Rb20det Stroker Motor

[r3240sx]

I recently picked up a set of Neo RB25 rods, and a Neo RB25 crankshaft. The motor was out of a friends car, so I got a steal of a deal on the set. The motor failed due to a clogged oil pickup and thus starved the motor of oil and spun a rod bearring. I took the rods and crank to a machine shop, and they told me they could salvage both.

The machine shop also told me that they need stock specs of the crank so they can fit rod/main bearrings.... Which brings me to question number 1...

1. Would he be selling me oversized stock bearrings? What is the benefit to using aftermarket bearrings over stock bearrings? I have a goal of 500 rwhp, are the stock bearrings sufficient?

My main goal with this motor is to be reliable, and withstand anything I throw at it. I'm not completely sure which turbocharger I'll be using quite yet, but I plan on it being efficient to around 530 rwhp. Realistically I'll never make enough power to max out the turbo, but if I only hit, say, 450 whp, the turbo will make very little heat.. None of this by any means is in a hurry. I plan on buying most of the rest of the parts needed in the beginning of next year, and building a short block outside of the car over the next year. I plan on using the 81.5mm or 82mm 4agze pistons which yields a 2200+ cc displacement correct? Which brings me to question #2

2. On a well sorted 4agze 300+ hp on a stock block is capable (4 cylinder). Will stock 4agze pistons meet my power goals? is it worth the extra money? A set of 6 stockers is about the same cost as a set of 4 aftermarket.

I would like to do as many mods as possible that dont put any more stress on the motor, yet add HP. Since money doesnt grow on trees, I'm thinking about doing used GTR camshafts/adjustable pullies, aftermarket intake and exhaust manifolds.

3. Is a knife edged crank worth the cost of machine work? Are GTR camshafts/aftermarket pullies, intake and exhaust manifolds sufficient head flow mods? Should I not bother with the 26 cams, and save for aftermarket? (costly in the states)

I want to rev this motor to about 8,000 rpm to give the large turbo a little more room to work with. My main concerns with this is my underpowered oil pump drive, lol! As you'll see on the pics of my crankshaft, there is only about 2-3 mm contacting the oil pump, and its wearing down. I will be ordering a Jun crank collar.

4. Are oil restrictors necessary for my application? is an rb20 or 26 or n1 pump necessary? What other oiling modifications should I do while its all apart? I do not want to do this twice!

5. Where do I get a larger bore aftermarket head gasket?

6. Anything else I'm missing?

I really dont want this thread to turn in to an rb20 vs 25 or rb20 vs 30 thread. I live in the states, rb20 motorsets are around $1200, 25's are about $3000, and I've never even seen an rb30. We dont have skylines, so I'm using an s13... which was about $1500 cheaper just in swap parts, than putting in an rb25 in.

This website has given me a lot of usefull information, so I just though I'd share my build with the rest of you guys..

Thanks!

-Max

[r3240sx]

Notice the end of the oil pump drive

Edited December 24, 2006 by r3240sx

[r3240sx]

Machine shop says they need to take 10 thousandths off... But definately fixable.

[DJRIFT]

sounds interesting the biuld up you have in progress.

this link here should solve all your oil control problems. well worth the read as everything sydney kid writes is valuble. http://www.skylinesaustralia.com/forums/in...howtopic=110680

i hadent heard about using a rb25 crank and rods. ive only ever heard about using rb26 items. plenty of people say that aftermarket inlet manifolds are not worth the while. they do look better and can be a bit more practical with intercooler piping but from what i read they give a loss to an already poor low down torque figure. just get it portmatched.

as for exhaust manifold you may need one depending on what turbo you use and a "tuned length" manifold will give better response with the turbo..

rb20 heads are suposed to flow pretty poorly so a good porting and maybe some tomei cams may be the way to go if you are chaseing that sort of power.

hope some of that helps.

[r3240sx]

Indeed it does, thank you!

I always thought the intake manifold was a pretty well flowing design myself, but I figured the reason everyone upgraded these things was not only for convenience and looks, but for less volume. The stock intake manifold is huge! It seems like you'd need a massive amount of airflow to fill that thing quickly. That settles it though, saves me $500-$700!

I read that thread, and yes it is very good information. I guess more of my question would be, how much of that is necessary for my application? or should I just follow that advice religiously and not worry? For only 500 rpm over stock redline I'm wondering if this stuff applies to me.

I would love to port the hell out of my head, and I most likely will do so if I feel confident enough to do it myself. The cash flow has to stop somewhere!

I will most likely be making my own equal length turbo manifold. I might buy a cheap ebay one and just use the design and turn around and sell it once I've made a stronger copy. I believe they flow pretty well, just fit poorly, and are made out of cheap materials.

[fEkuaR]

If you attempt to port a head yourself without any experience chances are you will make it flow worse and uneven. I wouldnt even thing about it..

This is going to be an expensive project ... all the best

Edited December 24, 2006 by fEkuaR

[r3240sx]

If you attempt to port a head yourself without any experience chances are you will make it flow worse and uneven. I wouldnt even thing about it..

This is going to be an expensive project ... all the best

Perhaps I'll leave the stock head on and build a head off the car... swap it on one day when its built properly.

[fEkuaR]

Perhaps I'll leave the stock head on and build a head off the car... swap it on one day when its built properly.

The heads flow is extremely important deffinately best left to a proper engine builder with experience.

[r3240sx]

The heads flow is extremely important deffinately best left to a proper engine builder with experience.

Okay. I'll put in a set of GT-R cams, and call it a day. That is, until I have the money for a real port/polish and aftermarket cams.

Merry Christmas dudes!

[DJRIFT]

im pleased the info helped.

as far as the oil part goes i would try to do all the things listed as RB engines are known of having poor oil control. and oil realy is the life blood of an engine of any specs.

im not totaly sure if GTR cams are an upgrade either. if you have some info on them id be keen to see.

also the standard plenum is so big because it has long runners. long runners are good for low down torque and shorter ones are better for high end power.

[fEkuaR]

info on rb26 cams in rb20 http://www.skylinesaustralia.com/forums/in...l=gtr+cams+rb20

[r3240sx]

Thanks for the help guys.. I've read just about all of that RB26 cam thread, and no one seems to have made up their minds if its a good idea or not (might not be drop in/might not be worth the headache/etc).

Now, I'm still a little curious about my questions 1,2,3 (mostly about knife edging the crank), and 5.

Again I appreciate the help!

-Max

[SoFreshSoClean]

Also dude, I'd say you're going to have a fair bit of trouble getting 500rwhp out of a 20, stroker or not. Especially with the 20 head.

It will be cheaper and more powerful to get an RB25 motor, even with the money you've already spent.

My $0.02.

[r3240sx]

I dont plan on getting 500 rwhp with a stock head. I will build the block first. The head comes next when I accumulate more funds. Final goal of around 500 rwhp.

Regardless, I already have the rb20... Already have the crank and rods. Lets do an over estimation of the costs... Berrings/rod/main, new studds all around/metal HG/crank collar = $1000 Pistons (OEM) = $500 Pistons (forged) = $800 Machine work = $1000 And lets just add another $1000 for kicks and giggles and the other parts that arent coming to mind.

Rb23 = $3500 roughly

Stock Rb25 motorset = $3000-$3500 + New driveshaft, mounts, more wiring.

The rb25 would be another sketchy unknown JDM motor

The rb23 would be completely rebuilt, and I'd know it would be less likely to crap out on me. Peace of mind if anything.

If I wanted to spend more on another used stock motor, I'd just save for an RB26.

I dont see what I'm missing, but let me know if I am missing something.

Thanks,

-Max

[andylaurel]

go buy an RB25DE from the wreckers for $700 and spend the mega bucks on that

youll have a better head to start with, and you wont have to f**k around with linishing the crank and rods.

buy some great pistons, maybe some rods if you are keen

and spend the big bucks you would have spent on your stroker 20, on a really nice new turbo kit from japan.

edit: or build a 30DET and it will turn a lazy 500WHP on 12 psi

Edited December 30, 2006 by andylaurel

[Adriano]

Dude i understand that you dont want to go through an rb20 vs rbeverythingelse, but ive been in a 260rwkw(350rwhp) rb20, and it was too laggy for the street, came on boost between 5-5500, in order to get the power you are eventually after, the conrods will not be close to reliable, what is the intended use of the car?

[legend01]

Hi Guy's

Read this post a couple time but been a bit busy to reply latley as its a bit long winded because im building this RB20 engine atm but using aries 79mm pistons and with the rb25 crank make it 2.108 litre

Q1. I would not be using stock bearings whith your hp goal ,go with the acl race series as there pretty cheap and a good bearing .I'd say he would be pricing you on oversize stock bearings,and aftermarket high performance bearings are normaly made and tested in high hp applications to meet the requirements og high performance engines stock ones arn't

Q2. 4agze pistons are forged so there they are the same as aftermaket and i found the same as you 6 4agze pistons are roughly the same price as a set of aftermarket but where they differ is pin height and pin diameter so you have to pay the extra on having the pistons modified to fit your engine and your rods an added cost. Anthing you do that adds hp to an engine adds stress to it ,its what you do when you build it to lessen the stress loads with better made components that helps make it reliable.aftermaket inlet plenum are one of the last things you will need but exhaust manifolds add hp but get a good one not a cheapie I use a hks low mount cast

Q3.No I would not go the knife edge was looking at this myself and was advised against it, but on an rb20 a short stroke motor it reduces rotating mass something short stroke 2ltr's need, better to go a lightened flywheel but not to light would not go under 5kg as standard are 10kgand no for just exhaust and inlet manifold are not enough by themselves the help but its like putting the small ends of 2 funels together the middle will not flow enough head needs match porting.Im running an n1 oil pump and I have the crank collar fitted here's a pic you need it to use the n1 pump this was supplied and fitted by proengine in Canberra lastly save for aftermarket cams once again I have hks 246 cams.

Q4. In a word YES oil ristrictors are necessary and there cheap and easy to fit. I see you have read the oil supply in rb engines so I dont have to go into it again

Q5 Japan is about the only place I could find that had anything over 80.5mm bore dia unless you went custom made, thats the biggest cometic make

Q6.Well a head gasket is the last thing to buy ,I just made this mistake ofter boring and decking of the block 10 thou taken of the deck height and facing the head 15thou the 1.2mm tomei head gasket I've got is too thin you have to take into account that when you stroke an rb20 your adding 2mm of stroke thats 1mm at the bottom of the stroke and 1mm at the top of the stroke so to keep your squich area's the same you have to add 1mm or 40thou to the thickness of your head gasket in my case i nedded a 74 thou gasket was the thickest i could get so leave this till all machining is done

Think thats answered most of what you asked but just reading through this post I think you rwhp goals will be hard to meet my old r32 made 282rwkw with cams, head ported, aftermaket turbo garrett gt3040r, 550 injectors, sard fpr,front mount ,exhaust manifold ,3.5 exhaust,spitfire coil packs and this new motor will be bigger and better and I'm hoping it reaches 300rwkw and id be happy

Just had a look at ya pricing estimations so I thought Id throw mine in here in sydney Arp head stud bolts $340,Arp main stud bolts $380, rb26rod bolts $180, acl race series bearings $240 rod and main,!st one tomei metal head gasket $470,2nd 1 cometic metal headgasket $280 got it cheap .Crank collar supplied and balanced $400,Pistons got these cheap at $970,RB26 rods shot peend balanced hardened resized and new gudgen bearings $400 got these dirt cheap too I wouls not use standard rb25 rods better of going aftermaket as it will save you putting one through the block there the thinest of the lot we did all the measuremenst on all three rods and they were all the same length rb25 and 26 same size big and little ends rb20 had smaller big end ,Machining must be pretty cheap where you are to get the work on my head done and block machining is costing me $3000 just for that and there will still be more after that

Told you it would be long winded

Cheers Peter

[signalpuke]

Max, I was looking into this idea a while back. This is why I chose NOT to go this route.

I am also from the states (Texas, but currently in Iraq) and I have an RB20DET in an S14 chassis. RB20 parts are a pain in the ass to find stateside, I waited 3 months for a new valvetrain from Japan. So, keep in mind, if you blow something you may be sat back for a while waiting. With the last "fast and the furious" movie parts will start coming in faster, as the demand will grow, but expect the prices to go up as well.

Ok, now on to some tech stuff. The RB20 has a great rod/stroke ratio, and piston speed is slow compared to other USDM engines. That is good. If you stroke the engine, you will end up increasing the piston speed and sidewall stress on the cylinders. Increased piston speed and friction reduce the reliability of the engine and will not allow you to rev as high

As far as porting the head - CFMs only tell part of the story. Your head porter needs to calculate the size of the port relative to the CFM. Any machinest with real racing background will confirm that high CFM numbers mean nothing if the ports are bored out to the point that the velocity of the air is not changed.

This is what I have planned for my RB are anti friction (teflon) coating of the underside of the pistons, the rods and crank. Rotational mass at high RPM is affected greatly by oil on your parts, it adds a lot of weight. With these coatings weight is reduced the higher RPM you go. This in turn will make more horsepower for your motor. And it does not sacrifice reliability or weaken the crank like knifing it does. I also plan on getting the pistons coated on the side and top with other coatings to reduce sidewall friction and to reflect heat from the combustion chamber.

I need to do a lot of reseach for this engine still. The coatings are great for all motors, thats why I am starting there.

[r3240sx]

Well guys I really appreciate the reply's. However, I've been thinking the past few days if I'd like to be waiting for months at a time for parts to arrive. I still really like the idea of a properly done stroker motor, but the cost combined with the time is massively discouraging. I knew there would be a lot of work involved, but it seems as though theres more waiting and BS with ordering the right parts than there is actual building. Like I said, I dont mind the wait... but if this motors going to take years to even drive again, forget it! lol.

I'll hang on to the crank and rods for a rainy day. For now I have a set of GTR cams on order and trying to decide on a turbo that will give me a nice powerband. Besides, a 2500 lb car will be nuts even with 300 hp!

Thanks again, I dont consider the research a waste, just more learning...

-Max

[johan.p.g]

i was planning on doing it the otherway round 20 crank and cons in a 25 block what i wanted to know was is the small end bearings the same for a 20 and a 25 also

does any1 have the conrod lengths and piston hights (small end to top) for both 25 and 20