RB26DETT Head - Fix or ******?

[r32_nate]

So when i bought my car it came with a spare head. Previous owner said he had a low cylinder, so he got a new engine, junked the block, and kept the "still good" head. This being said i started taking it apart now, as im gonna build a head with my new poncams, some manley springs/retainers, and maybe a +1mm exhaust valve bore with new valve seals.

So when I started taking ti apart, I noticed the exhaust cam had a chip or two out of it, and when removed it revealed more chip damage on one lobe.





So then i noticed the head. Theirs a gouge out of the head...







It doesnt seem to have any valve wear or anything out of the ordinary with the valve guide or anything... But for the life of me I cant figure out how this would happen. It would be a pretty serious jump for the lobe to hit the head that far away while still bolted down. The cam caps were all good, none loose. I did also notice a slight wear above the norm on that bearing too.

I guess my question is if this head is worth rebuilding. Im considering taking this to the local machine shop to see if it can be ground out of the head and plained flat. It looks to me like it wouldnt make much difference if repaired (cams are junk), but Im not sure what would cause this, so im timid about the valve guides and if its gonna have issues.

Just looking for input.... Please keep in mind I live in the armpit of canada and no one here has spare heads/blocks. I am still looking for a spare block without much luck cuz no one wants to ship one

[r32_nate]

Also, opinions on valve train with a set of poncam type b. I know these are designed to "work" with stock valve train, but im gonna remove the head and do valve seals regardless, so upgrading the valve train while im in there is a good idea.

This being said, whats suggested as a best bang for buck option for upgrades thats not too much of an upgrade to hinder me? what im saying is for a street/drag car, I dont plan on upping my rpm to a million, but id liek to be able to rev to 7500-8000rpm without worrying once i upgrade my oil pump and bottom end. So would supertech dual spring set be too much? should i get a less stron single spring option? opinions on +1mm over bore exhaust valves?

[r32_nate]

im thinking manley's spring/retainer/lock kit part number 26175k....

http://www.manleyperformance.com/sc/mk/nissan/rb26_kits.shtml

i just dont know much about this stuff... are those spring too much for my set up? will my stock buckets work with them? will stock valves if i decide to not upgrade them?

[caliber676]

It's only the mating surface for the valve covers, if you smooth it out inside and make sure it doesn't interfere with the cam lobes your fine. Your main issue aside from that is a leaking valve cover from an improper sealing seat, which can be fixed with a spot of weld and machined level

[r32_nate]

It's only the mating surface for the valve covers, if you smooth it out inside and make sure it doesn't interfere with the cam lobes your fine. Your main issue aside from that is a leaking valve cover from an improper sealing seat, which can be fixed with a spot of weld and machined level

Oh yeah I know that, im more concerned that the cam jumped or something and now a valve guide is bent or it warped all the cam bearing seats or something...

[caliber676]

Well if your getting new valves I would suggest getting guides. And when you swap cams you should always measure the bore and journal before install to make sure your clearances are in spec for oil and straight edged for straightness. If your doing it yourself and don't have the micrometers then maybe sending the head off with the new parts before assembly for a measuring/inspection would be good, it's not very expensive and worth the peace of mind. The only problem with visuals is you can't necessary see a bent or out of line part when your dealing in thousandths and ten thousandths of an inch/mm

[Skym]

If going to race the engine, then bronze valve guides are worth it to prevent cracking due to heat, constant high rpm. If street use, then stock valve guides would be best for longevity.

HKS sell some upgraded valve seals.

Valve size, that wouldn't be changed unless you change the port size and are running aggressive cams to suit, upgraded intake, exhaust manifolds, alot of boost. Cylinder head shop would advise on what's best for your application based on what mods are on the engine. If stock head, intake, exhaust, etc, Poncams, camtiming adjustments is all you need.

If changing valve springs, lifters, etc, might as well get the 270 duration Procam, lifters, valve springs to suit. More power, torque throughout the powerband.

Valve springs tend to sag over time, so make sure they are rated above the rev limit, lift you want and have washers to bring the valve seat pressure up to standard (Tomei sell these washers).

[r32_nate]

Well if your getting new valves I would suggest getting guides. And when you swap cams you should always measure the bore and journal before install to make sure your clearances are in spec for oil and straight edged for straightness. If your doing it yourself and don't have the micrometers then maybe sending the head off with the new parts before assembly for a measuring/inspection would be good, it's not very expensive and worth the peace of mind. The only problem with visuals is you can't necessary see a bent or out of line part when your dealing in thousandths and ten thousandths of an inch/mm

Yea im gonna take it to a machine shop to get it checked. As for the guides.... I drive street occasionally and drag race maybe 3-4 times a year, but that being said I dont wanna half ass build this either. Im thinking stock guides would be fine unless one is bent, then ill upgrade them all.

[r32_nate]

If going to race the engine, then bronze valve guides are worth it to prevent cracking due to heat, constant high rpm. If street use, then stock valve guides would be best for longevity.

HKS sell some upgraded valve seals.

Valve size, that wouldn't be changed unless you change the port size and are running aggressive cams to suit, upgraded intake, exhaust manifolds, alot of boost. Cylinder head shop would advise on what's best for your application based on what mods are on the engine. If stock head, intake, exhaust, etc, Poncams, camtiming adjustments is all you need.

If changing valve springs, lifters, etc, might as well get the 270 duration Procam, lifters, valve springs to suit. More power, torque throughout the powerband.

Valve springs tend to sag over time, so make sure they are rated above the rev limit, lift you want and have washers to bring the valve seat pressure up to standard (Tomei sell these washers).

Yea Manley have upgraded valve seals as well.

All I was thinking with teh +1mm valves is if Im gonna be inside replacing everything anyways, and having the head at a machine shop getting cleaned and spec'd, why not overbore the exhaust valves. But now Im thinking it would make much difference with the poncams, and the stock valve would likely be just fine with an angle job done.

So someone tell me, whats a valev spring/retainer kit that would be like 1 or 2 steps above stock? I might just build with new stuff so 25 year old things arnt inside the head, since I wont really benefit much off this stuff

[r32_nate]

stupid question, but with upgraded valve springs like the manley which are good to 13.5mm lift, would i still need shims?

[Skym]

Exhaust port matching to exhaust manifolds and to turbo exhaust housing inlet makes the engine a bit more peppy (I think revs quicker) and removing the bumps, etc in the ports helps the flow (what most people do).

Some remove the quench pad area (area around where the spark plug pokes through the head) on high hp RB engines to prevent knock. From what I understand removing the quench pad adjust's the angle of the explosion, shock waves. There's many opinions on when or if the quench pad should be removed.

With valve springs, the Tomei Valve springs are said by Tomei in their online catalogue to require the washers to bring the valve seat pressure up to standard. Would have to check with cylinder head specialist or Manley about if their valve springs require washers to get correct valve seat pressure.

Can fit a Tomei 270 duration Procam kit which includes (for racing) bronze valve guides, valve springs, lifters, shims, Procams, camgears and need a ECU tune to suit. Also the washers.

But check with the extra lift from the cams that the head doesn't need to be adjusted for the lobe to clear without fouling the head. I can't remember what lift it does it at. I think was 10-11mm lift, but might be wrong.

[r32_nate]

Exhaust port matching to exhaust manifolds and to turbo exhaust housing inlet makes the engine a bit more peppy (I think revs quicker) and removing the bumps, etc in the ports helps the flow (what most people do).

Some remove the quench pad area (area around where the spark plug pokes through the head) on high hp RB engines to prevent knock. From what I understand removing the quench pad adjust's the angle of the explosion, shock waves. There's many opinions on when or if the quench pad should be removed.

With valve springs, the Tomei Valve springs are said by Tomei in their online catalogue to require the washers to bring the valve seat pressure up to standard. Would have to check with cylinder head specialist or Manley about if their valve springs require washers to get correct valve seat pressure.

Can fit a Tomei 270 duration Procam kit which includes (for racing) bronze valve guides, valve springs, lifters, shims, Procams, camgears and need a ECU tune to suit. Also the washers.

But check with the extra lift from the cams that the head doesn't need to be adjusted for the lobe to clear without fouling the head. I can't remember what lift it does it at. I think was 10-11mm lift, but might be wrong.

Hmmmmm im gonna have to call manley again tomorrow and ask about the washers like tomei lists...

as far as i know anything with 10mm+ lift needs head work, the poncam type B is the largest lift drop in cam. they also dont require adj cam gears cuz they are both optimal at 0deg. I ahve haltech pnp.

Ive decided on reusing the stock valves and guides (as long as all are good), buying the manley spring/retianer/lock kit, and new oem seals. Decasting the valve bowls and removing exhaust hump and building from their. now i gotta check on the washers. so these washer would be added to the seats?

[r32_nate]

For the record, I decided to have the head decked, filed the little pieces from old damage down smooth, am using it. I ported and polished the exhaust, and went with the Manley 26175K kit, which seems to fit and work fine so far.