How to turn water into steam

[661]

https://youtu.be/DVl_8IL7Qqk

[rgh0]

Thats nasty

Been their done that also many years ago. I had the head welded up and the chamber remachined and the head is still running happily today

cheers
Rohan

[661]

Craig Beck seems to think this one is best as a coffee table.
The bore on this cylinder needs lining too
He'll crack test the cam

[Vali]

Oh man.

I‘m sorry for you.

[2mAn]

ouch!

[rgh0]

Back when I had this happen new heads or even good used heads were impossible to find in Australia so welding up was my only option. Depending on current costs you may find a new head is a better option these days

The bottom end will certainly need work If i recall correctly in addition to the piston being scrap, the rod was bent in mine also so a new rod and the crank needed straightening. I was lucky and no bore damage

cheers
Rohan

[nmauduit]

aouch... would you mind mentionning the valve material and spring rate ? Any noticeable play in the remaining valve guides (how many race hours since this head was built), or other warning signals (excessive oil down the stems etc)?

[661]

aouch... would you mind mentionning the valve material and spring rate ? Any noticeable play in the remaining valve guides (how many race hours since this head was built), or other warning signals (excessive oil down the stems etc)?

Stainless steel valves, spring rate unknown.
About 900 race miles

[mbell]

So the buzzing noise at ~13s is the valve failing/failed? The bang at ~15s is the valve piercing the water jacket? Followed by lots of steam.

[rgh0]

I would not have expected a valve failure at that distance / running hours assuming your running with a reasonable rev limit of say 8000 normal change point and 8300 rpm limiter

I would be looking for signs of a fatigue crack in the stem to see if that was the cause of the valve head coming off. Hopefully the upper section of the stem is still in the guide ? A little valve float at high revs can cause a valve head to kiss a piston with no significant damage but a slight stem bend can trigger a fatigue crack to then develop overtime. If the original build got the valve seat and valve head not quite seating right until a slight bend was imposed on the valve stem then that also can cause a crack to develop.

I would also be looking at all the details of the valve train assembly dimensions to try to find if anything else was not quite right which may have been a contributor.

cheers
Rohan

[2cams70]

I'd suggest you check all the valve stems and guides for signs of galling and scuffing too. If you run too little clearance between the guides and stems when things heat up they start sticking with Kaboom being the end result. Were they narrowed down "waisted" valve stems?

[661]

I'd suggest you check all the valve stems and guides for signs of galling and scuffing too. If you run too little clearance between the guides and stems when things heat up they start sticking with Kaboom being the end result. Were they narrowed down "waisted" valve stems?

Unknown, I'll enquire.
I had a bit of a misfire for about a couple of laps before the end. It wouldn't pull through the rev range and was reluctant above 7k. I'm unsure what was going on here.
There certainly are some interesting noises just before the valve was lunched

[vstibbard]

Hi Graeme
What a shame, definitely interested in understanding cause in due course and there was any sign of valve guide wear.
Who made the valves and are they standard or undersized stem type that are also necked behind valve face?
On brighter note I had a long call with Seb who we played water polo with, he sent his regards.
Cheers
Vaughan

[Spyder fan]

Ouch Graham!

Your car sounded really nice at Beachy Head, a shame we didn't get to talk further as you had to get away.

Are you going to Malcolms BBQ in the S4 this weekend? I'm there with my +2.

[661]

Hi Graeme
What a shame, definitely interested in understanding cause in due course and there was any sign of valve guide wear.
Who made the valves and are they standard or undersized stem type that are also necked behind valve face?
On brighter note I had a long call with Seb who we played water polo with, he sent his regards.
Cheers
Vaughan

Hi Vaughan,
More enquiries to be made once Craig Beck has looked at everything. Send my best to Seb. It seems like a lifetime ago. ( Oh, it was!)