Zero compression
Zero Compression
Greetings from Hawaii again. For a variety of reasons, I've been off the
site for a while. Nice to see the group has grown and the same wealth of
information still flows as freely as ever.. It is this fountain of answers
I need to tap into again. Many of you remember, I had an
unsolvable overheating problem. As a last resort, the head came off and was
completely redone, right down the the guides. The machine shop ( very
experienced with jags) shaved a few thousandths off the surface and it came
back to my garage looking literally like new. Sometime between then
and this morning, something went wrong. Reassembly went like clock work
with new gaskets going in and clearances being set with the greatest of
care. Every once in a while I'd get some advice from the books, the local
mechanic or the net, and this morning was going to be the "final exam". I
filled the radiator with new coolant and then disater struck. I was
recording the compression of each cylinder, from #1 forward to #6,
before starting it up. All went well with readings of 115, 125 and one even
135. Then came #6 cylinder. At first I thought the compression tester
broke. But after checking #5 again, there was no denying it. The sixth
cylinder had no compression. Not even1 pound. I pulled the car cover over
the entire heap and now here I sit. My next move will be determined by
which of the following arrives first; an offer to purchase, or some help to
guide me further in this seemingly endless quest for a car that works.To
say I am at the mercy of all of you would be an understatement. Ask any
question, make any suggestion, make any offer. I am open to them all. For
those of you who have been mercifily spared the history of my tribulations,
the subject is a 1957 MK1 engine installed in my '55 140 FHC. The
overheating problem became more and more sever until I had to stop driving.
Along the way, all the normal things were checked and either repaired or
ruled out. Getting the head redone was the last thing I have done in trying
to find the cause.. The compression in #6 was normal prior to removing the
head. During reassembly, all the cautions about #6 piston at TDC and turing
the cams to the proper position were adhered to. I can only hope that this
is some simple oversight that can be easily fixed. Please! - Aloha, Rob
XK-140 FHC
Rob, I would try pressurizing #6 through the spark plug hole with a source
of compressed air. Turn the crank so #6 piston is at top dead center on the
power stroke to close all valves. (I have made an adapter for pressurizing
cylinders by brazing the bottom half of a spark plug to an air chuck.) The
next step is to find out where the air comes out. Some possibilities are
the carb, the exhaust, the crankcase, the radiator, and the back of the
engine block. Once you find out where it's going, it will be easier to
determine how it's getting there. Good luck! I know you'll keep us
informed. - Mike Eck, '51 XK120 OTS, '62 3.8 MK2 MOD
Rob: Welcome back. I too have returned after a lengthy absence and remember
well from the "olde days" Sorry to hear of your ill fortune, but standing
back and assessing the situation calmly seems like a good idea. From your
description, you seem to have done everything right, but having 0
compression in # 6 says otherwise. Suggesting the obvious, reinspect cam
timing and valve clearances. If all seems right, introduce compressed air
through the sparkplug hole whilst #6 is at TDC on the compression cycle and
listen for the escape of air at the inlet side (carb opening) exhaust side,
water side (bubbles at filler neck)' oil side dipstick hole),and finally at
#5 sparkplug hole. If you bent a valve during the installation process, it
would appear at the inlet/outlet sides. In the unlikely event that a head
gasket was so damaged that it allowed full compression loss, it should
appear at water/oil sides or at #5 sparkplug hole. Keep in mind the
proffered advice is coming from a fellow still lifting engines from an old
pepper tree, but this is the approach I would take. Vaya con Dios! - Bruce
Baysinger
Rob: From now on I'll read all my mail before answering any of it! Well, a
little typing practiced never killed anyone. Regards - Bruce Baysinger
Rob, You didn't do a leakdown test before disassembly did you? If you did
and comps were OK, then you bent a valve during the clearance setting and
you now have to R&R the head again. I can imagine the disappointment. We
may be over around the 2nd weekend in April. - George Badger
Hello Rob, Don't panic ! There is an explanation! I have seen recently a
similar situation on a rebuilt head, a small piece of metal was stuck
between a valve and its seat. Check that both valves are closing properly
by measuring the clearance with camshaft. Good luck - Michel Gosset
Rob, Hi, I would guess that there are too many shims under the intake or
the exhaust valve cap. In essence, the valve clearance is too tight on one
of
your valves. Good to see you on the net again, I think we all were
wondering how you were getting along. - Edgar Blake
Oh, Maaaaan.....Isn't it time you tossed something in a volcano? Your saga
has kept me riveted for months. It's like a serial mystery. Go have a
couple attitude adjusters and a good night's sleep...we need you in top
form or we'll never get through this. - Jim Warren, in Vermont ...far
from your #6 cylinder
Rob, remember the thread about head gasket sealants a while ago? I got into
trouble once with just a little dab of Permatex somehow getting
onto an inlet valve stem and then being carried into the valve guide and
effectively causing the valve to stick open and on the first few turns of
the engine with a fresh valve job, the predictable result was that the
piston tipped the valve and I lost all compression on that cylinder which
happened to be #1, the rear one........right? Please tell me you haven't
made a similar mistake to mine! BTW, have you still got those air filters
for sale? - Good hunting, regards, John Morgan
Rob, Don,t go postal yet- I agree with Michel Gosset- you might just have a
chunk of foreign matter holding the valve open, which is causing your lack
of compression. Your travails have inadvertantly pointed out a common
problem that can appear when you do a head gasket or valve job; that is not
achieiving the desired results right off the bat. What to do, what to do?
When you are about to reinstall a rebuilt head, with valves closed and the
head upside down on the bench, fill the combustion chambers with gas,
laquer thinner, or turpentine and observe how good the valves contain the
fluid, if it leaks out the ports real fast, you have a valve that has dirt
under it, or a bad grind job. Do this test to each combustion chamber, I
have always found that the valves will weep very slowly, but if they drip,
you have to take it apart, and find out why. It is best to do this test
with the cams out, it makes it a lot easier. Okay you passed this test, now
prepare to test the head on the car. After setting your valve clearances,
reinstalling the head on the motor, connecting the chains to the cams,and
making sure the cams are timed properly, turn the motor over slowly by hand
using a socket on the front pulley( with plugs out). This will insure that
you will not have a catastophic mistake. (for instance if you timed the
cams improperly) Do not have the intake or exhaust manifolds on when you
perform these tests, you want to be able to hear the lack of wind coming
from the ports. Also you will need a helper to turn the engine, when you
are doing this testing. So let's set the scene: you have a strong helper
cranking the engine; the head is on with new gasket and new valve job; the
spark plugs are out; the head is tightened properly; the cams are timed
properly; and both manifolds are off. Install a screw in compression tester
in # 1 cylinder, have the helper turn the motor in the correct rotation
till he gets to the compression stroke (he will feel the resistance of the
compression as he is turning,( I'm being optimistic) when he arrives at
that point have him give a big burst of energy into his effort, you will be
monitoring the compression gage and the noises. You should hear the
compression leak down past the rings into the crankcase (this is normal
rings are not perfect sealing devises), if you have a valve sealing problem
the wind will rush out the port ( intake or exhaust), if you have a head
gasket leak, you will hear nothing at the ports, very little leakdown past
the rings, and also show low compression on the gauge. If everything is
working as planned, you will get a nice compression reading (about 125-160
psi.range via hand turning of the engine), and hear no noises at the ports.
If you get wind coming from one of the ports, spray a cleaner in the port
to wash off the seat, and then oil the clyinder, and retest, if the trouble
persists, you will have to take off the head and find out whats wrong with
that valve (this shouldn't happen if you did the fluid leak down test,
prevoiusly mentioned). If everything tests out nice, crank the motor over
with the starter, and you should get high and even compression readings
(I'm assuming that your rings, and clyinder bores are still in the
serviceable performance range). If the numbers are low read the above
again. I have found that if you do all the preliminary checks you will
insure excellent results; skip them and you will be tested by frustration.
Please don't throw in the wrench yet. - Regards, Wray Schelin
Hi Rob, I had a similar problem to this about 15 years ago. When I picked
up the cylinder head at the machine shop we backed off the cam bearing caps
to allow the valves to seat so they wouldn't get damaged on the way home. I
put everything back together and as a final check I did a compression test.
Everything was OK except no compression on #6..... Freak out time!!! I
called the machinist and he said I bet a valve shim dropped out of place
and it is between the valve keeper and the tappet, he was right. I hope
your problem will turn out as simple as mine was. If you check this out and
still no luck spin the engine on the starter a number of times and this
could dislodge any debris that might be caught under the valve edge. Good
Luck. - Bill
Greetings from Hawaii:
I come before you a humbled, but wiser man. Thank you all for the
suggestions to hunt down the cause of my latest problem. This time, I am
going to share the blame between myself and the book I used as a reference
during reassembly of the cams. You should all make a note of Autobook #702
by Kenneth Ball. I'm sure Ken is a nice guy, but he needs to brush up on
one thing. Let me explain what I found. There is a caution in his book
regarding the intake valves and how they protrude below the machined
surface of the head. So, keep the head elevated with spacers to prevent
valve damage. What the book fails to mention, and I learned the hard way,
is that the cams must be installed one at a time while adjusting the
lobe/tappet clearance. Do one and take it out before doing the other. Then
install them with the notch in the proper position. Don't turn them from
that point on until they are connected to both timing chains. My only
excuse is that I've never done this before and it would never happen with
my VW. I have removed the head again and did the leak test in each cylinder
head. With the exception of #6, they all seem to be tight. Two new valves
were ordered today and by this coming weekend I should have recoverd any
lost ground. Thanks again for all the help. - Aloha, Rob XK-140 FHC
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