Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing King pin options

Does your car have the Devol bushes?
If it does 27k seems early to need to replace them

There is a lot to read here on the subject

http://www.gomog.com/allmorgan/Greasing2002to2006.html

I have used Devol bushes and Hard Chrome pins on My +4-4Str for many years and miles without problems. If I had to find a problem I would mention Devol's and Vesconite have a tendency get and retain road grit acting like a file on the KP's. I recently inspected the +4 and merely turned the KP's 180 degrees and washed the road grit out with carb cleaner. I personally like Vesconite as it is self lubricating. But I am geared up for this material and it is easy for Me to use it. If I were to start over, I would use MULFAB's bronze bushes and Chrome KP's. I would need to buy a suitable long reamer. They are very expensive. I do not think the cheaper adjustable reamer are up to a quality job. Or at least the one I am using for Vesconite is not. Actually if I used bronze I would have My Machinist do the job on His Sunnen Hone (Not Inexpensive).

Personally, I would not consider the expense of having the kingpin bushes honed on a honing machine. There really is no point in such precision.

The problem that you have with the Morgan setup is that once in dynamic conditions, (actually in use rather than laid out on a workbench) is that all the forces when cornering and braking cause both the kingpin and stubaxle to deform (bend) once this happens, the suspension tries to lock up.

Precision engineering is not what's required. In reality, the clearance needs to be a tad loose relatively speaking, to allow it to work effectively. It is a common mistake for people to only consider suspension in static.

When I did mine I used a standard long series 1" reamer which given a small amount of runout etc did cut very slightly (.002") oversize.
However it occurred to me that perhaps we should get the king pins ground down a couple of thou if the chrome thickness allows.
Or start with the stock material 2 thou down before chroming and grinding.
I think the biggest mistake is trying to make the bushes too tight in the hope that they will then last longer.
If the pins were slightly undersize everyone could then use a standard 1" reamer and be sure of the correct clearance.

I have a set here still waiting to go in. Very difficult to check the chrome thickness on the pins but I bet with a commercial grade there is not much more than a thou. I’ve pre bored the bushes and gone with a .003” nominal clearance on the pins. They feel nice but hope it’s going to be enough (fingers crossed). Will attempt to bond them in so hopefully any axial error will be taken out as the pins will be used for alignment as the adhesive cures. Well that’s the plan at least

Sort of true I suppose, but "Spanner Juggler" gave Me the tollerance He used and that is the tollerance I used on bronze bushes. I went to a Sunnen Hone because of the expense of a suitable reamer and I wanted to insure they were straight. The Vesconite is reamed with a variable reamer w long shaft to 1.004+.

I read the GOMOG information on Devols. This is different than when I first read Lornes GOMOG information on this subject. I am confused on this, but no matter I have systems that work for Me.

I use an adjustable reamer.

How do you measure the clearance Rog? Do you put a .003" feeler gauge all the way around, so the diameter of the hole is 1.006", or do you measure it one place with the pin hard up against the bush on the other side, so the diameter is 1.003"?

I've only done my pins twice, the first time they were a bit sloppy, the second time I fitted hardchrome pins and got it a bit snugger, but neither time did I do any measuring.

Since I put the hardchromes in, the wear has been negligible, so I've not needed to do it again. If/when I do, I'll probably machine down the outer diameter of the bushes and bond them in as you have done, it seems a lot easier to me to ensure correct alignment that way.

If machining the bushes, just bear in mind that very few of the stubaxle bush housings are 'true'. The main component of the stub axle is cast; the two housings for the bushes are steel tube welded to the casting.

However good the jig used for alignment, the heat generated by the welding process followed by the subsequent differential cooling of the casting and tube produces distortion; maybe not a lot but enough to mean that the thing will need reaming again resulting in increased clearances. It's another reason why installing and reaming the bushes separately doesn't work.

Good point. Would it be feasible to get the stub axle line-bored true to start with, I wonder?

It's all a bit academic really, but if you could get the stub axle true then it should be easier to turn the outside of the bushes to size than ream the insides - but then it's not that hard to get a decent result, and with hard chrome pins it's a 100,000 mile job.