What year triples have cast iron cylinder head skulls?

I am not sure when the four "O" rings were added to the scdalloped out head gaskets, (which also crimps a half moon out of the flame rings) but fairly sure that by 1975 onewards, they all had the "O" rings, (and the squashed to oval one in the crankcase joint) maybe earlier than 1975, someone will know, but they never were fitted to the middle studs that also carry oil up to the cam bearings, there are six in total that do that from the gallerry in the base of the cylinder block, why did they not fit "O" rings to all six, I also have serious doubts that the "O" rings are thick enough, hardly thicker than the gasket in fact, but hey ho in most cases it works!. this could be the source of your oil leak, but before you go and tear it al down, be very, very carefull to check that oil is not dribbling down from a poorly sealed exhaust front pipe, very often this is the case, steam clean the area to cliniclal levels, do a test run, give it the beans, and then watch it for 48 hours.
 
O-rings were fitted from model year '74 at least, Clem.

Around '78-'79, the factory inserted thin dowels in these outer stud bores (required a counterbore in both head and barrel), probably an attempt to keep the o-rings in their place. Attempt was short-lived and soon aborted.

piet
 
Mottoddrob: So the acronym "Skull" indicates Hardened Nitrated Nickel Valve Seats punched into to the Alu- Head Castings ?

My 70 Breganzie 750 SF had that.

Never cared for large heavy cast Iron Valves - Aftermarket replacements made Ultralights in Stainless Steel or Titanium with smaller valve a stem diameters. Of course you had to replace the guides. That goes for any Hi-Perf engine.

Doesn't mean if you pound out the valve seats for, whatever reason, that you do not have to replace the seats but machine them to fit larger valves ;o)
 
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No Ron. A valve seat insert is just that: a valve seat 'ring' pressed into a combustion chamber, whether alloy or not.

A cast iron skull is in place when the alloy for the whole cylinder head is cast around it. So the stuff going on inside the cylinders never sees any alloy.

An all-alloy head means the combustion chamber is part of the actual cast, and valve seats are pressed into place after the casting process. Is this making sense?
 
Back in 1967/68 GM introduced the Nitrated Nickel process for their Hi-Perf SBC LT1 V8's for Valve Seats and Nitrated cast Iron Crankshafts and Engine Blocks - Kind of a powder treatment during foundry shit ?

Have to say the Chevy BBC 454 nitrated cast, cross drilled, crank at less then 1/2 the weight of a forged crank spun faster and did not break spinning beyond 7200 rpm in a 460ci V8 engine producing over 625Hp on pump gasoline with a Marine Cam with a Big Holley 4 Barrel Carburetor.

Gas mileage be damn ;o)

Does this make any sense of your "SKULL" definition ?

I think were are talking about the same thing but the word "SKULL" does not compute in my brain.

High nickel content castings #'s are highly regarded for building endurance and performance engines.

I have to add that word "Skull" in regards to metal urgency to my vocabulary - THANKS ;o)
 
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Laverda SF said:
I think were are talking about the same thing but the word "SKULL" does not compute in my brain.
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Blimey Ron, whats so difficult about getting the idea of a cast iron skull through your skull?

Imagine a tennis ball. Take a knife and cut it in half so you end up with a hemisphere a few mm thick. Now imagine that the half ball is made out of cast iron rather than rubber. Put it in a mould and pour molten aluminium around it to form the rest of the cylinder head, so that the cast iron hemisphere forms the combustion chamber. Machine some ports for the valves and spark plug, and that's pretty much what a Laverda cylinder head is. Although Laverda heads aren't hemispherical, the basic concept is the same.

I think someone posted a photo of a cutaway head showing the cast iron skull a few years ago. I can't find it now though.
 
Dellortoman: Now you are saying "Skull" means a Hemi-Sherical combustion chamber.

We are DOOMED - At least I am now - Even Harley's had a Hemi push rod cylinder head back in the 70's ;o(

Will someone please explain what "SKULL" means - Does it just refer to a Hemi Combustion Chamber - After all, all Breganzies were OHV camshaft Hemi's - SOHC Twins and DOHC Triples !!

With all respect: Perhaps the poster is a Harley Rider getting into Breganzies - Breganzie Enthusiasts just don't use that "SKULL" term because Breganzies's were always Over Head Cam Hemi's ;o)
 
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A simple term can be confusing or what - Love that Skull Chrisk ;o)

Harley enthusiasts named the Hemi Combustion chamber a SKULL so did Dellortoman.

I'm so confused ;o(
 
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Photo of a 750 combustion chamber Ron
And yes I know the value guides are cracked

You can see combustion chamber itself is cast iron whereas the head is alloy
That is what the term refers to, cast iron skull

Some triple heads do not have the cast iron skull chambers and are prone to cracking, a lot
 

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WOW! Red 1st time contact since our conflict - I will definitely give it my best - But you will have to hold on while I ponder about the demise of your Twin - Take that's a Magna Flux Pic showing that crack ?

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Damage like that to me is a sign of impatience after a rebuild to put approx 200 on an engine easily without changing the oil and re-torquing the heads. That's just about an impossible fix without getting a new cylinder head unless you know a gifted Alu-Welder with a Machine shop and it will cost you plenty for the time.
 
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Ron, there is no crack in the skull cap, the valve guide has cracks
Is a simple repair
 
GregT said:
Meds Ron - take the meds please.
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A big swig of Old Turkey might do too!

And it isn't just a Laverda thing either. Honda used this production method for many of their small twins in the '60s, pretty sure it was used in some of their production racers as well. Bound to be others that have used this in times gone by.

piet
 
Meds and more meds _ I did not need them cranking a 70 Breganzie 750 SF Twin up to 8000rpm.

Every other bike including Ducati - Eat your heart out until the late 70's.

Granted the Japanese Bikes eventually beat me - That's why I bought an 84 1100 Suzuki Kantana Gexer over a Breganzie Triple that year for 1/2 the price.

Ist time I ever ever went over 140 mph, on 2 wheels in 1984. Sold her after one season as I was sure she would kill me ;o)

Not saying that at 7800 rpm @ 120 mph+ on a 70 Breganzie 750 SF was not a death ride - But I loved her and kept that ride to the end and a survived a life of motorcycling. Not the fastest but fast enough to win races if you had the guts, concentration and stamina to do it. ;o)
 
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Looks like a bronze guide, Red ... non orig. Trackwork must be finished for the day up there if you're willing to throw a hand into this little ring!! Beer in hand by the pool helping us try and tame Ron!! :LOL:

Ron, did you have as much trouble with 'head' as you did with 'skull' ... nothing unusual about using anthropological terminology in other spheres of science and industry! I could probably reel off about a thousand off the top of my friggin' head!
 
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