Cam shaft rebuild

[Dhbangham]

I have decided to have my cam shaft built up and then re-ground by Newman cams Farnborough. https://www.newman-cams.com/ They have quoted £200 plus shipping. This quote was based on the photos attached. They will use the unworn area to to base the new shape on. I will report back once finished. I discovered that the gears are held onto shaft with taper fit and key. I needed a hydraulic press and heating the gears to break apart.

[David Morris]

Hi Dhbangham, this is a very interesting project, and I look forward to hearing the result. Guessing that Jowett's didn't want to invent something they already had on the shelf, is there a possibility that Jowett stationary engines used the same camshaft? If so, I expect there must be several stationary engines lying around that have probably only done a few hours work? Even if the engines have been lying hidden under the bench for years, their camshafts will be protected from the elements and might still be serviceable?

Going back to the work you propose with Newman Cams, does anyone in the Club have the specifications that Jowett will have used for the surfsce hardening of the original camshafts? I guess this will be specified as a Brunel hardness figure, and I am sure Newman Cams will be able to advise on the correct figure. Just building up the worn lobes and grinding to the remaining profile, will, I am sure, not be good enough. Additional surface hardening will be required, probably in two stages, build up, harden, grind oversize, harden, and then have a final grind? I am sure we have plenty of experts in the club who can advise you, with much better professional advice than me?

I look forward to hearing how this goes?

All the best, David

[Dhbangham]

Thanks David, I have not discussed any special requirements with Paul Newman, but thanks for the insight. I will probably just leave him to do his stuff, as his reputation is good. Finding a less worn shaft was an option, but the bearing on the one I have are still a good fit.

[AmilcarJohn]

Have you considered a small improvement in the profile? Fuels are very different now from when vintage Jowetts were built and I imagine that you could gain power without losing flexibility. Even a small grind to the base circle may yield benefit -would a Bradford cam show the way forward?

[Dhbangham]

I had not considered how the changes to fuel would affect the camshaft design. A quick search on google reveals that lobe design has changed, but as part of a complex evolution of the engine. The reduction in pre-ignition with modern fuels, in turn allows for higher compression ratios, which it not easy to achieve on the 29 jowett. The cam is with newmans now, but I will continue reading up about changes in fuel and how one might take advantage of it.

[Tony Fearn]

Hello everyone.
I seem to remember that Roy Braddock used to have some sort of wooden-profiling for pre-war camshafts, but I don't know about the vintage ones.
I think that Jowett car Spares had this when Roy died, but there again, I'm not sure.
Nevertheless, I am enjoying this post and the discussion, especially Jowetts in 2026.
Tony.
P.S. David (Morris), thanks for putting your knowledge about the Javelin on this site for posterity. Tony Fearn.

[Dhbangham]

The camshaft is back. I am interested to see that the profile of the inlet and outlet lobes are quite different, the outlet ports have a flatter top. I have not tried to calculate the dwell time of each lobe. I don't know if this is a common feature of cams, or if Newman cams have an archive of known profiles of historic engines, but it looks very good and quite different from what I sent to them. I can't wait to see how the engine runs.