Rb26 Head - Fixable?

[PHATR32]

hi guys,

looking at the pics, is it possible to get this head fixed? a piece of the valve guide snapped off and fell into the cylinder.

thanks,

steve

[Beer Baron]

bit hard to tell from the pics how deep the gouges actually are, but for starters you can remove the exhaust side squish pads and if it's going to be a big power engine remove the inlet side too. that has now solved most of your damage. the damage in middle should be able to be ported out, and of course do other cylinders to match and have them all CC'd. but bear in mind another head can be bought fairly cheaply, so if you don't want a modded head, just a stocky then I'd just buy another head.

[PHATR32]

thanks for that, problem is finding one here in perth. most people want too much.

[Guilt-Toy]

That looks very min damage.

It will buff out.

rub it with some paper and clean it up a bit and re-use it

[Butters]

Whats to much ?

I am in perth and can recomend someone. As long as your not a knob ?

PM me for details. Done two head squish area removes for me.

Beer baron is 100 % on the money with the solution too. Thats exactly what I would do.

You will end up with a lower compression engine though.

You can shave the head to get some of that back but thats not an ideal way to go.

Solution to that is --> MORE BOOST

[R31Nismoid]

thanks for that, problem is finding one here in perth. most people want too much.

Define "too much"

I mean, a reasonable job costs money, like all good things.

[PHATR32]

what i meant was, people are asking too much for a bare head, i wasnt talking about labour.

I totally agree with paying for good labour though.

I wanna do this right the first time, so im gonna buy another head. I allready have a top notch head dude here in perth, he's a bit pricey but the quality of work is the best.

no point in building up a brand new bottom end, and putting a shit head on top.

thanks guys

steve

[Brockas]

Don't mean to hijack the thread, but who are you guys using in Perth for Head work? Looking for a basic shim and valve guide job for somewhere in the $1100-$1500 range...

[Butters]

I've not found anyone that can confidently handle doing a RB26 guide job in perth

If you do let me know !!

It shouldn't be that hard a job but been a lot of failures around perth from replaced guides dropping or poorly installed guides damaging valves.

[bnr#@]

Had my head done at Bert Vosbergen Head Reconditioning. havent run it yet so cant realy say much but they didnt seem to have any issues. Work done was full recon, jun bronze valve guides and new valve stem seals and all shims replaced to spec with new ones (those were blody expensive from nissan)

[STATUS]

bit hard to tell from the pics how deep the gouges actually are, but for starters you can remove the exhaust side squish pads and if it's going to be a big power engine remove the inlet side too. that has now solved most of your damage. the damage in middle should be able to be ported out, and of course do other cylinders to match and have them all CC'd. but bear in mind another head can be bought fairly cheaply, so if you don't want a modded head, just a stocky then I'd just buy another head.

Hey BB

what is your threshold powerwise for removing them? i have spoken to variuos guys in japan and i get extremely confident answers but in totally opposite directions.... some say that removing both sides is only advisable for drag and over 700hp and another guy says dont do it and to keep the squish within the recommended range. This same guy tells me that the squish area allows for more timing per higher Comp ratio than without.... and he builds pretty nuts 26's....

pm is fine or a link if you done the yards before .

[Beer Baron]

yeah it's a pretty hairy question. squish or no squish? tuners I have spoken to in japan, and guys that have done it tell me this:

for street use only and small turbos leave it alone.

for small-ish turbos, and small-ish cams mainly street use but with some circuit running remove squish zone on one side only (exhaust side). this is the compromise set-up for guys running in the 500-650hp range that still want something cooking down low. mainly good gains come with the ability to run more boost safely, and more timing while you're at it.

for a car that is mainly circuit or drug use remove squish zone both sides. this will definitely cost response, but you can balance that against more boost, more timing, less rebuilds!

this is what the majority of japanese tuners I've been able to ask have told (and shown me). and serious guys here in aus that are willing to share tell me pretty much the same thing. that for big power, removing squish zone allows more detonation threshold so you can sail a little closer to the wind tune wise (well boost and timing).

my new engine will be around the 600hp mark. and it fits nicely into the middle category. and has squish pads removed on one side.

pics ahoy. it's the work of an RB Zen master. with nearly 20 years building RB26s from mild street cars, to 1200ps+. (note: head not compeltely finished in these pics, but pretty close to it)

the head in it's earlier stages:

[Beer Baron]

you can see how much different the combustion chambers are before and after.

and a bit OT, but man your silvia has me sorely tempted....

[Wheezy]

Fark me BB, that is a world of difference with the SZ removed. Im impressed with how much has been removed.

OT: URAS' S13 gave me a chubby when I went for a ride in it, you should buy it

[Beer Baron]

lol, yeah engine will be lightweight now with all that material removed. have a look at how straight the throats are now into the chamber. plus of course usual stuff like lumps, casting marks removed. you can see the difference in the shape of the bowl too. it's probably what I'd call a step 3 head. step 1 is clean up and a light port. step 2 is open out the ports much more, knife edge etc. step 3 is as above but with squish mod, cams, valve springs, maybe larger valves, open up the oil returns etc. . after that all you are left with is a full race head which is a whole new level. exotic valves and guides, big cams, big lift, squish removal, water gallery mods etc. basically the full monty.

the head is really the difference between good engine and bad engine. anyone competent can build a bottom end (check clearances, balance components and assemble), but to get a head spot on takes lots of experience, a little bit of talent and lots of time.

[Butters]

Got any higher detail shots of your exhaust port side after the work has been done ?

The work done to the squish looks really good. Probably better then the ones I have had done.

My old engine is now being used as a daily with a smaller turbo. Doesn't really lack any responce.

I know in theory you loose effeciency as the fuel / air is not pushed towards the spark. I think you would be

VERY hard pressed to tell the differnce in a real world situation though. Impossible to notice seat of the pants at any rate.

You would loose a lot of responce though from the dropped compression ratio. There are ways around that but.

Beer baron what do your engine guys do to avoid the compression ratio drop ?

..

Edited February 1, 2008 by Butters

[Beer Baron]

sorry, don't have any really decent shots of it. when I was there it was not finished, and my friend took the rest of the pics after it was done and they are not so hot.

probably the best one is the third pic. but here is one more. they are substaintialy larger now. I have a pic somewhere before they started with the scribe lines around the exhaust ports and you can see how far out they are now.

found it. here is the exhaust ports 'before' pic.

compression ratio is a combo of things. it gets a bit too detailed for my simple brain, but the deck height obviously a big one, using small gasket also (1.2mm) and pistons all play their part. I'm pretty confident it will be spot on for what I need. they are very good.

[Butters]

That exhaust port work is tops. Taken it out a lot further then I thought they would.

Also help me heaps when I do mine, cheers dude

[STATUS]

fark nice work....

have you seen the cnc work done locally? would it compare to this below? if not looks like i may run the gauntlet and ship the head OS

[Beer Baron]

I haven't seen any 26 heads done CNC here (or in japan for that matter) but I have seen other types of heads done and the result is pretty good. I'd probably still want it hand finished, but the CNC would save heaps of time and get you 95% of the way there for sure. the only question is how good the head was they wrote the program from. if it's good then for sure CNC it, but getting a good head job in japan is not unfeasibly expensive if you know the right people. lol.

the head you posted looks pretty good to my (amatuer) eye. the only things I would look at closely (and it's had to tell just in pictures) is the transition bit from where the squish pads used to be into the bowl. looks like some high spots there (like maybe needs a few thou more taken out).

the photo quality is better than mine though... hehe.