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  #16 (permalink)  
Old 05-15-2002, 07:10 AM
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I run a tunnel ram on my 383ci and cold start ups are not a problem, fires right up but it does have the occasional lean backfire until it warms up. In the January Hot Rod they did a intake shootout and the Weiand tunnel ram and Holley 450 cfm made the about the same hp but the interesting thing was the tunnel ram made 40 more torque and more hp below 3,600 rpm, the average torque from 3,000 to 3,600 was 400 with the four barrel (Holley strip dominator with the Holley hp-series 830 cfm carb.) and 414 with the tunnel ram.
Peak #s
4 barrel 491.5 hp @6300 & 436 t @ 5300rpm price:917.41
tunnel ram 491hp @ 6200 & 443t @ 5500 price:from Summit 546.95 (complete kit)
Edelbrock tunnel ram with 650 cfm race demons 503.3 hp@6100 & 452t@5600 Price: expensive
Test motor ? You guessed it 350 sbc
Drifter

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  #17 (permalink)  
Old 05-15-2002, 10:38 AM
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Hey Faust
Unless your going to run some really low gears
and high rpm a tunnel ram isn't a good idea. A tunnel ram makes hp at real high rpm. While it looks cool your gas milage and low end torque
will suffer greatly. However if that isn't a problem for you then go for it.

5.0killer
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Old 05-15-2002, 12:23 PM
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I ran a tunnel ram with 2 750 Holleys in my Pro Street 66 Nova for 7 years. It had a .060 over 454, roller cam, etc, etc...4:10 geared Dana 60 outback, and yeah...it backfired a little on cold starts, it was a ***** to see around, and gas mileage ?.....well there wasn't any. But boy was it fun to drive! I liked it so much I'm doing the same thing all over again in my 30' Ford Coupe. You guys are all right in your opinions, but I like the looks and the push yer foot to the floor performance, so I put up with all the other crap. No, I didn't drive it to work everyday, it was a toy.
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Old 05-15-2002, 03:10 PM
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Well I'm not big on holly's, I'm more of a carter/edelbrock kinda person.

I'd like to get a 6-71 for the ol' girl but money's tight since i'm trying to start my own business. I have a 3:73 rear, not running anything meatier than those, had a 4:11 in a camaro, gas mialage, nope, try again, more like whats the most direct route to the next gas station. Not going for anything that will give me a 6ft wheel stand, just a bit of gumption to go along with the look. Wanting something with some height to it, since this will be a "cartoon cruiser" I need to give the 350 some nice dimensions, hehe. Guess i'll hold out for the 6-71 or the twin side scoup that I really want
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Old 05-16-2002, 03:36 PM
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In answer for more info: Use an intake manifold gasket (or a tracing of the intake surface on the head for more accuracy), draw an accurate ink line drawing and take it to a machine shop to have the flanges flame cut in 3/8" steel plate, just like exhaust header plates. Then get some 1 1/4" exhaust tubing and make a set of runners (can be a snake nest, straight, mile-high stands, etc.) that meet at a carb mounting point. The shape of the tube doesn't seem to make any difference (within reason)to it's perormance, diameter and length are the important parameters. 18" length will both look awsome and will perform very well for low end torque. At the top, have another 3/8" plate made that matches the carb base. Make a small sheetmetal plenum that is brazed to the base of the carb(s) flange and has the runners welded in. An upside-down tent shaped box is perfect. Braze a divider plate of sheetmetal that divides the tent lengthwise (both sides should have a primary and secondary bowl form the carb), carbs barrels and runners in half. This will measurably improve low end torque. Make the plenum as small as possible to just act as a junction box and it will have more than enough volume to give nice strong pressure wave reflections. One drawback is there will be no manifold heat unless you add a runner for that and weld it to the plenum but that gets pretty tricky. I have a cold blodded 354 hemi that had a lot of trouble running when cold but I added a late model Mopar electonic ignition and an MSD5 ignition module and that made up for the lack of pre-heat. Once warm the engine runs great. The other drawback is that you will need to make a water outlet-themostat tube but if you got this far, that will be easy!

As all of the messages here illude, most commercial plenum manifolds are designe for +6,000RPM. Runners are too big in diameter, too short, and the plenum is too big in volume. The big plenum is to isolate the pressure waves in the intake runners from any signal from the carbs. In effect, the manifold runs like an individual runner fuel injection manifold without the fuel injection.

As an endorsement for the desigh I suggest, look at the late 50s cross ram manifolds that Chrysler put on hi-performance passenger cars. Those are WILD and work great. Long, small runners w/ small plenums!
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Old 05-16-2002, 04:15 PM
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I used to be research and development for a two stroke company and I made Y pipes left and right so this shouldn't be to difficult.

Could I use aluminum instead of steel? I have aluminum coming out my ears, from T-6 aircraft stock to aluminum pipe. I can get it machined no problem, but my question is, will I have to use a thincker peice of aluminum, or just the same 3/8th plate?

If you don't mind me asking, where did you learn about the intakes and carb pressure waves and everything else, I would love to read up on it.

I'm thinking this sounds familiar, the smaller the plenum box the more pressure builds up and shoots it down the tubes, the shorter the tubes, the more high rpm hp, the longer the tubes the more low end torque and low rpm hp. So if I play around with a few different lengths from say a 15"-20"(example) I could basically set the intake to the performance level I'm looking for?

Am I on the right track or should I just keep my mouth shut and listen, hehe Thanks alot for the help and the information, its always great to learn more.

[ May 16, 2002: Message edited by: Halloweenking ]</p>
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  #22 (permalink)  
Old 05-16-2002, 04:29 PM
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[quote]Originally posted by Halloweenking:
<strong>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 </strong><hr></blockquote>

no ,no ,no .no tunnel rams for the street ,all the negative replys are right ..plus you stand the very real probability of "reduced/obstructed vision" citaions..besides the fact that they really just dont work right on the street ,slow speed ,low rpm driving ..always overcarbed ,which tends to wash down cyl walls ,which reduces ring life ,and can dilute the oil to point of failure/premature rod bearing wear ..nope ,NOT a good idea .good luck ..jim p ..
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Old 05-16-2002, 07:28 PM
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Jim, thanks for the advice, but as the visability is concerned, I'm not worried, I'll only have a 6" windsheild anyway so visability is pretty much all shot out the window there. As for the street use, it will be fine, I don't go far and where I do go I usually go at 80-85 so i think i'll be fine, this truck is just a play toy and is basically just something awsome to look at so I'm not to concerned about taking her on long trips. I'm bored too so I'd like to try out building my own engine parts, have to start learning somewhere, I choose the intake.
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Old 05-16-2002, 10:25 PM
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Wow! You are way ahead of the game if you have and can work aluminum. By all means, go with that. I'm guessing that 3/8" might be fine but 1/2" would be guaranteed heavy enough.

I have been studying this subject off and on for 30 years. My degree is in mechanical engineering and my senior project happened to be designing and building tuned exhaust and intake systems for a 5 hp Briggs & Stratton engine. Yes, varrying length will vary the tuned RPM. Basically, when the intake valve opens it sends a negative shock wave up the tube at the speed of sound in the gas it is travelling in. For an intake manifold that speed is about 1100fps. When that negative wave reaches the tube outlet it sends an opposite or positive pressure wave back down the tube at the same velocity. Obviously, the tube should be designe for the positive pressure pulse to reach the intake valve just as it closes for a free supercharge of the cylinder. There is a secondary harmonic boost at half, twice and 4 times the tuned speed also. Thus for slow engine speeds you want a relatively long pipe and vice versa. This is independent of the pipe diameter or presence of turns and twists. The second item you need to design for is tube diameter wich affects flow velocity. The faster the air speed the quicker the carb can respond to mixture demand and the better the gas/air distribution since the liquid will not be as likely to fall out of the flow. The drawback is that at very high velocity, friction loss becomes excessive and pressure losses cause low density of the gas and low power. Offy tried to overcome this with their dual sized runner manifold, Edelbrock does it with two different sized manifolds, the Performer for normal day to day driving with smaller tubes and the Performer Plus or what ever it is called for street-strip. Unless your engine will see +5000rpm very often, the manifold I described will make you much happier in the long run. Also it will look a lot more menacing the taller it is!

I have a couple of very good technical books on the subject but I am sure they have been out of print for a long time.
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Old 05-16-2002, 10:40 PM
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I've learned that most anything that is out of date is pretty good. Well look whats talking, I have a lordship title in the 21st century! Now how outdated is THAT, about 300years

I'm trying to start my own custom billet parts business, so I stocked up on aluminum. I can honestly say I never thought a intake was simple, but I surely didn't know it had this much to learn about it.

I think I'm going to work one out with aluminum, while I'm at it, I'm going to polish the inners of the tubing can't hurt to get it a tad smooth, help with airflow restriction. Thank you for all the information, its great help.
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  #26 (permalink)  
Old 05-17-2002, 05:44 AM
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I would like to see your progress. Here are some references to look for;

Carb Ramduction, Roger Huntington, Car Craft, August 1966.

Intake and Exhaust Tuning, John Kopper, Road and Track, May 1966.

Smith, Phillip H., The Scientific Design of Exhaust and Intake Systems, Cambridge Mass., Robert Bently, Inc., 1970.

The latter is a comprehensive text on the subject. If you can find it, you will know just about all you need to for your application.

For a startng point try the equation,

L = (72*V/RPM) +-3".

where,
L = pipe length in inches
V = velocity of sound in pipe ~1100fps
72 = empirical constant

[ May 17, 2002: Message edited by: willys36@aol.com ]

[ May 17, 2002: Message edited by: willys36@aol.com ]</p>
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  #27 (permalink)  
Old 05-17-2002, 02:17 PM
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Oooo math, scared me a bit there. Its quite intimidating to see at first, hehe :p

I'll look for those books and rags, I think this stuff is very interesting and great to know. Thanks for all the help, I'm going to recommend you for "exspert" status, you should look into it, think about it.
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