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  #16 (permalink)  
Old 02-03-2007, 03:18 PM
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Quote:
Originally Posted by BOWTIE JIM
I'm thinking about getting a tunnel ram kit for my '56 chevy truck. I keep hearing about driveability issues. Lack of low end torque etc. The truck is running a 350, decent cam, late 60's vette heads and a B&M turbo 350 with a 2500 stall (about),valve body set on "whiplash". 3:73 gears in back. It runs great with the speed demon carb and performer RPM intake but I just like the visual impact the tunnel ram gives. Any thoughts? Thanks.
First, What cam do you have now? ("decent cam")

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  #17 (permalink)  
Old 02-06-2007, 06:31 PM
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Originally Posted by willys36@aol.com
That's news to me!! If that's the case, why doesn't Detroit put tunnels on all production cars? Why do Edelbrock and Weind, et al, produce dual plane manifolds? Guess my physics books are all wrong.

Single-plane and dual-plane intakes operate differently, as you know.

All new SFI cars ARE long single-plane tunnel-rams with small plenums, layed over sideways because they are dry flow, so they can lay them over. That is also why they require such large LSA cam angles to idle.

The primary purpose of a tunnel ram is not to shorten the runner, but to give the air a straight shot into the intake valve, which improves fuel atomization because the fuel does not get slung out by centrifugal force and run down the port walls. (New cars with SFI eliminates the fuel distribution problems.)

The true tunnel rams can be short, or long. Plenum big or small.

Look at the new Weiands for good tunnel rams. Lots of things have changed over the years, including tunnel rams. I just put a new one together last week.

Properly done tunnel rams will make more torque and power across the board, except at the very lowest rpms where all single plane intakes suck, literally, figuratively, and poorly, pulling exhaust into the intake manifold.

You are probably like most of us. We have always seen big carbs on big plenums on overcammed engines with crappy ancient heads running for 7500 rpm. Ya, they really suck, in every sense of the word.

Last edited by xntrik; 02-06-2007 at 06:44 PM.
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  #18 (permalink)  
Old 02-06-2007, 06:47 PM
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this is interesting,Intrix how about the Wieland tunnel ram, on an 383 stroker engine cammed dur @ .050 246 degree .515 gross lift intake and exhaust
stall is 3400 rear gear 343, with what size carbs
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  #19 (permalink)  
Old 02-06-2007, 07:01 PM
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Originally Posted by pepi
this is interesting,Intrix how about the Wieland tunnel ram, on an 383 stroker engine cammed dur @ .050 246 degree .515 gross lift intake and exhaust
stall is 3400 rear gear 343, with what size carbs
Our set came with dual 500 Holley small body mechanicals. They are very rich.

I believe that dual vacuum secondaries would be mucho bettero without overcarbing at low rpms. 500-600 OK... Lots more than you need, that's where vac secondaries or Carter/Edelbrock air valves would be better. Holleys would probably need to go sideways, Edel I don't know, didn't measure.

Whats your LSA overlap on that cam?
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  #20 (permalink)  
Old 02-06-2007, 08:04 PM
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LSA? are you talking Lobe separation if so then it is 108 degrees. Rich.. I see that ( slurp, slurp), was also considering 2x4s and now I have seen the in line 4 by BG so this is more bench racing and information gathering at the moment. But there is for sure an intake change in the wind. The intake I am running is the Weiand Team G intake.
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  #21 (permalink)  
Old 02-06-2007, 11:38 PM
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Quote:
Originally Posted by xntrik
Single-plane and dual-plane intakes operate differently, as you know.

All new SFI cars ARE long single-plane tunnel-rams with small plenums, layed over sideways because they are dry flow, so they can lay them over. That is also why they require such large LSA cam angles to idle.

The primary purpose of a tunnel ram is not to shorten the runner, but to give the air a straight shot into the intake valve, which improves fuel atomization because the fuel does not get slung out by centrifugal force and run down the port walls. (New cars with SFI eliminates the fuel distribution problems.)

The true tunnel rams can be short, or long. Plenum big or small.

Look at the new Weiands for good tunnel rams. Lots of things have changed over the years, including tunnel rams. I just put a new one together last week.

Properly done tunnel rams will make more torque and power across the board, except at the very lowest rpms where all single plane intakes suck, literally, figuratively, and poorly, pulling exhaust into the intake manifold.

You are probably like most of us. We have always seen big carbs on big plenums on overcammed engines with crappy ancient heads running for 7500 rpm. Ya, they really suck, in every sense of the word.
I was using the single plane comment sarcastically. TPIs can use long inlet runners to take advantage of organ pipe theory and get a tuned boost without the danger of liquid dropout since the gas is injected near the intake valve. Detroit TPIs have the x-over long tubes on production cars since they are designed for low to mid range speed boost. The lower the design boost speed the longer the tubes need to be.
Tunnel rams are designed for organ pipe boost at the tuned length (short runners @ high rpm). There is no way to get the uniform short length in a dual plane or single plane manifold, that is what they designed the tunnel in the first place. What you gain in high speed organ pipe boost you lose in low speed loss of velocity in the relatively huge plenum. Tunnels as opposed to TPIs are hampered by the fact that the fuel is introduced at the inlet not the outlet. Once atomized gasoline ends up condensing and puddling resulting in bad distribution in a tunnel at low speed. It is unavoidable, regardless of the size of the carb. And the number of turns has zero impact on organ pipe boost, the only critical parameters are flow area and runner length. Think of a tunnel as injector stacks (tuned for high speed organ pipe boost) with a carb on top instead of injectors at the base.

Tunnels are great for drag racing for which they are intended and for looking mean on the street. However, if used in the latter application they will perform poorly at the rpms encountered 99.999% of the time.

Here is a photo if me in mid construction of the tunnel I built circa 1968 when I was in college. I used it as a physics project as well as a cool looking street manifold. This was before commercial tunnels had hit the market. I designed the runners for 3000rpm primary boost and as you know there is a harmonic secondary boost @ 1/2 design rpm or 1500rpm in my case. Worked great when I put my foot in it but regardless of the size carb I used (I tried several including a Rochester 400cfm 4-jet clear up to my current Holley 950cfm 3-bbl) it was terrible at normal driving speeds. These things just are not intended for the street.

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  #22 (permalink)  
Old 02-07-2007, 01:00 AM
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Cool. Who's that young guy in the picture???????

Agree. I have put some tunnel rams on that do well across the board, in town, etc. It has a lot to do with the combination. Don't overdo the top end.

Check out the designs that Weiand is using now. Smaller, thinner plenums, bet not 2" thick, so the carb barrels shoot straight down into each runner, but with a common plenum joined together almost like a big spacer plate under a single carb. The street power and response is good. I still like the vac sec, the new set he bought with mech sec and the tuning is rich, need time to do it.

A few years ago we built a 440 magnum mopar with long 30" cross ram intake from 1960 with dual Edel 600s out by the fenders. Everybody said it would be a dog above 5000 rpm. In a 4000 pound rig it went past 5500 like it went past 3000. You had to be careful to keep in under 6500 it wound so fast. Nobody could believe it, combination.... It would rev so fast spinning the 50 series tires/ spool that you could rev it to 6500, let off and the engine would be slowing down and the tach needle still going up.... idled at 700 like a kitten. (its sitting here on an engine stand now. First time at the strip did 8.40s with little traction 1/8.
Have another 426 wedge in the works now with 30" long rams.)

Said all that to say.... ram effect, too short or too long...... depends on scavenging
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  #23 (permalink)  
Old 02-07-2007, 10:32 PM
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Quote:
Originally Posted by xntrik
Said all that to say.... ram effect, too short or too long...... depends on scavenging
Sort of. Actually, pressure/vacuum waves exist in both intake and exhaust runners. Both can be tuned independently. Design the intake to have a pressure maximum at intake valve closing and the exhaust to have a pressure minimum ('scavenging') at exhaust valve closing. My senior project @ Fresno State was designing and building independently tuned intake and exhaust manifolds for a 1 lung Briggs and Stratton 5hp engine. I designed and built a port pressure recorder that tracked pressure for the entire cycle of the engine at a given port and I calibrated the manifold designs using that and a dyno. Got a really good power boost at design rpm but of course gave up power at other rpms. I compared stock manifolds to the tuned ones and the stock ones had no big high or low pressures. No big power boost but no power loss at off optimal pressure points, thus a nice flat torque curve. Tunnels were invented to do just that on a V8 - max HP at optimal rpm, giving up power at other rpms. By design they have a peaky torque curve. They can be made to run on the street but they were designed for WOT at the drags. That's a fact.
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  #24 (permalink)  
Old 02-07-2007, 10:54 PM
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Quote:
Originally Posted by willys36@aol.com
Sort of. Actually, pressure/vacuum waves exist in both intake and exhaust runners. Both can be tuned independently. Design the intake to have a pressure maximum at intake valve closing and the exhaust to have a pressure minimum ('scavenging') at exhaust valve closing. My senior project @ Fresno State was designing and building independently tuned intake and exhaust manifolds for a 1 lung Briggs and Stratton 5hp engine. I designed and built a port pressure recorder that tracked pressure for the entire cycle of the engine at a given port and I calibrated the manifold designs using that and a dyno. Got a really good power boost at design rpm but of course gave up power at other rpms. I compared stock manifolds to the tuned ones and the stock ones had no big high or low pressures. No big power boost but no power loss at off optimal pressure points, thus a nice flat torque curve. Tunnels were invented to do just that on a V8 - max HP at optimal rpm, giving up power at other rpms. By design they have a peaky torque curve. They can be made to run on the street but they were designed for WOT at the drags. That's a fact.

Roger dodger ole buddy.

I guess these things would really run well with a modern air gap intake and one 4........
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Old 02-08-2007, 01:27 AM
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Old 02-08-2007, 01:33 AM
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Old 02-08-2007, 01:33 AM
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Popular Hot Rodding Magazine, December 2006, THE X FACTOR, p 75, David Vizard.

He back to back tests a SBC 383 with Holley Strip Dominator and the Weiand Tunnel Ram and the tunnel ram won across the board from below 3500 to 7500 rpm.

Using the Comp Cams solid flat tappet cam of 288 x 106 LSA

The peaks = 4bbl 488 lb/ft and 561 hp.... the tunnel ram 501 lb/ft and 573 hp.
The 4 bbl made 395 lb/ft at 3500 rpm, the tunnel ram made 415 lb/ft at 3500 rpm.

Back to back test.

Not on the web site yet, that I could find.

mutiples..... site going nuts?????
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  #28 (permalink)  
Old 02-08-2007, 06:40 AM
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As Willys has stated on average a Tunnel Ram is designed to a more specific power band than a single or dual plenum single 4bl intake manifold.

There are pros and cons to both set ups. It's all a matter of what's going to work best in the specific combination. One of the problems you can run into with a Tunnel Ram is getting it sized properly for the specific combination. Unless you're going to build the runners and plenum yourself they probably not going to be optimal for the combination you're running, and then you have to crutch with the carburetors. I prefer to not use vacuum secondary carburetors in a 2x4 application due to fuel distribution issues. If your front two barrels are wide open, and the rear two only open as much as is needed you will get different amounts of air and fuel to each cylinder which is less than optimal.
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  #29 (permalink)  
Old 02-08-2007, 08:44 PM
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I've posted it so many times I'll just briefly add my two cents worth.

A proper PACKAGE will run with no troubles. I've ran tunnel ram 2x4bbls more than anybody I know, on daily driven work trucks, daily driven cars (the WIFE drove) and numerous high performance cars.
Not only were they responsive, trouble free, great cold and hot drivability, they also had power brakes on everything I built, some had mild cams, some not so mild, and all my stuff had to pass AirCare emissions testing.

Too many misconceptions about tunnel rams out there IMO.
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Old 02-08-2007, 09:59 PM
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Quote:
Originally Posted by Crazy Mopar Guy
I've posted it so many times I'll just briefly add my two cents worth.

A proper PACKAGE will run with no troubles. I've ran tunnel ram 2x4bbls more than anybody I know, on daily driven work trucks, daily driven cars (the WIFE drove) and numerous high performance cars.
Not only were they responsive, trouble free, great cold and hot drivability, they also had power brakes on everything I built, some had mild cams, some not so mild, and all my stuff had to pass AirCare emissions testing.

Too many misconceptions about tunnel rams out there IMO.
You beat me to this post. I have been running tunnel rams on my street driven vehicles for over 20 years. As I have stated before, the main areas to focus on are 1) runner length-longer makes more torque, 2) plenum volume-use the smallest plenum you can find for increased throttle response, 3) proper carb sizing-use carbs with small venturies, 4) proper ignition advace curve-more important than you think and very often overlooked. Check out the pic below. It's a 406 sb with 9.6 comp and a Comp 280 Magnum cam. A completely incorrect Edelbrock Pro Ram II tunnel (rpm range 6500-10,000) with Holley 9776 465 cfm carbs. The engine idled at 850 and it never turned over 6000 rpm. With 3.08 gears, floor the pedal and smoke the tires from a dead stop. The car was a 71 Camaro. Trans was a turbo 400 with TCI 11" conv. This engine was my daily driver and the car was driven to many national shows. It can be done as has been proven to a few members of this board. PM me with a phone number and I'll be happy to talk to anyone about it.

Barry
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