tuning a tunnel ram intake

Jonny Monza

New Member
Awesome read. Huge fan of Grumpy. Here's my 355 Team G Super Ram street motor that's been together for 21 years. I found the tunnel ram at a swap meet with both carbs. I cleaned it up, detailed it, bolted it on, setup the enderle linkage, fuel lines, etc--- and it fired right up and idled! After all these years, I still have amazing idle to redline throttle response, performance, and even gas mileage (highway)--- When I was freshening up the carbs one day I was curious about what jets it had. I found that someone filed off the numbers. I'm a lucky mother, but damn I'm tired of not knowing why!
 

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Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
jet sizes on the jets can be determined in most cases,
by simply measuring the internal hole diameter
( be well aware that, some jets are not properly marked,
others have been drilled larger than the marked size
)
years ago I purchased two of these assortment packs,
when they cost about 1/2 the current price , Ive tried hard to keep 4 jets in each size in inventory as I use those,
72 jets in assorted sizes for $52 is still a good deal ,
and it gets better if you buy the pack or two of them, when summit posts a discount code

http://www.summitracing.com/parts/hly-36-181
hly-36-181.jpg


http://www.mortec.com/carbs.htm
holleyjeth.png

if you have a complete set of drill bits they can be used to get a good idea on jet size


DrillSizeChart.gif

DrillCharts.gif


13cal.jpg

12cal.jpg
 
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Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
one factor I see virtually ignored is the idea that a properly installed hood scoop duct ed tunnel ram intake,
can be installed to have a great deal of the surface area of the tunnel ram intake runners and air flow,
entering the tunnel ram intake be rapidly flowing cooler outside air this can easily be over a 100 deg F cooler than air in the engine compartment!

http://garage.grumpysperformance.com/index.php?threads/cooler-denser-air.8961/

http://garage.grumpysperformance.co...ferant-c-4-hoods-and-hoodscoops.353/#post-434

https://www.linkedin.com/pulse/air-ducts-down-earth-guide-motorsport-applications-willem-toet

http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/

https://wahiduddin.net/calc/cf.htm

https://wahiduddin.net/calc/calc_da.htm
for about every 10 degrees C of increase or decrease in air temps, entering an engines carb, the horse power changes about 1% (hotter is less efficient, as cooler air is denser and contains more oxygen)
IF your not familiar with temps in C celsius that equates too about..
FOR EVERY 15 degrees change in F temp, the horse power changes about 1%
(hotter is less efficient, as cooler air is denser and contains more oxygen)


http://www.celsius.co.uk/converter/
think about that..under hood temps can easily be 100F-120F higher than outside air temps, thats a potential 7-8% decrease in effective horse power over cool air induction

Effect of Ambient Air Intake Temperature on Horsepower Output
Because the BHP of an engine varies with intake ambient air temperature and pressure, the rated BHP of an engine is measured at sea level air pressure of 29.92" Hg and air temperature of 59 deg F or 15 deg C. If these parameters are not available, then the obtained BHP is corrected to account for any variation making possible accurate comparisons among engines, regardless of the measurement environment. Considering only the relationship of intake air temperature to HP, the power varies essentially as the square root of the change in ABSOLUTE temperature.

For references consult:
High Speed Combustion Engines by P. M. Heldt, 16th edition, p.638

The Design and Tuning of Competition Engines by Philip H. Smith, 5th edition, p.370-71.

Assuming the Protege 2 liter engine develops 130 HP at 59 deg F which = 15 deg C, this represents 288.15 deg K on the Celsius absolute temperature scale. To calculate change in HP, take the square root of the quotient of the standard temperature (288.15 deg K) divided by the proposed temperature in deg K and multiply that by
130.

For example:
What is the HP output at 30 deg F (-1.11deg C) where the absolute temperature is 272.04 deg K?
1. Divide 288.15 by 272.04= 1.059
2. Take the square root of 1.059=1.029
3. Multiply 130(1.029)=133.8 HP

What is the HP output at 0 deg F (-17.78 deg C) where the absolute temperature is 255.37 deg K?
1. Divide 288.15 by 255.37=1.128
2.Square root of 1.128=1.062
3. 130(1.062)=138.1 HP

Conversely, one can calculate the HP decrease as ambient temperatures rises above the standard.

The temperature at 80 deg F (26.67 deg C) where the absolute temperature is 299.82 deg K.
1. Divide 288.15 by 299.82=.961
2. Square root of .961=.980
3. 130(.980)=127.4 HP

In the same manner some other representative temperatures are:
100 deg F=37.78 deg C=310.93 deg K=125.1 HP
140 deg F=60 deg C=333.15 deg K=120.9 HP

To calculate HP at any given temperature, simply convert the ambient temperature either F or C to absolute. For those of you who want to work exclusively with the F scale, you can use the Fahrenheit absolute temperature scale where 59 deg F=518.67 Rankine.

To convert temperatures from one scale to another see this website: www.onlineconversion.com

Clearly the results indicate we should attempt to provide ambient temperature air, as opposed to underhood air, to the intake for maximum performance.

003-2-1.jpg

IMG_1698.JPG


Ive suggested your average skilled mechanic or hot rod enthusiast,
spend time in doing research in, and then if they choose too,
cleaning up the bowl area under the valves , of casting flash,
and valve seat machining ridges,getting a multi angle valve job,
narrowing the valve guides port matching the heads/intake manifold,
and polishing and ccing the combustion chambers,
you should not be significantly altering or enlarging the ports or runners,
multi angle valve jobs should be left too the pros with the correct machinery,
and precise measuring equipment,
but a home shop can certainly lap valves and clean up the port and bowl area ,
and port match, and blend , polish and cc combustion chambers, etc.


reading links and sub-links generally helps
http://garage.grumpysperformance.co...ng-combustion-chambers.2630/page-3#post-77963

http://garage.grumpysperformance.com/index.php?threads/ccing-my-heads.14187/#post-71989

http://garage.grumpysperformance.co...needs-clean-up-equalization.12474/#post-62647

http://garage.grumpysperformance.co...r-piston-dome-or-port-volume.2077/#post-61068

http://garage.grumpysperformance.co...ing-tools-abrasives-sources.10683/#post-46209

http://garage.grumpysperformance.co...lve-seat-angles-and-air-flow.8460/#post-29682

http://garage.grumpysperformance.com/index.php?threads/multi-angle-valve-job-related.3143/#post-8387

http://garage.grumpysperformance.com/index.php?threads/how-to-lap-valve-seats.1159/#post-2362

http://garage.grumpysperformance.com/index.php?threads/valve-train-clearances-and-problems.528/

http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

http://garage.grumpysperformance.com/index.php?threads/rocker-push-rod-wear-issues.9815/
 
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steve16

Orange, California
Dear Grumpy, I am looking to change my current single plane, 1050 Dominator intake to a tunnel ram set-up. I don't know of any algorithm to figure out
what carbs to use on the tunnel ram system. Can you make a suggestion? The motor currently is a 496making 748hp and 660ft/tq. It is static compression at 10.7
and is currently(which I am going solid roller) using a hydraulic roller set -up with a 110 lobe separation 242/248 lift and a 106 intake centerline. I am running 1.8
rockers to increase duration. I feel I screwed up on the type of cam I used...listening to Comp Cam's tech.
It is a very efficient motor which I plan on using for the year to figure out the chassis.
Since the car is heavy, I want to get the most amount of torque from this 496 as I can.
I felt tunnel ram is the way to that goal. Can you suggest an appropriate carb set-up? Thanks, Dr. Grumpy!
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
well the first thing Id do is call holley in the morning and give them all the info you can and get their suggestions
and you also failed to mention the cylinder heads, port type and size, and tunnel ram intake your intending to use drive train gearing and exhaust which are all important.
you might want to ask if a second dominator carburetor matching your current carburetor could make a good combo to reduce potentially total cost of concerting to a dual carb tunnel ram
 
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steve16

Orange, California
well the first thing Id do is call holley in the morning and give them all the info you can and get their suggestions
and you also failed to mention the cylinder heads, port type and size, and tunnel ram intake your intending to use drive train gearing and exhaust which are all important.
you might want to ask if a second dominator carburetor matching your current carburetor could make a good combo to reduce potentially total cost of concerting to a dual carb tunnel ram
More info coming your way. I have Brodix BB3 xtra Os. Oval port. I ported the heads myself. They flowed very good at mid rpm(low too) as I ported for velocity, not volume. I also did the Brodix intake with a twist. I lessened the plenum volume squeezing it tighter and then raised it with a similar spacer of 2 inches. I configured the exhaust using an algorithm from the book Performance Automotive Engine Math. They are 2.125 internal(not external) diameter. I think I may buy the Dart Tunnel Ram or the fabricated intake kit from Wilson. TH 400 built to handle over 1000khp. I have 3 different Ford 9 inch gear sets. The first is so I can drive the car on the street for a few months, 3.73, second for 1/8ths at 4.56, lastly 1/4mile at 4.11. I just finished tubing the car with an HD 4-link and also installed a complete roll-cage. Tires will be big slicks as the rear rims are 15x14. I know most people do not port their $27oo.heads themselves. But, I have been porting for years
and have engines I built holding 13 land speed records, 4 Daytona wins and 4 AMA titles among others. Granted, it is all in two strokes. But, I was contracted to build 2 motors raced in MotoGP which took 4th in the world and won numerous races in the 1990s with John Hopkins riding. That was my indoctrination into 4 strokes.
Grumpy, I would LOVE to use my 1050 as the second carb. But the CFMs seem too far apart. I am just getting into drag racing. I read your impressive background and couldn't think of a better person to ask.
BTW all my dyno time was with 91 octane unleaded as the shop I was using forgot to purchase the fuel I had ask for. I will be using 108-110 at current timing and compression. I like to use octane that is "just" sufficient to stop detention, so BTUs are up.
 

steve16

Orange, California
jet sizes on the jets can be determined in most cases,
by simply measuring the internal hole diameter
( be well aware that, some jets are not properly marked,
others have been drilled larger than the marked size
)
years ago I purchased two of these assortment packs,
when they cost about 1/2 the current price , Ive tried hard to keep 4 jets in each size in inventory as I use those,
72 jets in assorted sizes for $52 is still a good deal ,
and it gets better if you buy the pack or two of them, when summit posts a discount code

http://www.summitracing.com/parts/hly-36-181

https://www.summitracing.com/parts/hly-0-9377-1/overview/
hly-36-181.jpg


http://www.mortec.com/carbs.htm
holleyjeth.png

if you have a complete set of drill bits they can be used to get a good idea on jet size


DrillSizeChart.gif

DrillCharts.gif


13cal.jpg

12cal.jpg
 
Last edited by a moderator:

steve16

Orange, California
As I understand it there are carb/engine bay separators available for that hood. I purchased that same hood for this reason,... and it looks cool.
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
550-529_0219200.jpg

something like this holley system has potential, throttle body EFI , matched to a correctly modded/ported tunnel ram has the potential to be a real game changing addition.
I can easily see the correct tunnel ram/efi, combo having added 50-80 hp or more,
over what a stock dual plane intake with the stock carb has for power potential on the same engine
835171_0117356.jpg

 
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