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Old 05-12-2002, 10:42 PM
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Post Ramming for distance?

Alright I'm no wrench I'm a bodyman so I need some heeeeeeelp, I've been told if I'm going to run my truck as a daily driver/semi daily, that putting a tunnel ram dual carb intake on it isn't a good idea, tell me the pros and cons of a tunnel ram, not for just my situation but altogether. A pre-emptive "greatly apreciated" is in order and so forth given
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Old 05-13-2002, 07:16 AM
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Hello.
Im no pro either, but I'll tell you some things Ive heard.
First, its obvious that any problems will be overturned by the great looks. There is problems with hard starts, backfires, loss of tourque and if your running in all weathers, a hole in the hood.
If you run smaller carbs like Edelbrocks 500cfm or Holley's 390's it wont be as bad, but be carefull not to overcarb it.
I know these are not specific helpers, but it will maybe get the ball rolling. HG
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Old 05-13-2002, 07:41 AM
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Heres something that every engine owner should konw. Velocity equals torque, flow equals horsepower. The reason low rise dual plane manifolds make so much low end torque is because its not an easy flow path to the valves so the air/fuel mixture has to travel faster, creating greater low end torque. The higher rise manifold you go, the easier the flow path, so the greater the horsepower. But, you also loose that torque. For a street rod or a race car i think that a tunnel ram is cool, but for a daily driver i think that its simply overkill and highly impractical. I would suggest an RPM air gap manifold from edelbrock for the street. I think this is as good as carberation can get as far as good torque and horsepower. If you notice most rpm ratings for tunnel rams you'll see that they are only good for about 3500-8000 rpm. That means that anytime below 3500 itll bog and be a waste of time. TO make it better youll need to match the rest of the engine components to the intake and you'll probably end up with a race engine by the time you get done...not good for the street. If i were you i would focus on torque if its used on the street.
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Old 05-13-2002, 01:57 PM
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One of my high school friends had a 289 Ford in a Mazda 808, it had a tunnel ram but it was not like the others I had seen. It had quite small runners and a small plenum under the carb that was not linked to the rear carb. From the outside it looked just like any other tunnel ram I had seen with dual carbs etc. He ran two 600 cfm vacuum secondaries on it which worked just fine. The car was driven daily but wasn't winter driven of course. I rode in it many times and once the carbs were jetted properly it never backfired or ran funny, it had a 280 duration cam which was pretty radical for a 289 Ford. It was a very strong runner even with an automatic, the rear axle was a stock Mazda 3.92:1

The one thing I have to say is it was impressive looking but a total pain to drive because of the restricted view, he constantly was leaning over the passenger side at lights to check for pedestrians on the right. I would rank this mod up there with Vertigate shifters, cool to look at but very tiring to drive all the time.

I have built 302's that were as strong or better performers than that engine, so I don't think you can really realize the benefits of a tunnel ram on the street.

Still think they look great though, especially raw cast not polished.
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Old 05-13-2002, 02:46 PM
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unless you are running at least 3.90 gears it will be a pig to drive. only a big block with some commpression will live with this setup.
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Old 05-13-2002, 06:01 PM
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Ok, I'm no engineer but I remember back in school I think I remember they called what happens to the fuel particles atomizing as they travel through the intake. This is affected by velosity and shape of the runners. From what I remember when the rpm's are low on a tunnel ram set-up the fuel particles can't atomize properly and form tiny fuel droplets along the walls of the intake runners. That's why their idle quality isn't as good as a dual-plane with a smaller plenum chamber, but their design also allows for terrific high rpm power. My opinion, looks cool but I would probably not use on a daily driver, and definately not with a stock auto trans. Just me .

[ May 13, 2002: Message edited by: dmorris1200 ]</p>
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Old 05-13-2002, 10:15 PM
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Thanks for the advise, I heard all that from my late brother but was just conferming, I can't afford a blower so I was thinking about the tunnel if there wwas anyone who could say anything good for the daily but i presume I'll just run an edelbrock air gap with some velocity stacks with some cool custom covers
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Old 05-14-2002, 12:25 AM
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You're looking for double trouble! You'll have problems synchronizing carburetors AND when one goes south, which one will it be? And when and where will it happen? You didn't mention engine size, so I'm going to assume, you're reffering to a small block. Tunnel Rams are great for balls out performance but on the street nothin but trouble. I would heartily suggest a super victor dual plane, or an edelbrock air gap. You can't go wrong. Both are fantastic performance wise from 3500-6500 RPMs. I've been drag racing since the late 50's and would've gave an arm if they would've had one of these manifolds availavle back then. I have one on my camaro 383 ci, and when you open the secondaries you bettter have a tight grip on the seat covers coupled with fuelie heads and a crane roller extreme energy cam and 10.5:1 child's and albert's its heaven on earth! Go is better than show. And if it don't go, chrome it! Best of luck!
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Old 05-14-2002, 02:35 AM
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alot of guys have problems running multiple carb setups.alot of spitting sputtering choppy dogging,etc.
the key is( and it`s no magic solution,but usually gets overlooked)you have to deliver more fuel for it to atomize properly, so it isn`t dripping down the throats,you need a second fuel pump ,electronic that you can regulate.we have always put them midway on the car so you get good draw and some line pressure before the engine,and run a splitter so it ties in the two lines or three that feed the carbs,better to have more fuel
and regulate it down than to starve the carbs, how many guys can synchro carbs at a 4000 rpm idle??when you ask around,apparently alot of them.
good luck!
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Old 05-14-2002, 03:59 AM
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i wouldn't run a tunnel ram on the street everyday either. it requires a lot of rpm, the carbs are a pain to get adjust, they can flood, it will be really bad if the aren't cailibrated.
It also depends on how built your motor is. If it is nasty a tunnel ram would work okay if you get the carbs adjusted. But if it is mildly built I would put a good dual plane manifold or a LOW RISE single plane such as the wiegen X-celerator.
or even if your dual carbs a regular LOW RISE dual carb mainfold such as the offenhowsier. A tunnel ram will deliver the power on the right engine.
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Old 05-14-2002, 05:41 AM
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The problem is that the tunnel ram manifold is DESIGNED for high rpm. Period. An intake manifold must do several things all at once and it's not possible to design one for high and low RPM at the same time reguardless of wht the manufacturers say. For low RPM, one wants relatively high runner velocity, relatively long runner length (about 18" for 1088-2000RPM), and definitely no big plenum between the runner and carburetor. The runners need to send a strong signal to the carb venturis. It's really pretty simple in theory; there are pressure and vacuum pulses flowing in the intake runners at the speed of sound and you want a strong pressure pulse at the intake valve at the instant it closes to "supercharge" the cylinder. For the 1800 rpm stree cruiser a boost happens at about 18" runner length. The shorter the runner, the higher the optimum RPM. Also, the plenum in a tunnel ram is bad at low RPM because isolates the carb from the very short runners which in turn are too big and too short to give the low speed performance you need. The carb will see a very weak vacuum signal, the plenum velocity will be so low that gas will condense and drop out of the flow stream, and low RPM performance will be very disappointing. Runner distribution will be very poor so you will need to jet rich to avoid lean cylinders. Add to that the lack of exhaust preheating and it will be less attractive.

If you want that monster engine look, consider building your own! You can make a great looking intake that will work fairly well on the street. 18" runners of 1 1/4" exhaust tubing and a very small plenum, preferably with a divider plate to isolate half of cylinders from the others and a 650 carb would be a good start.

Can you run a tunnel ram on the street? Sure. Will it be easy? no. Will you get tired of the poor performance? Depends on how much attention you get at the Sonic Drive-in!
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Old 05-14-2002, 06:50 AM
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I'm gonna have to disagree with the majority of responses. For years there have been too many "old wives tales" about tunnels rams. Most of this comes from trying to run race car setups on the street. The fact is a well tuned small runner tunnel ram works fine on the street. I have run three different setups. On a 331" small block I ran two 625 AFB's with an automatic in a Chevy LUV with 4.11 gears and it ran great with lousy mileage. I ran a 427 Chevy in a 69 El Camino with two 600 Vac sec Holleys and it did hiccup a little when cold but most of that was the heavy overlap cam. I even towed a sand rail with this quite a lot with NO PROBLEMS! Currently I have a mild 455 Olds with an Offy Port-O-Sonic tunnel ram with a single Demon 750 in a '27 Ford. It runs perfect! I drive this car 3-4 days a week and except for the visual impact you wouldn't know it wasn't low rise with a stock carb. HOT ROD magazine did a tunnel ram teat a couple of months ago and dispelled many of the myths, go back and read it and then put that tunnel ram on with small carbs and dare to be different.
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Old 05-14-2002, 08:57 AM
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Iam not a pro either but have Plenty of Years on Both Big and Small Block Chevy's And I Will Tell you,It would be a BIG Mistake.IF you want to "Lug" your 1000Amp Battery in evry Night to keep it warm.(So it will start)Also get your self a Case of "Starting Fluid",A Cell Phone
(For when it runs your battery Down)Also you may want to toss in some Jumper cables.You better put in a set 4.10s or 4.56s (Bye,Bye Gas Milage)You also Might want slip out to your local airport and Pick up some (Air plane Gas)Leaded 106 Octain here. Good Luck on Your Project! BLK70Z28
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Old 05-14-2002, 01:00 PM
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Heeeeeey Willy's tell me some more about building my own intake, sounds like I might want to do that. You've already helped a great deal but I'm one of those "special" students I need a bit of tutoring, any help would be peachy.

Building building building I love it
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Old 05-14-2002, 09:08 PM
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Remember when Billy Crystal's Richardo Montelban character used to say "It's better to look good than to feel good"? Go to the Jegs catalog and buy the Weiand Street Tunnel Ram Manifold (Jegs # 350-7110). The catalog description does say, "where low end torque is not a prime factor". The carbs that go with it are two 450 cfm (Jegs part # 510-0-9776). Holley designed them especially for that manifold. If you decide to build your own manifold, I still recommend the small cfm carbs. Hey I've got two like new 450's that I'll sell you reasonably priced. I got them with a 671 blower set up for my 350, and I want to use 600's. Anyone out there got a thought on that?
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