My email is adam@yoafrica.com

But if prefered i can post pics and some questions about parts.

Thanks all and welldone great post.

[djz]

Very informative thread, thanks very much. I'm in the process of rebuilding the RB26 I just bought, it has spun the #1 rod bearing and scored the first 3 cylinders.

 

Is that an actual aluminium grinding burr you are using in the porting video? The flutes look very close together compared to the ones that I have seen and it doesn't seem to be removing a lot of material.

[rayaapp2]

A stock rb25det direct from japan, never run here in the states. Around 80K miles.

Crank snout

 

See how little drives the pump and the wear on the snout that is present

[KillerZombie]

Hey great write-up. One quetion, how important is it to grind the block for 600hp? And about how much would that cost?

[helghast7]

None of the pictures work anymore....kind of makes the thread a lot less informative

[stony]

I was just looking at this yesturday adn they worked. may be a photobucket issue. Check back tomorrow

[redlinevo7]

No pics for me either. I can host on my server if OP is interested. Would just have to edit links to point to new ones.

[helghast7]

That would definitely be much appreciated since I've been dying to learn as much as I can about these engines.

 

This thread loses so much without those pictures.

[redlinevo7]

More than willing. OP would just have to send me the pics. info@redlinebarbados.com 

[cheftrd]

Woot! Stony's been after me for a while to take care of this... I cancelled the "motorworx.com" contract, and switched over to MJRPerformance.com. All the pictures were hosted on my morotworx server, and I lost them. The pics were on also an external hard drive with a bad power source. I had someone dig  the pics out, and finally got them loaded on the MJR server.

 

Had no idea this was so popular. Sorry for taking so long.

 

Cheers,

Matt

[helghast7]

Woot! Stony's been after me for a while to take care of this... I cancelled the "motorworx.com" contract, and switched over to MJRPerformance.com. All the pictures were hosted on my morotworx server, and I lost them. The pics were on also an external hard drive with a bad power source. I had someone dig  the pics out, and finally got them loaded on the MJR server.

 

Had no idea this was so popular. Sorry for taking so long.

 

Cheers,

Matt

 

Thank you so much, such a wealth of information restored.

[stony]

Thanks Matt!!!!!!

[redlinevo7]

Hey Matt, or anyone else, can you tell me what paint you used on the block? About to mask mine and was wondering what kind would be needed to last with the heat etc. Thanks.

[RB26powered74zcar]

I used plain ol black engine paint from NAPA Auto Parts. It's held up fine for 8 yrs.  I'm not sure how it would stand up to something like carb cleaner or such...