ok here goes. many of you guys already know Im building a new 347 and Im wondering what the advantage would be (if any other than the factor) to running 2 4barrel carbs and a tunnel ram as opposed to a single 4 barrel carb? what exactly does a tunnel ram do? is it designed to enhance the air flow and speed of the fuel delivery? Ive also been thinking of a super charger (I dont know if I can get away with the super charger let alone afford one) it would AWESOME if my engine was super charged I would love to see my engine sticking out of the hood so high I have to look around it to make a right turn lol thanks for any info you guys have
For $2600 or so, you could do a low-rise charger with a single carb. But I agree, Mavs look GREAT with a huge 6-71 or 8-71 sticking out the hood, or even without a hood.
I'm not a hundred percent sure but i think tunnel rams give the air flow/fuel mixture a little high velocity into the engine. more of an old school approach..IMO i would supercharge it if you can get the cash because i think tunnel ram intakes are pretty pricey vs. a normal duel plane intake. but that's just from my understanding, second opinion are good.
I checked out summit and for a tunnel ram and 2 4's and this seems like a decent price and a low budget option http://www.summitracing.com/parts/cmb-03-0179/overview/make/ford
I've messed around with a few tunnel rams and we actually had one built for a friends 351C in a 32 Ford. By the time we put everything together he had almost $2k invested.............the car ran great from about 4000rpm to redline at 7800..................and got about 8mpg. We eventually went to Holley carbs as they gave better results. There are three areas that make tunnel rams just a little dicey for the street; 1. Tunnel rams are single plane intakes with a huge plenum....this large plenum reduces the signal to the carb at low rpm and part throttle. 2. Two carbs connected to the large plenum mean each cylinder is drawing through four venturis at part throttle.......this will seriously reduce venturi velocity, giving poor atomization and fuel distribution will be the pits at part throttle. 3. When only the primaries are open, the runners directly below the primaries get much more fuel than the others. I guess what I am trying to say is that all of the above issues make a tunnel ram extremely hard to tune for the street...............not saying it can't be done............but you will start applying band-aids like running richer jettting to get the lean cylinders approximately right........at the cost of further richening the already too-rich cylinders..................and using huge amounts of initial timing to light the lean and poorly atomized mixture you will end up with. Plus you really should have at least 11.0 to 1 compression and have a camshaft that is over 600lift to make the tunnel ram come alive. Tunnel rams were and still are made for race only WOT applications where the work very well.....................................................IMHO
"Tunnel rams were and still are made for race only WOT applications" not this one sitting in my shop...it's Mikes (M.A.V.) street car...
Frank, is that one of those Wieand Street Tunnel rams or have mod's been done to improve the manifolds shortcomings?
olerodder is generally right with the above. BUT.. the smaller design "street style" tunnel rams can be EXCELLENT streeet/strip manifolds for more moderately built engines.. IF.. they are heavily mod'd and welded/epoxied up to increase low rpm velocity. Then of course the motor needs to be "tuned" to maximize it. No easy task.. unless you're a hardcore engine builder that uses a grinder every day. Look around at many of the old timers mod's.. filled floors..shrunken plenums.. balance tubes..adjustable progressive linkage.. etc. Then take a look at the engine masters challanges to see how much low end torque those manifolds can make if set up correctly for the particular engine it's sitting on. Most engines there are better suited for them with longer strokes with decent compression though. Smaller/lower compression motors would surely need twin 390's to really keep a stronger booster signal though. On another down side.. they are very cold blooded design for a street type motor. They need just a bit of heat to really work well.
I ran a tunnel ram on the street with hi compression 289 for years. You should use 390 - 450 cfm carbs for best results on the street. Still have the intake and inline linkage and would consider selling it.
Had a friend that had one on a 4V Cleveland in a 68 mustang and it was a great running street car. I really couldn't tell you much about the engine though and as stated before, the engine needs to be built with the intake in mind and this one must have been.
I ran one on my 429 back in the 80's. The Weiand had a smallish plenum and long runners. The long runners helped you get the low end and if it had a larger plenum (like the same manifold, but built by Offenhauser) it would have given it more top end. Essentially you are tuning the intake runners so that the overlap of the cam isn't able to pulse back out through the runners. Anyhow all that said, the intake I used was incredible in my opinion. I really liked it, but then I had a big cam, big cubic inches, heavy car and twin 660 center squirter Holleys. If you take a look at the intake manifolds on the fuel injected 5.0's of the late 80's and early 90's they are essentially a tunnel ram that was folded over to one side (note the long runners). They are able to get away with this on an injected car because the fuel isn't put into the airstream until right before the valves. If you put it in the intake with a carb where the throttle body would be, then it would most likely drop out of suspension with all the turns in the intake. Sorry for all the long technical stuff, but this all interests the crap out of me.
I have a Weiand tunnel ram on my 393 Cleveland using dual 450 Holleys and I gave all the info on my induction combo to Comp Cams during the cam selection. My speed shop also built my C - stroker with the intake in mind and I even went to 390 gears with this set up in mind.
I have an Offenhauser intake on mine, it has a split plenum and I figured it may run a little better on the street than the Wieand (I have no proof of this however). I run 2 holley 450`s with mechanical secondaries,they are only around $180.00 each from Summit or Jegs.I have a Mallory unilite distributor ,it has a small cap and body and clears the T-ram easily. My carbs are mounted inline (not sideways) and use a Summit brand chrome fuel line set up that has a built in filter. Of coarse any car will require its own tuning set up, but I can tell you that I ended up stepping the discharge nozzles (squirters) up several steps larger than the carbs come with. I also stepped the jetting down a few sizes. My car always starts up instantly, Idles well,never "loads up"and has VERY quick throttle response. When running a tunnel ram you will need to run a fairly high rearend gear (Mines a 4.11 with 28" tall tires) and a looser converter (mines a 3,800 !) I don`t know, but you might be okay with something like 3.55`s and a 3,000 stall converter. I would only cut the hood if I had a spare ,and then only AFTER I had ran the T-ram for a while and was happy with it! Do a search and you will find a few other threads here about Tunnel rams and some of the myths with running one, along with Facts about them posted by those of us who actually have been running one
