Torque Setting needed

[Michael Oritt]

I am about to replace the connecting rod and center main bearings on my 100 and do not understand the following statement in the Service Manual:

"Main Bearing Stud Nuts/Connecting rod big end nuts.....................Castellated-tighten to Nr. Slot."

The rod and main cap nuts are not castellated and even if they were shouldn't there be a torque value given?

An archive/online search showed suggestions of 50 & 55 ft/lbs for the CR nuts and 75 ft/lbs for the Main nuts. They sound reasonable but I really would like to get this right the first time.

 

[roscoe]

Historically castellated or castle nuts were used for applications that are in shear more than tension. The "tighten to Nr. Slot" refers to snugging the nut just past it's drag torque or until the torque value would begin to go up very quickly and going to the nearest castellation in the tightening direction tha t allows you to put the cotter pin in. If your nuts have been replaced with a nut that is self locking you have a couple of choices. The best one would probably be to call a shop that does lots of Healey engines and ask them what they use when not using castle nuts. You could also just treat it as you would a castle nut and tighten until snug and then 30 degrees more or 60 degrees if you are nervous and the torque is not excessive (your call). See what torque that brings you to and just as a guess I would think the torque might be in the 25 to 30 foot lb range but if it starts to get easier during the torqueing please don't be mad at me.

 

[Jim 58 BN6]

Here's a link to a chart I found. Maybe it will help (or not!). Notice the first four sizes list the torque specs in in-lbs rather than ft-lbs. Good luck, Jim

https://www.repairengineering.com/bolt-torque-chart.html

 

[red57]

The six cylinder motors call for 50# for rod bolts (7/16" dia.) and 75# for mains (1/2" dia.) so if the four also uses 7/16 & 1/2 sizes then I think you should be fine with that. But I too would want confirmation.
Dave

 

[Michael Oritt]

It's back together with a new oil pump and spindle, new pressure relief valve and spring, new rod bearings, new thrust washers and a new center main bearing. I used 50 foot pounds on the rods and 75 on the main.


I spun it over with the plugs out and oil pressure came up after what seemed like five minutes but was probably only 15 seconds. With plugs in the oil pressure is 40 psi at idle and 50 psi at 2K. I'm trusting that all is good and taking it out for a ride in a few minutes. Fingers still crossed, but all seems good.

 

[Michael Oritt]

Yesterday afternoon I posted:


It's back together with a new oil pump and spindle, new pressure relief valve and spring, new rod bearings, new thrust washers and a new center main bearing.

I spun it over with the plugs out and oil pressure came up after what seemed like five minutes but was probably only 15 seconds. With plugs in the oil pressure is 40 psi at idle and 50 psi at 2K. I'm trusting that all is good and taking it out for a ride in a few minutes. Fingers still crossed, but all seems good.


During that ride, once the engine came up to operating temp of 180 the oil pressure needle began acting erratically during deceleration and at idle. Whereas In the past the oil pressure would fall off gradually by about 10-15 psi from maximum during deceleration, the needle was dropping very quickly whenever I took my foot off the throttle, and was falling to 20 psi--and sometimes less--at idle. Clearly something was wrong!


This morning I drained the oil that I put in yesterday and inspected it for any debris--NONE. I removed the spin-on filter and cut it apart to inspect the filter medium--it too was clear of any debris. I began to suspect that the new oil pressure release valve was not closing all of the way, allowing oil to bypass it and giving lower readings, so I decided to remove and inspect it as well as the passage in which it operates (though I had done this yesterday prior to installing the new valve).


When I disassembled the engine last week I used a 1/2"-13 tap and with finger pressure engaged the inside diameter of the oil release valve and extracted it from the passage. This morning, however, that same tap did not seem to be working on the new valve. I finally got the valve out using a tap with a slightly different taper and when I compared the new valve to the old I saw that there were some slight differences: while the outside diameter of the two valves measured the samec the new valve was made of much thinner material--.0047" versus .0057", which explained why the ID's were different and I could not extract the new valve with the same tap as worked on the old one. See the attached photo--new valve on left.


I reassembled the relief valve using the old part, spun on a new filter and refilled the engine with the same oil. On cold startup the oil pressure was about 5 psi higher than yesterday, varying between 40 to 60 psi from idle to 2500 rpm's +. I drove the car for an hour and at OT of 180 the oil pressure held at 55-60 psi at constant throttle and 35 psi at idle. This conforms to past performance and all seems right!


I can only conclude that the thinner wall construction of the new valve allowed it to expand more when heated--just enough to allow it to jam in its passageway, not seat fully, resulting in lower OP. The Lesson Learned is not to assume anything, especially that new parts are the same as old ones!

 

[CraigC]

Michael, that is interesting information. In looking at the BCS website, they show a different spring to suit the "replacement" valve as compared to the OE and OE replacement. I suspect that the new valve also has a deeper bore than OE. If you could measure the replacement, I'll measure my OE for comparison.

 

[Michael Oritt]

Craig--

The depth of both valves--the old and the new--is the same at 3/4". The spring supplied with the new valve was perhaps 1/8" longer than the one that was in the car and that might be attributed to its having become slightly compressed with age (15 or so years at least, maybe more).

Beyond the wall thicknesses there are some other differences between the valve that was in (and is now back in) the engine and the one supplied by Moss. Though both are of the same length overall the straight shoulder on the new valve is slightly longer with a bit steeper angle on the tapered section. Also, the nose of the new valve is flat whereas the old one is dimpled. See the two attachments--in both shots the new valve is on the left.

BTW the real old valve is back in the car and the "old" one pictured is out of the MGA engine in my Courier--but it is identical to the one I pulled out of and have since reinstalled in the 100's engine. I'd guess the was some commonality within BMC, even between the series B and C engines

Someone over on the Autox list responded to my post there saying that there would be more growth with a thicker-walled valve--perhaps he is right and these other variations made the difference. In any case the valve that was in the car is back in the car and it is performing just fine.

 

[Bob_Spidell]

Wasn't the original problem you were dealing with was falling oil pressure? Mightn't that come back with the original valve?

 

[Michael Oritt]

Bob--

No, the low oil pressure was due to a very worn oil pump--see attached pic. I got the new one along with a drive spindle out of Denis Welch. I guess there was a bit of "mission creep" and I decided as long as the pan was off I would replace related stuff such as the pressure relief valve which, as it turns out was fine and also do the thrust washers and rod and center main bearings.

 

[CraigC]

OK, pulled the valve and spring out of my spare block. I have no doubt they are original based on the wear on the valve and the fact that this engine hadn't been run since at least the mid-70's. I bought it in 1981 from a shop owner I met at Sears Point Raceway.

Spring length = 2.980" (Per BCS, the OE is 3.0" and spring for Moss' valve = 3.125")
Exposed spring length with spring in valve = 2.270"
Calculated depth of bore for spring = 0.710"
( I did it this way because the bottom of bore is also tapered )
Overall length of valve = 0.940"
Length minus taper = 0.750"
Wall thickness = 0.050"
Unlike your "old" valve, mine has more of a relief cut on the outer edge of the open end and is machined flat on the closed end (although it is rough and you can see where it was "parted off" from the raw stock).

I'll add pics later, and if I get bored, I'll pull the valve out of my engine(known to be original) and compare it to my "spare".