Join Date: May 2008
Location: Madison, Wisconsin
Spica to Weber Conversion - Fuel Supply
I am converting my 74 Spider to Webers, euro intake manifold, filter box, along with significant headwork, cams and compression changes plus new Motronics.
What is the best way to handle the fuel delivery system? I would like to hear from others who have done this conversion on their Spica system and what worked best for them. I have Pat Bradens "Weber Carburetors" book and it describes the Shankle conversion kit and reuse of the Spica fuel delivery system.
Here is what I have now. I restored and upgraded these components just before taking the car down for painting and engine and other work.
Refurbished fuel tank from later S2 with internal pump.
New hard lines in trunk to route fuel over the exhaust pipe.
New inline filter and new primary fuel pump with modified supports behind differential.
New rubber fuel lines on supply and return.
Supply line from tank output to inlet side of fuel pump is 12mm, 1/2" diameter. The rest of the system is the metric equivalent of either 5/16 or 3/8, can't remember which.
The fuel delivery system, including the low pressure light worked well before I pulled the car off the road for painting and engine work.
I know the Spica pump system runs at 12-14 psi at 0.6 gal/ min and the pump does not like to be dead headed. I know the Webers like fuel delivered at about 3.5psi.
I like the idea of leaving the existing Spica front fuel filter in place along with the return lines but do not want to compromise the Weber performance or over stress the primary Spica Fuel pump.
I understand there are a couple options but not sure what others have done to overcome some of the issues.
I am told Carter pumps will fit in the Spica pump bracket and put out 4 psi.
I think they have components that will allow them to mate up with 1/2" inlet and 5/16" outlet. Their techincal service dept is out until Jan 2.
Have any BB'rs used this pump?
Did you leave the intank pump in the system?
Did you leave the Spica filter and return lines in place and simply use a tee connection to carb supply and return line?
Shankle's kit shown in Pat's book, utilized all of the Spica fuel supply components. It appears he provided a tee fitting to a regulator that fed the carbs and the other side connected to the return lines.
Has anyone implemented this system.
Another option may be to modify the Spica final filter housing to reduce the outlet pressure to 3.5 psi and leave the whole system in place. The low pressure light would have to be disconnected. I am not sure exactly what would need to be changed here and how. I am ok with doing this if it has worked well for others, not looking to experiment though.
I think that tuning the Weber carbs will be enough of a challenge all by itself. I would like to keep the fuel supply system simple and reliable.
I do intend to preserve the Spica components so nothing will be discarded.
Sorry about the long post, appreciate any insights.
74 Spider - Re-Assembly Underway
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74/80 Spider - Down for significant refurbishing
76 & 79 Spiders - Crushed but parts live on