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MG TD TF 1500 - Front cam bearing wear and roller kit
|How should a new front cam bearing be fitted? As can be seen in the pics, the first is the original one ,which spalled and the second has 6000 miles on it and is going the same way. All damage/wear is on the inner lower on both. The cam fits very nicely with no discernible play and spins freely. I know the roller cam kit puts extra pressure on the components but this is not a common problem with the kit ( I gather )
Should a new one be scrapped after fitting?
I have ordered one from Edney in England and would like to do this job correctly
|Sorry that is the second pic of the latest bearing , you can see it beginning to spall behind the oil hole|
The pic of the original bearing is too large to submit but there are chunks missing from the same area. They ended up plugging the oil hole for the timing chain tensioner , causing a loud chain rattle on start up.
That is how I originally found the issue. One ignores new odd sounds in antique cars at your own peril !
|Keith - note that your front cam bearing should be peened into the notch by the retaining plate bolt hole, to prevent it from rotating - nothing else holds it in place.
I don't know about Edney, but most suppliers get cam bearings (and valves, pistons, bearings and other internal parts) from XRN in the UK, which has them manufactured in a variety of coutries - UK, Israel, etc. In general I have found their quality to be perfectly fine, although the main and rod bearings could be better by being tri-metal like Vandervell, rather than bi-metal.
I have no cars in my shop running the roller cam, and have never seen significant front cam bearing wear - certainly nothing like what you show. Is it possible that while the roller cam solves the usual flat-tappet problem, it introduces other potential issues related to high valve spring pressure, like broken rocker shafts and premature cam bearing failure?
|Spalling and bits of bearings breaking away from the backing are usually due to acid in the engine oil. The front bearing does not need to be scrapped.I have tools to install the front cam bearing. I have seen a few center bearings or center cam bushings that did need hand fitting to the cam, and alignment pin holes on the wrong side!Oh and line boring of the cam bearings is not needed. I have over 12 years and Many hard miles on my engine with no issues with my roller cam kit.|
|Tom you bring up an interesting observation re pinning the front bearing. Some thing that Ive neglected to do on my car and never checked on dads when I tore it down for inspection. When I set the bearings in my car the front bearing was definitely a press fit. I didnt give it a second thought. Now Im having some concern whether the bearing will actually spin in its seat. Thanks for that snippet of information I must have missed that step in Blowers and the WSM
Len also brings an important comment to this discussion. This confirms the need to change oils at regular intervals. Even when manufacturers claim that their oils are good for extended life. As for me I regularly change oils in all my vehicles at 3000 mi and do regular oil analysis to confirm the used oils condition. There are those that will say that this is unnecessary but this what I choose to do. The oil analysis allows me to either shorten or extend the intervals based on a particular engines needs. If my cars dont get regular usage annually to need an oil change it will get changed annually regardless of its mileage.
|W A Chasser|
|Thanks for the comments
My oil is changed every year with out fail and the engine never sees more than 1600 miles before the change so acids are out. I doubt the cause is the roller kit. But it may possibly be making another problem worse.
I believe there is something off about the engine.Remember one was a factory original bearing which spalled very badly. The newer bearing shows no signs of spinning.
I am having the cam bearings holes alignment checked as I can think of no other cause for this.The cam does not have a scratch on it and there is no perceptible play in the cam at the front.
Does any one know how to resize pictures for this site
on a Mac computer?
|Nocking (peening) the front cam bearing into the cutout is a standard procedure, as far as I know. Doing so will automatically cause a portion of the bearing to rise up and it will need to be cut down. I took the first XPAG cam that I replaced and had the machine shop cut a diagonal groove into the front bearing. I then use it as a cutter to smoothen the front bearing. Bud
|Yeah as Len says it's not the cam or springs causing that--|
If you're changing the oil regularly then it could be moisture related(coolant) does the oil go milky at all
Has it got good oil pressure normally
What oil are you running
|Ken, here's how to resize photos on a Mac.|
1. Open the photo in Preview (a very versatile program).
2. Go File ... Export ... and in the options box at the bottom choose JPEG.
2. In the options box again, use the Quality slider to reduce the file size.
Here is a pic of the original 1952 front cam bearing
|Still looks like an oil dilution / low pressure issue to me|
So what oil and pressure ---?
It looks as though you have the motor stripped, what were all the other bearings like and why is it apart if this bearing isn't very old
|Here's a photo for interest. A correct XPAG cam bearing reamer...
|Oil pressure is 43 psi at 3000 rpm at 85c oil temp|
55 psi at start up cold
Thanks for the picture of the reamer Steve. Where can I find one in the frozen North ?
|I don't know if anyone is still making them. This one is a factory item. Maybe check with some of the older sports car shops in the area.|
This thread was discussed between 02/12/2018 and 07/12/2018
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