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MG TD TF 1500 - Pinch Bolt Orientation
The service manual says the gudgeon pin pinch bolt must be on the right hand side of the engine. But the manual does not say if you look at the engine from the front or the rear to determine this. I am guessing you stand behind the engine, and if so, my engine (XPEG) has it backwards. The bolts are on the cam side of the engine. So what is correct? I'm overhauling this beast. What is the result of the pin on the wrong side of the engine? I see all the threads in the archive about new pinch bolts, so that is great!
The good news is that the bearing journals and inserts look good except for some wear on the center main. But the clearances are all at the maximum. Well, it would rev pretty well, I bet! It has not been run in 30 years. So the journals/inserts are worn about .001. While I'm at it, I see the XPEG crank is not supposed to be turned, per the manual. It must be a crappy crank to start with. Mine has never been turned.
There is also the small issue of the #2 connecting rod now in the #3 hole. Oh, well...So lots of challenges are cropping up, including some spalled tappet faces. But there are lots of threads on these things.
Thanks, Mike Davis
the pinch bolts should not be on the cam side of the engine see plate A33 in the manual. There is a drillway which directs oil to the thrust side of the bore only if the rods are in the correct way round. I have seen engines after many thousands of miles that have come to no harm though.
If you renew the bearings don't forget that the new centre main will require easing to fit as they are made oversize to account for wear.
Easy enough, as the very nice cross section picture at the front of the WSM shows the bolts on the non cam side. That'd be the right side as viewed from the driver's seat, which is the convention in all factory references.
Congrats on finding a good one, at least if whoever put it together all askew didn't hurt anything!
Thanks for the input on this. I feel pretty silly at not having looked at Plate A33, frankly. So I hope I did not waste a lot of your time! I need to spend more time studying the pictures and combine that with the text. This was my Mom's car in the 60's and it had a hard life in Michigan so I am bringing it back from a dead basket case, literally. It's slow going! I have the only mgtf in existence with a custom intake manifold and a Ford Pinto carburetor. The SU's are stuffed into a milk crate.
|mike, if the crank maganafluxes good you will probably be ok to turn it. from the information i have seen going to .030" under is not a problem. mine was at .050" under when i removed my engine. no problems with the crank, but at .050" under i chose not to go any farther and picked up another crank. regards, tom|
|Mike -- Look at page 14 in the shop manual. There is a cut-away picture of the engine taken from the front. There is enough detail from the starter and oil pump to assertain it is from the front of the engine. It shows the pinch bolts on the opposite side from the cam as mentioned above. Page A30 shows a similar view of the engine with the pinch bolts on the same side (away from the cam).|
Don't know why the factory advised to not regrind the crank in the XPEG engines. Maybe they felt that the additional displacement put too much loading on the bearings. Experience has shown that the XPEG cranks can be reground and will survive quite well.(don't know about going 0.050" under).
|R. K. Jeffers|
|"There is also the small issue of the #2 connecting rod now in the #3 hole."|
Mike, I considered the number markings on my rods and caps as an assembly aid to keep the pairs together. After my machinist balanced my engine (a super good idea) I weighed my pistons and rods to find the four sets that balanced the best. I have no idea which rod went in which cylinder.
My crank had a minor stress point, and I had it ground and reused it anyway. So far so good.
Where in CO are you?
Ed in Crested Butte
|Dave Braun is spot on. I was told many years ago (in the 50s) that rods were balanced by hand to 5 grams in pairs. That would be interpreted as the engine fitter going to a bin and selecting rods that had been weighed and labelled.|
Now 5 grams at 5,000 RPM is a hell of a lot!
In my most recent rebuild, I first polished my rods to a chrome-like finish. Then shot peened them. Using 2 pan balances, I then balanced the rods end-for-end 'till all matched, grinding as little as necessary from the side of the journal side.
I did the same with the pistons, the rings, the wrist pins, the pinch bolts, small-end bolts etc; 'till I got all rod/piston assemblies to within .1 gram of each other.
Took me about a week of nights, but my engine today is unbelievably smooth - of course all rotating parts were dynamically balanced too. I often cruise at 4,500.
A great investment in time.
|Gordon A Clark|
This thread was discussed between 15/10/2009 and 16/10/2009
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