Hi,
As I’m in process of assembling the timing gear I noticed some scoring on the bushings on the intermediate sprocket and the idler sprocket. The scoring marks pair up with where the oil delivery holes are on the shafts. The fitment seems great and but I’m debating replacing the bushings here because of the scoring. I wanted to ask if it’s really necessary to replace them for this reason? What type of pressure and fatigue do these bearings/bushings see? I’m sure it’s good practice to replace them but is it needed. I doubt they are under the same load as the mains or rod bearings… or maybe they are??
Also, are there measurable specs to inspect for sprocket wear other than eyeballing a sharp point to the teeth? I can’t find much information on this yet.
Oh, another question:
I am updating to the front Teflon crank seal set up. The new spacer or “Distance piece” has a chamfer on one end and an O ring on the ID that is closer to one end of it. It seems to have a front and a back face but I haven’t read anything that says you need to install it in a certain orientation. I’ve read the article by Dick Maury and some threads that pop up but none really address this and the related photos are too small to see. Any advice?
An interesting question - wear on the intermediate and idler sprocket. Each of the manuals I’ve got (from 3.8l up to Ser III XJ6) suggest checking these for wear, but none say what wear is acceptable. Nor do they suggest what the clearance should be after you re-bush it. I anticipate that if you do re-bush them they will have to be fitted to the shaft with a reamer. Online searches suggest brass bushing should have a clearance of .001 to .002. I miked an old eccentric shaft for the upper idler that I’ve got to see if I could detect any wear. It had visible marks stretching out from the oil holes, but you couldn’t catch any thing on them, or feel them for that matter. I couldn’t detect any wear on it by the mike - in particular it was perfectly round. I suspect the scoring you see comes from dirt in the oil. I don’t have any sprockets to check. I’ve never re-bushed or replaced either of these sprockets as best as I can recall on any engine I’ve rebuilt, but that’s probably from just not wanting to get into that. I think that if your sprocket is still reasonably tight on the shaft, and there are no thin spots or obvious wear on the bushings you’re ok.
As I understand the chain sprocket wear issue you primarily need to check the bottom, between the teeth. This wears into a shape that is larger than the roller in the chain, and that’s bad.
I’ve used those distance pieces with the o ring when I had them to use (they are post most E Type production). As I recall the o ring end is out - the chamfered end is in towards the engine. As long as the o ring doesn’t interfere with one of the keys or key slots you are probably ok either end out with the only caveat to that being to check and see if the end of the taper for the damper butts up to the flat part on the chamfered end if you are putting the chamfer end out. (The inside end of the taper has a cut around it for some reason IIRC)
Indeed this is correct; the new bushes are about 10 thou undersized and need to be correctly reamed to fit.
I haven’t replaced one for a long time and only did it then because I didn’t know any better. If there is not perceptible lateral movement I would leave well alone.
I think this is correct. The chamfer gives you something to hammer against to remove the distance piece as the o ring will otherwise lock it in place.
It may be just me but I have had no end of trouble with the Teflon seals leaking. I have gone back to the regular nitrile seal on my 3.8 roadster and intend to fit one to my current rebuild 3.8 coupe.
As always thank you for the information and experience. It’s worrisome that the teflon seals have a bad score card but I guess I’ll try this route now that I have the parts. I won’t be replacing the bushing which makes me happy. I checked two motors and both had very little wear except for the slight scoring at the oil delivery hole.
Photo shows the early and late spacer with O ring seal. The relief cut into the later spacer is to clear the
protruuding woodruff that locates the bottom chain sprocket ,oil thrower and early spacer.
I also have had aggravation with the teflon timing cover seal. When fitting the sump the sharp edges
of the seal recess seem to grab the seal and deform it. If I were to use this type of seal again I will
assemble the timing cover, sump and seal to check for fit before fitting said components to the block.
Terry I do not get the meaning of your last post
Peter B
It’s possible I don’t understand the terminology being used here. The couple of late spacers I’ve dealt with had black o rings, just like the one in your photo. Others here refer to a Teflon seal. To me that’s not the same as an o ring – but maybe that’s what people are referring to. Seeing yours I recall now the relief cut which pretty much seals (har har) the direction to install.
Terry I think the Teflon seal refers to the crank/.timingcover/ sump seal not the O ring.
Be it Teflon or not, some of these seals sold as “uprated” do give trouble.
Peter B.
