Intake Manifolds

[elwaupo]

Ok this is the weekend I’m finally going to install my Holley Sniper EFI into my 69 Camaro. I’ve already bought an ‘In Tank EFI’ fuel tank and fuel pump, installed my headers with the O2 bung and sensor installed and ready to go.

My questions are this, I’ve heard that Dual plane manifolds don’t work well with EFIs. Should I change out my Dualplane to a single plane intake manifold? My second question; I do have my factory fuel line and a return line for the canister already, can I use that extra line as a return line and do I need to use a bigger fuel line for the EFI?

My engine is a mild 350/TH700R

[572Camaro]

Good morning. I noticed no replies yet and you are planning to do the work this weekend so let me try..,
Dual plane intakes can create fuel charge reversion which carbs like but self learning EFI systems do not. I have tuned EFI systems where dual plane intakes have caused issues like surging and hard to control air/fuel ratios.
If it were me, I would take the time and money, and convert to single plane intake.

Next, what are your tubing diameters? I would prefer 3/8" minimum supply and return. I personally run 1/2" supply and 3/8" return on my 572ci beast. With you running a 350ci, 3/8" diameter supply would be fine. As far as return line, do the test. With ignition on, fuel pump running, engine off, set your fuel pressure. If it controls, you are fine; if it climbs, you need a larger return line.

Now for a few other things..,
What is your idle vacuum reading in "Hg? I like to see at least 10" of vacuum at idle with engine warm. The reason is when self learning systems learn, they need wider variations in manifold absolute pressure which is the primary indication of load.
What are your cam specs? Lobe separation angles between 112 and 116 is optimum for efi.
Finally, be super careful when you run wiring.., keep your efi wiring away from noise producers like spark plug wires, ignition boxes, etc
Please reply back and let me know .., I want to help!

[572Camaro]

Any update?