Bent Valve..

[proengines]

bnr#@, it depends what cams you are using. I prefer to fit the heads with no cams so I can use a shorter socket to tighten the head bolts/studs. Have you seen how many degrees a long 10mm allen key can twist when you are tensioning the bolts?

Anyway, just looking at the photo again, is that a metal something jammed between the exhaust valve and the side of the chamber?

[rb26s13]

Talk to the shop who did the job first. As for the Port match, the exhaust gasket means very little, if they matched it to the gasket you have shown your head would be completely f**ked. Port match doesn't mean a match to a gasket, particularly if it's that much bigger. As for the intake, it's not real close, did they have the manifold to match it to?

With one valve being bent, are you sure that all the shims were sitting properly in place when the cams were bolted in after you fitted the head? I've seen similar damage because of this.

exhaust side i wasnt to fussed about.. however the intake side i sent the the whole farken side.. plenum throttle bodys and TB to head adapter all shims were sitting in place proper when cams were put in afterwards

bnr#@, it depends what cams you are using. I prefer to fit the heads with no cams so I can use a shorter socket to tighten the head bolts/studs. Have you seen how many degrees a long 10mm allen key can twist when you are tensioning the bolts?

Anyway, just looking at the photo again, is that a metal something jammed between the exhaust valve and the side of the chamber?

no.. thats were the valve has been smashing the side of the chamber(if its the part i think your refering to).. and you cant fit the head with the cams still in there when using arp head studs

Edited January 1, 2008 by rb26s13

[RB30-POWER]

double check the shim/bucket clearances are to spec when cold/hot whatever the specs list.

double check the cam lobe is the same as the others. (seen defects on this front before, usually not jap cams but)

maybe get that valve spring tested also, might be weak and the valve hung at high rpm and got smashed.

[mjfawke]

If it wasn't an over-rev, I'd be betting on a stuck valve due to the guide not being reamed to size after fitting.

[The Dan]

and you cant fit the head with the cams still in there when using arp head studs

You actually can. Have done so many times.

I know it's obvious but did you have the crank back 15 degrees or the cams in the correct position for assembly when you bolted the head down. Even if you have pulled the cam down and only ever so lightly touched a valve on the piston, you may have bent one slightly. This may have caused a very rough idle/missfire at startup but maybe it just took 100k's for the valve to give up with a 0.001" bend in it...get's stuck in place and waits for the piston to come up and hit it. That would be the only way I could see (given all the above information) that you could stuff only one valve.

If the valve got hit, then bent....it would have got stuck straight away so the guide will show no signs of rubbing etc.

If the valve had a 0.001 or 0.0005 bend in it already then it would have rubbed up and down in the guide for some time before failure.

So the key to finding out what went wrong is to dis-assemble the head at that cylinder and inspect the valve and guide, spring etc.

Either that or you could leave it in one piece and take it to Chilton Engineering in Deshon St Wooloongabba and he will tell you exactly why it failed.

Chilton does engineering work for Ivan and Theo as well as Marty White just to name a few. Very respectable and very honest. Will explain everything so nothing goes wrong.