| Author |
Message |
    
Jim Bettison (203.166.57.11)
| | Posted on Tuesday, 16 July, 2002 - 20:24: |    |
Can anyone give me some details about a camshaft stamped RE3672 and found in a 4-1/2 litre Dawn of 1951 vintage? It doesn't appear in our spares lists. |
Bill Vatter (67.35.48.21)
| | Posted on Sunday, 21 July, 2002 - 12:37: | |
Jim,
I am looking at service bulletin RE 67 issued for SIlver Wraith 8-10-53. This bulletin states camshaft RE3672 was fitted to cars WTA1 to WVH38 inclusive and to ALW1 to ALW29 inclusive and also to a few other chassis not in these sequences. I would suppose that this camshaft would also have been used in Silver Dawns built at the same time, which is 1947 through sometime in early 1952 I think. The bulletin goes on to state that a replacement camshaft (RE6885) with altered timing was used as a replacement for any car originally fitted with RE3672 and also on chassis not listed.
The principle difference is that the later camshaft has advanced inlet opening at TDC vs 10 deg. after TDC with RE3672. I guess the newer camshaft provides a little more power, maybe with a small sacrifice of smoothness.
I also have a camshaft I cannot identify. It is marked RE 23639 and came from a KL series MK VI Bentley.
Somewhere in my manuals I remember reading that there is a wear limit of about .007 inch or so (can't really remember and can't find the page right now). I also remember seeing some lobe measurement data on the Silver Wraith camshafts, and if you are interested, I will try to find it.
Although I do not know what the lobes on my unknown camshaft should measure, they are all within .003 of each other, so I assume it is a good camshaft.
Now, in my opinion, with the present difficulty and expense of obtaining a new camshaft or having an existing camshaft reground and re-hardened, I would use whatever in any of these cars, as long as it was in spec for wear. |
Jim Bettison (203.166.57.11)
| | Posted on Sunday, 21 July, 2002 - 22:19: | |
Bill,
Thanks for all that. We will now go away for a bit, and figure out what it means to/for us ...
Regards, Jim |
Bill Vatter (67.35.48.21)
| | Posted on Monday, 22 July, 2002 - 06:19: | |
Jim,
Aditional information obtained from "Service Handbook, applicable to post war chassis," republished by RROC (US) in 1989:
lobe height dimensions, measured across the cam from heal to tip of the lobe (no information provided as to which camshaft the data applies):
Ex. cam: 1.575 in.
In. cam 1.517 in. (for B VI and Phantom IV
In. cam 1.512 in. (for SW and SD)
Lobe wear limit .016 inch.
Ovality of journals, limit .001 in.
alignment, .002 out of perfectly straight as measured on "V" blocks with a dial indicator
Valve timing:
SW and SD:
inlet opens 12 deg ATDC
inlet closes 35 deg ABDC
exhaust opens 44 deg BBDC
exhaust closes 6 deg BTDC
Bentley:
I.O.: 3.5 deg ATDC
I.C.: 43.5 deg ABDC
E.O.: 40.5 deg BBDC
E.C.: 1.5 deg BTDC
Hope this helps. |
Norman Geeson (80.225.191.192)
| | Posted on Thursday, 25 July, 2002 - 03:10: | |
Jim
I see that Bill has already forwarded most of the data, but the following may be helpful.
The RE 3672 camshaft was in fact fitted to the Dawn's up until chassis no LSMF64 on LHD cars that was about June 1953 chassis and up to chassis SMF72 on RHD cars. However I believe this change was done for cars with Auto transmissions and that the RE 3672 camshaft was retained for manual transmission cars until March 1954.
Besides the timing aspect I believe you will find the cam lobe ramps faster than the RE 6885 shaft which replaced it. In other words the RE 3672 camshaft lifts the valve quite rapid. This shaft may have replaced yet an earlier camshaft which caused problems with wearing off the lobes. One of these early shafts certainly had that problem and normally would wear off no 5 inlet cam from memory. This camshaft was specifically used on single carburettor S/ Dawns/Wraiths. On at least the Bentley the earlier camshaft change it also involved changing the inlet valve springs. However the camshaft RE 3672 would have been original in a 1951 Dawn, but I would not fit it, unless I had to, into a twin carburettor Bentley engine as I believe it may alter the gas speed sufficiently to cause problems |
Jim Bettison (203.166.57.11)
| | Posted on Thursday, 25 July, 2002 - 10:51: | |
It would be interesting - and probably useful - to know the difference in cam profiles as between the camshafts RE3672 and RE6885. Does anyone know?
More detailed answer on other matters later.
Jim. |
N.W.GEESON (80.225.186.1)
| | Posted on Tuesday, 22 October, 2002 - 05:59: | |
Jim
I would further add to this thread that I have established that the RE 3672 is actually a high lift camshaft, as I stated before specifically for the Silver Dawn / Wraith. The RE6885 is however a low lift camshaft.In essence this only confirms what I have already suggested and I definately would not fit this camshaft in a Bentley. |
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