Tunnel Ram's on the street - who's run em?

^^^^^Good game! I say, good game!

 

He may be a jailbird but he can make the dead rise and walk again.

I watched that Green Mile movie a couple of times.
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I wondered how come I had never got in on this thread......then I seen the year....wah wah wah

 

Resurrected zombie threads always crack me up... usually takes a FNG to ferret them out....

 

My avatar has a BBC with a Tunnel Ram and it seems to run good. First time out was a trip for about 450 miles and did not have any fuel issues. I also ran one for years on a 34 Chevy Coupe (60k miles) and did not have any issues after I changed from a 2 four to a single four set up.

 

real question is what hood scoop do you run with a tunnel ram?

 

I built a home-made tunnel ram for my '53 Hemi in 1967! Probably predates the commercial ones. I designed it in my college physics class. Ran really crappy on the street.


Need to understand what a tunnel ram is for to know how to properly apply it. Can be streeted but not the most efficient manifold there, main benefit is looks.
Think of an intake manifold as a reverse exhaust header. Whereas an exhaust header is designed to provide a power boost at a specific RPM by generating a negative (suction) pressure at the exhaust valve seat as it is closing. a performance intake manifold is designed to provide a positive 'supercharging' pressure at the time the intake valve closes. As with headers, it is the length of the intake runner which is the design parameter, as long as the runner diameter is adequate and there aren't any severe kinks in the path. The speed of sound in air/gas vapor in the cold intake is a lot slower than in the hot exhaust gasses so intake runners are a lot shorter than exhaust tubes for the same design boost RPM. As with headers, the longer the intake runner, the lower the tuned peak power RPM the engine will experience. Street tunnel rams have longer tubes. The theory is that as the intake valve opens, a suction pulse is sent up the runner at the speed of sound. It reaches the plenum and expands generating a complementary positive pressure pulse that transmits down the tube and, reaching the intake valve at the proper engine RPM, gives the cylinder a slight supercharge load of air/gas.
The size of the plenum doesn't have to be gigantic. Its only purpose is to isolate the tubes from the carburetor so the suction pulse can expand like it is free air. Too small and the pressure pulse sees the mess inside the carburetor and disappears and too big and the engine will be bog-central, take forever for a throttle change to transmit to the intake valve. the plenum I build for my hemi was WAY too big and the engine bogged badly. If I was drag racing it at +6,000RPM, my manifold would probably have been a champ.
The speed of sound at normal air temperature is just over 1,100ft/sec. At exhaust temperature, the speed of sound is over 2,100ft/sec so headers must be longer. Chrysler Corp. published a bunch of intake manifold design info in the 50s. A simple formula for calculating runner lengths is 1100fps * 60secpm /RPM or 66,000/RPM. You might think the length must be shorter since the pulse must travel up the runner then back down but remember that the engine is 4 cycle so for purposes of this calculation is effectively running at half speed. If you want peak power at 4000rpm, runner length (measured from the plenum port to the intake valve seat) is 16.5". That is based on the speed of sound in air, other calculations recommend other constants to account for the difference in speed of sound in the gas charge. Constants up to 84,000 have been suggested. A side benefit is there is a lower but measureable power bump at 1/2 design RPM, in this case 2000rpm.
Realize there is no free lunch; these manifolds provide more power at design RPM but result in less power at other speed.
In the final analysis, to paraphrase a famous Saturday Night Live sage, "It is more important to look good than to run good!"

 

I was kidding about 2006 and tunnel rams... who hasn't seen 2 Lane Blacktop at least 10 times???

 

American Graffiti, Hot Rod Willys, yes. Two Lane Blacktop, UGH! Worst hot rod movie ever!!!!!!!!!!

 

Can't beat the look of a scoop through the hood.

 

Sometimes the old threads are better reading than the "is this traditional" ,"what do you think about" and "what color should I paint "threads. Keep them coming.
Doubt he's a jail bird with over 60,000 on his ride. Maybe work release from a few states away.

 

Ran this set-up ( .030 over tunnel rammed 427 Chevy ) for years on my model A, went to NSRA Nats in Columbus ( twice ) and St. Paul. Got almost 16 MPG on the highway and turned 11.6's at the strip. Once I got it dialed in and yes it took a bit, I put on 35,000 miles on it in 5 years and it drove like a normal motor until you put your foot in it.

 

George Fitzios, 427 Sideoiler, Detroit '72. A local tech built the lower, runner portion.

 

There is a tunnel ram on the Blue coupe...with Hilborn scoop adapted on the top. g-willys

 

Like this one?

 

<--- Edelbrock TR2X with a pair of Thunder series Edelbrock 500 cfm carbs were my break in combo before the blower. No issues, big blocks have plenty of torque so no low end issues. Seemed like it could have been stronger with a pair of double pumpers.
660 Holley center squirters were made for tunnel rams.

 

HI, I have been running the new quick fuel 450's for a little while. With correct jet change (smaller) power valve change and secondary settings. I have them very close to perfect!!! You would be happy done correctly. You do need to be willing to spend some time making them exactly correct for your application and have a low first gear. I am picky so I kept at it until I GOT IT!

 

Ain't that the damn truth, how many threads a day can one person come up with...
I'm a 2x4 oholic, low, tall, cross ways and pressurized...I like them all.
Here's my old tunnel ram on the small block and the new one for the big block, hopefully I'll have no issues with the new just like the old.

 

Well I picked up my first tunnel ram a couple weeks ago off ebay for the 440 going into my model A.

It's a single 4 barrel version. Thought about a dual 4 but as this is my first and I do plan on driving the wheels off of it the single carb would be the way to go....

Next I'll figure out which carb to run.

 

Have a TR1X on my 37 two Holley 600s on a 406 sbc. Choke horns milled off ,vac secondaries linked together. Fairly mild solid flat tappet with a 5 spd. Fires right up and pulls like a bear from 3000 to 6500 .

 

I have one for a roller 302.....

 

Only problem I have with mine is a cold start up in the Pennsylvania winters. Love old treads btw! Lol

 

I think aside from having properly prepped and set up carbs (I’m running a pair of 750’s built by a local racer/engine builder with 30 yrs of experience in M/P,Stock Eliminator,and SuperStock,cause it was a little beyond my scope of expertise),the overall combo has got to be pretty close to optimal,and needs to be fairly aggressive to make things work right.
A stock long block with 8.7 compression,1.78” intake valves,tiny,restrictive ports,an “rv” style cam,stock distributor,and a tunnel ram with a pair of 660 Holleys in a 3700lb car with an automatic and 3.08 gear is obviously going to be misery.The whole package is just fighting each other.
But with really decent carbs,distributor with an aggressive advance curve,plenty of compression,good heads,an aggressive cam grind,a manual transmission,a deep set of gears,and a tunnel ram is going to work well,and be fun to drive.
Bigger cubic inches,and/or lighter cars are more fun too.
My o/t 66 Ford weighs around 2900lbs with me in it,runs a 368” sbf with 12.1:1 compression,258@.050”/.733”lift/108lsa solid roller cam,heavily ported Vic jr heads,1-7/8” headers,a Doug Nash 5-spd with a 3.50 first gear,and it sees as much street time as track time.
Don’t get me wrong,it wants to be in the correct gear if you’re suddenly going to slam the pedal to the floor,but it starts easily,settles right into an idle(although it’s close to 1200rpm),runs clean and never sneezes through the carbs,and will absolutely punish a set of 28”x9” slicks on the street,and has run a best so far (with lots of work to do to the car still) of 10.998@124mph
A tunnel ram will run great if you give it the parts and tuning to allow it to.Tie one hand behind its back,and the motor isn’t going to reward you with great performance or manners,in my opinion.

Scott

Ps:Just realized how long winded that was....Sorry for rambling on,I just like to fire a harpoon into the old “tunnel rams don’t work on the street” myth every time I get a chance.[emoji16]



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Runs like a champ.