PAGE 1: "THE SKUNK"
PAGE 2: ABOUT TUNNEL RAMS
PAGE 3: HOW & WHY
PAGE 4: BUILD NOTES -- 302/5.0 SWAP, C4/5.0 NOTES, MII ENGINE MOUNT FABRICATION

ABOUT TUNNEL RAMS

A tunnel-ram intake uses wave reflection to increase volumetric efficiency, which is the degree to which the cylinders fill on each stroke. The fuel and air mix together in the top end of the intake (called the plenum), and this mixture is forced into each cylinder down cylinder-specific runners (the tunnels) that are extended vertically, which effectively increases the internal volume of the cylinders by loading them with the ram effect, which is the key to volumetric efficiency. Simple, no? More fuel & air in the cylinder = bigger bang = more torque.

A dual-quad tunnel ram supplies the cylinders as if the engine was 2 separate 4-cylinder (V4) engines. The dual 390cfm carbs I'm running, when wide-open, provide 780cfm of airflow, which is considerably more than optimum for a 5-liter, even at the efficiency provided by the tunnel ram. The tunnel-ram won't "drown" the engine, however, because the fuel/air mixture is already mixed, and suspended in the plenum waiting to be used; the engine pulls as much as it needs.

I read and heard a lot about tunnel ram intakes when I was spec'ing this out, some of it positive but most of it negative. I saw the tunnel ram and the carbs on eBay for what I thought was a steal; I bought them 'cuz I thought they looked cool, and then started researching. I'm glad I bought them first, because I ran into so much negative information on tunnel rams that I never would've done this had I not already owned them.

I was told at least a dozen times to drop the idea -- that it would never work, that tunnel rams aren't for street applications, that I was wasting my time, "You'll put your eye out with that thing" ;) , etc. (See below.)

Nearly everything we were told when we were asking around about tunnel rams -- particularly dual-quad tunnel rams -- for street applications in person and on forums, included but is not limited to:

- needing a cam too large for the 5.0 to accomodate
- fouling plugs
- making headers glow red-hot
- idling at 1500+
- no power below 2500 rpm
- no power below 3000 rpm
- no power below 4000 rpm
- needing to rejet carbs
- needing to run off one carb
- roller cam engines will valve float in ideal tunnel-ram rpm band
- vacuum would be too low for ignition advance; would need to change to a pure mechanical advance distributor
- needing to block off 4 of the runners of the tunnel ram
- less power than with a good single quad
- impossible to tune
- needs tuning every weekend
- runs like crap when cold
- runs like crap when hot
- needing a hotter fuel pump
- needing high-octane gas
- needing a bigger coil
- electric chokes won't work
- chokes will never sync
- will die at idle
- risk of a blower-type explosion at wide-open throttle

Everything listed above is wrong.

I am running a dual-quad Weiand 289 street tunnel ram with sync'd, electric-choke vacuum-secondary 390 cfm Holley carbs on a beefed-up 5.0L H.O. with a custom cam, gasket-matched heads, and a seriously built C4. It runs killer. (For what it's worth, I was also told that the later-model 5.0 H.O. motors wouldn't fit in the Mustang II. Technically, they were right, but I made it work anyway.)

The intake assembly swapped right in (granted, once I cut the hole in the hood) and all I had to do was replace the cap and rotor (clearance issues.) It starts on the third stroke and idles at 800 with an intimidating rumble and enough torque to shake the entire car.

The roller cam 5.0 is a high-revving motor with excellent throttle response, and seems perfectly mated with the tunnel ram, which comes alive at about 4000 and pulls long past what my rpm gauge will show. When the secondaries kick in it's like being shot out of a cannon.

Maybe it's from using small marine carbs instead of dual Street Demons, which would've been a nightmare to tune on an engine this size. Maybe through blind stupid luck we got everything exactly right. Maybe the Horsepower Gods accepted the sacrifices of knuckle skin and blood and finally had mercy on me.

Or maybe it's that the naysayers either never tried it, or went too big on their dual carbs. Most of the horror stories I heard came from someone who'd heard of someone whose friend tried a dual-quad tunnel-ram. I did hear from a guy who had tried dual 750 cfm's on a 350 Chevy and gave up after months of tinkering because he "could never get it to run right." Big surprise.

If you want two fours ridin' high on a small block, I say go for it, and don't let anyone tell you that it can't be done.

NEXT PAGE: HOW AND WHY