need info :tunnel ram advantages and disad.
11-11-2002, 10:19 PM
#1
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need info :tunnel ram advantages and disad.
anybody using tunnel ram?
what are the advs and disadv?
do you gain more hp as much as you spent more gas?
what kind of cams have to be used?higher lifts?
thnx
what are the advs and disadv?
do you gain more hp as much as you spent more gas?
what kind of cams have to be used?higher lifts?
thnx
11-12-2002, 01:51 AM
#2
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Tunnel Rams are good for high rpm engines like those in drag cars that run 6000+ rpms. Not really a good set up for boat where there is a lot of 3000-4000 rpm cruising.
11-12-2002, 08:00 AM
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The old TR debate starts again. The "drivability" of a TR comes down to how well matched all the parts are for a particular set-up. If you do your homework and properly match heads, cam, and carburation you can't beat a TR for mid range TQ and upper range HP. The long runners are perfect for making big TQ in the midrange. I know on my motor a TR is good for about 50HP over a single quad @6000 rpm. The motor idles very well, (smaller cfm carbs) and never hesitates or stumbles anywhere from idle to max rpm.
Now if you throw a TR on a 502 with twin dominators you WILL NOT be happy with the results, again it all comes back to set-up and matching a combo to your particular application.
As for fuel economy I would guess I use a little more than a single quad would, but it sure seems I get much better economy than blower motors do. I see about 2 mpg at a 70mph cruise in a 26 cat.
Do your own homework, but I know from experience a TR can work exceptionally well in the marine environment.
Now if you throw a TR on a 502 with twin dominators you WILL NOT be happy with the results, again it all comes back to set-up and matching a combo to your particular application.
As for fuel economy I would guess I use a little more than a single quad would, but it sure seems I get much better economy than blower motors do. I see about 2 mpg at a 70mph cruise in a 26 cat.
Do your own homework, but I know from experience a TR can work exceptionally well in the marine environment.
11-12-2002, 11:39 AM
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Tunnel Ram
There are two styles of intake manifolds, single plane and dual plane. The ultimate single plane intake manifold is the tunnel ram.
A standard single plane (one four barrel) intake manifold is a very compromised intake manifold designed to replace the stock dual plane manifold, fit under the hood of an engine compartment, increase high speed performance (at the expense of low speed performance) and utilize only one carburetor.
In fact the standard single plane (one four barrel) manifold is very crude. The four inside runners are much shorter than the outside runners and make an extreme turn to enter the four inside intake ports.
If you consider a 2X4 tunnel ram as a no compromise single plane intake manifold you will see that it is really a single plane manifold with the runners stood on end.
With a standard single plane (four barrel) intake manifold the air/fuel mixture must make a hard 90 degree turn as soon as it leaves the carburetor barrel to enter the manifold runners. The air/fuel mixture leaving the carburetor barrels of a 2X4 tunnel ram drops directly down into a long gently curved manifold runner and straight into the intake ports.
With a carburetor barrel for each cylinder mounted directly over each manifold runner the 2X4 tunnel ram has much better fuel distribution than any standard single plane (one four barrel) intake manifold.
Installing an open spacer below the carburetor on a standard single plane (one four barrel) intake manifold will increase high speed performance by allowing the air/fuel mixture to slow down slightly to make the 90 degree turn into the runners. Without the spacer the air/fuel mixture slams into the bottom of the plenum (like filling a bucket by holding a high pressure water hose too close to the bottom of the bucket) separating the air and fuel mixture. Obviously if the runner is directly below the carb barrels the sharp turn doesn't have to be made (tunnel ram).
The reason for a large plenum on a tunnel ram is for extreme high rpm. For increased low speed performance from a tunnel ram the plenum volume can be reduced considerably (by moving the carb closer to the runner inlets). For a marine engine running between 3000 and 5500 rpm a modified tunnel ram would make an excellent, no compromise, single plane intake manifold capable of much more power than a standard single plane (one four barrel) intake manifold.
By using two 390 CFM Holley carbs (total flow of 780 CFM) instead of one 780 CFM four barrel the engine would not be overcarbureted with a tunnel ram.
Tunnel rams are not popular with automotive hot rodders because they require a hood scoop and obstruct the forward view of a car. For this reason the intake manifold manufacturers do not find tunnel rams profitable and they do not invest much time or money into them. These installation problems (for a car) are not much of a problem for a boat.
Hope this helps someone!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
A standard single plane (one four barrel) intake manifold is a very compromised intake manifold designed to replace the stock dual plane manifold, fit under the hood of an engine compartment, increase high speed performance (at the expense of low speed performance) and utilize only one carburetor.
In fact the standard single plane (one four barrel) manifold is very crude. The four inside runners are much shorter than the outside runners and make an extreme turn to enter the four inside intake ports.
If you consider a 2X4 tunnel ram as a no compromise single plane intake manifold you will see that it is really a single plane manifold with the runners stood on end.
With a standard single plane (four barrel) intake manifold the air/fuel mixture must make a hard 90 degree turn as soon as it leaves the carburetor barrel to enter the manifold runners. The air/fuel mixture leaving the carburetor barrels of a 2X4 tunnel ram drops directly down into a long gently curved manifold runner and straight into the intake ports.
With a carburetor barrel for each cylinder mounted directly over each manifold runner the 2X4 tunnel ram has much better fuel distribution than any standard single plane (one four barrel) intake manifold.
Installing an open spacer below the carburetor on a standard single plane (one four barrel) intake manifold will increase high speed performance by allowing the air/fuel mixture to slow down slightly to make the 90 degree turn into the runners. Without the spacer the air/fuel mixture slams into the bottom of the plenum (like filling a bucket by holding a high pressure water hose too close to the bottom of the bucket) separating the air and fuel mixture. Obviously if the runner is directly below the carb barrels the sharp turn doesn't have to be made (tunnel ram).
The reason for a large plenum on a tunnel ram is for extreme high rpm. For increased low speed performance from a tunnel ram the plenum volume can be reduced considerably (by moving the carb closer to the runner inlets). For a marine engine running between 3000 and 5500 rpm a modified tunnel ram would make an excellent, no compromise, single plane intake manifold capable of much more power than a standard single plane (one four barrel) intake manifold.
By using two 390 CFM Holley carbs (total flow of 780 CFM) instead of one 780 CFM four barrel the engine would not be overcarbureted with a tunnel ram.
Tunnel rams are not popular with automotive hot rodders because they require a hood scoop and obstruct the forward view of a car. For this reason the intake manifold manufacturers do not find tunnel rams profitable and they do not invest much time or money into them. These installation problems (for a car) are not much of a problem for a boat.
Hope this helps someone!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
