At 03:30 PM 12/30/97 -0500, you wrote:
>Hi, I have been "hanging out" on the MGs list for the last 3 months and
>wondering why there was so little Spridget stuff on there. Now I find that
>you are all lurking just up the street on another list !!
>
>I need advice on a 1275 engine rebuild.
>1) Camshaft bearings are shot. Workshop manual lists an expensive
>sounding job of replacing them using a special tool and reamer. I have
>also been told that you just press out the old liners and press in new with
>engineering adhesive to stop them spinning - no reaming required. Anyone
>done that job ?
The reaming is on the bearing material after the new bearings are pressed
into the block. After doing the job myself once, primarily because I like
to be able to say I've done every job on the car personally at least once, I
get the machinist to install the new bearings. You have to do this after
having the block hot-tanked, which is a good idea too. Don't ever use any
adhesive to stick engine bearings in place - they're designed with a crush
factor built in that keeps them from spinning. The layer of adhesive tends
to block heat transfer from the bearing into the block, and can cause problems.
Not owning the proper reamer, I scraped the bearing surfaces one at a time
to get the cam to rotate smoothly, using a scraper jigged up from the side
of a wood chisel. That motor is still going strong as a race engine in a
Mini Cooper.
>
>2) Block needs a rebore, + 10 thou should be sufficient. Current pistons
>look good to use again. Can this be done using oversize rings in standard
>pistons or will I have to buy new +10 oversize pistons ?
Piston to bore clearance is critical to good performance, so you must use
pistons to match the bore. The pistons need to support the rings properly
in order to allow them to seal, and small pistons tend to rock back and
forth, killing the rings in short order.
One thing I did do once, having a brand new set of Powermax pistons at .030
over, and no rings available, is fit a set of .040 over rings by sizing the
ring end gap correctly. This worked just fine - the difference in the rings
is pretty small.
Brian.
>
>Can anyone give advice ?
>
>Guy
>78 Midget 1500
>70 Sprite 1275
>
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