Tunnel Ram VS Single Plain manifold for drag racing - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-21-2007, 01:25 PM
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Tunnel Ram VS Single Plain manifold for drag racing

I have a 2500 lb car with a 406 sbc, Dart pro 1 215 heads, 10.5 compression, Comp Cams 590 lift 260 dur, Power Glide, 4.10 spool rear, and a 30" slick. Car will be Drag only. A year after I get it racing I will install a 250 shot. Right now I have a World Products Motown single plain manifold. Several of my friends have insisted that I would find another 20 to 30 hp out of a tunnel ram. I have played with it a little on my Performance Trends Engine Analyzer and this software seems to agree. When I call an engine builder he says "maybe, maybe not you would have to dyno both and see what your engine likes". What do you Think?

Bob
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Old 02-22-2007, 08:58 PM
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With only 10 to 1 comp and a small cam,the tunnel wont do too much. Get the comp up to around 15 and a cam that will work with the heads,somewhere around .720/288@.050 and 108-110 center. Your money would be better spent on a dominator. The gear is awful tall for 2500 lbs also. If you want the car to be consistent,get the comp and the cam where it needs to be and go n/a alcohol. Easier than carbs and less expensive to run.
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Old 02-22-2007, 09:43 PM
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Tunnel Ram information
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Old 02-22-2007, 10:06 PM
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That is a pretyy good size cam for the compression but it will want to breath on top, which is where the tunnel ram will shine. Will it really make more power, nothing is a given. EA basically looks at the runner dimensions of the base manifold you choose, assumes a pretty accurate efficiency on the intakes and spits out a number. If you actually programmed in the actual dimensions, via EA Pro, and flowed the efficiency on your current intake then the numbers are accurate. If you didn't then numbers are nothing more than a guess and by golly.

We ues EA Pro all the time, then build the engine then dyno it. If all the data is accurate in the model the results are very close. If the data isn't accurate it's way off.

I think you are a bit short, or long actually, on gear as well. It's a light car so will be interesting to see how it likes that. That will be a better gear I think for the nitrous. You will likely want a 4000 to 4500 converter as well. The converter will have to be changed though once you hit it with the juice.
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Old 02-23-2007, 06:32 AM
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Since this will be a Drag Race only is there a reason you're going with such low compression?
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Old 02-26-2007, 03:07 PM
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Answer to some questions

I went with 10.3 compression so I could run pump gas and keep the operating cost down. I realize this was a mistake, but what I have is what I have. Are you guys saying I need to go with a 3.90 gear ratio? I do have a steel Ohio crankshaft, steel h beam rods, and forged pistons. I have Comp Cams Pro magnum 1.52 steel rockers and Comp pushrods. My rocker geometry has been adjusted correctly. When I bought the Cam kit from Comp Cams they said it was on the edge of too big but with a 4500 stall and Dart Pro 1 215 heads it was their recommendation. I have been working on this car for three years and have made a lot of mistakes. Unfortunately I did not find this site until about a year ago and I appreciate how much the members of this site have helped me work through my mistakes.

Bob
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Old 02-26-2007, 03:44 PM
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Hey Bob, I read your journal. Congratulations on choosing a very intelligent lady for your wife, one who can deal with neighbors and anti-freeze on the spot.

As far as the tunnel ram, I tech inspected for the last 50 years and can count on one hand the number of guys who have used that system. I realize the little lady wants to go low 10's, but there are probably other areas of the car that you could improve to get there. Single plane intake and big carb seems to be the combination of choice with the hot shoes.
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Old 02-26-2007, 03:53 PM
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Journal

Thank You for taking the time to read my journal. I was not sure what the response was to it. I know a lot of people looked at it, but with a journal I don't get any feed back. This being my first project my journal may be more about what not to do than what too do.

PS My wife was the best choice I have ever made. I know how bad a marriage can be if she's not your friend and how good it can be when she is your best friend. My first marriage "never were friends".

Bob

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Old 02-26-2007, 04:01 PM
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Angle mill the heads and the intake to match. That might put your compression in line with the cam. You may need to have the pistons notched for the better valve angle as well. This will go alooong way toward making that extra 20-30hp.

A 950HP Holley on that intake will work fine. It's easier to tune one carb as well.

Pull the valves out of the heads and knock the sharp edges off inside the bowl area. It always get's left behind after the valve job is done. They knock a little of it down but it's never smooth. The bumps will be there and are sometimes fairly large. That alone is worth 10-15hp and it basically free.

If you feel froggy, narrow the valve guide bosses, they are HUGE. I can't give you a possible hp number to go with it because I've never done that by itself.

Good luck with the build and have fun with the car.



Larry
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Old 02-26-2007, 04:12 PM
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Bob, if you do angle mill the heads, here's how to square the intake with the head ports.......
Measure the thickness of a new gasket. Get flat washers or shims that will measure that thickness. With the manifold off and the mating surface on the cylinder heads de-greased, put a dab of RTV on them and stick them on each corner bolt hole on the cylinder head. Let the RTV set up. Stuff paper towels into the ports to keep debris out. Make up 16 pea-sized balls of modeling clay. De-grease the intake manifold at the ports. Place the balls of clay on the top and bottom of each port, squishing them down well so they will stay in place. You want them to be thicker than the shims/washers that are RTV'd to the heads. With your fingers, coat a little oil on the heads where the clay will meet the head to keep it from sticking to the head. Now carefully place the manifold into place on the heads and use bolts on the four corners to just snug the manifold down until you feel resistance against the shims/washers. Remove the manifold carefully and mesure the thickness of the clay at all 16 positions with the depth function end of your 6" dial caliper. You'll know pretty quickly if the manifold/head interface is square. Record the measurements on the manifold with a permanent marker like a Sharpie. The widest measurement will be the standard to which you will want your machinist to cut the other positions on the manifold to make it square with the heads, thusly sealing the motor up.
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Old 02-26-2007, 04:17 PM
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Heads

The heads and manifold have been port matched, the bowl areas have been smoothed and the valve stem area has been shaped like a diamond pointed from the port angle. I did not remove any material from either port floor and used an inside mic to keep the ports consistent in size.

Bob
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Old 02-27-2007, 07:07 AM
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Heres an article I ran across earlier comparing single vs tunnel http://www.hotrod.com/techarticles/1...plate_systems/ They also put nos to it. If anything it's interesting read
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Old 02-27-2007, 07:55 AM
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Article from Hotrod Mag

Good article Thank You

Some in this thread mentioned that my diff ratio may be off for my application. Given I have 4.10 ratio now do you think I need to go toward the 3.90 direction or the 4.56 direction?

Bob
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Old 02-27-2007, 02:30 PM
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For a drag vehicle I thought the rule of thumb was to shoot for a 10 to 1 range ratio for lauching the car. Take 1st gear times rear gear 1.76x4.56=8.02 here is a site with some info on ratio's rhttp://www.2quicknovas.com/tranny.html
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Old 02-27-2007, 02:59 PM
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Rear End Ratio

The way I choose the rear end ratio of 4.1 to 1 was using Drag Racing Analyzer v 3.2. If my engine pulls 565 hp @ 6250 rpm and 561 @6500 and has 500 lb ft of torque from 4750 rpm to 5750 (Engine Analyzer v3.2) If I have a 30" wrinkle wall slick, 4600 stall, 2600 lb car and a 4.1 ratio I should run a 9.873 @136.33 mph. Given all that information, according to Drag Racing Analyzer I should go through the traps at 6747 rpm. So lets say I run a 10.2 to 10.5 @ 128 or 130 I should still be in there. Now remember this is my first complete build and I have never gone this fast before. I have been told that my software is fairly accurate. I can't say all this is fact because the car is not running and I have been slapped for bench racing before.

Bob
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