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Rb26 Valve / Guide Wear .


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Finally got around to having a look at my RB26 head last night and found more wear than I'd run it with in some exhaust guides . SK once said that this is not uncommon for these heads due to the Japanese refusing to change their oil . By the nature of these cars you'd have to say that most of them have had a hard life in the old country as well .

I'm curious as to why a cam lobe over bucket valve train would allow enough side load to wear the guide (or valve stem) - are the std exhaust guides a little on the soft side ie some sort of exotic Hidural Bronze or some such for better heat conduction ?

Can I take it as granted that K Lines are not an acceptable fix .

The burning question is do these heads eat valve guides over time even with good maint/oil/bit of mechanical sympathy ?

My previous experience of this kind of valve train ie FJ20/4AGE/7MGE is that the guides seem to live forever so this is new to me - though was told to expect it .

I guess this leads into what makes these valve trains reliable long term . A good friend of mine (SC) who's been on the tools for ~ 30 yrs said that while hollow sodium cooled valves are good , if they hit anything they tend to break rather than bend . He was recently given two transverse 4AGE's , one of which had dropped a valve or seat and destroyed the chamber and daylighted the piston .

Obviously no one intends for this to happen but I prefer bent valves to destroyed engine .

Also while I'm here , some in the aftermarket are offering different buckets to go with reduced base circle cams for more lift and alternate material guides . Is this the way to go - dread to think of the cost ? Wish list includes highest lift ~ 260 cams but at what cost .....

Sorry so long but need all the facts , don't want to do it twice .

Cheers A .

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Finally got around to having a look at my RB26 head last night and found more wear than I'd run it with in some exhaust guides . SK once said that this is not uncommon for these heads due to the Japanese refusing to change their oil . By the nature of these cars you'd have to say that most of them have had a hard life in the old country as well .

I'm curious as to why a cam lobe over bucket valve train would allow enough side load to wear the guide (or valve stem) - are the std exhaust guides a little on the soft side ie some sort of exotic Hidural Bronze or some such for better heat conduction ?

Can I take it as granted that K Lines are not an acceptable fix .

The burning question is do these heads eat valve guides over time even with good maint/oil/bit of mechanical sympathy ?

My previous experience of this kind of valve train ie FJ20/4AGE/7MGE is that the guides seem to live forever so this is new to me - though was told to expect it .

I guess this leads into what makes these valve trains reliable long term . A good friend of mine (SC) who's been on the tools for ~ 30 yrs said that while hollow sodium cooled valves are good , if they hit anything they tend to break rather than bend . He was recently given two transverse 4AGE's  , one of which had dropped a valve or seat and destroyed the chamber and daylighted the piston .

Obviously no one intends for this to happen but I prefer bent valves to destroyed engine .

Also while I'm here , some in the aftermarket are offering different buckets to go with reduced base circle cams for more lift and alternate material guides . Is this the way to go - dread to think of the cost ? Wish list includes highest lift ~ 260 cams but at what cost  .....

Sorry so long but need all the facts , don't want to do it twice .

Cheers  A .

i'm sorry if you already knew this but you are awhere that the rb26 exhaust valves run very large clearances i believe because of the sodium find valves that exspand conciderable when they heat up. I found this out rebuilding the last two rb26 (R34,R33) the head shop thought the exhaust guides were gone but once we checked to factory tolerences we found that was how they were surpose to be setup quiet loose.

pete :O

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Have you measured your guide clearence?

RB26 max EX guide clearence is something like .004"

(will feel quite loose with valve in guide)

Factory guides are cast iron and prone to cracking,

I change guides in brand new heads for bronze guides in BIG HP GTRs.

Klines are definately not an option.

I have seen a few bent sodium filled valves (RB26 and others) none actually broken.... yet.

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You'll find if you check the exhaust guides with a 7mm valve seat cutting pilot they will more than likely be ok. They do feel like they are pretty rooted (technical term) if you check them with the valve.

Edited by proengines
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  • 5 years later...

I'm sorry for reviving an old topic, but I've got something to ask.

So there is ABSOLUTELY no need to use sodium-filled exhaust valves if an engine doesn't feature forced induction and I want it to be pretty durable, right?

I'm building a russian engine in 4AGE style, changing all the valves to light 6 mm stem ones. I've got a set of Subaru WRX STi sodium filled exhaust valves, but they would require larger clearences than solid ones, would they? So if I'm likely to build the engine in Toyota durability style, I'm better to switch to solid valves and tighter clearences.

The engine is quite known for burning exhaust valves, that's why I've chosen the WRX STi sodium-filled exhaust valves. (They are almost completely identical, only +0.5 mm in height)

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