Tunnel Ram Question...

I was looking at a Weiand tunnel ram I have had for some time and started wondering about the plenums....some rookie questions.
What is the purpose of the gap between the two carbs?
How does plenum size affect performance on a given engine?

The reason I ask is, when I obtained the intake, I also got 3 tops with it.
A Weiand 4150 base, 4500 and, a sheet metal 4500, which is larger than the cast piece.

I'm not considering trying to run it at this time....just wondered about the differences in the plenums.
Jeff

There are different plenume volume formulas and carb height formulas but, they will only get someone in the right ballpark, "usually".
Actually trying everything around those parameters is the only way to know what works best ... one thing will also have an effect on the other and so on. Sometimes actually going against known principals works best with a given engine combination.
Testing is the only real alternative.

sell it and turn it into a TFS Mafia intake................

richter69 wrote:sell it and turn it into a TFS Mafia intake................

X2

What do you want for it

Who said anything about it being for sale?

They look cool too.............

If this is a fashion show please put the sparkplugs in the carbs

Lem Evans wrote:If this is a fashion show please put the sparkplugs in the carbs

The guy that usually does that for me isn't around................. Besides , that's a speed secret.........

IDT-572 wrote:They look cool too.............

That they do!!

Treeyasoon wrote:What is the purpose of the gap between the two carbs?

I'm still wondering about this too...Why not feed four holes with each carb?

Treeyasoon wrote:

Treeyasoon wrote:What is the purpose of the gap between the two carbs?

I'm still wondering about this too...Why not feed four holes with each carb?

If you set the carb down directly on each runner, that turns it into an I.R. system. The NHRA Pro Stock 426 Hemi Mopars learned that doesn't work, back in 1970/71.

Charlie

c.evans wrote:

Treeyasoon wrote:

Treeyasoon wrote:What is the purpose of the gap between the two carbs?

I'm still wondering about this too...Why not feed four holes with each carb?

If you set the carb down directly on each runner, that turns it into an I.R. system. The NHRA Pro Stock 426 Hemi Mopars learned that doesn't work, back in 1970/71.

Charlie

Like Charlie said...the IR setups were tough to tune for a drag application. They like to run at a very tight RPM band depending on runner length, cam design and 20 other factors. I believe that a nice respectable plenum volume settles the booster signal down a bit. That is why the 2 plenum sections are joined...just for volume and balance. If you observe tunnel ram evolution, you may notice that the plenums have become one big area instead of 2 smaller ones joined in the middle. This just makes the carburetor folks enjoy a wider power band with less "peaky" tuning issues.
At least that is my perspective.
Thanks!
Keith

I have been helping a friend of mine with a small block Mopar that has I.R. injection. When one cylinder doesen't have the ability to pull air and fuel from a common plennum, the single butterfly or barrel has to be a hell of a bunch bigger to supply the cylinder.

This engine didn't seem to be super peaky, Good spread between torque peak and hp peak. He moved the stack length longer to shorter to get the curve where he wanted it.

On engines the size we run, to run one I.R. with a carb set down on the runner opening, one barrel per runner , I don't know if there is a carb that big..............

Some of you may have seen the pictures of the 1 cylinder A headed engine I helped build, it Had a 56 mm S&S D series Harley carb on it, and it was two small. The engine was 73 C.I.D. turning around 8000 rpm. That carb had a 2.250 inch venturie.

The IR stuff does work, but the problem is the carb size required is gigantic on big inch motors and not readily avaliable or produced. The carbs need to be set-up and tuned differently than a regular set-up. On something like a 351" Cleveland it works great with some dominators and itss done every now and then.

We tried it on last years emc boss 429 and it had awsome throttle responce and and wide power band, but we just couldn't get large enough carbs to make it work well over 6500. Its the same princable as webbers or kinsler/hilborn injection.

As Dave said, two 1250's weren't big enough to get near maximum horsepower for an I.R. set-up with a 429 inch engine having street manners. Low speed throttle response was great, mid range power was great and power leveled out at 6,000 RPM. It needed MUCH bigger carbs for the I.R. to work WELL on that relatively small big block engine.

Just for clarification. I agree with what Dave and Randy said. In my short response about Mopar Pro Stockers back in 1970/71,,,,the problem was that the Dominator style carbs had just come out, and they couldn't get a big enough cfm carb on those engines back then. Even with todays engines and the currently larger 1450 cfm Dommies, you still don't see I.R. systems in the "open" drag racing classes.

Charlie