I have been working on a new tunnel ram design. It uses four small plenums instead of one big one. Each cylinder draws through one side of one carburetor like a dual-plane, so it makes a lot of low-end torque.
Nice.... Will the long runners play into it? seems dual planes arent high rises although some put spacers under the car for an added lift. The design has me curious
Will be interested to see the result. I thought the whole point of the large plenum was to smooth out fuel and air flow at anything below WOT, so it will actually idle and not bog down when you accelerate.
Yes, we've done tons of dyno testing. I have filed a patent pending too. Didn't really feel like I could talk about it during the development phase. We've did most of the design work with a bone stock Goodwrench 350 as the dyno mule. Also ran it on a 11:1 compression 350-inch engine with a .570-lift roller cam and ported L98 Corvette heads. I have it mounted in a 1971 El Camino now with a stock 350 (with headers) and a TH350 transmission with stock stall. It is ultra-responsive. On the Goodwrench motor it made more torque and horsepower than E-brand idle-5500RPM manifold. On the roller motor we made less peak power than the RPM air-gap (440 vs. 460), but we made more power below 4000RPM. I think a 450HP engine is about the limit for the current design.
The big plenum is there to provide you with a big reservoir of mixture at high RPM for the runners to draw from. It actually hurts you a ton at part throttle. You get bad signal to the carb boosters because the big plenum absorbs the airflow and keeps the boosters from seeing the pulse. Also you have four venturis open at part throttle, which hurts the velocity through them. Dividing stuff up to get the velocity up through the venturies works awesome at low RPM. Makes it act like a dual-plane.
I think the long runners contribute to the big torque increase everywhere below 4000RPM. Can't really prove it though. The runners are long and also very straight, so once you get the fuel in suspension there aren't any corners to make it want to drop out. Honestly I just had the idea and starting making stuff and testing it. Why it works as well as it does I only have theories on. Somebody with $50,000 worth of fluid dynamics modeling stuff could probably explain why the volumetric efficiency is better. Besides the runners I think the other key is getting strong signals to the boosters. With the small plenum, every induction event makes a rush of air through one side of one carburetor just like a dual plane - only in this case with an even smaller plenum.
Yeah, the normal ones have all kinds of problems unless you are running above 4000RPM at all times. I have a cross-ram on my '67 Corvette with a 327. I have a wide ratio Muncie and 4.11 gears though, so low-end torque is not really required. Even with that gearing the car would run better for street use with the Z28/LT1 GM dual plane I had on it before. This manifold is radically different from any tunnel ram you've every worked with though.
I see this is just to make the tunnel ram more street useable. My only tunnel ram car so far was in the late 90's I had 0.060" over 283-TH350-3.08:1-28" tires in my 28 Chevy roadster. I had Edelbrock street tunnel ram and two Carter AFB's of 60's Buick. Problem was not having enough torque to move 2300 lbs car but getting it off the line without bog. I had to start very lightly and I couldn't floor the pedal below 30 mph. My best 1/4 et was poor 15.2 with 95 mph when I spent first seconds easing it out. The first torque converter was Hurst Indy Trophy taker around 1800 stall. I replaced it with looser ACC Boss Hog which gave about 2300 stall. First cam was Crane/Cam Dynamics hydraulic "3/4" and I loved the sound and upper range pull. I replaced it to Edelbrock TBI cam with very short intake duration and it boosted mileage and smoothed the lower end. It didn't hurt the upper end either in such small engine and I was always running muffled full exhaust. Still it bogged off line. No matter how I tried to tune the AFB's no help because the air just didn't move enough for carbs to work. I never tried smaller carbs like 450 Holleys. I had thoughts to make some filling the plenums too but not figured how. This was it to the end and the guy I sold it took off the tunnel ram for single four barrel. Sure it worked much better but lost the appearance. He heard he still owns the car after ten years. I haven't seen him for years so I don't now the current engine. By the way I think the Edelbrock and Holley tunnel rams with more open lower part look way better than bulky Weiand style.
I went with the Weiand because it brings the runners together into two groups that are completely evenly spaced. That makes getting the fuel distribution even much simpler. I have an Edelbrock bought for research early on, but the way the left side runners are offset forward of the right side runners would make this scheme way more difficult.
The only thing I see is it looks like you put a 4 barrell top with a two barrell opening. You could do the same thing by sizing the carbs correctly on your tunnel ram. Most people make more trouble by running race car tunnel rams on street motors, instead of picking a street style tunnel ram to begin with. Small carbs keep up the signal at low RPMs and with some tuning can be flat footed from the light. Kinda the princable behind the single four tunnel top that most run as its sized more correctly but distrabution sucks.
I came across your website yesterday, and today bought a weiand t-ram with 500 eddy's. I want to know if you're gonna sell the part you made, or are you gonna sell the whole package? I think your design is great.
You can find it by Googling "Real Street Ram". I can't just sell the tops. The carburetors are full-custom all the way through to work with the weird dynamics of the plenums with only two runners connected to them. I am selling the tops and carbs only without the base, linkage, etc., but the carbs have to go with the tops.
Well, there is quite a bit of work in it even though it looks simple. You cannot do the same thing by correctly sizing the carbs on a normal, single plane tunnel ram top. No matter what size carbs you have, you still have at least 4 venturies feeding mixture when a cylinder draws from the plenum. So you get lousy mixture velocity at low RPM even with 390CFM vacuum secondary carbs. I know because we ran that setup. You can tune a normal top to be semi-OK, but it will never work right with a stock stall converter and highway gears like this one will.
in the pass run home made wooden spacers mainly for heat as i raced on the street and drove it a butch before each race.......... had dashman here on hamb make up a phelonic spacers & some alum risers........ have ALWAYS been able to tune the different tunnel&carb combinitions to work....have used 3barrel hollys 450x2 &660x2 ..... all the bad hipe is from those w/o knowning what they are doing or giving up too soon..........
You certainly can make it work - it is just a question of how much funkiness you are willing to live with. With this setup you don't have to trade off street manners at all. You can run stock stall and highway gears and it still pulls like crazy from any RPM. My Corvette with the cross-ram works well too, since I'm willing to live with very deep gears and trading off low-end torque.
One more note: This is a fully engineered solution. No fooling around with "what should I run for a power valve," "do I have enough pump shot", "how much idle timing can I dial in and still start the engine", etc. You bolt it on, set up the idle, and drive. If you have to adjust anything, it would just be changing the main jet size a little for altitude. The best carb setup on the 450HP motor also made the best results seen on the Goodwrench 350. You run a normal timing curve, including vacuum advance. Your gas mileage is good because you don't have to over-richen to compensate for poor fuel distribution.
JEEZ MAN! just how fricken tall is this tunnel ram!!! Put it on and have to jet for new Altitude! -rick
""looks like you put a 4 barrel top with a two barrel opening"" My thought, from the top view only and I wonder if the openings can pass the carb cfm? ...If one runs a tunnel ram on the street its their choice but I can't help but feel it's "for the look" mostly, gasser john is height winner so far ..Damn!!.So what does this top look like from the side? Personally I would have made carb reversion inserts; thin spacers with tubes [anti-reversion] that extend the carb bores down into the plenum, in effect reducing the plenum at lower air flows but its still all there at high flow times, at least thats the thought..And no, not my idea, just some thing I would try as they would still allow the full plenum "look" also....I'm pretty sure Grumpy Jenkins or someone else in that era was the one I read about using them; the tubes could be angled to match with the base..I could imagine extreme flow bench/dyno time in sorting things out...
The windows are sized to flow a little more than the carbs do. TR on the street is definitely for the look - but so is everything else on a street rod! The point of this project was to build up the eye candy such that you got no-compromise performance at real-world RPM. Something you can put on a car that you want to cruise in without dealing with horrible gas mileage, a slip-n-slide torque converter, poor low-end throttle response, etc. There definitely is reversion, just like in a Weber individual-runner setup. When you have cylinders firing far enough apart in a plenum that you stop the airflow for a significant time in between events, you get reversion, that no tricky tubing is going to prevent. That's why we are running a power valve plug - you would never normally do that on the street because your cruise mixture would have to be jetted up way too rich to get the power mixture right. But here, the reversion at low manifold vacuum actually handles the enrichment function under power. To dial it in we have staggered screw-in high speed bleeds, and stagger jetting. Every circuit in these carburetors is heavily customized except idle and accelerator pump. Even the emulsion circuit is custom drilled.
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