Technical Should I Even Consider A Tunnel Ram? Let's Get Scientific

I say screw the science

 

A good 10 years or so ago, Hot Rod Magazine did a good Intake shoot out on a baseline single 4bbl 355” SBC that
made 486 hp with $1500 carb and intake. The two best over all combos were the Weiand tunnelram with 450 vac secondary Holleys, and the Edelbrock “street tunnel ram” with 650 double pumpers. Both the tunnel rams made more average torque, and more torque below 3500 rpm, than the best t 2 plane tested. The Edelbrock/ 2 x 650 setup was the only one that made 500hp. The only down side to these two Tunnel ram combos, was cold blooded start up, and most passenger cars would require a hole in the hood/hood scoop. They even quoted Barry Grant as having said, “ he always believed that a smaller plenum, long runner tunnel ram set up would make a killer street/strip combo. At the time, both tunnel ram combos, including carbs, were half the price of the baseline manifold carb setup.A good friend has a really good pump gas hyd roller street 406 SBC. With a professionally ported Victor Jr. intake, it made 647hp @ 6600 rpm & 570 lb ft tq @ 5100.
With a port matched Weiand single 4bbl. Weiand, and the same 850 double pumper it lost 10hp to 637, and gained 10 lb ft to 580, both at the same rpm.

 

Don't own one.........always wanted one.
I mean you are bound to pick up 50/60 mph in the quarter AND on the street. They make a car look like it going 70mph...just sitting still"!!
From what "I heard"...and "they say"... a good stiff gear (4:11 sounds good) and don't be afraid to put some big carbs on it.
Just because a 454 performs great with an 800cfm Holley does NOT mean you need two 400cfm Holleys on your STREET TR. I don't think it works that way.
Good gears...4 speed tranny is a + also. All the CR you can manage LOTSA initial timing to clean up the idle with a healthy cam. You got most of the ingredients now.
Post lotsa pics!!!
6sally6

 

The 37 in my avatar has a 406 sbc with 9.5 compression Holley systemax aluminum heads , a mild comp cams solid flat tappet cam. I'm running a TKO 600 5spd and a 12 bolt with 3.42 gears. It also has an Edelbrock TR1X and two 600 vac secondary Holleys...It starts right up with two pumps of the throttle and drives very well, with only 50 miles on the odometer I hopped in and drove it to from San Diego to Bakersfield for the Hot Rod Reunion. Only stopped for gas once at Magic Mountain. Pulls like an F ing bear from 3000 to 6500.

 

Nothing should cause a hole in a hood except louvers.

 

Or a connecting rod.

 

Luckily it fits under the hood of my 37

 

or a torch, drill, sawzall, or maybe a plasma cutter for you high tech guys

 

Small carbs are important but the real killer in tunnel rams is the big plenum between the carbs and the runners. Once the air and fuel are mixed in the carb, the worst thing you can do is slow the mixture velocity down which allows the liquid fuel to drop out of the mixture and puddle, flow to one or two runners and not others, etc. The purpose of the tunnel design is to use the 'organ pipe' effect to super charge the cylinders at a narrow design RPM range and divorce the dynamics of weird pressure pulses thru a carb from the intake valve. They are an attempt to make velocity stacks, so important on injected engines, for a carbureted engine. Exactly the same technology of tuned exhaust headers. The idea of the big plenum is to divorce the 'velocity stack' runners from the messed up dynamics inside the carburetors so the tuned length runners can do their Helmholtz resonator thing. This design RPM is usually @ WOT at max power in a drag machine so low velocity isn't a problem. Try to idle one though and all bets are off. The theory shows the longer the runner, the lower the tuned RPM, and vice versa.

If you want to run one of these things on the street and you want streetability, consider filling the majority of the plenum with something that will reduce the size to that equivalent to a standard hi-rise manifold. this will give you streetability and the power benefits of the longer runners. Devcon plastic steel is great as a filler 'cause it is inert to all chemicals and can stand a bunch of heat. I have used it in modifying intake runner shapes in cylinder heads with great success. The ideal situation would be get one of those tunnel manifolds with the removable top. Then form the filler inside the lower portion of the manifold, grind and sand it to the perfect shape and bolt the top back on. You could even make the insert removable by casting the epoxy paste in the manifold with some sort of release agent (tin foil liner B4 the epoxy would be great).

I did my senior project in college on intake and exhaust manifold design and built a tunnel ram from sheet steel and exhaust tubing in about 1970 for the 331 hemi in my Willys. I think I was one of the first to make one, maybe beat the commercial guys to the punch?! Here is a picture of me in the process of making it circa '70. Note the hair! I ran it for a while on a Quadrajet carb but it wasn't very nice on the street. The car isn't a race car so I junked the tunnel and adapted a Holley 3-bbl carb to a stock 345 Chrysler manifold and the car came to life. The stock Chrysler manifold is a really good design, as good as any modern 180deg aftermarket manifold. Chrysler was a leader in manifold technology in the 50s.

Here is some reading material on the subject.
https://www.allpar.com/mopar/sonoramic.html
http://www.chrysler300club.com/uniq/allaboutrams/allaboutrams.html
http://www.chrysler300club.com/uniq/allaboutrams/ramtheory.htm

 

My previous reply was about the small block in my car, the new big block will also get a tunnel ram. This time around I'm going to try out a short plenum design with slightly diagonal 750 carbs, can't wait to start tuning it for the same 50/50 street strip action.


The extra Weiand on the left that I love the design of

 

Well I bit the bullet tonight and bought myself a Christmas present from a local guy on craigslist. A Weiand 5985 Tunnel Ram. I have decided against pulling the 450s off of my small block tunnel ram and am going to buy a pair of 600 Holley vacuum secondaries tomorrow for a different guy on the local craigslist.

My question is this, where am I supposed to hook the vacuum secondaries to? I literally have no vacuum assist on anything in the whole car.

 

I'll put my 2 cents in here. Tunnel Rams benefit with a longer runner in some cases, what does this mean? TORQUE! That will help a lot on the street, the bigger issue will be dialing in the carbs or go EFI. One year at Engine Masters they were required to run Tunnel Rams and everyone thought the engines would peak at a high RPM, make tons of HP, and not make TQ. Quite the opposite happened, big lesson learned for many on the subject. With that said if done properly it can work well and who doesn't like to see something sticking high above an engine?

 

vacuum secondary carbs have an internal passage that gives the diaphragms the vacuum they need to open. You don't need to connect anything to a port on the manifold to make them work...

 

Thanks squirrel. You'll never know unless you ask I suppose.

 

Make sure to check those internal bolts on the tunnel ram for tightness, you never know what the previous guy did, a little "small screw" threadlocker on them will make your engine happy.

 

I was actually giving them a look last night, completely loose. This TR actually has never been bolted to a car, doesn't even have the gaskets for the top plate.

 

Okay. Let me throw a "what if " question to all of you in hamb land. If you took say a 283/327/350 with either a stock or muscle car bump stick say from the high 3.90s to a4.60 lift, and you had a vintage single four barrel Edelbrock tunnel ram and you wanted to use multiple Holley 94s (2 or 3) is it feasible? Some will say why, but I am just throwing out hypothetical ?. I am sure the bigger Buick cfm 2 barrels would be better but I just want everyone to throw their opinion.

 

Sorry Smoothy, not trying to steal your thread but your question intrigued me.

 

Let the beer can throwing commence.

 

And to clarify, DDDenny has stated he wouldn't want to order a pizza with me.

 

Someone say popcorn and beer????.....

 

Did somebody say PIZZA!
If you're buying you won't hear anything out of me because my mouth will be full of pizza.
Oh yeh,, hold the anchovies

 

Late to the party & you already got the tunnel but I “feel the need” to throw in my 2 cents worth. U get what u pay for. Do not cut hole in hood. Go single 4 on good manifold with spacer & get it well tuned. NOTE all HAMBs stop reading. Add & at the track turn on 25 or 50 horse nitrous kit.

 

Cars on Drugs aren't what the H.A.M.B. is about even just a little bit. Leave that to the Tuners and Tweekers with there Imports.

 

I like what you have to say 99.98743% of the time, but for all out "greed for speed" there's nothing like a blue bottle tune up. As most know it really has been around since the end of WWII but it was a practice held as secret as J. Edgar's files on everybody. Just because it's in the open now doesn't remove the brutal increase in TQ and HP with a simple flick of a switch. Does it sound like I'm a fan? You bet your tunnel ram I am...

In order to stay in keeping with what we like it would have to be as hidden as can be. Some things will always make the Haterade list in the world of 2 furlong competition. "Juice" and delay boxes are always in the top 5 list, yet both will take the most dedicated from hero to zero in the blink of an eye on occasion. I have a 477 block missing the whole #4 cylinder wall from deck to bottom, from 9 o'clock to 3 o'clock, thanks to the wrong tune in a modified plate system. I also have a few "foul" and really late time slips due to miscalculation in delay. Doesn't make em bad, good, necessary, etc. For serious racing I'll always take both.

Carry on, just an opinion...

 

Yes but a balance tube should be used to connect the vacuum diaphragm together so they keep pace with each other..Holley should still sell the diaphragm covers that have a small tube installed so a rubber hose can be used to pair them together..

 

Are these the diaphragm tops you're talking about? These carbs came off a 396 in a 33 Willys with a low rise dual quad intake, so I'm hoping they're in the ballpark.

 

Yes those look like the balancing modules, also do yourself a favor and just use right stuff black rtv instead of the gasket in the tunnel ram, which are prone to leaking.

 

Alright, will do.

 

Here's some info... I run a weiand tunnel ram on a SBC with two Holley 600's , 4spd , in a 55 Chevy for a few years ....drove the car year around in Oregon....only problem I had was getting into the distributor, Accel duel-point,to due any adjustments .... depends on if your just going for a visual effect or you actually want to put it to work and your drive style....by the sounds of things it's looking more like you just want something poking out of the hood...with several little carbs instead of some real carbs for serious power....not saying it wouldn't work but I guess it's the same as other guys saying why a tunnel ram when you can get the same or better results with a single carb on a short intake...well if we did everything the same as the other guy it would be boring....so if your going to go for it just do it before you or someone else talks yourself out of it ...if your unsure from the start then don't even bother......

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