MP source for guage and Lightspeed ignition

I have a Vans MP gauge and Lightspeed ignition, which both need to be hooked up to read manifold pressure.

Van?s MP gauge directions have you getting the pressure from the #3 primer fitting location. I have heard others say that MP reading should come from the around the carb (exactly where, I am not entirely sure).

Is it ok to have a tee connection from the #3 primer fitting to drive the LS? Would I be better off teeing off the carb connection? If so could you please explain where the fitting is? Or is there a better way to do this altogether? Thanks.

A tee off the primer fitting will work great.
Std auto vac line and plastic tee fittings from your local auto suppliers will do the trick. You will need a fitting from the cyl. though.
Best

mp source

Kahuna said:

A tee off the primer fitting will work great.
Std auto vac line and plastic tee fittings from your local auto suppliers will do the trick. You will need a fitting from the cyl. though.
Best

Click to expand...

I ran a single line from the primer fitting to a T @ the electronics box. then straight to the mp guage.
Tom
RV3
Lightspeed (BRAIN UNIT AFT OF FIREWALL per Klauses recommendation)
flying 2000+

Use a restrictor fitting

As the other Gent's say the primer fitting, usually the right rear #3 jug. You will see little pipe plug in the head, usually two plugs, one on top and one bottom. The top ones are usually for fuel injection and bottom for priming for carb installations. Older Jugs may only have one lower plug.

Once the plug is out of the cylinder you screw in the AN fitting. You run a hose to the firewall and usually a bulkhead fitting, you than can "T" off that and feed both the LS ign and the MAP gauge on the back side of the firewall. I assume you will mount both LS ign and MAP sender on the backside of the firewall.

Suggest you use a substantial hose on the firewall side. ON the back side of the FW you can transition to poly-flow or other suitable light hose with barbed connectors, which are fine. It is a little tricky to transition from heavy hose to light plastic/vinyl hose, but check out Dan's site for one idea.

Some links to Dan's site might explain.

http://www.rvproject.com/20030729.html
http://www.rvproject.com/20040514.html
http://images.rvproject.com/images/2003/20030720_man_press_hose.jpg

If you don't get a restrictor fitting (AN fitting with a small orifice of say 0.030) you can get some gunk (fuel/oil) in the line. You can buy it from Van's or make your own by drilling out a rivet and bonding it into the AN fitting. Also a big leak without the restrictor can cause the engine to run real rough.

George