On Fri, 24 Aug 2001 10:45:08 -0500 "Den's E-mail"
<dbuster@integraonline.com> writes:
> Hi--
>
> My son and I are about to attempt the first engine rebuild of our
> lives --
> the 1275 engine from my wife's beloved '71 Midget.
>
> I plan to get a book and video on the process but I'm curious about
> one
> thing before I start: Should I automatically assume that I'll need
> to have
> the block rebored or do I assume that I can just buy a new set of
> pistons
> and will need to do nothing to the cylinder walls? How do I tell
> which
> course to pursue?
>
You won't really know until you get the head off, and likely not until
the machinist has a look at it. If it is worn enough to need a rebuild,
it is likely it needs to be bored out. A worn cylinder bore will have a
slight lip at the top and/or will be oblong shaped. Again, the
evaluation is best left to a good machinist. You're going to need one to
"deck" the block (flatten out the top) and to do all of the head work,
anyway. I suggest you also let the machinist assemble the bottom end
(put the crank and pistons in the block). This can be a bit touchy for
an amateur since it is rather easy to break a ring (don't ask me how I
know) or to not get the ring gaps right. Don't skimp on this sort of
stuff when you rebuild it, or you'll find yourself doing it again long
before you want to.
You'll find that motor assembly is a lot easier than it sounds. Just
make sure that you take good notes when you take the motor apart. Pay
particular attention to where each bolt and nut goes. Some are
specialized for certain things, like the flywheel bolts. I use ziploc
bags and scratch paper. I draw diagrams on the paper and put them in the
bags with the fastners. DON'T THROW ANYTHING AWAY until you have the the
motor in the car and running and you have triple-checked that you don't
need it anymore. A good manual will lead you through the rebuild pretty
handily, even if you don't have the video.
The weakest links in amateur-built engines are (in my first-hand
experience) 1) oil leaks, usually from front and main seals and the oil
pan gasket, 2) head gasket leakage or failure, 3) lack of knowledge about
running in the cam, 4) (relatively rarely) getting oil pressure, and/or
5) using WAY too much silicone gasket sealant, bits of which will break
off and end up in an oil passage. The last two problems I (fortunately)
have no first-hand experience with.
For 1) and 5) I use Hylomar gasket sealant, which does not solidify like
silicone, therefore will not break off in bits and end up in passages.
When used properly, it makes a very good seal. It is available from your
local Jaguar dealer in its pure British form, or you can find a
made-under-license version made by Permatex, called HPF Hylomar, at your
local auto store. Moss sells both versions, search the Lbcarco.com site
for parts numbers. The Jaguar number is the "real" British stuff. I
don't think there is a difference, but I have a friend who swears there
is.
For 2) I suggest using Copper Kote on the headgasket and sticking with
the stock-type gasket. DO NOT use the competition copper gasket on your
street car. They will hold well if used properly, but they tend to be a
bit tricky. I use a copper one on my race car, but I also use ARP bolts
and studs (not necessary on a street car) that are torqued more than
yours should be. I know several people who swear at the copper ones,
including me, since I had one fail on my MGA. It now sports a stock
gasket.
Here is the drill for 3): When first starting the motor let it idle for
20 minutes at no less than 2500 rpm. Some guys will set their idle speed
at 2500 and just go for a drive. This is important to run in your new
cam without tearing it up.
For 4) I do what the old timers used to do. I pack the oil pump with
Vaseline when I install it. I'm sure there are some people out there
laughing at their keyboards, but this ensures the pump will pull oil into
it right away. Probably not necessary on a MGB or MGA, where the pump
sits down in the sump, but on a Midget (where the pump is high up) or a
TD (pump is outside the motor) it surely can't hurt. The Vaseline will
just dissolve in the oil and not hurt anything. You should change the
oil shortly after you first run the engine anyway, 'cause it will have
cam lube and filings from starting in it. The downside is you get funny
looks buying those huge jars of Vaseline at the drugstore. (That's my
story, and I'm sticking to it)!
Good luck!
David Littlefield
'62 MGA MkII
'51 MGTD
'74 MG Midget vintage racer
'88 Jaguar XJ-S
________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today! For your FREE software, visit:
///
/// mgs@autox.team.net mailing list
/// (If they are dupes, this trailer may also catch them.)
|