Camshaft idea

[wildthings]

Has anyone tried narrowing down the lopes on a Type 4 camshaft to the width of the lopes on a WBXer camshaft? Was wondering what that might do to the longevity of the cam and lifters? WBXers seem to go 300K miles without much camshaft wear, whereas Type 4 motors typically see odd wearing of the cam and lifters by 80K miles. For one once the Type 4 lifters wear concave it is impossible to accurately set the lash at TDC as the depth of the cavity is kind of a hidden lash which can't be accounted for but will cause loss of lift, noise, and the valves pounding heavily on their seats as they close.

[Marc]

Type I (and the Type I - based Wasserboxer) have narrow lobes because the lifters which share each one are placed exactly across from each other. Both develop a near-identical wear pattern, and the cam develops one. In operation, to the cam it's almost like it was operating a single lifter at twice the speed.
Type IV displaces the "paired" lifters so that straight pushrod tubes can be used. This makes it necessary for the lobe to be wide enough that both lifters make full contact. The resultant double wear pattern, specifically the points at which the two intersect, is what causes the Type IV cams to fail as they do.
The design cries out for roller lifters - I suspect they were considered in the original plan but not adopted for budget reasons. As produced it's arguably the major defect in the Type IV design.

[raygreenwood]

Has anyone tried narrowing down the lopes on a Type 4 camshaft to the width of the lopes on a WBXer camshaft? Was wondering what that might do to the longevity of the cam and lifters? WBXers seem to go 300K miles without much camshaft wear, whereas Type 4 motors typically see odd wearing of the cam and lifters by 80K miles. For one once the Type 4 lifters wear concave it is impossible to accurately set the lash at TDC as the depth of the cavity is kind of a hidden lash which can't be accounted for but will cause loss of lift, noise, and the valves pounding heavily on their seats as they close.

Just asking.....where did you get the idea that type 4 engines "commonly" develop cam wear by 80k miles?......more precisely.....in what vehicle?

In the vehicles the engines were designed to go into....411/412 and later the 914.....the type 4 engine typically sees well over 100k miles before camshaft wear in the center crossover area of the two lobes becomes excessive. Your results may vary......depending on how lazy you are with oil changes and valve adjustments.
Except in the 914 2.0 liter....which ran hot and had head reliability issues at high miles......typically a well cared for 1.7 or 1.8 in a 411/412/914......delivered about 150k miles before a rebuild was necessary....usually due to valve wear.

The type 4 engibe in a bus?.....buses are overweight, brick shaped parts grinders. A waste of good type 4 parts.
The type 4 engine was not designed with the bus in mind at all. It became a necessity for use as the only larger, inproved air cooled engine in the pipeline....as the growing volume of US spec busses..... driving US speeds in heat uncommon to other areas....combined with the first two issues.....began to take its toll on the type 1 engine platform.

While using the type 4 in a bus was an improvement over using a type 1 in the later heavier buses.....in its detuned, re-geared state....it was underpowered and had a short life.

The primary reason a WBX sees 300k miles before csm wear.....is overall better control of heat snd expansion....due to being watercooled.
Type 1 aircooled engines live shorter lives than type 4....and they have similar lobe structure to a WBX
Its not the cam design. Ray

[Piledriver]

The mid-lobe "notch" on t4s comes from the lifters wearing to the point they are cupped.
The edges of the lifters are hard as hell, as any sharp corner that is nitrided or flame hardened will be.
The other edge just misses the lobe outer edge.
The center area of the wide lobe gets "clearanced" by two lifters.

I have seen T4 cams that go a ~half million miles, >400K after that "failure".
(In other words: It's funny looking, but isn't really a "cam lobe failure" by itself)

Some of the "stock" replacement "German" lifters I have seen have NO radii, absolutely flat as manufactured.
(Febi-Bilstein. They went back)

It might actually be beneficial to pre-grind out that ~useless middle area of the lobe, at least would generate less iron trash. IIRC Jake talked about doing that at one point, I'm sure he at least tried it.

[wildthings]

Here are several pictures that I turned up showing camshaft wear. They are pretty much identical in appearance to the cams from the engines I have pulled down over the years.






I have begun chamfering the faces of Type 4 lifters which seems to help with the wear and certainly gives more lift and cuts down on the pounding compared with hollowed out lifters. These lifters have about 100K miles on them since they were reground to a slight crown and chamfered. The chamfer was much more noticeable when first applied, the face of the lifter has been worn away at this point to where there is little chamfer left, the lifters are only very slightly concave at this point, just a couple of thousandths.



This is the cam those lifters were run with, it had about 150K miles on it when the lifters were reground, the cam was getting a pretty funky wear pattern at that time. It now has about 250K miles on it, it is certainly worn, but the funky wear pattern mostly disappeared in the last 100K miles since the lifters were reground.

[raygreenwood]

Here are several pictures that I turned up showing camshaft wear. They are pretty much identical in appearance to the cams from the engines I have pulled down over the years.




I have begun chamfering the faces of Type 4 lifters which seems to help with the wear and certainly gives more lift and cuts down on the pounding compared with hollowed out lifters. These lifters have about 100K miles on them since they were reground to a slight crown and chamfered. The chamfer was much more noticeable when first applied, the face of the lifter has been worn away at this point to where there is little chamfer left, the lifters are only very slightly concave at this point, just a couple of thousandths.



This is the cam those lifters were run with, it had about 150K miles on it when the lifters were reground, the cam was getting a pretty funky wear pattern at that time. It now has about 250K miles on it, it is certainly worn, but the funky wear pattern mostly disappeared in the last 100K miles since the lifters were reground.

Nice!....and a good test of the chamfering. I have to ask...along with what Piledriver noted....have you felt that even though your other...no chamfered type 4 camshafts developed the "divot"...did you feel it was an issue that required replacing the cam?

In my experience...you only REALLY have an issue with the lifter to lobe interface if you let it go FAR beyond the pale. Meaning...if you let the lifters and cam keep wearing once you find this issue....eventually there is not much supporting the edge of the lifter, they start to get ragged but more importantly the metal it sheds and the excessive load supported by the now flat faced center of the lifter....starts heavily wearing the lifter face or cam lobe.

If the oil was changed regularly with good oil, and the valve train was kept adjusted.....I usually find that what I just described above...happens at around 100k+. A change to new or rebuilt lifters that are properly hardened....will insure the cam survives just fine toward 200K miles....if the rest of the engine survives. But it does not require a new cam.

This is why I commented that a properly/normally maintained type 4 cam is not shot by 80k miles. Ray

[wildthings]

At around 80K miles normally machined lifters are beginning to show concave wear and will begin the process of digging into the cam. If you don't do something to correct the concavity of the lifters the wear to the cam and lifters will accelerate causing numerous problems. It is my feeling that if your added additional chamfer to the lifters when the cam and lifters were new and then reground the lifters once they were worn flat, cam life would noticeably increase and while the engine ran quieter, cooler, had more power, and had less chance of valve/seat problems as a result. I don't think there is a lot of negative with adding the extra chamfer, others may think differently and may prove me wrong if they are willing to do some experimenting.

[Piledriver]

The only downside of a edge chamfer is if you are running a radical cam and need absolutely all the lifters surface.
T1 lifters would be a better plan in that case.

The edges should be broken with a whetstone or diamond hone in any case, as should the sharp edges on the cam lobe itself. I do not suggest using a dremel due to the much higher probability of an expensive oops.

[Clatter]

This is golden.

Nice post Wildthings!

I'll chamfer the edges of the lifters on my next build.
Looks like a great idea..

[Mase_00_7]

How do you chamfer the edges and how do you properly grind a crown into the lifter?

And what would you say has the most effect, the chamfering or regrinding the face?

I'm planning a new 2.0l build for a 914 and want it to last at least 100k miles.

[Piledriver]

Knocking the super hardened sharp edges off the cam and lifters is the point.
A hand diamond hone (usually used for sharpening knives or fish hooks) will work with great patience.
A dremel tool works as well, but with haste comes the danger of unintentional damage.

Regrinding the lifters requires special equipment, there's a place in the US is usually recommended, SLR.
Getting the correct radii and finish is critical. Typically you also get the faces Parkerized to aid break in.

Aircooled.net sells Web Cam/lifter combos with new, reground & coated lifters like this as an option.
The regrind is actually reasonably priced from memory.

[Mase_00_7]

Thanks for that, just seen aircooled.net will re-work a set of lifters for $35 which sounds like a no brainer if it works as above.

Cheers, Paul.