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cheftrd

RB Rebuild

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Thanks for that Matt!! I can't wait to see Your write up on timing the cams. This is one area I know nothing about, and I'm sure I can gain something on my motor by properly getting that correct.

 

I just set my HKS wheels to zero, and went with that. I don't have any info on my cams other than being told the lift and duration (and that may not even be correct...). I know I had to clearnce the head for the lob wipe, so they are not stock spec.

 

BTW, great pic showing what needs to be milled for a high lift cam lob to clear the bucket area!

springdone.jpg

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Excellent thread

good pics and info

In my experience with jetski porting and other two stroke engine porting i have found that running in the carbide in a buffing stick stops the alloy sticking to the teeth

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Just a note... I haven't forgoten this thread. My computer crashed and I lost a lot of pictures...

 

In the coming weeks, I'll do the build up on the new race motor going in a long-time friends R34 GT-R. It'll have the full port and chamber mods. I won't really go too much into the bottom end, because it's about the same, but the head is substantially different.

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Great post and thank you sir for sharing your knowledge with others, I have found that most people with the know how, never want to share, which I guess is some what justified but thanks again.

 

I agree. sometimes it's not what you learned or experienced, but it's what you had to do to get to the point to where you had the opportunity to do so.

 

the people with good beating hearts, and heads on their shoulders know the difference between the two, and when helping goes a long way.

 

I think that's why I like this thread.

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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 .016".

ringgap.jpg



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

soldiers.jpg



An army of one. Arias pistons and Carrillo rods.

soldier.jpg



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

carr.jpg



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.

carrtor.jpg



All masked up and ready for paint.

mask.jpg



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

paint.jpg



A few words on studs. Studs are not necessarily stronger than bolts (ARP are). 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.

stud.jpg



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.

head.jpg



The head installed.

headon.jpg



Another shot.

headon1.jpg


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.

http://http://www.youtube.com/watch?v=fv53RbvgfGc

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.



bbrear.jpg



bbbolt.jpg



bbout.jpg



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.

Edited by cheftrd

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Very interesting Matt and thanks for letting the "cat out of the bag" so to speak. I was wondering why I had not seen this return oil mod on all high hp RB's.

 

Another point, is that I have heard everyone and their brother talk about, if you punch out the block to 87mm, the walls will "flex" because of material thickness of the cylinder walls. Good to know that once I rebuild after 86.5mm, I can reliably run 87mm and not have worry to much.

 

I was wondering what you thought about Wiseco pistons?

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Very interesting Matt and thanks for letting the "cat out of the bag" so to speak. I was wondering why I had not seen this return oil mod on all high hp RB's.

 

Another point, is that I have heard everyone and their brother talk about, if you punch out the block to 87mm, the walls will "flex" because of material thickness of the cylinder walls. Good to know that once I rebuild after 86.5mm, I can reliably run 87mm and not have worry to much.

 

I was wondering what you thought about Wiseco pistons?

 

 

Wiseco's about all I use these days. Arias was having a hard time getting their act together where rings were concerned. A couple of years ago I bought around 10 sets of Arias pistons for the 26 and a bunch had the wrong rings... They were "kits" in Arias boxes and had the wrong rings. Some had four correct oil rings and two were the radial wall was too deep, some had ring sets that were for 86mm when the pistons were 87mm, and so on... The rings now come in boxes with sealed packages and high QC, but it's too late. You just can't beat the price of Wiseco kit pistons. They've been in the business for a loooong time. Years ago when import pistons were all custom, I was a Wiseco dealer. I stopped using them when they increased the minimum order for custom pistons to 50 from 24!!! I was like, when am I ever going to use 50 of the exact same piston?? Now that they've got their act back together, I'm back to using them but don't order direct. Race Engineering gives me a good discount on parts so I order through them.

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Interesting, I know they a good following amongst circle track guys here and alot of the domestic V8 guys running them around here, but had not heard a bunch of guys in the RB community running them, good to know, thanks.

 

I received mine last week and has a black coating on the skirt. Do you have any idea what company the skirt is done by? Do you ever have your crown ceramic coated, any negatives on this? I have heard people telling stories of how the ceramic coating came off the crown, got blown through into the compressor blades, found this hard to believe but what experience do you have with these coatings or just steer clear.

 

Thanks

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One of the best descriptive/informative RB build I've read to date. Maybe because you didn't "hide" really anything. Awesome read I just spent the last 1.5 hrs reading through this 2 page thread and it was great!

 

What are you using the seal the rear vent you have on that 26 head? Is there a recess cut for an o-ring back there?

 

As for the quench pad removal. I'm currently starting a build up of an e85 67mm build. Looking to make mid 6's through it to the ground. Car will be mainly street driven/highway car, with the occasional journey to the drag strip.

 

My question (s) for you here is from your experience how much additional timing was a rb26 head able to take with the pads removed, keeping all other variables the same (boost, fuel)? What pistons did you have made, or did you use to bring the compression ratio up? Most say there will be a loss in mid range, and efficiency slightly but how much exactly?

 

What it comes down to is I'm questioning removing the pads or leaving them. I burnt up two rb25 cylinder heads really bad, and the quench area pretty much took all the heat, with no signs of pre-det showing on the plugs, when obviously inside it was blowing itself to bits. This issue was more caused by a ECU/CAS related problem in picking up the cas single properly. (timing was really low values like 15-16 from threshold on at 12-13 psi boost, engine was obviously seeing a lot higher timing that it was supposed to on 93 oct)

 

Any bit of information you can provide would be awesome, I really want a well running mid-higher HP RB to run correctly and for a while, its been a few year process of blowing cash, and engines, while finding the issue far too late..

 

-Cory

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I know cheftrd has talked about all your questions before but i cant remember where. I would suggest search for all the posts he has made in the rb forum and read through them. it may take some time but everyone of them are very informative.

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I know cheftrd has talked about all your questions before but i cant remember where. I would suggest search for all the posts he has made in the rb forum and read through them. it may take some time but everyone of them are very informative.

 

Thanks for the tip Stony, Nice times in your sig too man. Very impressive Z.

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Interesting, I know they a good following amongst circle track guys here and alot of the domestic V8 guys running them around here, but had not heard a bunch of guys in the RB community running them, good to know, thanks.

 

I received mine last week and has a black coating on the skirt. Do you have any idea what company the skirt is done by? Do you ever have your crown ceramic coated, any negatives on this? I have heard people telling stories of how the ceramic coating came off the crown, got blown through into the compressor blades, found this hard to believe but what experience do you have with these coatings or just steer clear.

 

Thanks

 

I've heard the same thing, but have no first-hand experience with the ceramic coatings on the crown. The way I look at it, I've never had a problem, so why should I introduce another potential problem into a critical area? No idea who does the coating for Wiseco, but they're a pretty big company, so they may do it in-house.

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One of the best descriptive/informative RB build I've read to date. Maybe because you didn't "hide" really anything. Awesome read I just spent the last 1.5 hrs reading through this 2 page thread and it was great!

 

What are you using the seal the rear vent you have on that 26 head? Is there a recess cut for an o-ring back there?

 

As for the quench pad removal. I'm currently starting a build up of an e85 67mm build. Looking to make mid 6's through it to the ground. Car will be mainly street driven/highway car, with the occasional journey to the drag strip.

 

My question (s) for you here is from your experience how much additional timing was a rb26 head able to take with the pads removed, keeping all other variables the same (boost, fuel)? What pistons did you have made, or did you use to bring the compression ratio up? Most say there will be a loss in mid range, and efficiency slightly but how much exactly?

 

What it comes down to is I'm questioning removing the pads or leaving them. I burnt up two rb25 cylinder heads really bad, and the quench area pretty much took all the heat, with no signs of pre-det showing on the plugs, when obviously inside it was blowing itself to bits. This issue was more caused by a ECU/CAS related problem in picking up the cas single properly. (timing was really low values like 15-16 from threshold on at 12-13 psi boost, engine was obviously seeing a lot higher timing that it was supposed to on 93 oct)

 

Any bit of information you can provide would be awesome, I really want a well running mid-higher HP RB to run correctly and for a while, its been a few year process of blowing cash, and engines, while finding the issue far too late..

 

-Cory

 

There's a 10mm deep pipe that goes into the head. It's a tight fit with the hole and uses regular silicone sealant.

 

I don't have any experience with E85, as we don't have it in Japan. However, with gasoline up to 600 I don't even mess with the quench pads. Over that and you may take just the intake side. Mid 6's with E85 and I seriously doubt you'd need to take anything out. Alcohol loves compression and boost.

 

As far as the exact amount of power and efficiency loss with removing the pads, I don't have an exact #, but let's say it's considerable. I tell people that removing both pads is a max power drag mod. The pads do more than increase compression and contribute to inert effects. They add to chamber turbulance and increase burn efficiency. It's a trade off. You give up efficiency and response to be able to make the big numbers. But if you don't really need to remove them for 600hp, you certainly wouldn't need to remove them with E85. The GT500 engiens I've seen have the intake side removed, but they're not running E85. That could also be done to unshroud the valves and has nothing to do with knock...

 

With Japanese Esso high-octane fuel and good fuel trimming, I can run 35 degrees of advance at WOT without pulling any timing until around 6-7psi. Without the pads I don't start pulling timing until around 10psi. Too-retarded timing makes for very high EGT's and will burn thins up, as well. I'm a big fan of efficiency in street motors, so as a rule, if I have to pull more than 15 degrees or drop below 11.5 AFR, I throw in the towel and look elsewhere like lowering compression or octane improvement.

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There's a 10mm deep pipe that goes into the head. It's a tight fit with the hole and uses regular silicone sealant.

 

I don't have any experience with E85, as we don't have it in Japan. However, with gasoline up to 600 I don't even mess with the quench pads. Over that and you may take just the intake side. Mid 6's with E85 and I seriously doubt you'd need to take anything out. Alcohol loves compression and boost.

 

As far as the exact amount of power and efficiency loss with removing the pads, I don't have an exact #, but let's say it's considerable. I tell people that removing both pads is a max power drag mod. The pads do more than increase compression and contribute to inert effects. They add to chamber turbulance and increase burn efficiency. It's a trade off. You give up efficiency and response to be able to make the big numbers. But if you don't really need to remove them for 600hp, you certainly wouldn't need to remove them with E85. The GT500 engiens I've seen have the intake side removed, but they're not running E85. That could also be done to unshroud the valves and has nothing to do with knock...

 

With Japanese Esso high-octane fuel and good fuel trimming, I can run 35 degrees of advance at WOT without pulling any timing until around 6-7psi. Without the pads I don't start pulling timing until around 10psi. Too-retarded timing makes for very high EGT's and will burn thins up, as well. I'm a big fan of efficiency in street motors, so as a rule, if I have to pull more than 15 degrees or drop below 11.5 AFR, I throw in the towel and look elsewhere like lowering compression or octane improvement.

 

i must say that you are doing an awesome thing by posting all of the info you have! im sure most of us cant say thanks enough for what you have took the time to post here!

 

so if im reading the above correct that once you would get above 600-650 HP only maybe the intake quench pad would need to be removed? what would be a power level to remove the quench pad/pads? and would it be beneficial to maybe leave them to slightly remove them/round off the edge or is it an all there or nothing situation with them at the powerlevels they should be removed?

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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...

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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.

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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€.

 

ringgap.jpg

 

 

 

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

 

soldiers.jpg

 

 

 

An army of one. Arias pistons and Carrillo rods.

 

soldier.jpg

 

 

 

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

 

carr.jpg

 

 

 

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.

 

carrtor.jpg

 

 

 

All masked up and ready for paint.

 

mask.jpg

 

 

 

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

 

paint.jpg

 

 

 

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.

 

stud.jpg

 

 

 

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.

 

head.jpg

 

 

 

The head installed.

 

headon.jpg

 

 

 

Another shot.

 

headon1.jpg

 

 

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.

 

 

 

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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 :)

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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

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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

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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 [email protected]

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

Thanks all and welldone great post.

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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.

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