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 ‘Tanks 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

[cornfedbill]

I would switch to a single plane intake for the EFI. You will be happy you did. EFI does not have the throttle response issues that come with carburetors and that dual plane intakes were designed to correct.

You should have a 3/8" feed and not less than 5/16" return for a moderately built 350. If you have a big fuel pump, you may want to use a 3/8" return line also.

[btmatt]

there is a video in the Motor Trend TV series Engine Masters that covers your exact question. If i remember correctly, they attempted to compare a carburetor and Holley Terminator back to back on SBC and had to switch from dual plane to single plane intake for the fuel injection to tune properly.

Video should be on YouTube

[SSLOW6.0]

there is a video in the Motor Trend TV series Engine Masters that covers your exact question. If i remember correctly, they attempted to compare a carburetor and Holley Terminator back to back on SBC and had to switch from dual plane to single plane intake for the fuel injection to tune properly.

Video should be on YouTube

I wouldn't necessarily ditch a dual plane, the key thing is to make sure that there is at least some plenum area under the throttle body. I'd use a 1 inch spacer under the TB first and see how it runs BEFORE swapping an intake. The issue with the dual plane intake that they used was as design that didn't allow any crossover between the two planes.

Notice how the center rib of the intake goes right to the base of the carb or the TB? This is what a caused the issue.



The SBC RPM has a drop in that plane divider.

[SSLOW6.0]

I would switch to a single plane intake for the EFI. You will be happy you did. EFI does not have the throttle response issues that come with carburetors and that dual plane intakes were designed to correct.

You should have a 3/8" feed and not less than 5/16" return for a moderately built 350. If you have a big fuel pump, you may want to use a 3/8" return line also.

EFI or not, the trade off isn't throttle response, its torque. A Single plane on street driven mild 350 is going to kill a bunch of low speed torque.

[Mr Nick]

I have the Sniper on my SBO, Performer RPM intake with the center divider not cut. 1/4" 4-hole spacer to stop the annoying whistle at part throttle.

Runs excellent.

[elwaupo]

Sniper Install Update!

Ok my old high school buddy and another friend insisted on not doing this without them. I did switch to the single plane manifold, really dont know if made a difference but I’m glad I did. It actually went fairly smooth with the exception of learning how to install -AN6 fittings, BUY THE KOUL TOOL KIT! I did run 3/8” fed and return steel braided lines into my “Tanks” kit taking my time to route , secure and make it as clean as possible. I had to use my HEI distributer for now but I’ll install the Duel Sync in a month to see the difference. So far the HEI performs very well.

First start up went very well aside from minor wire tie ups and cleaner vacuum hose routing. On the first test drive I couldnt believe the throttle response as I described it to my buddies as ‘Crisp’, almost too snappy from a dead stop but I’ll take it! I drove it to my girlfriends house which is a 40 mile round trip and it runs so smooth but the real test will be my 84 mile round trip commutes to my job.