valve hardness is this an issue

[pete roper]

It is relatively difficult to detect this condition without disassembly.

13188[/snapback]

 

Yup, afraid so. made doubly difficult on Guzzi big blocks due to their never smoking even when their top ends are comprehensively 'Donald Ducked'!

 

I agree wholeheartedly with what Jeff says and would hasten to add that there would seem to be something seriously amiss here. While I have not a lot of experience with the 1100 Sport/V11 top ends I do have considerable experience with earlier models up to and including the Big Valve LeMans models and it has been my experience that the bigger the valves the greater the wear of bott valve and guide. The question is why? OK, here's my take on it.

 

If you look at the various different designs of valve it is fairly easy to *roughly* assess where the centre of mass of the valve is. As the heads get bigger this moves closer and closer to the head and further and further down the stem/neck of the valve. Also the larger ports mean that the valve is unsupported for further up it's stem the bigger the induction orifice.

 

As previously noted the rocker sweeping across the top of the valve will impart a side thrust on the valve which will try to rotate around it's centre of mass. This will set up a rocking motion of the valve in the guide and the greater the distance the C of M is from the bottom of the guide the more extreme these loadings are going to be. Another factor is the cam profile. The V11 cam is very close to the old P3/SS grind that has been around for yonks and is, in Guzzi terms, a fairly aggressive profile that will impose condiderably greater side thrust on the guides and valves than the old 'Bumpless' cam us old farts have been giggling at for years.

 

Before you think that this problem of rapid wear is new let me inform you that the 'Big Valve' models with larger than V11 valves and the B10 cam have always been murder on their guides and *sometimes* valve stems. I rarely take the heads off a big valver without having to K-line the guides and quite often, nay, usually, replace at least the exhaust valves. Anything over about 45,000km/25,000miles and they're usually well knackered. Having said that the odd thing is that they very rarely drop a valve!????? They just seem to get floppier and floppier and, yes, performance drops off appreciably.

 

My guess would be that Mike Rich would get valves made by Manley or one of the bespoke valve companies and would probably specify valves of his own design with a different back-shape to the standard units, (My own experimentation with small and mid valve heads has led me to believe that it is largely the back shape, especially of the exhausts, that enables smallvalve heads to flow better than the mid valvers without a lot of radical work!). These amy even have the advantage of moving the C of M a bit further up the stem of the valve, I dunno, Mike's 'The Man' on this stuff.

 

One point though that is worth considering. If you catch the guides before they become loose in the heads, (Rare on Guzzis I've worked on.) then K-Lining them is a far better option than replacing the guides. The scrolled nature of a K-line insert not only holds what minimal lubrication gets in there better than the parent material so it wears more slowly but it maintains the concentricity of valve with seat meaning less material has to be removed from the seat to re-seat the valve.

 

Looking at the pics it certainly looks to me as if there is something not right with the valve stems there though. That sort of wear seems to be uniform along the length of the valve stem where it travels in the guide. As suggested by John or Jeff I'd think insufficient clearance on assembley and the fact that the FI bikes tend to run hotter plus the greater diameter of the port preventing such a long length of stem being available for heat dispersion may be an issue too.

 

Can't really say much more than that. I hope it gives food for thought.

 

Pete

[slug]

 

Do you know any other source than Mike Rich for new valves and guides made of better material than the original ones ? Don't want to say that he is not a good source, because I think that he might actually be the best one, but I would still want to know what are the possible options here.

 

39726[/snapback]

 

 

Ferracci sells their Stainless Race Series valves for $69 each:

 

39.5mm - exhaust Valve - Stock Size

40mm - exhaust valve - oversized

46.5mm - intake valve - stock size

47mm - intake valve - oversized

 

They don't mention anything about valve guides though...

 

- slug

[pete roper]

Ferracci sells their Stainless Race Series valves for $69 each:

 

39.5mm - exhaust Valve - Stock Size

40mm - exhaust valve - oversized

46.5mm - intake valve - stock size

47mm - intake valve - oversized

 

They don't mention anything about valve guides though...

 

- slug

39746[/snapback]

 

Why you'd bother with a 1/2mm increase in valve size is beyond me??? The gains made would be absurdly small in terms of flow. If the valves are of a better material and/or different/better shape then maybe but from a size point of view alone it's certainly not worth paying a premium for.

 

Pete

[jrt]

Maybe to put into the wallered out seats of the (previously) soft valves?

J

[Guest davidb]

69$ per valve... sound like a part off the space shuttle.

[JuhaV]

Thanks Pete and others,

 

Now, when the valves are off from my heads I could use some advice how to perform some mild porting stuff by myself with my Dremel

 

Any pics available from those who have ported heads in their engines ?

 

There must be some basic things that are reasonably easy to do and do not require severe removal or adding of material from the channels ? I am after some kind of "blueprinting" type things just to fix those small issues that usually are there in these "non-japanese" product-line engines.

 

Yes, I know that I could take my heads to an expert, but it is more interesting to learn something by doing even if there is some possibility to go a little wrong.

 

The valves and guides will be replaced with something else than original Guzzi parts.

 

br, JuhaV

[gthyni]

since this is a valve thread I will steal some attention too:

 

I got this tip from a guy with a Norris RR3 camshaft

Jag använder Norris trippelfjäderpaket med titanretainer, som säkert är onödigt kraftiga.

Fördelen här är att de har ett dämpband som ska dämpa eventuella svängningar i paketet.

 

"Norris triple-spring package with titanretainers"

any ideas where to get something like those?

Are Norris still in business? My camshaft is a Megacycle RR3-replica.

[andy york]

I have 31,000m on my 02 LeMans. Docc might be able to say that there has not been a lack of performance in my bike If I get the time to build this motor I will be sure and post the findings on my valves. Right now I need tires more than a valve job( i hope )

 

later andy

[Skeeve]

Thanks Pete and others,

 

Now, when the valves are off from my heads I could use some advice how to perform some mild porting stuff by myself with my Dremel

 

39825[/snapback]

 

There's some stuff on "home porting" on the cage hot-rodding sites; try rooting around in here:

http://www.moparmusclemagazine.com/techarticles/index.html

& similar sites to see what you turn up...

 

G'luck!

[JuhaV]

There's some stuff on "home porting" on the cage hot-rodding sites; try rooting around in here:

http://www.moparmusclemagazine.com/techarticles/index.html

& similar sites to see what you turn up...

G'luck!

39912[/snapback]

 

Thanks,

 

I picked up some of the following stuff from there. Might be interesting also to some others. Here it comes ...

 

 

BACK-CUTTING VALVES :

 

Flow gains can be achieved by back-cutting the exhaust valve. However, the lip on the exhaust side does serve to impede flow reversion--we've already discussed that. Back-cutting the valve 30 degrees (right) relieves the valve of its flow impeding ridge (left). The result--a significant gain in low-lift flow at all levels of modification, and virtually free horsepower.

 

The stock intake valve has a lip backing the valve seat face, which acts as a ski jump to the airflow on an engine where the airflow predominates across the back of the valve. The first step was to remove this lip with a 30-degree back-cut to the valve.

 

Traditionally, a high-performance Wedge, three-angle valve job is performed with the stock 45-degree seat angle, with a 30-degree top cut and a 70-degree bottom cut. While the production seat angle on Chrysler engines is 45 degrees, a properly done 30-degree seat often can pay big dividends, in terms of low-lift flow. Because of the geometry involved at low lifts, the 30-degree seat will open more area to airflow for the same amount of valve lift--this can provide an advantage. Switching from a 45- to a 30-degree seat can be done only when the valve size is increased.

 

Low-lift exhaust flow is significantly enhanced by grinding a radius in the exhaust valve’s margin (arrow, right). This can be done by hand with a grinder, with the valve chucked into a drill press or lathe, and turned at low speed.

 

In fact, back-cutting on the exhaust valve helps improve flow in both directions. So, as much as it helps low-lift flow out of the cylinder, it will promote undesirable reversion when used with high-overlap performance cams. Since exhaust flow from the cylinder is what we are after, looking for improvements to the exhaust valve's profile is not quite the same as with the intake. To help exhaust gas flow around the face of the valve, and outward back across the seat, putting a radius on the valve margin is successful. The radius margin brought low-lift flow back into line, to the tune of a 14-percent improvement at .100 inch over the out-of-the-box big valve.

 

PORT WALL SURFACE :

 

A fine grinding stone can be used to blend the rough surface left by the cutter. Further polishing can be done with the sanding roll. Although the effect on airflow is insignificant, the rougher surface helps promote the boundary-layer turbulence desirable for keeping the fuel in suspension.

 

PORT VELOCITY / PORT SIZE :

 

Implicit with higher port velocity is the notion that the air column is moving faster. Basic physics tells us that a body in motion (in this case, the air column) will build momentum and will want to keep moving in the same direction, even as the force acting on it is removed. In the case of the air within the port, the force acting on the air column is the pressure differential in the cylinder as the piston moves down. When the piston slows as it reaches the bottom of the cylinder at the end of the induction stroke, good port velocity is helpful to continue filling the cylinder, due to the air column's inertia (especially if there is good low-lift flow, as the valve is now closing more quickly).

 

In the exhaust port, many of the same considerations apply. While here, we are not drawing air in to fill the cylinder. Maintaining good velocity helps to scavenge the cylinder of spent gasses to promote good cylinder filling of fresh air/fuel charge. Consider an oversized exhaust port with poor flow velocity. In this situation we have a large, slow-moving tub of burnt mixture hanging around just outside the valve. As the piston reaches the top of the exhaust stroke, lack of inertia in our lazy, oversized port can allow the spent gasses to stop, and actually reverse direction during the overlap phase of the valve timing. This creates dilution of the fresh mix. This effect is progressively worse at lower rpm, where flow rates and velocity are at their lowest. Increased overlap with high-performance cams magnify the problem. The result--an engine that is slow to get on the cam as rpms pick up velocities in the port, and poor low-speed operation.

 

The bottom line: Both the intake and exhaust ports must balance flow velocity and flow capacity to achieve flexible performance over a broad range of rpms--a necessity in a street performance engine. We should maximize the efficient use of the port to achieve the required flow, instead of simply making bigger ports.

SQUISH BAND :

 

If the area between the flat face of the head and the piston top is sufficiently close, as the piston reaches TDC on the compression stroke, the mixture that occupied the area over the piston is forced at high speed into the direction of the advancing flame front. The net effects are faster burn and greater turbulence at the time of combustion--advantages for efficient combustion. This is the squish effect. A second benefit is the mechanical resistance to detonation is improved when a closed-chamber head is used with a close piston-to-head clearance. Detonation begins at an area other than the main flame front. With a flat-top piston, the area opposite the spark plug in the quench area is prime detonation territory. If this area is sufficiently tight, the ability for it to detonate reduces since the combustion at the desired flame front occurs quicker (squish effect), and lessens the time for heat rise in the mixture at the far end of the chamber. Furthermore, the thin section at the squish area exposes only the small volume of mixture to an equally high surface area, diminishing the heat rise in this part of the mixture.

 

br, JuhaV

[Rusty Bucket]

So no response from a high-mile stock V11 owner? Nobody has any thoughts about how this situation might be avoided/ might fail to apply? It would seem that, lacking evidence to the contrary, this problem will afflict all of us, to a greater or lesser extent. I haven't even picked up my new Sport Naked from the shop yet, and I am thinking I will need to shop for new valves already. Drag.

[Guest Brian Robson]

Moderate mileage...73,000Kms in less than 21 months. No oil burning, no oil used between changes, valve clearences remain the same at service intervals, the noise remains the same and compression is normal and equal on both sides...what symptoms could I expect to see?

Buy the bike, ride it like buggery, and if the valves and guides do go, its something you could tackle yourself.

The cost of work can be offest with the savings you make evrytime you service the bike yourself, because it is easy compared to most other brands.

[Steve G.]

Listening to your bike last week Brian, I noted to myself that the mileage that you have on your machine [which I consider moderate, but pat your back at the time it took to rack it up] has actually been good to your engine. It seems to run smoother than mine, less lumpy, like it has nicely settled into itself internally. I thought "thats a bit alright!"

Earlier on in the thread I noted someone talking about stainless valves. No problem there, just make sure you install stainless applicable guides, as stainless has a much more dramatic temperature expansion factor than normal steel valves. I've seen stainless valves get stuck in an engine that got hot.

Ciao, Steve G.