A question on the point/benifit of the "HI-CAM" motors. DAYTONA ETC

[1down5up]

Why did guzzi go down this route of cam in heads but still with puahrods, rocker gear etc etc.

I get that they are 4v heads, but they could have done this with push rods from the standard cam location...

I get that there is slightly less mass in the valve train, but it's pretty small reduction in weight when there is probably a bigger increase in weight due the the rockers.

Why didn't Guzzi just make a 4v head on the standard big block instead of add the complexity and cost of an idler gear, belts, and and extra camshaft? Even if they went to the expence of lighter more exotic material for the  puahrods and rockers, surely that would have been magnitudes cheaper for the same result?

What am I missing?

[jacksonracingcomau]

A very good question, albeit 30 years too late, especially as the 8 valve Ducati (DOHC , knicker elastic drive from crank) was all conquering by then, our BOT racing at the time became nonsense, twins beat anything, subclass unnecessary.
But, with the right rider and tuner they could compete, one hand tied etc

As a new Lario lover and Irving Vinvent fan, I too think they should have left cam where it was, pushrods to 4 v rockers
A German firm did this in 80’s, mate of mine has a couple of kits
Will happen, they have hp/weight/parasitical loss on their side, will be fast
But 851 and derivatives changed the game forever, we can’t go back and change it with 2022 perfectly ground single camshaft, I wish we could, roller followers, Ti pushrods, valves etc.

[Murray]

They were trying to extract a bit more out of the at the time 30year old castings of the original 2 valve motor. A full overhead cam setup would of made the heads ludicrously tall. There may have been an ambition to offer a 1225 as a factory model (they did eventually) for this the bores would of impinged on the existing push rod tubes. Extra material was welded on the engine casing to give the cylinder studs somewhere to bolt into. Admittedly it had a higher redline spun up quicker and was a lot smoother than the equivalent performance pushrod 1100's at the time. Although I suspect trying to do it on the cheap is what cost them in the end, unexpected issues along with tightening emissions and a long drawn out development period ended up with a sub par solution.

If they had got it to market in C kit form in the very early 90's after its 80's development they might of had a bit more success remembering in the early 90's you could still buy a brand new Moto Guzzi with twin point ignition.

[Chuck in Indiana]

Dr. John needed more power for his race bike. This was a quick way to get it. It was never intended to be a 100000 mile engine like other Guzzi big blocks. (cough cough) Aluminum timing gears. Unbushed oil pump..
Then.. they *had* the tooling, why not sell some bikes with this engine?  Don't get me wrong, I put a lot of miles on mine, and loved it. I maintained the crap out of it, though.

[Tusayan]

The development of the Hi-Cam engine and John Wittner’s racing efforts coming together was a coincidence, not a plan.  Umberto Todero wouldn’t have known a thing about racing in the US when he started development of the engine, and the only reason they learned of each other initially was that Wittner got on a plane and visited Alejandro Detomaso to ask for help.  Todero was then talked into sending Wittner a set of heads etc. but sent worn out development test parts that he didn’t mind giving away. Later on they worked together in Mandello but the engine existed in prototype form before Wittner came calling.

The reason it’s a high cam is the same reason that BMW did the same thing with the initial R1100…. because you have to make the engine package fit into the bike as well as make power, and there are limits on how radical a change should be made in one increment.  In Guzzi’s case it was important to keep the weight low in the frame and the cam drive out of the way of cooling air flow: moving the cam drive to the back of the cylinders (as Piaggio later did) or liquid cooling was beyond the scope of the project. Also, Todero was working essentially alone and although highly experienced he was not a degreed engineer.  The latter point contributed to the heads running hot despite moving the cam & drive off to the side, and to the production delay associated with finding an alloy that would take the heat and still cast into the required shape.  Guzzi was assisted in analysis and finding solutions to that problem by their involvement with the Hunter UAV program, TRW in the US (the Army prime contractor for the Hunter program) had some contacts that helped Guzzi.

After he started using the Hi-Cam engine Wittner had the heads ported in the US and sent them back to Guzzi as patterns to use on the production engines.  Similarly, the cam for the 1100 Sport was developed by Crane Cams because by that time Wittner was working closely with Todero.  Wittner eventually left and G&B got involved for chassis development (on the MGS-01) but the next iteration of the engine didn’t occur until Guzzi’s small engineering department was closed and replaced by Piaggio people in Pontedera.  Todero didn’t ever retire but passed away in 2005, well into his 80s.

[blackcat]

The development of the Hi-Cam engine and John Wittner’s racing efforts coming together was a coincidence, not a plan.  Todero wouldn’t have known a thing about racing in the US when he started development of the engine, and the only reason they learned of each other initially was that Wittner got on a plane and visited Alejandro Detomaso to ask for help.  Todero was then talked into sending Wittner a set of heads etc. but sent worn out development test parts that he didn’t mind giving away. Later on they worked together in Mandello but the engine existed in prototype form before Wittner came calling.

The reason it’s a high cam is the same reason that BMW did the same thing with the initial R1100…. because you have to make the engine package into the bike as well as make power, and there are limits on how radical a change should be made in one increment.  Also, Todero was working essentially alone and although highly experienced he was not a degreed engineer.  The latter point contributed to the heads running hot and the delay in finding an alloy that would take the heat and still cast into the required shape.  Guzzi was assisted in analysis and finding solutions to that problem by their involvement with the Hunter UAV program, TRW in the US (the Army prime contractor for the Hunter program) had some contacts that helped Guzzi.

Thanks, interesting info.

[Wayne Orwig]

I would guess that the load of the extra valves simply means having a push rod that is very strong and heavy. Easy to manage if it is short, but too much weight for a longer push rod.

[Turin]

I just installed the C-kit cams and the cylinder head set up is pretty slick.

[Tusayan]

Turin, what did you do about your pitted cam followers?

[Turin]

I bought new. also bought new valve guides. I have a spare set of centauro heads as well.

I had the new lifters and the cams polished and DLC ( cams lobe only) coated to hopefully help against future wear.



 c-kit on right.

[1down5up]

Yes I guess that the 4v rockers would need stronger (heavier)push rod's, along with probably even stiffer springs increasing the rod's size further......but I would of thought it much cheaper and easier to go to some exotic material for the push rod's than redesign the whole valve train and timing drive assembly

[lucky phil]

I bought new. also bought new valve guides. I have a spare set of centauro heads as well.

I had the new lifters and the cams polished and DLC ( cams lobe only) coated to hopefully help against future wear.



 c-kit on right.

Well I hate to be the bearer of bad tidings but the DLC coating is a mistake in my view, Guzzi applied it to the lifters on the pre roller Griso 1200 engines and it failed causing engine damage due to extremely hard flaked off material contaminating the oil. I've also read opinions of pushrod race engine builders in the states that wont use it due to similar reasons and no great evidence it's going to gain them a whole lot. Currently they can wipe a cam lobe in an engine and not need to do a full strip down to fix it, just a new cam and lifter and clean out. These are engines that use flat tappets due to racing regulations. The accepted upgrade for this cam train is to gas nitride the lifters and the cam. This gives good service and wear reduction. I do like this engine and have rebuild the one in my V10 Sport but I'm probably more aware of it's considerable design limitations than most. I have another on the bench to build as a 95mm bore engine with all the usual stuff like Caruso gears and oil pump etc. Joe is making me a 16mm wide cam gear down from 20mm as well to save some weight.
The head has quite a few design limitations in reality including a lot of oil feed loss points and pretty poor valve geometry which leads to high valve guide wear. Once again a change of guide material and gas nitrided valve stems helps a lot with the wear. Chrome valve stems are quite poor with regards to valve guide longevity in most engines and it's worth using nitrided valves in any rebuild. The heads are also prone to cracking from the valve guide bores and tend to run quite hot and have various points that leak externally. Why did they build it? Not sure precisely but probably because they were hamstrung at the time fiscally and had to work with what they had on a limited budget. I mean why do Guzzi spend money developing hydraulic lifters on an engine with the easiest valve clearance adjustment you can imagine or build the MGS-01 which was never going to be a money maker. The 8 valver is basically a pushrod, OHC hybrid head and why technically it's referred to as a "high cam" engine because it's a halfway house. It keeps the cylinder head height down compared to an OHC engine and also keeps the cam drive system inboard of the head as much as possible on an air cooled engine to allow better air flow from the front for cooling. To use a twin OHC designed head on these crankcases you would need to water cool the head and cylinders as the cam drive would shroud cooling air to the head. Interesting to note that there was only ever 3910 eigth valvers ever made across all models total so they are pretty rare engines.     

Ciao