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questions regarding findings on my son's 79 MGB

To: mglist <>
Subject: questions regarding findings on my son's 79 MGB
From: rexcats <>
Date: Sun, 22 Jul 2001 13:40:44 -0700
Greetings to the list.

So far my wife has been making all the posts to this list. Now I've
got a report on the progress of getting a B on the road again, and
some questions to ask.

Our son's 79B won't pass the wonderful California smog test and I 
was told, when I took it for a precheck, that it wasn't firing on
one cylinder at idle. I've tried removing the plug wires while it
idles to determine if this is true. It seemed to be the case once,
but now it appears to be firing. The B also appears to burn some
oil. The opinion is that the engine needs new rings and who knows
what else will be found (or missing).

Yesterday Justin (our son), and I began to check the B and prepare
for the major task. First thing I wanted to do was to check the
compression, before tearing apart the engine. The compression check
shows 150-155 lbs on all four cylinders. Since the spec in my shop
manual says compression should be 130 lbs, I'm assuming 155 lbs is
good. Can there be too much compression? 

After compression check we inspected other parts of the engine bay.
The air filter to the carb was reasonably clean, probably not too
many miles through that one. The filter for the air pump is pretty
dirty, so we'll replace that one straight away. The air pump is
also working. Justin found a rubber tube with a small plastic pipe
extending out the end. I traced it back to the intake manifold and
looked in the manual. This tube connects to the running-on valve. I
located the hole for the tube and it would appear to be broken off.
Plugging the tube in where it belongs and running the engine didn't
seem to make much difference. I'll try reattaching this later to
avoid replacing the valve.

Next thing, Justin asked if we should check the absorption canisters,
so we proceeded to remove them. Here's where things got interesting.
Because the 79B has two, we realized they are connected together via
a hose. Justin removed the secondary canister (the one on the left)
which revealed the connecting tube. To remove the primary canister
from the engine bay, we needed to remove the connecting tube. When I
removed the tube, oil leaked out of the canister. I replaced the tube
and we proceeded to remove all the mounting brackets for the canisters
and the windscreen cleaner bottle (had to clean up that oil puddle).
Disassembly of the canisters revealed both were empty. Not a stitch
of charcoal to be seen (charcoal evaporates doesn't it <g>). Instead
we found an oil (gas?) soaked filter and the remaining parts of the
canisters' interiors. I think we'll clean and refill these ourselves
since replacements are pricey. 

We were able to start up the car without these parts installed, enough
to move it back to her parking spot next to my driveway, but we won't
be taking her on the road just yet.

So, here's my questions. I hope I can get some suggestions from those
of you who have also done engine work.

1. Is the 150-155 lbs compression okay? We tested each cylinder three
   times and got the same readings, +/- 5 lbs. With this compression,
   can there still be ring problems? Perhaps we should replace them

2. The threads on the spark plugs are a bit wet with oil and there is
   some oil on the rocker cover around the base of the filler. Since
   we put a new filler cap on, and have not added oil since, I don't
   know why there is spill there. When running, there is very little
   oil pressure showing on the gauge. When starting up, the gauge 
   reads pressure, but this drops to almost nothing soon after. 
   I don't suspect the gauge to be faulty, so I'm wondering if there
   is a problem with the oil pump or oil flow through the engine.
   Could this be the cause of the spill? There is also spill on the
   engine side that seems to be coming from the filter area.

3. We'll attempt to reattach the tube to the running-on valve so I
   don't have to replace it. I bench tested it with a 12V power supply
   and it seems to work okay. I don't know when the running-on valve
   does its thing, but it is part of the emissions system.

4. If indeed we do need to pull the engine, either for upper work 
   (rings, valves etc.) , or lower problems (oil pump, oil flow...),
   can we remove the mechanicals in pieces by disassembling the engine
   from the top down? In other words, can we start by removing the
   head, then remove the block after disconnecting it from the tranny?
   We'll replace the engine and tranny as a unit, but if the engine
   can come out this way, we could possibly avoid the need for an
   engine lift for the disassembly. If the block would be too heavy
   to lift out, then this is probably a moot point. Is it better to
   pull the engine and tranny as a unit and disassemble on the bench?
   Without the benefit of an engine stand, is it better to loosen the
   torked bolts/nuts before removing the engine? I've read a number
   of accounts about pulling engines and the consensus of opinion
   is to raise the tail end to get the proper angle for removal.

I'm not averse to the idea of pulling the engine if necessary. I did
this to our Midget about 18 years back. I didn't take that engine
apart then, so this will be new territory for me if we must. I have
a proper shop manual (Bentley, don't cha' know), but we'll be working
in a garage without the benefit of all the tools of a professional.

Thanks for taking the time to read this long-winded post. We look
forward to your replys, all "The Good, the Bad and the Ugly" tales
anyone has had <BG>.

TTFN and Safety Fast!

Michael and Justin

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