I have quick question,
I used a nice FelPro compression tester the other day on my newly rebuilt 71
Spit engine.
the engine was cold, I got the following
#1 119lbs
#2 112lbs
#3 119lbs
#4 112lbs
Anything unusual, or is this good ?
-----Original Message-----
From: wizardz [mailto:wizardz@maxinter.net]
Sent: Wednesday, July 14, 1999 9:18 AM
To: MishimaSky@aol.com
Cc: 'Spitfire List'; Andrew Mace
Subject: black cloud
this message was forwarded from the VTR to the Spitfire list.....
It sounds like your valve guides may be badly worn.
At idle, oil is being pumped up into the valve cover, and at lo
rpms the oil is running down the valve giudes and accumulating in the
cylinders.
As you hit the gas to go... this excess oil has to burn away first, before a
good clean
flame front can expand in the cyl. as the gas ignites.
This puff of black smoke is either the oil being burned off, an overly rich
mixture burning off
or the carbon in the cyls. being burned.
My ...best guess... would be oil in your exhaust ports via the valve giudes.
At speed this would burn off drip by drip as it entered the ports, so you'd
never notice it.
Do a compression check. ...all spark plugs removed, carb throat wedged open.
Do it once dry, then a second time after injecting 10-20 cc of light oil
into the cyl.
you are about to test. If both sets of comp. tests show less than a 10-20
psi change
chances are your piston rings are not the problem.
Do a vacuum test. A steady idle vacuum should be roughly 19-22 in/Hg of vac.
and very steady. If it jumps around more than 2 in/Hg.. chances are you may
have a burned
and/or very worn valve.
YMMV ... just a few thing to consider.
Paul Tegler
1973 BGT - Daily Driver
1975 Spitfire -in Cherry Shape
1980 Spitfire w/ O/D - in re-hab
email: wizardz@toad.net
http://www.teglerizer.com
Follow 'Projects' for MG and Triumph stuff)
|