2.1 WBX engine rebuild noob....

[itchyfeet]

Three cams is good if they all have different gears, you can then get a feel for the size you need. Somebody must sell aftermarket 4 bolt gears for aftermarket cams?

I'd bet most of the budget rebuilders are refitting old cams so don't have this problem.

[ajsimmo]

For this very reason, I have a batch of cams (various sizes) away being reground at the moment. Should be back this week, and fitted. I'll post results soon, and if all goes well I'll be sending another boxful to be done.

[itchyfeet]

I remember tencentlife being a little scathing of regrinds.

If you regrind a cam then you will change the profile and you'll struggle to get it properly hardened again I think, tbh the forging they are made from was just good enough for 100k miles

No, none of those things are true. Here's why I won't use a regrind. When it's reground the lift profile is the same, profile meaning the lobe height relative to the base circle radius at any given degree position is reproduced (within machining tolerances). If you measure and plot the action of the reground cam it will produce the exact same valve lift curve. The problem is a simple geometric one: to reproduce the lift profile, the reground lobe's cross-sectional shape is not a simple shrinking of the original, with all dimensions reduced proportionally. The entire lobe is reground, resulting in a smaller base circle, but the same peak height relative to that base radius, and a shorter circumferential lifter travel distance in which to produce the same lift curve. So the primary geometric problem is that the attack angle of the lifter face on the lobe flanks is steepened. The main concern then is that lobe/lifter interface stress is increased during the transition from base circle to initial lift phase on a hydraulic grind, or from the take-up ramp to initial lift phase on a normal grind. The same goes for the other side of the lobe when it has to slow the valve down when it comes to a close, where the stress can be just as high. Initial lift event and last closing phase is already the most stressful part of the cycle and on a reground lobe it is made even worse. Sideforce on the lifter is also increased during those phases, for the same reason, the steeper attack angle.

So, even ground and finished competently, the reground cam will cause a higher wear rate at the lobe/lifter interface and in the lifter guide bores. That's why, to me, a reground cam is false economy. If it were an overhead cam engine where the cams are easily changed, maybe one could argue for the economy of a regrind vs. new, but in a VW boxer or other pushrod type engines where the cam is buried deep in the block and a complete overhaul is required to repair it, I think it's unwise.

Cam's are made of chilled cast iron.

There is only one crank gear size.

Lifter faces can be reground very easily, to a domed profile. Here a machinist will charge $3 apiece.

[sherlylock]

Three cams is good if they all have different gears, you can then get a feel for the size you need. Somebody must sell aftermarket 4 bolt gears for aftermarket cams?

I'd bet most of the budget rebuilders are refitting old cams so don't have this problem.

Yep - having those cams is def. a bonus



L-R

1.9DG cam - 0.038 measured backlash between the teeth.....just noticeable when rocking the cam back-forth

NOS 2.1 cam (+2) - 0.076 measured backlash between the teeth......quite noticeable when rocking the cam back-forth

Original cam from DJ engine I'm rebuilding - can't fit smallest feeler (0.038) between the teeth and no backlash evident when rocking the cam back-forth. Cam doesn't lift out of the bearings when rotating crank backwards either.

Looks like the original cam gearwheel is good to go. Just need to swap the gearwheel across to my new cam......I notice that you riveted yours Itchy? Difficult to achieve? I have access to machine tools to make up some tools if need be (I'll have a look back at your WBXlog in the meantime).

Is bolting an option?

[itchyfeet]

I have tried bolting M7 and riveting but never fitted either in the end so maybe you would like to be the guinea pig, I can help with details.

[sherlylock]

I have tried bolting M7 and riveting but never fitted either in the end so maybe you would like to be the guinea pig, I can help with details.

Yep - happy to be a guinea pig for this - I need a solution after all. The M7 fixing solution looks achievable with the tools I have to my disposal....although I love the neatness and closeness to original spec of the riveting.

How do you tell what size the gearwheel is? The DG cam has a -2 stamped into it.....yet it's got less backlash than the alleged +2 NOS cam! (the +2 has penciled in on the front of my cam so presumably not accurate!) and neither of the other cams have a size stamped anywhere I can see

[ajsimmo]

I remember tencentlife being a little scathing of regrinds.

If you regrind a cam then you will change the profile and you'll struggle to get it properly hardened again I think, tbh the forging they are made from was just good enough for 100k miles

No, none of those things are true. Here's why I won't use a regrind. etc etc

Yes, I have considered Tencent's comments, but decided that it is probably still a viable alternative because there is so little being taken off the base circle. None of the cams I sent were destroyed, they just needed a little cleaning up - maybe 0.5mm. They are also chill cast iron so well suited to regrinding. Similar increases in forces as mentioned are introduced with ratio rockers, with little or no ill effects on these very under-stressed engines, so I think a mild refacing will be fine. I am prepared to try it, and warrant the work.
However, to regrind a cam to a different grind (eg DG or Aircooled to DJ spec) would mean taking up to 2mm off the base circle to achieve the required lift, which is far too much, and all of Tencent's reasoning then makes a lot of sense to me.
We are now in a new situation where it seems there are few, if any, new cams available (of the correct size gear, anyway). Therefore are faced with a stark choice:
a) Aftermarket cam of unknown quality/spec and bolt-on gear which might be made of Chinese cheese, and different oil pump. (a gamble)
b) Genuine new cam with lots of lash, and all the noise/wear/performance issues that may bring with it (horrible)
c) Stick the old one back in as it is (no!).
d) Original well matched gear riveted/bolted onto new camshaft (possibly a good solution* but risk of coming loose)
e) Original cam reground to original spec by Newman Cams.

I'm preferring e) at the moment, but always open to suggestions/recommendations based on others' experience.

*I might also mention that David Newman (of Newman Cams) commented that the "NOS" cam I sent him as a pattern did not look genuine, as it was of a different construction i.e. not chilled cast iron, but most likely hardened steel, and therefore of inferior quality. Now that's a whole new discussion...

[itchyfeet]

It's stamped on opposite side to oil pump, some are not stamped, the one I got NOS from heritage was not and it was sold as the wrong number, if it's not stamped they can get mixed up.

Bolting M7, need high tensile bolts and they were not readily available but are now on ebay, I cut to length, M7 taps are easy to find.
I was going to peen the end of the thread over then I though why not rivet.
https://club8090.co.uk/forum/viewtopic.p ... 5#p8142886" onclick="window.open(this.href);return false;

Riveting you need 6mm rivets not 1/4" which most are, I found them on ebay with round heads flat heads hard to find when I looked.
https://club8090.co.uk/forum/viewtopic.p ... 0#p8158748" onclick="window.open(this.href);return false;

I have tried bolting M7 and riveting but never fitted either in the end so maybe you would like to be the guinea pig, I can help with details.

Yep - happy to be a guinea pig for this - I need a solution after all. The M7 fixing solution looks achievable with the tools I have to my disposal....although I love the neatness and closeness to original spec of the riveting.

How do you tell what size the gearwheel is? The DG cam has a -2 stamped into it.....yet it's got less backlash than the alleged +2 NOS cam! (the +2 has penciled in on the front of my cam so presumably not accurate!) and neither of the other cams have a size stamped anywhere I can see

[itchyfeet]

still a viable alternative because there is so little being taken off the base circle. None of the cams I sent were destroyed, they just needed a little cleaning up - maybe 0.5mm. They are also chill cast iron so well suited to regrinding

good point well made, you are not changing profile.

*I might also mention that David Newman (of Newman Cams) commented that the "NOS" cam I sent him as a pattern did not look genuine, as it was of a different construction i.e. not chilled cast iron, but most likely hardened steel, and therefore of inferior quality. Now that's a whole new discussion...

worrying, how do you know that profile is right?


Any chance of a ball park price from your man? if he has done it for you then I assume he has the cam profile and anybody could send him a cam for reprofiling

I have a NOS DG cam unused if you don't which could be used a pattern? ( but not for sale)

[ajsimmo]

Yes, he has the DJ profile saved in his cam-o-matic machine. He checked all mine against known, and there's 3 x 2.1 & 6 x 1.9, plus the NOS one. I don't know if he also has both DG versions (or the DF). I will find out imminently. Cost is around £50 a cam, so a bargain if it works! Much cheaper, quicker and easier than buying (what might be a lower quality part) from Classic and having to swap the gear. Fingers crossed...

[itchyfeet]

Thanks forthe info
I guess the only way of knowing how they last is to strip one down afer a few thousand + miles.

[itchyfeet]

One issue with bolting a cam gear on is you are using a thread in shear which is not good, the friction of clamping the parts may be enough but under shock stress it may slip and then the thred is in sheer, the rivets could do the same it not tight enough but at least they are designed to be used in sheer.

[itchyfeet]

look closey amd the NOS cam has slightly different shape around rhe cam thrust bearing, flat rather than curved

[sarran1955]

Hello,

Hovering..

I love the charger plug for the electric back hoe..

Cordialement

[sherlylock]

Hello,

Hovering..

I love the charger plug for the electric back hoe..

Cordialement

Haha! Yep - got my digger plugged in.....ready for action.