RB26 Valve Train - Need Advice

[evilgtr]

So I recently had my engine rebuilt (less then 2000kms ago) and re-used the stock valve train because I was told they are very strong and will support up to 550whp.

Problem is I just found out that I may have a chipped or burnt valve on my exhaust side (found TDC and pumped air into cylinder and heard it hissing out exhaust - repeated the test 5 times with same result) I had my head vacuum tested, ported and polished and springs tested and a 5 angle valve grind done before it was all put back together and everything was good to go. I am having the issue with cylinder no.6 exhaust valves (cylinder no.6 is also the piston I melted when I killed my engine) so these valves have seen some extreme heat and stress.

My question for you experienced RB26 people out there is - what should I do when I have the head off - should I replace the damaged valves with OEM ? should I replace all the valves ? what about the seats ? retainers ? ( sorry if my lingo is out Im not familiar with head pieces or parts) should I have all my springs tested again ?

This is a big job and a expensive one and done want to do this again if I dont have to,I also dont want to sink $1000 - $2000 into the head.

Looking for advice on valve train set ups you guys are running and what works and what doesnt.

My target after this is done will be 550whp with the meth so Id like the top end to handle it,everything else has already been built to support.
thanks in advance for you advice and direction

cheers

[Marke]

RB26 valves are very hearty. They will stand up well to your hp target.

You can get away with just changing the valve that is giving the issue. I would replace the seals, all the valve guides with after market.(OEM are know to crack) seat grind and valve grind.

I actually replaced my guides with Acura Legend guides. All the head work I mentioned cost me about $1400, 3yrs ago. My valves, springs and retainers were all in tiptop shape.

[bobbo]

For those numbers I'd be gettng the head cc'ed, ported, polished and gasket matched. A good head shop will be able to flow test your head and with flow numbers from your turbos, cam specs and a few other required numbers can provide you with "theoretical" hp numbers.

[NismoS-tune]

Some with say OEM engines could do a 9 second pass. Others say the bottom end is only good for 400whp or 450whp. the tuner I used stopped me at 300whp on stock head/bottom end. I've since went crazy on the engine and head but the same tuner will most likely not let me go over 500whp.

If the tuner says it's good, then listen to him I guess OR go elsewhere. Stock valves are good till 800hp but if I had known my engine would be gone so long (4 months or something), I would have gotten better valves. Is your car running fine or is there some problems? I do remember reading why you did the test. Is there a chance you are doing it wrong? The builder you used wouldn't have let your engine go out with that kind of issues... I hope.

[NismoS-tune]

For those numbers I'd be gettng the head cc'ed, ported, polished and gasket matched. A good head shop will be able to flow test your head and with flow numbers from your turbos, cam specs and a few other required numbers can provide you with "theoretical" hp numbers.

I asked about this kinda work but there was no real answers meaning the shop probably didn't know any head shops. Woulda been nice to get everything tested.

[evilgtr]

Hi nismo-stune, yes there is a chance I am doing it wrong lol Im not a mechanic. I tried the leakdown test 5 times with the same result. Lightspeed is going to do a leak down test and also go in with their scope and see if they can identify the problem before they pull the head.
It was NOT the builders fault no,I had Andrew from Ztune (now monkeynutz.ca ) build me engine and as far as Im concerned would be one of the top RB builders in North America. I was allowed to touch the car until it was triple inspected from him after the dyno pulls and everything,he drove it to and from the dyno,after the dyno had it on the shop and went over it with a fine tooth comb looking for leaks and listening for anything abnormal and there was a compression test done before and after the dyno so it had to have been when I had the car which sucks.

Heres the kicker though - The car is making every damn ounce of power it was the day it rolled off the dyno,explain that ? the only reason I found the low compression was I had my plugs out to put new ones in and decided to do a comp test. If I hadnt done the comp test Id be driving it right now like everything was normal. Having a forced air engine sure compensates for alot of things when trying to trouble shoot.

What kind of valves would you have run with ?

Marke - what kind of seals and valve guides do you reccomend and where should i source them ? approx price ?
thanks again guys your awesome as usuall

[Skym]

I would do -

Valve springs (can get valve float with stock valve springs at higher rpm's and sets head up for cams)

Tomei mention rpm, lift that their valve springs can handle -

http://www.tomei-p.co.jp/_2003web-catalogue/e095_valvespring.html

Also a good idea to change valve spring retainer at same time -

http://www.tomei-p.co.jp/_2003web-catalogue/e094_titanium_vs_retainer.html

Valve guides (bronze valve guides as stock valve guides can crack when engine is reved above factory rev limit's and Tomei gives a more detailed explanation of how they fail) -

http://www.tomei-p.co.jp/_2003web-catalogue/e100_Tbelt.html#valveguide

As long as tuner keeps stock revlimiters and produces hp lower in rpm's, stock head can take a pounding. But if they decide to rev engine above stock revlimiters to gain a little bit more hp, the above starts to happen and get increased inertial load on bottomend that can make conrod bolts fail, conrods fail, etc. Nismo keep the stock rev limiters, as they still use stock conrods, etc. So they know what they are doing.

Stock valves are ok and are usually not changed unless the cams used dictate that they need to be changed or head becomes a restriction. Cams, ports and valves work together to produce a good result, but can lose bottomend and gain more mid to topend when oversized valves, porting, more aggressive cams are done. Can gain up to 100hp on extreme ported, etc Subaru? heads.

Usually port matching exhaust manifold to head, port matching exhaust manifold to turbo's (I noticed Nismo do similar exhaust manifold to head port matching, etc with N1 engines, etc) smoothing the ports on intake, exhaust (deshrouding valves, etc) and fitting of cams, pressure testing + reseating valve seats + reseating valves, skimming head to make sure it's straight, fitting bronze valveguides, aftermarket valvesprings, aftermarket retainers, metal headgasket is enough for a 700hp capable engine. Most cams from Japan work with stock ports, valves.

Tomei catalogue has good info on RB engine known problem area's -

http://www.tomei-p.co.jp/_2003web-catalogue/efr_index.html

[NismoS-tune]

You know, after engine damage, even if it's repaired, it's never new again. We never know if the heat changed the metal or anything. I made the mistake of trading my mint block for a blown one (early block) to get rebuild which I now know means nothing different.... My loss i guess. Hopefully the previous failure isn't gonna cause another.

[evilgtr]

Skym - Thank you for the wealth of info wow ! I had a look at all the links you sent and couldnt find any after market parts for my cams,all I found was a/m options for huge lift cams. Maybe I was reading it all wrong ? I am only running Tomei poncams type B. There are 260 degree duration with a 9.15mm lift.

Could you and anyone else reading this please reccomend the valve train parts you would run for these cams ? Like what brand and which parts you would uprgrade ?

As i mentioned I will be shooting for around 515 - 550whp with the Meth,I am running N1 turbos so will prob be around 24psi max Im guessing. If I can I would like to keep the rev's under 7500rpm since there is no need ringing its neck if its not making more power.

NISMO-STUNE - What will you be running for head upgrades ? did you go with the stcok valve train like I did ?

[NismoS-tune]

NISMO-STUNE - What will you be running for head upgrades ? did you go with the stcok valve train like I did ?

Well, I can't say all but I do have everything done except for the valves themselves. Mostly tomei. 5 angle job like you.

[Skym]

Oh, didn't know you had cams already.

Look at bottom of valve spring link for lift, rpm specs of valve springs.

1.) Tomei Type-A valve springs, good for 10.85mm lift max and 8500rpm max and don't need the retainers. If you were reving higher than 8500rpm, then Type B valvesprings, retainers are needed according to Tomei.
2.) Tomei Bronze valve guides

Or some of the best valvetrain parts are made by Naprec in Japan for RB26 -

http://www.naprec.co.jp/e/product/n_rb26/index.html

But probably not as cheap as Tomei. Tomei parts are used on racecar engines in Japan, so are quality parts.

[disrupt]

Sorry to thread jack but i have a few on topic questions. During my rebuild i discovered the exhaust valves had to much play side to side and decided to replace the valve guides.

What clearances are you using for intake valve stems to valve guides and exhaust valve stems (oem sodium filled) to valve guides? I am using tomei valve guides. My understanding is .001" to .003" for intake and .003" to .005" for exhaust.

Ignoring the whole bottom end and oil pump. what is the maximum revolutions for an rb26 head in stock form. What is the limiting item? With everything in spec and balanced i would guess the springs?

[NismoS-tune]

550whp seems like a long shot for N1 turbos. You talking pump gas? R34 N1 though right?

[speedfreak]

Have you rechecked the valve clearances to see if one is too tight?
If you suspect it could be too tight, you could TDC the cylinder then loosen the cam off to make sure the valve is closed.
If you unsure of what to to do then I would suggest getting a shop to do it.

GL with the problem finding!

[mitch32]

Ok I coming into this thread really late and everything that is said I'm kind of going to bash a bit (well not everything), so I apologize.

I built my engine over the winter and dyno'ed it on April, well my valves let go at 8000rpm and with only around 450whp. I had OEM valves, tomei poncams, tomei valves springs type-a, and supertech exhaust guides.

Now after everything in my build I will never ever buy Japanese stuff if I can get it in USA or Canada. Supertech and Ferrea stuff is better then the Japanese stuff and cheaper. Formula 1 and Nascar run Supertech and Ferrea gear, they don't run Tomei, HKS, or Greddy. Ferrea and Supertech will sell you (at a relatively good price) the Nascar and Formula spec stuff. Tomei's valve spring are about 5% stiffer then the stock valve springs (and the stock springs I test the spring against were 20years old vs the brand new tomei's, pretty shitty isn't it).

Now valves you don't buy for power, you buy them for safety. Aftermarket valves do not break they bend, they are forged. Stock valves are press fit, then welded, and then grinded. Stock valves will fall apart and break.

You can get supertech springs for about 200$ and 500$ with the titanium retainers. They will be good for 10,000rpm cause they are about 30-40% stiffer then the stock springs. They also will be good for 11mm lift. These are the single springs I'm talking about, they also make dual springs that are even crazier. Also don't run crazy springs on the stock valves because the caps will break off and destroy your motor (because they are welded and not forged). Welding makes stuff brittle. The welds are seam welds so they are not very thick (i'm talking about stock valves).

If the exhaust valve is hissing your valve is probably bent. Also don't forget valve clearances.

If your stick with stock cams then stay with your stock springs, and go with better valves.