EXUP Worldwide

Race day for me lasted precisely six laps. We finally (finally, finally) had the jetting somewhere near right and apart from a slight part throttle cough it was flying. I was just starting to enjoy myself when it staggered on to three cylinders on the main straight...

Long story short, number three cylinder, one exhaust valve folded in half and wedged in the exhaust port, the other one bent and jammed, guides broken etc

It seems my quest for a decent compression ratio has left just too little room for the valves, I suspect its been desmoing for a while and one valve has finally cried enough. Back to the drawing board.

This 911 has been an exercise in frustration. Its got so much potential - before it died it was an absolute joy to ride, a real screamer of a race engine - but it looks like being long road to get it right.

Noooooooooo... that's really bad news Duke. Really not the outcome wanted after all the hard work and thought you put into it.

So what is the plan? A wiseco 1029 piston set, and a couple of new valves and guides

Keep at it Mate, sounds like you are close. I'm putting mine together atm... I'm a bit nervous

Bad luck, but I guess stay with it is the only thing we can say! We need you at the Barry Sheene next year, no??

What about the rest, chassis-wise etc - all ok??

Kiwi thinks I should give up on it and build a 1040, and I did get as far as dragging my old EXUP motor out and looking at it ... but I can't do it. That 911 is addictive

I've got a set of 1040 pistons and EXUP rods and barrels which I was planning to use as the next stage of development, so I'll just have to hurry them up. The Exup pistons have a slight dome instead of the recess in the Genesis pistons, so I'm hoping I can get the high compression without going so tight on valve clearances. The bigger bore means more swept volume which will help. I'm not sure how salvageable the head is but I have a spare race ported head so no rush there.

Chassis wise the bike is fine, not much to do there. Its a fine, stable bike and I do enjoy riding it. All it needs is reliable horsepower. We WILL be at the Barry Sheene...

duke22 wrote:Kiwi thinks I should give up on it and build a 1040, and I did get as far as dragging my old EXUP motor out and looking at it ... but I can't do it.

Did you get a chance to compare the 911 with Kiwi's powerhouse 1040?

I saw the carnage last night - it ain't pretty, but it will rise again

Oh no, tragic!

At least you have lots of parts lined up ready to go, if you hadn't it would
be even more heartbreaking. Still noone likes that to happen.

The 1040 pistons have valve pockets milled deeper to account for high
lift cams and bumped compression, when you check you might find that
they don't have to be milled out any.

Did you get a chance to compare the 911 with Kiwi's powerhouse 1040?

Well I did outqualify him... But then it was his first time back after the Pukekohe dramas. We were never together on the track so no chance to make a direct comparison.

The 1040 pistons have valve pockets milled deeper to account for high
lift cams and bumped compression, when you check you might find that
they don't have to be milled out any.

That makes it even easier, hopefully I can get lots of compression without endless hours of setup. Despite the hole in the piston there doesn't seem to be any bottom end damage (just some bits of aluminium in the sump!) so fingers crossed the rebuild shouldn't take too long.

Duke, any sign of valves touching in the other cylinders?

Ow that damage looks awful. Much sympathy to ya, and hopefully
the bottom end, oil pump etc are all fine (a good chance).

Well I did outqualify him...

Yeah, but I out finished you

Duke, any sign of valves touching in the other cylinders?

No sign of impact but there is some erosion (lots of tiny pits) in all of the other exhaust valve pockets which suggests the valves have been getting awful close. I think this one valve must have had just 0.1mm less clearance, just enough to make contact and start fatiguing away.

I spoke to the engine guy today and the good news is that not only can we rebuild the cylinder head we can (like the Six Million Dollar Man) make it better, stronger, faster...

Sorry 'bout your engine Duke, hopefully with this next rebuild you'll get more than 6 laps out of it.

Motorcycling, Expensive?? Naaaahhhhhhhh!!! What would ever give you that impression?

Racing is like shoveling money into a pit, winning races depends upon the size of your shovel.

As Ozzy's sig says... how do you make a small fortune in racing? Start with a large one!