William wrote:
Subject: Intake manifold fabrication tips.
For all you guys getting injector runners this week I have a few
suggestions for putting them together. The most important thing
is getting all the injector sockets to line up so you can use one fuel
rail. To minimize the work you should build the fuel rail first
and use it along with the four injectors as the alignment jig.
You need to make a decision on how far apart you are going to space
your injector runners I chose to space them the same as the first
batch manifold casting I was using. Bill Schertz I think spaced
them a bit further apart.
Since I did not have my injectors
yet I took another approach. I made a block of wood out of a 2 by 4 and
used a 21/32nd counter bore to make four holes. The size of the block is
12 inches long 1-1/2 inches thick and 2.6 inches high. I used
a wood band saw but on hindsight a table saw would work better.
I machined four slugs of aluminum .68" in diameter and two inches
long. I pressed them into the center of the block of wood with .65 inches
protruding. These just fit the injector sockets on the intake
runners. I realize you don't all have lathes so four 23/64 dia.
drill bits will works as well. Let them protrude from the
block of wood about 2 inches. Cheap 23/64th drill bits cost
about $2 to $3 each.
I have a CC (Cheap Chinese) table saw I bought from Harbor Freight
for $100. I bought a $50 carbide saw designed to cut aluminum.
Goes through aluminum like a hot knife through butter.
The same blade will work in a cut off saw or a Skill saw.
Be very careful when you trim the injector holders to size.
The piece cut off will take off and fly back towards your chest at
high speed. Don't stand behind it. It will travel at least ten
or fifteen feet. Make sure the table saw is bolted down or clamped
to the work bench and use both hands to hold the injector holders
while cutting them. This saw blade will cut a finger off in one milli
micro
second or less.
Use a die grinder with carbide burr to remove the casting flash on the
intake
end of the injector holder and sand it smooth before you attempt
to trim it to size. That will allow it to slide on the table saw
with out catching on anything.
------------------------
Paul,
All good tips. One might want to talk to your welder about the close spacing
of the tubing when it becomes time to weld the bends to the injector
holders.
I naively assumed that the distance from the flange to the face of the
injectors was uniform between the two size of castings, now I am going to
have to go check the alignment between the inner and outer injectors to
verify or determine alternate fuel rail construction.
Bill Schertz
Good point. I am planning on using this on the dyno so will use
rubber hose to make the connections. The rubber hoses will have sections
of tubing inside them to smooth the transitions. This will allow me to
tune the engine for max HP by moving the torque peak around a bit.
The distance IS controlled between the BACK of the flange and the
injector sockets. If you jigged off the FRONT of the flange you might
be OK but no attempt was made to hold THOSE dimensions.
There is a bit of in and out allowed on the fuel rail but you
might need to place a shim washer here and there between the fuel
rail and the back of the injector if the force on the
sealing O-rings is not uniform. Belleville spring washers
in the connection between fuel rail and injectors would be ideal.
However air leaks in this area matter not. It just affects
the position of the throttle at idle.
When everything is working right you could put a thin layer
of teflon tape around the injector and press it in the hole to
further seal it. I would suggest red RTV but that is not impervious
to fuel and some small amount of fuel could leak back around
the body of the injector and attack the RTV. Perhaps there is another
sealant that remains flexible and that is not attacked by fuel.
Paul Lamar
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