Which is better - tunnel ram or single plane

Howdy,

I do the spanner work on a Falcon coupe tube chassis drag car with a 545 BBF. The BBF runs a Weiland TR with twin 950HP Holleys. Currently it runs 9.1 sec quarters at around 145MPH. I've been wondering for a while whether the TR is robbing time and MPH. Any views on whether a good single plane manifold with a Dominator would be worthwhile. The engine is running OOTB SCJs at the moment. Cant recall the cam specs off the top of my head.

Thanks in advance.

Ian

Twins typically outperform a single carb in almost all combinations for WOT performance. Kinda small on the carbs for that much displacement. What RPM is the engine turning?

7000 RPM, two 1100cfm carbs would be more what I would look for on the combination. Biggest gain would be different heads. Even well ported that much displacement under those heads is asking a lot of a warm street head. Ive got a 525cu in engine with Blue Thunder Chevy port heads that are max effort (still too small) and with two 1050s on it I've got .5" manifold vacuum WOT up to about 7500 RPM, then it starts to pull more manifold vacuum up until the 9200 RPM shift point. It maxes out at almost 2" so besides bigger heads, I could actually use more carb on my little engine.

ianxy351 wrote:Howdy,
 Currently it runs 9.1 sec quarters at around 145MPH.  I've been wondering for a while whether the TR is robbing time and MPH.  

Thanks in advance.

Ian

Could be ... Tunnel Rams usually are more efficient up near and past the horsepower peak so, it is ALL about the entire combination.

The test Charlie and I did showed the tunnel ram not giving up any anywhere over A good single plane, it made more power and a big surprise was it made more torque and lowered the torque peak in the rpm range also...........

Thanks for the replies fellas. To answer some questions - the engine has a 8000rpm limit but usually sees 7600 or so. We try to avoid banging it off the limiter at those revs. It has a modified Glide with transbrake behind it. Car weighs around 1350kg with driver.

I am keen on some Dominators but I agree that the heads are a limiting factor. So, is it worth CNCing the heads or just go to something better? If so, what would you recommend. We have contemplated a bigger cam too, but need to think that through - any recommendations. If we went to new heads, I would also consider some upgrading the rockers from the Crane Golds it has now. Any suggestions there? T&Ds maybe???

Its easy for us to spend your money. Combination has to be something that's in your speed/budget. Step up would be some A heads, matching cam, tunnel and twins.

And if going with A heads, twin carbs in the 1400 cfm range would be suggested.

A heads? Sorry but what exactly are you referring to? Bit of a newby to different head types so need to ask some questions.

If you are going to use a TR ditch the 4150 carbs and get a pair of dominators. Its worth a bunch of power.

The Weiand tunnel has runners that are too long and have a reverse taper in them. It is not a high rpm manifold if you wanting to make power in the rpm range your saying your running with that CID  , as others have said here go to the TFS A head and matching tunnel ram

The weiand tunnel ram can be worked quite a bit. With a little cutting and welding it can be damn formidable up to stepping up to the A heads and beyond. Mine has been redone to get rid of all the taper. Its actually got proper flow and is opened up so that the runner to head interface is actually perfect, and I mean not catch a nail kinda perfect. But its still not going to flow enough for an A head.

kim wrote:The weiand tunnel ram can be worked quite a bit.  With a little cutting and welding it can be damn formidable up to stepping up to the A heads and beyond.  Mine has been redone to get rid of all the taper.  Its actually got proper flow and is opened up so that the runner to head interface is actually perfect, and I mean not catch a nail kinda perfect.  But its still not going to flow enough for an A head.

 
They have more than taper issues, the runners are way to long for any thing like a 8000 rpm engine, got to cut them up like I did, but unless you can do it yourself it's entirely too expensive to do vs just getting some A460 heads and a TFS TR. Getting a Hogan or HRE sheet metal one is more cost effective.

snake modded mafia intake will pull well past 8000 rpm on a 560" motor, proved that last night........

This is great info guys - please keep the commentary and photos coming. We are getting plenty to think about. Much appreciated.

tell us more about that motor? comp, heads carb! 

The Holley HP950's are made with progressive linkage.  So the primaries open almost 1/2 way before the secondaries begin to open, the secondaries then ramp in twice as fast to allow all throttle blades to be WOT at the same time... now there are linkage kits out there to convert 4150 series carbs to 1-1 but have yours been converted?  The idea behind the twin 4bbls is to copy the predecessor of EFI and that was having weber IDA carbs over each intake runner.


The IDA's were a pain to tune, and to be honest were small for big cu in engines.  So...  the adaption of the 4bbls.  There are even split dominators to allow the dislocation of the carbs so they sit more closely to the runner end.  As was pointed out, as displacement comes up, runner length goes down...  similar for RPM.  
With tall deck big displacement engines, its difficult to keep runner length short, and the fuel shot from the carb straight (curves allow for dead air and fuel fall out)

So, to allow moving the carbs more closely over runners, there are now split dominators.



Work best on the tall deck 12.3 and big bore space 5.3" center stuff.  Allows the runner to stay straight and the plenum area small, so fuel is a direct shot into the runner and into the head.

But..  for a 10.3 deck height and your engine displacement, a conventional pair of dominators on something like the TFS tunnel ram will work fantastic.

What he said............... Good response.

nitrous.f wrote:tell us more about that motor? comp, heads carb! 

Sorry - I missed this post.

Comp is around 13:1. The engine runs Sunoco Supreme. Cam is a solid roller around 265@50 and 700-ish lift. Haven't been able to put our hands on the cam card so cant be precise. As mentioned earlier, we have two 950HPs on a Weiand TR. Currently running the HPs without power valves. Jetting is sitting at 84 square at the moment. Bottom end is a Dove-A 2 bolt block. Studded mains with a girdle. H beam rods. Cant remember what the pistons are - forged jobbies of some sort. All balanced to 8000rpm. Rest of the drive train is a Glide and 4.11 9".

The car ran 6.09 on the 1/8th last weekend. Best we have managed so far so we think the tune is heading in the right direction. We are busting to get a 5 second pass. We have been using a Innovate LM2 to monitor fuel ratios. At WOT its running around 11.5 - 12:1 so we may be able to pull a bit of fuel out of it. We dropped the jetting from 86/84 splits to 84 square on the weekend - didn't make a difference initially but then we advanced the total timing from 28 to 30 deg and picked up the PB. So maybe it can take some more timing? Any suggestions most welcome here.

We have started thinking about what to do in the off-season. CNC the heads, port match the TR or different TR and some dominators. Or just gas it for an extra 300 - 500hp  

Do a bowl blend on the heads (they respond big time) and put two 1150s on it and you will see a good pick up in performance.

Thanks Blake. Seems like a good plan to me.

i read your posts about the issues that the weiand has, my question is how much shorter runners are you talking about?