Tunnel Ram Like Billy Glidden's

[nhrastocker]

There are over 20 classes between NHRA Super Stock and Comp Eliminator that require a single carburetor only.
Depending on the class, the largest carb is a Holley 850 and minimum, a Holley 750.
Not a single engine in those classes is running a single plane cast intake; everyone runs a tunnel ram with a single 4bbl top.

Many years ago I tested in the dyno a fully modified 18 degree Chevy cast intake, ported by Jim Bell against a Hogan's sheet metal tunnel ram with a single 4bbl top with a Holley 850 carb.

The sheet metal tunnel ram outperformed the single plane intake by a ton throughout the full RPM range of the engine.
It was also more responsive.

In a nutshell, a well designed tunnel ram for a single 4bbl for a drag racing application, will outperform a single plane cast intake, no matter how much is modified.

[MadBill]

..In a nutshell, a well designed tunnel ram for a single 4bbl for a drag racing application, will outperform a single plane cast intake, no matter how much is modified.

How about a belt-driven cast manifold?

[cgarb]

Has anyone used one of the Holley fabricated intakes yet? I remember a thread on here about them and people were concerned about the way the runners exit the plenum on an angle on the sbc intakes. To me it looks like an effort to more evenly grab fuel out of the plenum. An angled runner and a straight runner, how that equates into the real world on the track HP I'm not sure. I would like to try one of the single carb versions on my 377, but don't really want to blow 450 dollars if its worthless.

[nhrastocker]

..In a nutshell, a well designed tunnel ram for a single 4bbl for a drag racing application, will outperform a single plane cast intake, no matter how much is modified.

How about a belt-driven cast manifold?

[F-BIRD'88]

Has anyone used one of the Holley fabricated intakes yet? I remember a thread on here about them and people were concerned about the way the runners exit the plenum on an angle on the sbc intakes. To me it looks like an effort to more evenly grab fuel out of the plenum. An angled runner and a straight runner, how that equates into the real world on the track HP I'm not sure. I would like to try one of the single carb versions on my 377, but don't really want to blow 450 dollars if its worthless.

The single carb (girlie-man) version is going to suck. The dual carb versions might be fun and has much more potential. Should have been made with a removable top.

[nhrastocker]

Has anyone used one of the Holley fabricated intakes yet? I remember a thread on here about them and people were concerned about the way the runners exit the plenum on an angle on the sbc intakes. To me it looks like an effort to more evenly grab fuel out of the plenum. An angled runner and a straight runner, how that equates into the real world on the track HP I'm not sure. I would like to try one of the single carb versions on my 377, but don't really want to blow 450 dollars if its worthless.

A well built fabricated intake is made to specific engine and racing applications.
I don't believe the new line of Holley fabricated intakes meet the criteria.

[cgarb]

Yeah, its cheaper to ask and realize its not worth it...lol. I can"t find much about them on youtube other than the holley promotional video, probably a reason for that. If it were decent by now someone would have dyno figures posted somewhere. Just stick to the tried and true strip dominator. Guess I could bust out the ol' Weiand cast high ram and the 660 center squirters, but I sold that 30 years ago along with my coon skin cap collection.

[BlackKnight]

This (below) makes complete sense to me.

There are over 20 classes between NHRA Super Stock and Comp Eliminator that require a single carburetor only.
Depending on the class, the largest carb is a Holley 850 and minimum, a Holley 750.
Not a single engine in those classes is running a single plane cast intake; everyone runs a tunnel ram with a single 4bbl top.

Many years ago I tested in the dyno a fully modified 18 degree Chevy cast intake, ported by Jim Bell against a Hogan's sheet metal tunnel ram with a single 4bbl top with a Holley 850 carb.

The sheet metal tunnel ram outperformed the single plane intake by a ton throughout the full RPM range of the engine.
It was also more responsive.

In a nutshell, a well designed tunnel ram for a single 4bbl for a drag racing application, will outperform a single plane cast intake, no matter how much is modified.

[Newold1]

It's called plenum!

[Ron E]

Only exceptions to the blanket endorsement I've witnessed is on a small engine (sub 3" stroke). We did a cast intake for a 300" motor that picked up over a custom-made" name" manifold. I believe its hard to get the plenum small enough for those fickle motors. One thing worth watching is on a single carb'ed tunnel ram manifold, the EGTspread is often pretty big as delivered. As in 250° from cold to hot. Its much less an issue with 2 carbs. But, fully developed and tweaked any engine should benefit from the zero restriction of tunnel ram's straight runners.

[Newold1]

Here are some of my thoughts about air and fuel distribution in NA single carburetor manifolds single plain and dual plane on SBC and BBC stock port location heads. With a 2 barrel or 4 barrel carburetor the air/fuel mix is pretty much determined at the exit of the throttle plates in the carburetor via venturi size, shape discharge nozzle and jetting. Once this mixture is pulled into the single plane or dual plane manifold area under the carburetor which is either divided or even open as a small plenum area it is passing into runners that vary in length, angles and volume before it arrives at the manifold/ cylinder head junction. I feel that especially at higher rpms under higher cfm requirements the individual charges of air/fuel differ slightly cylinder to cylinder and as such each individual cylinder is igniting and burning a slightly different volume of fuel and air and subsequent power output. These differences cannot be measured on a complete engine on a simple aftermarket dyno without individual cylinder probe testing. Even though dyno measured EGT's may show some level of evenness they do not actually measure the power output of the individual cylinders. My feeling is that bigger tunnel ram manifolds or larger plenum manifolds either single or multiple carburetor configurations allow a larger sort of reserve capacity of premixed air /fuel that is more evenly drawn to each cylinder thu what are usually intake manifold runners that are closer in dimension, shape and volumes. This distribution issue was born out even more identifiable with the "Good port, Bad port" configuration of the conventional big block chevy head. I believe this is the determiner and reason that you will notice that the trend in both OEM engines and the new breeds of racing engines is to eliminate this intake port delivery imbalance with symmetrical cylinder head port loacation and shapes and the resulting intake manifolds with symmetrical even volume port configurations.

The single carburetor tunnel ram type manifold discussed and shown here for example in that very nice M&M design tends to make this unequal charge distribution less of a negative effect on VE differences cylinder to cylinder in these engines. The differences are somewhat masked but I believe they are there none the less and as we all know in racing-"little improvements are sometimes the difference between winning and losing a race!"

I may be out on a limb here with my thoughts, but a little fall from that low lying branch "ain't gonna kill me!

[nhrastocker]

Here are some of my thoughts about air and fuel distribution in NA single carburetor manifolds single plain and dual plane on SBC and BBC stock port location heads. With a 2 barrel or 4 barrel carburetor the air/fuel mix is pretty much determined at the exit of the throttle plates in the carburetor via venturi size, shape discharge nozzle and jetting. Once this mixture is pulled into the single plane or dual plane manifold area under the carburetor which is either divided or even open as a small plenum area it is passing into runners that vary in length, angles and volume before it arrives at the manifold/ cylinder head junction. I feel that especially at higher rpms under higher cfm requirements the individual charges of air/fuel differ slightly cylinder to cylinder and as such each individual cylinder is igniting and burning a slightly different volume of fuel and air and subsequent power output. These differences cannot be measured on a complete engine on a simple aftermarket dyno without individual cylinder probe testing. Even though dyno measured EGT's may show some level of evenness they do not actually measure the power output of the individual cylinders. My feeling is that bigger tunnel ram manifolds or larger plenum manifolds either single or multiple carburetor configurations allow a larger sort of reserve capacity of premixed air /fuel that is more evenly drawn to each cylinder thu what are usually intake manifold runners that are closer in dimension, shape and volumes. This distribution issue was born out even more identifiable with the "Good port, Bad port" configuration of the conventional big block chevy head. I believe this is the determiner and reason that you will notice that the trend in both OEM engines and the new breeds of racing engines is to eliminate this intake port delivery imbalance with symmetrical cylinder head port location and shapes and the resulting intake manifolds with symmetrical even volume port configurations.

The single carburetor tunnel ram type manifold discussed and shown here for example in that very nice M&M design tends to make this unequal charge distribution less of a negative effect on VE differences cylinder to cylinder in these engines. The differences are somewhat masked but I believe they are there none the less and as we all know in racing-"little improvements are sometimes the difference between winning and losing a race!"

I may be out on a limb here with my thoughts, but a little fall from that low lying branch "ain't gonna kill me!

Your observations address a lot of the issues and your statement about the plenum size is also correct.
As an example, in the early days, there were BBC single plane and tunnel ram intakes that angled the carburetor for better fuel distribution.
There was also lots of combinations that used staggered jetting too.









With the advent of CFD design tools, intakes have developed in leaps to the extent that runner lengths and plenums have been optimized for specific applications and allows for final tweaking if necessary.

[Steve.k]

There are over 20 classes between NHRA Super Stock and Comp Eliminator that require a single carburetor only.
Depending on the class, the largest carb is a Holley 850 and minimum, a Holley 750.
Not a single engine in those classes is running a single plane cast intake; everyone runs a tunnel ram with a single 4bbl top.

Many years ago I tested in the dyno a fully modified 18 degree Chevy cast intake, ported by Jim Bell against a Hogan's sheet metal tunnel ram with a single 4bbl top with a Holley 850 carb.

The sheet metal tunnel ram outperformed the single plane intake by a ton throughout the full RPM range of the engine.
It was also more responsive.

In a nutshell, a well designed tunnel ram for a single 4bbl for a drag racing application, will outperform a single plane cast intake, no matter how much is modified.

So is a dual Dommy setup that much better again?

[statsystems]

There are over 20 classes between NHRA Super Stock and Comp Eliminator that require a single carburetor only.
Depending on the class, the largest carb is a Holley 850 and minimum, a Holley 750.
Not a single engine in those classes is running a single plane cast intake; everyone runs a tunnel ram with a single 4bbl top.

Many years ago I tested in the dyno a fully modified 18 degree Chevy cast intake, ported by Jim Bell against a Hogan's sheet metal tunnel ram with a single 4bbl top with a Holley 850 carb.

The sheet metal tunnel ram outperformed the single plane intake by a ton throughout the full RPM range of the engine.
It was also more responsive.

In a nutshell, a well designed tunnel ram for a single 4bbl for a drag racing application, will outperform a single plane cast intake, no matter how much is modified.

So is a dual Dommy setup that much better again?

The emphasis for the TR x 1 carb in NHRA is REQUIRED. If not REQUIRED they'd all be running 2 carbs.

[F-BIRD'88]

"Better" enough that the single carb guys will not compete against them.

SuperStock / Girlie Man eliminator