Here's a nice B20 Head that I reworked to provide 9.8 compression and ported the
throats. This was done last year (2003) and the performance increase was
readily evident. I drive this car as my only transportation and therefore
clocked 16,000 miles with this head.
Same time but from a different angle. Please notice that they are not all
the same height! A Volvo B20 has exhaust valves on the outside and the two
middle ones. I adjusted the valves 4 times because I kept listening and
could hear a difference. Each time the valve gap had narrowed...mostly #5.
Here is a close up of what I found occurring. They're coming up!
From
the bottom. The valve has begun to be pulled into the head.
A
close up reveals the extent of the damage. Without hardened valve seats,
the softer metal just gets banged and hammered into itself. Loss of
compression is the least of the problem. Performance is terribly effected
as is the heat dissipation and even the timing. The valve will close well
after it is designed to close. The heat at those edges will burn the valve
and the valve guides wear. Thinking more about it, If I open the gap to
.020 as per the cam spec, how much am I "clearing" my little tunnel I
have begun to dig??
Different view. Cylinder #2 and #3 are the worst.
Here is the beginning on cylinder #1
I have the head getting new hardened seats and will provide pictures next
week with the head done!
volvo1800@georger.com
Fixed Head !!
Here is the straight, finished top view of the repaired B-20 Head
This is what a hardened insert looks like after it has been installed.
Different valve but better view. Not easy to see unless you know what you
are looking for.
Another
view. Remember ...this is the same head as above.
Oh! I am so happy!
This
is a view of the new valve guide. I now have 4 new exhaust guides.
This
head has been "ported" and "decked" with a .060 removed from
the bottom to change the "CC" of the combustion chamber from 57cc to
47.5cc. This results with a compression ratio of 9.8:1.
This
is a "F" head and I have reverted to SU carbs. When this is done
the injector hole needs to be blocked. It can be done with a soft plug but
the small hole should be blocked all the way into the throat to avoid disturbing
the air flow and direction.
Intake port close up. Extreme "porting" for racing and high
performance will go into the throat and cut away some of the valve guide to open
up the volume and increase the velocity. This needs to be done by an
expert. There's water flowing through the head and you can get too close
or you might shape the chambers and not get the desired
results.
This condition is only present in the exhaust valves. The intake valves
are closed when the big heat goes by as the cylinder breathes out. I am
very happy with the work and recommend whenever you are next busting into
your engine... have this work done. The cost of the work was $350 for 4
exhaust guides, 4 hardened inserts, and one exhaust valve (it was
"burnt"). The burned valve was from the valve going down the
tunnel and essentially disappearing and not performing the function it for which
it was designed.
The amazing thing was how well the car ran right up until I put it away for
the winter. I listen very carefully to my car and have for 23 years.
I really know what is right by the sound of the B20. The performance was
not noticeably impaired for a road car and although I adjusted the valves 4
times in the 16,000 miles I drove in the first season since the rebuild, I
cracked open the engine only to investigate the frequent valve
adjustments. Why was the adjusting necessary? Bingo! I am now
enlightened.
