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Old 02-15-2012, 08:33 PM
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To tunnel ram or not to tunnel ram

Hello everbody

Although i am new to this forum, i have been finding a lot of very useful info on this forum for a long time. Figured it was time to join : )

I am toying with a 1984 chevy Camaro that i plan on drag racing mostly. It will not be a daily driver at all, but it may circle the block on occasion once or twice every so often. Currently, the engine is a 355 SBC, four bolt main, trick flow twised wedge heads, keith black pistons, stuck to a mildly built th350 tranny. Cam is a 244/245 int/exh, with about 450(ish) lift at .5". Currently running 1.5 rockers.

I love the aggresive look of a T-ram with two carbs poking though the hood. I ve ran the weiand T-ram with twin holley 450s mechanical secondaries for a bit -not too impressive. It bogs off idle when hammered and it does not seem very powerful, although it fires right up every time, and holds idle beautifully.
Would i have better luck switching to a dual plane air gap-style maifold and a single 650 cfm vacuum sec. carb, or should i try to downsize the carbs i have to twin 390 cfm holleys (in combo with the t-ram)? Converter stall speed and gearing should not be an issue(they will soon be changed depending on the route i take).

Any input would be greatly appreciated since i am really torn and cant really decide. Any help will be greatly appreciated.

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Old 02-15-2012, 10:34 PM
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Quote:
Originally Posted by maverickmechanic13
Hello everbody

Although i am new to this forum, i have been finding a lot of very useful info on this forum for a long time. Figured it was time to join : )

I am toying with a 1984 chevy Camaro that i plan on drag racing mostly. It will not be a daily driver at all, but it may circle the block on occasion once or twice every so often. Currently, the engine is a 355 SBC, four bolt main, trick flow twised wedge heads, keith black pistons, stuck to a mildly built th350 tranny. Cam is a 244/245 int/exh, with about 450(ish) lift at .5". Currently running 1.5 rockers.

I love the aggresive look of a T-ram with two carbs poking though the hood. I ve ran the weiand T-ram with twin holley 450s mechanical secondaries for a bit -not too impressive. It bogs off idle when hammered and it does not seem very powerful, although it fires right up every time, and holds idle beautifully.
Would i have better luck switching to a dual plane air gap-style maifold and a single 650 cfm vacuum sec. carb, or should i try to downsize the carbs i have to twin 390 cfm holleys (in combo with the t-ram)? Converter stall speed and gearing should not be an issue(they will soon be changed depending on the route i take).

Any input would be greatly appreciated since i am really torn and cant really decide. Any help will be greatly appreciated.
First what is duration of the cam and final gear ratio? What is the stall on the converter? What is the max RPM you be shifting. BTW: The reason the 450 Holley bogs when you hammer it is because there is no accelerator pump on the secondary. And if you do not have the gears or a 3000RPM stall converter for it, it's even worst. Using two Holley VS390 will give all the power you need.
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Old 02-16-2012, 07:41 AM
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Currently rear end and gearing is stock for a 1984period camaro. Im assuming they are low 3 s. That will be upgraded to a ford 9 inch with taller gears for sure. Stall speed is stock also which will be changed soon depending what route I take. Camshaft is an an summit one, p/n sum 9000
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Old 02-16-2012, 08:41 AM
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Forget the T-ram for now. Focus on changing the rear end and get a higher stall converter, first. Then you can work on the motor. Get 390 - 410 gears if you are going to do a lot of drag racing.
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Old 02-16-2012, 02:31 PM
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I would change your stall before you change anything else, even gears. Find where your tq peak is at and set your stall for about there, a little "2500 stall" isn't going to come close to cutting it. After that get your gearing changed so you are crossing the line right below redline.

A SWAG is that you'll need about a 5,000 stall and 4.10 gears. Those 2 items will probably knock a second and a half off of your time, maybe more.
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Old 02-16-2012, 02:54 PM
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You do not need 650-750cfm carbs. I spined my 355sbc to 7000RPM with a pair of Holley 390CFM carbs. That is 780CFM total. Your lucky the 350 produce 650CFM at 7000RPM with a VE of 80%. Time after time, That is the #1 mistake people do. Over carberate. I have been running T-ram for well over 30 years. That is all I ran in my Chevelle. Nothing else. With 302 202 heads on a 355cid

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Old 02-16-2012, 03:48 PM
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The small block edelbrock tunnel rams power comes in at about 2800 rpm, the Weiand comes in about 2400 rpm, it changes with each individual intake! Both will peak about 9500 rpm depending on eng. Cfm demand At specific peak rpms! 2 4oo cfm carbs are fine if run at lower rpm ranges 2500 rpm to 7000 peak rpm. As demand increases( rpm ) cfm increases and bigger carbs are needed. the number of carbs you run does not effect eng demand it doesnt matter if you run 1 or 8 if your eng is rated 800 cfm at 6500 rpm ! one 800 cfm carb , two 400 cfm carbs or eight 100 cfm carbs fill that same demand !

2 350 or 400 carbs on a smallblock would work well on the street or track with a cam of around 500 lift 244 duration 110 lobe separation as duration increases rpm increases and cfm increases,You can run 2 500 cfm 2 barrels with 50 cc pumps on your tunnel ram and it would work great (this was a dino tested combination) It is a must to run a higher stall converter picked to match cam power band, & good headers. On clutch and 4 speed cars tunnel rams are fantastic on the street or track! With automatics it takes quite a bit to get the car tuned in to run em! You cant idle at 600 to 1000 rpm and expect them to to come alive when you stomp the gas off idle. Some designs puddle gas at low rpms and must Idle around 2500 to 3000 rpm to stop puddling (hell on the street) some designs need anti reversion plates! The edelbrock and weiand work well on the street and great on the track. Ive been running Tunnel rams on my cars for almost 40 years Track and street! And with a little common sense they work very well! Edelbrock makes a manifold with a vacuum port already drilled & tapped for the street! With the weiand high ram you have to drill and tap the port ( put it dead centered in the plenum between the 2 carbs if you need one)! There are also tri power tops I dont know if any are still available but you still see em at some swap meets! I think they look kool!

If you run the tunnel rams on the street the cams you need will have low vacuum for power accessory's! You must take precautions for that!!!! your power brakes may work fine just cruising around. But one day your going to mat it and have to let off and hit the brake quick and have none!

If your power starts at 2500 rpm try to match a converter to that, If it comes in at 3000 get a converter that stalls at 3000 ! Remember a converter rated at 2500 might actualy stall at 3500 depending on torque applied to it !!!!


Most every one on here is giving you good info! Just on different builds & uses they all work!

Just my opinion: Jester

Last edited by painted jester; 02-16-2012 at 03:59 PM.
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Old 02-16-2012, 04:06 PM
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Lg 1969 : hit the nail on the head !!! good info without all the writing LOL I wish I saw his post I could have saved myself a lot of time Nice eng compartment Lg 1969

Jester
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Old 02-16-2012, 05:04 PM
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Thanks....Oh BTW: that was my 355, now I'm running a 406cid with the same T-ram setup...google it
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Old 02-16-2012, 10:01 PM
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Like I wrote before I made power all the way to 7000RPM. You put large carbs on a T-ram and you will hear "why is car sluggish of the line" or "every time I hit the gas it bogs on me" or " Why my eyes stings when I'm behind the car" or
"The car is running rich" I heard them all. The larger the venturies the sluggish it gets.That is why Q-jet are so responsive because of small venturies on the primary. Are you saying the one 780CFM carb on single plain manifold is too small for a 350 motor? A motor is just an air pump. So much air is going to flow depending on the size of the displacement and RPM of an air pump. You just cannot stuff a 1400CFM of carb into a motor design to pull 650 CFM.

Last edited by lg1969; 02-16-2012 at 10:21 PM.
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Old 02-16-2012, 11:22 PM
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upon digging, i found the exact specs on my motor:
Cam: SUM-9000 (from a long ime ago) 454 lift intake and exhaust, 216/ 216 int/exh @ .50 adv dur 272, LSA 112; Springs 130 @seat, 300 open; 15.7 cc pistons, trick flow heads (31400001) 170cc intake, 63 cc chambers. Its an old summit crate, that they had advertised as a 360hp motor.

Also, i fouund this info on another forum. A few different articles that illustrate the points mentioned above:

http://www.stevesnovasite.com/forums...p/t-43076.html

thank you for all your input huys, its awesome. It seems that tunnel rams still have a few fans out there : )
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Old 02-16-2012, 11:24 PM
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I've had the same experience as lg1969, put too much carb on a tunnel ram and you basically lose all metering signal at the carb which requires huge squirters to make up the hole.

I think the twin 390 cfm carbs is the hot street setup for any small block, twin 650 double pumper spreadbores for a big block...but you need a cam/engine combo that can make power in the top end of the rpm range.

Sorry F-Bird, I've had the exact opposite experience than what you recommend. The reason why big carbs aren't the ticket is because each cylinder breathes through both carbs, so when you double the number of primary carb bores to breathe through, your metering signal goes to zero.

Best combo I've seen in real life was a 351 Cleveland running two 650 Holley spreadbore carbs, it peaked at 7500 rpm with shifts at 8000. If anything it was overcarbed but the smaller primary's of the spreadbore carbs helped it out of the hole...it still needed 5.13 gears to move the car on the dragstrip with a 3200 pd car.

When in doubt, consult the manufacturer of the manifold you want to run...they will give you good advice for the cubic size and cam you want to run. Just realize for good all around performance you would be better off running an open plane manifold, tunnel rams are old school and really a stop gap measure until they came up with better single plane designs...they are not superior.

Look nice though!
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Old 02-17-2012, 11:01 AM
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So f-bird, what would you suggest i run cam-wise? I already have a msd 6al box with an msd distributor, longtube flowmaster (open) headers. Like i previously stated, i do not have a converter or gears yet, so i will purchase accordingly. I am building a transmission for it at them moment so ive got time to play with the motor.
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Old 02-17-2012, 02:52 PM
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I read all this,this morning fire bird is on point. I run 2 450s on the street mainly because my wife drives it a lot for just cruising! But if I want more out of the tunnel ram to fool around a little on the street I go to 650s and at the track I bolt on 2 750s to bring it alive! I never heard of anyone running spread bores on a tunnel ram??

Any one can set it up however they want it might seem to run fine and operate well and if your happy with that fine! But you'll never Know what the true potential of a tunnel ram is! The smell of gas the big bogs etc,etc. Is all in the tuning !! None of my carbs have choke housings, all are mechanical secondary's, the 650s & 750s are double pumpers ,my eng's a 355 cu. in. 4 bolt main, forged flat top pistons, I run a comp cam CS 292h-10 (gross lift 501, 106 degree center line, @ .050" 244 I 244 E duration, I install my cams advanced because I run a timing chain and with initial stretch after installing of new chain the cam is straight up the chain I always use is about 3 degrees stretch (other chains I dont know) If I ran gear drive Id put em in straight up, I run 1.5-1 rockers on intakes & 1.6-1 exhaust, 11to1 static comp, 62 cc'ed heads including plug cc , B&M 2500 advertized stall ( actual brake stalls at 2700 & flash stalls at 3300 ) 3.73 posi, B&M 500 hp rated trans, in a 77 vette. This combination works well for me! If I was to put in more track time Id run a much bigger cam (solids) installed straight up, and probably 4.88 gears. I wouldn't run a cam any smaller then the 292 with a tunnel ram (but thats my opinion). I only go to a track a couple of times a year if that, I try to keep it in the 12s or I have to add roll bar, drag loop trans blanket etc if it hits 11s ! Thats just my set up its built for fun (and it is )

When you go to pick out a stall converter! Some company's advertize brake stall and some advertize flash stall !!! Make sure you call the company that builds the converter before you order it and find out the actual stall for your combination. you will need the weight of the car with driver, the build of the engine, the trans ratios, rear end ratio, tire size and sometimes the elevation of the track you run at (stall speed drops at higher elevations not because of the converter but because of air fuel mixture & its affect on torque)

As for your cam, and your set up, fire bird can probably help more then I can! Im old school and Im getting older He sound's like he is more knowledgeable on the new cams and set ups then I am. I build my cars for speed!! Id talk about it but this thread would get dumped. Guys that stay off the throttle & just run tunnels for looks more power to you. But if you want a real adrenalin rush build it right!! And youll have the devil ridden shot gun !!!! Thats written on the doors of my car!

Jester
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Old 02-17-2012, 04:17 PM
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F-bird, You seem to know a lot about T-ram. Do you build a T-ram motor before using two 750CFM carbs?
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