can my 350 handle the 2-4 tunnal ram it has - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-18-2007, 09:11 AM
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can my 350 handle the 2-4 tunnal ram it has

i was givin 76 monza it was runnin and i drove it home but it had a hesitation from idle till bout 2500 rpm. when at stop and stomp it, motor would take big breath and choke sometimes back fire threw rear carb. my uncle had car from high school and ihave been tryin to bring it back to life . 350 chevy he had tunnal ram with two 450 holleys, stock monze exaust no headers. 350 trans 3000 stall.

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Old 06-18-2007, 09:29 AM
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It sounds really wicked. Depending on what heads it has on it, it would handle it. If it were mine, I'd put a nice street head on it (180 - 190 cc intake runner) and a nice set of headers on it. That will help you get the most out of the dual quads.
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Old 06-18-2007, 09:34 AM
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Yank the carbs and freshen them up if the car sat for a long time. Sounds like lean backfire/ not enough initial timing. That should keep you busy for a bit.



Larry
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Old 06-18-2007, 10:46 AM
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green monzter, what you describe is classic tunnel ram behavior. TRs were designed for high-rpm performance, as you have observed with yours "coming in" at 2500. They can be a real PITA for normal street driving. I have friends who are running TRs on the street, but they are constantly fussing with them. You definitely need a 2500 or better stall converter. You may want to disconnect one of the carbs, especially if you don't have progressive linkage.
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Old 06-18-2007, 09:05 PM
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Fresh spark plugs and good ignition wires will help a lot.
A intake manifold works a lot better once it has warmed up. Helps to vapourize the fuel ( liquid fuel does not burn) A tunnel ram needs extra time to warm up the runners.carbs and plenum. Don't expect good throttle response until it has fully warmed up. I t will cough, spit and back fire as long as it is cold.
Tunnel rams by nature need increased initial timing and lots of accelerator pump shot volume and some engine heat to get good throttle response.
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Old 06-19-2007, 02:01 AM
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Carb Problem?

Since this has sat for a while do kit the carbs,the older Holleys were bad for blowing out the power valves especially after a backfire,the newer power valves have been improved.I have found that when running a tunnel-ram on the street drivability will improve by going down in power valve size from what the carbs came with.You might want to get a copy of HP Books Tuning Holley Carbs,lots of good info there.And get some headers on it,"cause what goes in must come out!"
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Old 06-19-2007, 08:01 AM
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hey fellas thanks for the info. i need all the help i can get. this car has sit abou 10 yrs he pulled it once in while to nock dust off. since i got it ive completed body and paint. it got some fresh parts too mallory ignition taylor wires carbs been jetted down. two 450 holleys mechanical secendarys. iv though for most part the problem was in the heads and stock manifolds. 194 heads uncle said he had em milled so compression is in 11s. the one thing that cant figure out is my uncle said he pluged power valves in carbs why?
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Old 06-19-2007, 08:21 AM
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If the car was a drag only, plugging the power valves is normal. On some TR applications, you have such low vacuum, you would need a small numbered power valve. When cold, they could actually be opening due to the shaky idle.

Definately get some new gaskets in these carbs. Use liberal amounts of a good carb cleaner. Spray all passageways and little openings. The little tube that comes with the can is for letting you direct the cleaner into the small openings.

I have always had the best luck with BerryMan's carb cleaner. I keep several cans on hand. I typically used one can per rebuild on a running carb and 2 to 3 on one that had been sitting.

The time and $$ you spend freshening up the carbs will pay you back right quick.
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Old 06-19-2007, 10:44 AM
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In full race motor with a huge long duration camshaft there is little or no manifold vacuum at idle. The power valve is controled by vacuum. Without manifold vacuum at idle the power valve stays open (rich) this causes a over rich idle. So some people remove the power valves and plug the hole in the metering block. Then, you must INCREASE the main jets size by 6 to 10 jet sizes to account for the amount of fuel that flowed thru the power valve @ WOT or the carb will be very lean @ WOT. If you remove the power valve do not "jet it down". That makes it very very way too lean.
You want to run a power valve if at all possible. You motor probabily does not have a full race cam in it and can run with a power valve.
YOu need to know what the manifold vacuum is at idle. Then select a power valve with a rating that is just lower than that vacuum reading.
eg: if you have 5" of manifold vacuum at idle, use a 4.5" power valve.
Put the stock jets back in. get two 4.5" power valves and install them.
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Old 06-20-2007, 09:40 AM
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all the info has helped me understand more about the sacrifice of runnin tunnal ram . but i think it looks cool and it can be intemidating to those who dont know. what would be the ideal cam for my application cause i sure the one i got cant be it. and what about the milled heads culd this cause a problem if i wanted to try 1.6 rockers. i have so many questions and i cant think of them
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Old 06-20-2007, 08:57 PM
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You didn't say exactly which cam you have. What do you intend to do with this car?
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Old 06-25-2007, 11:45 PM
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not exactly sure on cam duration my uncle knows and he told me once. i find out what he knows. what would be a good cam choice for my set up. i prob wont race it but i dont want to kill it at the light if i had a competitor. like say your run of the mill teenager wit the 93 pony 5.0 . cause now i gotta slowly bring up the rpm's or it will fall on its face. back fire sometimes or just die. the manifold vac. was 3.5
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Old 07-02-2007, 08:37 PM
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Green: i want tyou to remove the carbs. Turn them over> look at the bottom at the throttle blades. The idle fuel transition slot should be just exposed under the throttle blade on each barrel ( both primary and seconday. Adjust all the throttle openings exactly the same on all eight barrels. The secondary throttle opeing is adjusted by a small set screw on the bottom of each carb.
Set them all the same so just a little of the transitin slot is exposed (.020")
reinstal the carbs with the stock jetting and 3.5" power valves. Do not touch the throttle speed screws. Turn in the idle mixture screws on each carb and turn them out 1.5 turns. Do not touch the throttle screws. Disconect the vacuum advacne on the distributor and start the car and set the timing with a advance timing light to 32deg BTDC. Let the car warm up to full operating temp. When the motor is fully warmed up adjust each idle mixture screw slowly in ( the motor will slow down) and then out (it will recover) Adjust them all slowly and all the same. to achieve the best idle. the idle speed should be about 1000rpm.
Do not drive the car at this time. just do as described and report how you make out.
Your cam is likely installed correctly and does not require degreeing.
But the mechanic that laughed at you for sugesting that is a fool. Do not take any more of his advice. Degreeing on a cam and adjusting its position on the motor ( advancing or retarding the cam) is an effective way to "dial in your motor" and getting best power. You can leave that for another day thou.
But you do need to modify your distributor advacne curve and timing to suite the cam you have.
A motor with a big cam like yours need a distributor advance curve that is different than the advance curve that a "stock motor" has.
basicly it needs a lot more initial timing at idle than a stock motor does. This requires that you shorten the travel of the mechanical advance curve or the motor will be over advanced at high rpm.
Some people just "lock out" the advance curve and run full timing (32 to 36deg BTDC) at idle and hi rpm, to good effect. By doing this you correct the ignition timing at idle and low speed. Your throttle response and idle quality will be muched improved. Your tunnel ram will be a lot lot sweeter to drive.
it will no longer seem over rich and back fire. (once the motor is fully warmed up). You must allow the motor and intake manifold runners to warm up before expecting good throttle response and driveability. Tunnel ram manifolds by their very nature take extra time to warm up.
I want you to set up the carbs as described above with the throttles PRESET UP as described and then once the motor is warmed up and you have adjusted the idle mixture screws for best idle quality, i want you to leave the throttles alone and adjust the engines idle speed soley by adjusting the ignition timing at idle. More timng at idle = more idle speed. Less timing = less idle speed. You are looking for a idle speed of about 800 to 950rpm in neutral.
you should end up with a timing of between 24degBTDC to 36deg BTDC to achieve this idle speed. TRy it and tell me how you make out. Do not drive the car yet. Just set it up as described and tell me how you make out.
work slowly and be patient. let it warm up fully.
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Old 07-02-2007, 10:38 PM
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Good advice from F-bird! With a 3000 stall converter and a properly tuned engine that tunnel ram should work just fine. Get the idle circuit and initial timing dialed in like F-bird recomends then move on to main jet, enrichment circuit tuning and timing advance curve or lock it out at full advance and give her a try-might not like to start at that setting though unless you kill the ignition untill the engine is turning over well. Some 4.10 gears would also really help a lot!
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Old 07-02-2007, 10:40 PM
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Do a compression test and let us know what she is pumping, this will shed some light on how well the combination of internal parts are matched.
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