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Tunnel Ram 327

37K views 57 replies 20 participants last post by  willys36@aol.com 
#1 ·
I am going to order a Duel Quad Tunnel Ram for my 68 SS 327 smallblock. I know what it is and how it works but what will it real do for my 327?

Its mostly a stock 350 Hp 327 (ran The numbers) so im hopeing i can get in to the 13.0s at the track. I would just like to know how and What the tunnel ram would do.

thanks for your help
 

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#27 ·
lluciano77 said:
A sleeved 950? Did you adjust anything to compensate? Did you enlarge the air bleeds, PVCR restrictions, idle restrictions, change jetting, anything? If not, I can tell you right now for sure your carb isn't metering right.

Vacuum secondaries? I know what they knew. They knew if people had a carb that was too big, it would be a lot more forgiving with a vac. secondary. You get better customer response, and can sell a lot more carbs that way. I'm not saying they don't have their place. I have one on my SBC 400 right now.
That's bad news! I have only gotten 15 years of trouble free daily driving out of this setup @ 15mpg. I was hoping for 30 years but I guess it will blow up B4 then? :confused: Of course I changed the metering with the new barrels, like I said these carbs are great if tuned properly. I set up all my custom carb installations w/ an Edelbrock O2 sensor so they are optimal at all driving conditions.

And the 950 and 1050 Holley 3-bbls were designed for NASCAR, not the street market. You had to special order one and the box said "not for street use". And they came race ready as vacuum secondaries. They were never made as mechanical secondaries. Couldn't have been too bad, NASCAR banned them after less than 2 seasons for being too good!

Again, I have seen and installed many dual 390s on medium sized engines and they work marvelously if tuned properly. They are no different than 650s or 750s etc. as far as metering tuning goes. Jet, secondary spring, power valve, and accelerator pump them correctly and they purr! And some of the cars can lift the front wheels too. One thing they do provide is better off idle response which is preferable for the street. For sure if you want WOT performance at the drag strip @ 8,000rpm, go for the 750 or 850.
 
#31 ·
If you tune both carbs every time, before you take your car out, then the tunnel ram will make more peak power. If you get in your car on a daily basis and drive away without turning a screw, then the single carb will make more power throughout the RPMs consistently. "Consistently" being the key word.

A tunnel ram and two fours doesn't require twice the tuning of a single four. It requires at least four times the tuning.
 
#33 ·
I just PM'ed 327 camaro,and we discussed this.My take on it was that the tunnel ram requires about the same amount of adjusting as a single 4 barrel on a single plane performance intake.By that I mean an "air gap" style manifold.I told him that similar to the race manifold setup,he was going to find that he needed to make seasonal changes to the carbs to get the optimum tune up.He would find that with the summer tune up the car wouldnt start up and run in the winter.Aside from having twice as many screws and jets to tune there isnt much more to setting up a tunnel ram compared to something like a 750 double pumper on an RPM airgap intake.If the fuel pressure is corect an the carbs are set properly,he shouldnt need to touch them unless there is a major weather change.I recommended that he run some kid of street type carbs with choke provisions,and run electric chokes if this is to be a regular driver.Aside from that,there is no reason to think that 2 small single pumpers would work any worse then a big double pumper,and the fact is that a street tunnel ram has longer runners then a single plane intake,and the length is similar to a dual plane intake only the runners are straight and raised.It should have a powerband more similar to a good dual plane with a cut plenum divider rather then the powerband of an open plenum single plane intake.
Either way the gain will be very minimal,but if he really wants the killer look,he wont be hurting performance to get it if he chooses his parts right.
 
#34 ·
You have to reference the secondary cannisters together. The throttle positions on both carbs have to be the same. The mixture screws have to be as close as possible. It is a lot different than a 750 on an RPM Air Gap. With all multi carb setups you need to balance the carbs. That isn't easy.
 
#35 ·
Many small tunnel ram carbs are mechanical secondary.Some have no secondary metering block or accelerator pump because the venturi are so small that 1 acclerator pump can supply enough shot for all 4 barrels just on the primary side while some had a single 4 port center squirter.That is the hot setup to use.The hardest part is getting the idles sychrononized,but in reality with a large open plenum even that isnt super critical.as long as both carbs are opening at the same rate,and the metering is the same you should have no problems uning it as if it were a single 8 barle carb.As a matter of fact you dont usually need to jet tunnel ram carbs at all when they are propely setup on a stret manifold,and that is why most tunnel ram carbs come with metering plates.But I wont get too involved with that subject.
 
#36 ·
I know this thread is old and dead, but i just wanted to add that i ran an eldebrock tunnel ram with dual 450 holleys on the street. wasnt a daily driver but i drove it (for fun) 2 or 3 times a week. after the carbs were tuned it made serious power. especially after i upped the stall from 2500 to 3500 and got a bigger cam (244i244e, .510 lift)
 

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#38 ·
The one thang that may not have been mentioned is that a tunnel ram is best suited for higher rpm use. Since it's going on a 327, its a great match because the chevy 327s were high reving motors. I have a Weiand mini ram on a sbc 406 and I love it. You can buy carbs that are pre-setup for tunnel ram use in matched pairs. It may require tuning, but it sure as hell beats a quad Weber or mech fuel injection setup.
 
#39 ·
Any induction system can be made to run on the street. I know a guy in LA who has gotten a 4-hole Hilborn blower injector to idle, do low and high range etc., sitting on top of a 671 blower on the street. If you want that look, then it can be done but don't expect it to ever do things it was never intended to do. Tunnel rams were designed for a very specific purpose. They have short, equal length runners that open into a quite large plenum chamber. This divorces the organ pipe waves from confusion in the bores of a carburetor which results in much better top end performance at high rpm. The short runners tune the organ pipe pressure waves to do their supercharging at quite high rpm. The big plenum smooths out the vacuum signal to the carb(s) and, at high rpm, draws air and gasoline much more uniformly form the carb bores which improves the charge going to each cylinder at high rpm.

The thing is specifically designed for a high rpm range. Sorry, but them's the facts. The price you pay to get that look on the street in a grocery getter is that bottom end performance is severely compromised. The divorce of the flow signal from the cylinder to the carb bore, so beneficial at high rpm, results in sluggish response off throttle. That monster plenum, again a great benefit @ WOT, high rpm, results in gas condensation, puddling, and poor air/fuel ratio distribution at the bottom end.

That's why Edelbrock, Weiand, Holley, etc., all offer so many manifold options for a given engine. Each is best suited for a specific and limited type of engine performance.

But, as a guy running a 950cfm Holley 3-bbl on a 354, "It's so much better to look good than to run good!"
 
#40 ·
How right you are willys36. When I had mine in my S10, I tried to drive it on the street. 4:56 gears and an 8" converter got me close. Idle at 1500 or so. The thing would still foul plugs at idle, sitting in traffic. The gas pedal was either all the way up or all the way down for it to run right. Part throttle cruise sucked, it would buck and jump...really got the attention of the local lawmen!
 
#41 ·
Lonestar said:
How right you are willys36. When I had mine in my S10, I tried to drive it on the street. 4:56 gears and an 8" converter got me close. Idle at 1500 or so. The thing would still foul plugs at idle, sitting in traffic. The gas pedal was either all the way up or all the way down for it to run right. Part throttle cruise sucked, it would buck and jump...really got the attention of the local lawmen!
I have written several chapters in that book!
 
#42 ·
tunnel rams

Ive ran Offenhauser, Edelbrock and Wiend on the street :; 283s and 350s , 11 to 1 engines mostly but some less. 488 gears , Muncies ( never an auto.) They looked good and ran good , I dont see all this fuss about low end power etc. When I released the clutch they all drove smooth and good . My main problem was gas milage . Id fill up cruise up town head home later near empty . Most were in a couple 55 Chevys and they were not my everyday drivers : as Im older now I wish I still had one of them again , and yes I would tame them down and probably run a single or maybe a tri-power so I could go on longer cruises . But in those days the cars served their purpose well . I just dont see all the belittle ing of tunnel rams .
 
#43 ·
Like I have said many times it just depends on what spins your prop. Sure you can use them on the street but that isn't what they are intended for and you will pay a price for doing so, in your case it was gas mileage because you made up for the bad low end mixture problems by over jetting. Good solution to get some responsiveness and protect from burned valves but costs $$ in extra gasoline use. With gasoline over the $2 hurdle permanently and probably heading higher (eat your hearts out over there in the old country - you haven't seen gas that low in decades!), most of us need to seriously consider the cost of looking good over running good.
 
#44 ·
Your so right willys36, over jet to get an idle...hence why my plugs were always fouling.

Definately is a fun ride above 4 grand, but the public doesn't care much for that!!

I am in the process of trying to make my '85 Bird street legal again, it has a single 4 tunnel ram on it. I have to go out and run the thing to 7,500 to clean the plugs!
 
#45 ·
tunnel rams

We all realize that a 2 fours tunnel is not going to be an everyday driver . I Mean if I were a rich person , could afford to replace plugs real often and gas was no issue I could enjoy driving one . As for a vehicle driven around on say weekends to cruise a little up town : no problem , thats what most of us do with our hotrods anyway. I have an 82 Chevy truck Im driving tonight just during the weekend : it feels pretty good tonight coming to my girlfriends : another Chevy truck came zipping around me ;;when we came to the light , he just sat there. He could hear the cam rocking my truck. All week I drive my other one with a v6 . Ive also got a Samurai with a mild 350, 63 Chevy 2 convertible in the works 283 to be a cruiser in the spring. It all depends on the purpose of the vehicle.
 
#46 ·
Actually,if you set up a tunnel ram correctly the first tiem,it wont foul plugs at idle either.The tunnel ram has the upper hand on this one since with 2 carbs to idle the engine off of,you can keep both carbs closed more then a single 4 barel would sit,and in doing so you kep the idle transfer slots from being exposed.If you are an idiot and try to run non tunnel ram carbs on a street application,or if you try to idle the entire engine off of one carb it will run like a pig,but with the right setup it wont be a problem.The bigest issue with a tunnel ram is warm up time since a race type tunnel ram runs very cool and takes a long time to warm up and never gets very hot up near the plenum.A better solution is a tall "street type" tunnel ram with long runners that are webbed togehter and dont have an air gap between or under them.These setups have long runners that favor a 2500 to 6500rpm powerband,but you still have to give them a decent amount of warm up time.Dont just jet the heck out of the carbs to make it run better while warming up.If you wanted to do something really trick you could fabiracte a set of "stuffing blocks" to epoxy into the plenum in an area that doesnt effect flow{between the carbs would be good as long as it doesnt block the passage entirely},and this would give a little bit beter throttle response,and would allow the engine to run better in cool air since the accelerator pump shot would be more concentrated.If you could bolt a mini plenum un place of the large open plenum{some street rams come like this} it would be even better.Other then that,it is a piece of cake.
 
#47 ·
I found this thread on a Yahoo search a few months ago.

I am running a dual-quad Weiand #1988 street tunnel ram with sync'd, electric-choke Holley 390's on a .030 over 1978 302 with '66 289 Shelby heads and a built C4.

Nearly everything I was told when I was asking around about this and spec'ing it out, in person and on forums, including but not limited to:

- needing a bigger cam
- fouling plugs
- making headers glow red-hot
- idling at 1500+
- no power below 2500 rpm
- no power below 3000 rpm
- no power below 4000 rpm
- needing to rejet carbs
- needing to run off one carb
- stock motors will valve float in ideal tunnel-ram rpm band
- needing to block off 4 of the runners of the T/R
- less power than with a good single quad
- impossible to tune
- needs tuning every weekend
- runs like crap when cold
- runs like crap when hot
- needing a hotter fuel pump
- needing high-octane gas
- needing a bigger coil

All of the above is WRONG. It swapped right in (once I cut the hole in the hood) and all I had to do was replace the cap and rotor (clearance issues.) Starts on the third stroke, runs killer, idles at 600 when warm, comes off a dig like a cat with its *** on fire, and gets double-takes everywhere I go. It sounds KILLER!

It is ridiculously, irresponsibly, sphincter-clenching, what-the-hell-was-I-thinking fast.

Maybe it's the 390's. Maybe it's that we rebuilt the carbs completely (stock Holley 4160 rebuild kit). Maybe I got the linkage exactly right (home fabbed). Maybe the Horsepower Gods accepted the sacrifices of knuckle skin and blood and finally had mercy on me.

Or maybe it's that the naysayers either never tried it, or went too big on their dual carbs. (Most of the horror stories I heard came from someone who heard of someone whose friend tried a dual-quad tunnel-ram. I did hear from a guy who tried dual 750 cfm's on a 350 Chevy and gave up after months of tinkering because he "could never get it to run right." Big surprise.)

Don't give up. Just find 390's for a small-block.

If you're still around (or if you found this thread, as I did, through a search), check out my build page at http://home.comcast.net/~lostpony . Or email me through this site if you have questions. Good luck.
 
#48 ·
Thats' good to hear form the horses mouth. I know it can work and have always said that. The drawback is for the amount of money and time spent you can go just as fast or faster with a single carb. On a street car there is no "real" advantage of running a tunnel ram. I have always liked them and if someone want to run one because "it's their car and they like the look" I am all for it. In most cases people have a mis matched setup and can't get the tunnel ram tuned. Sounds like you have yours dialed in, right on!!

The tunnel ram design is not torque friendly, nor is it low RPM optimal but, that doesn't mean they can't be run on the street. I doubt you are making the most of that tunnel rams potential but, you like it and that's all that matters. That is what hot rodding is all about.

Royce
 
#50 ·
camaroman7d said:
The tunnel ram design is not torque friendly, nor is it low RPM optimal but, that doesn't mean they can't be run on the street. I doubt you are making the most of that tunnel rams potential but, you like it and that's all that matters. That is what hot rodding is all about.

Royce
That is a good statement, the tunnel ram is capable of going beyond 100% VE but you have to keep the rpm's high and that is not a good thing on the street in the eyes of the local law enforcement. I run a single 4 on my ram and it runs very well, but I know that for street use I would be better of with a dual plane intake...I just like how the ram looks and performs. Dyno figures show a much higher horsepower output with the ram at higher rpm over any other intake I have compared it with and I really don't care about the loss of torque on the bottom end for my application.
 
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