3.0t 930 engine questions

[quattrorunner]

this is a cross post.
My cousin drove my car and immediately afterward this.

I have some issues with my 930 engine I think along with a case leak I've had for 35,000 miles. Time for a rebuild I think.
This time I'd like to upgrade performance wise.
As far as cylinder size what's the largest reasonable upgrade for the 3.0 turbo case?
Would 3.3 cylinders and pistons fit?
It will go efi this time I'm thinking.

On a side question deserving another post probably, What could a missed shift do to an engine on a mild over rev? My symptoms are a slight rattle type sound around 3krpm under light load. full throttle is not as or at all noticeable. Is that rod bearings?
Thanks

[gumba]

missed shift/overrev could cause bent valves. A leak down test would be a good idea.

[quattrorunner]

I don't even know it happened, I guess we need to ask what else could have happened or if it was just maybe coincidence.

[T77911S]

check for broken valve spring.

[quattrorunner]

Ok.

[TurboKraft]

3.3L P&Cs don't fit the 3.0L: the wrist pins are a different diameter, the rods are a different length, and you'd end up with miserable base compression.

The largest we go on that case without machining is 100mm Nickies, which makes it 3.3L displacement. Add some base compression -- especially given your home altitude -- and EFI, and that will be a blast.

[quattrorunner]

Thanks Chris

[quattrorunner]

I'm looking for broken valve spring but I can't see well enough to tell if anything is broken. Is there something that might be obvious without having to take the valves out?

[Rawknees'Turbo]

Brandon, what you want to do is put each piston on TDC of the compression stroke (aka - no cam pressure on rocker arms) and then look at the springs while trying to turn them as best you can with your fingers, etc. Also, try to lever the spring down with a larger screwdriver, metal bar, or similar and look for one that has too little resistance or moves in a strange manner. Sometimes a cracked or broken section (inner and outer springs) will become obvious when you do those steps.

[Rawknees'Turbo]

Also, here are the tools to actually compress and remove the springs, even with the engine still installed (one for intake and one for exhaust) -

1977 Porsche 911 Turbo Carrera Coupe - Cylinder Head & Valvetrain - Page 4

[quattrorunner]

Thanks bro

[pkabush]

Sorry to hear about that. Any news?

[quattrorunner]

Valve springs look fine. I haven't done anything since draining the oil.
Thanks. Working on a rebuild plan.

[pkabush]

Right on. Bigger, better, stronger and faster. Turbo powa

[quattrorunner]

Exactly

[T77911S]

did you do a comp or leak down.

may just be a lose bracket

[quattrorunner]

Bracket?