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cam oil ports  Rating:  Rating
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 Posted: 05-18-2011 02:43 pm
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sjensen24
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The valve adjustment instructions in the newsletter describes an O-ring around the oil feed tube at the front of the cam tower.  It also describes modifying the head to allow for this O-ring.  My car (1974) #15020 has the tube but no O-ring.  Is some modification necessary to install this ring.  It appears that there would need to be a space between the mating surfaces.

Last edited on 05-18-2011 02:44 pm by sjensen24

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 Posted: 05-18-2011 03:45 pm
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Jensen Healey
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You need to do the modification. I'll check the service bulletins for the dimensions.

Kurt

 

Last edited on 05-18-2011 03:57 pm by Jensen Healey

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 Posted: 05-18-2011 03:46 pm
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sjensen24
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what does that look like?  What is involved?

Last edited on 05-18-2011 03:58 pm by sjensen24

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 Posted: 05-18-2011 04:49 pm
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John Finch
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Steve, Per Tim's recommendation, I had mine modified. I had the work done at Creative Metalworks in Blaine. 9206 Isanti Street NE 763-784-2997. I'll send you a PM with addtl info on the counter bore.

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 Posted: 05-18-2011 04:53 pm
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Jensen Healey
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Service bulletin 74-23 describes the procedure but I can't find it in my stack of bulletins (which were acquired before the club store started offering the reprints).

There is a relief in the cam carrier 9/16 (.585") X 1/16 (.062).

Kurt

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 Posted: 01-06-2012 10:04 pm
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Bob 13902
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The 74-23 is not in my service bulletin...does someone have a copy they could send/email?

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 Posted: 01-15-2012 03:10 pm
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John Finch
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Updated info for the Cam Carrier Counter Bore:

"The OLD, measured numbers I gave you back in ~2005

0.484" / 31/64” / 12.281 mm  Diameter, concentric about the oil passage.
0.075" / ~5/64” /   1.905 mm  Depth

 

However, I have since struck up an email friendship with an engineer at Lotus Engineering, and he's been very helpful about digging through the archives and finding old info for me.    One of the tidbits I asked for was the design dimensions for the O-ring c'bore.   The most notable dfference is that the spec depth is less than I measured on both of my engines (I don't know why... Quality Control??).   Too deep means the O-ring isn't sufficiently compressed to seal as well as it could.   Too shallow over-compresses the O-ring and crushes it.


FYI... the numbers I got from Brian at Lotus are:

O-Ring Counterbore Details:
.......... SPEC  METRIC   /  Calc'd Inch Decimal / approx inch fraction
Dia.   12.30 -12.44 mm  /  0.48425" - 0.48976" /  ~31/64" (.484375")
Depth  1.20 -  1.30 mm  /  0.04724" - 0.51181" /    ~3/64"  (.046875")


The factory service tool back in the day was a 31/64" cutter with a 11/32" pilot drill and a T-handle.   With that you could hand cut the c-bore (forget it, the OEM tool is now imposible to find).   Without that, any competent machine shop can cut a proper c’bore for you... as you have found."

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 Posted: 01-17-2012 09:44 pm
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Bob 13902
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OK - one last question. What is the proper tube material...Aluminum?

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 Posted: 01-18-2012 08:26 pm
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pbahr
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If anyone wants Service bulletin 74-23, send me an email and I'll forward it.

It does not talk about o-rings, but rather using Loctite to seal that joint.........

peteb01@comcast.net

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 Posted: 01-18-2012 10:16 pm
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Bob 13902
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There are several bulletins...that were not in my manual. 75-8 and 76-2 address the Oring...if only they told me the material for the tube/pin...bob

74-1 oil tube install
74-23 supercedes 74-1; removes gasket and uses Loctite sealant and maintains 74-1 oil tube or roll pin (depending on engine number)
75-8 Oring+recess+tube/roll-pin (ground if necessary as some too tall when installed per 74-1 because still had gasket then)
76-2 Modification tool for Oring recess
 

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