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Old 02-15-2012, 07:33 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, 09:25 PM
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Your carbs are too figgin small. DO not choke off a tunnel ram with small carbs if you want to actually go fast.

a pair of 650-750 carbs is what you need. a pair Edelbrocks will work fine.

Get a 3500+++up to 5000 stall converter and 4.10+ gears.

The distributor will need to be recurved. The carbs will need jetting and accelerator pump tuning.

The t ram wil be much more responsive if you lock out the distributor timing curve. 36deg full time.
Thats where you start. The bog will be instantly gone.

Twisted wedge heads will limit piston to valve clearance, complicating cam installation.
Ditch the little carbs.

It wil run very well on the street too once set up correctly.
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Old 02-15-2012, 09:34 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, 06:41 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, 07:41 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, 12:53 PM
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That cam # is not listed on the summit site.
What is the cam?

Pretty much everything you have there to start with, will work against you and limit the performance of a tunnel ram. Other than the car itself.
(I would ditch those heads for a lot of reasons)
small 390-450cfm carbs will severely limit the power the tunnel ram can make
They are for street, cruiser - showcars only mild motors like you see on T-buckets

A tunnel ram motor wants to and needs to breath deep to work.

Basics:

350 flat top pistoned SBC
Good high perf cylinder heads 64cc ported prefered
10.5:1 compression ratio (pump gas) ...more 11:1++ for race gas
Solid lifter or solid roller race cam 248 to 275@.050" .530"+ lift
two 650 to 750cfm carbs Edelbrock, carter, holley etc.
4.10-4.88+ gears ( larger if using very tall tires 32"+)
8" to 10" race converter (3500 to 5500 stall)
High performance ignition (hei is fine)
Hi flow fuel system from tank to carbs.
Long tube headers, open or free flow large dual exhaust.

While a tunnel ram motor is very driveable on the street when set up correctly, the basic best power range is 3500 to 7500rpm+
All the stock, near stock and mild stuff will limit power performance.

This Hot rod mag engine build up series "Anvil" is a real good example of a tunnel rammed 350 street strip motor
A good reference for you :
There ar3e multiple progressive articles
This is the link to the index.
http://www.hotrod.com/techarticles/i..._anvil_series/

Last edited by F-BIRD'88; 02-16-2012 at 01:07 PM.
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Old 02-16-2012, 01:31 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, 01:54 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

Last edited by lg1969; 02-16-2012 at 02:16 PM.
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Old 02-16-2012, 02:48 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 02:59 PM.
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Old 02-16-2012, 03:06 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, 04:04 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, 08:32 PM
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LG you are wrong. There is a difference between a engine that runs and one that actually makes the power it should with a tunnel ram.

If you use conventional thought and choices when carbing a tunnel ram motor you will miss out on most of the advantage of this manifolds power capability.

Your engine runs well with the small carbs but will make more power with larger carbs. Just cause you rev it to 7000 rpm does not mean you are making any power. If you want the power that a tunnel ram can and will make over and above what a good single plane manifold will do, you must carb it correctly with large cfm carbs so it can breath deep with minimum airflow restriction.

If its just a cruiser-poser-show car, it does not matter. If you want the power of a t-ram, get some 650-750cfm carbs for it.

Again if you just want a cruiser with the look, go ahead and use a small cam and small carbs. But you will not make big power using these.

Last edited by F-BIRD'88; 02-16-2012 at 08:38 PM.
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Old 02-16-2012, 09:01 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 09:21 PM.
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Old 02-16-2012, 09:20 PM
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Quote:
Originally Posted by lg1969
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.
Boging, "sluggish" throttle response and "rich" smell is not caused by large carbs. It's 100% caused by a inability or unwillingness to correctly tune the carbs and ignition curves correctly.

The typical 390 and 450cfm holleys that people much like you run on tunnel rammed street cars were never designed or intended for tunnel rams.
Ya they run but:
They really limit the performance. You don;t know what you are missing.

You'll never see them on a serious effort car that makes the real power a tunnel ram can make. Street or strip or marine.

Small carbs on a tunnel ram ='s limited horsepower. if thats all you want , go for it.
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Old 02-16-2012, 09:32 PM
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the 1400cfm carb or combo of carbs will make the engine work less hard to draw in the air it needs to make power. the result is more poewr at the crankshaft to go faster. As long as the carb(s) can meter the fuel correctly the engine will be very responsive.

Engines are not just simple air pumps. You will not make the real power with a tunnel ram if you prescribe to that myth.

Your engine may only have 80% volumetric efficiency, but don;t project that onto a correctly built tunnel ram motor like the one in the article I pointed too.

Swap your little wee 390 carbs on that baby and the power will nose dive.
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