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L79vette 08-27-2011 08:10 PM

Tunnel Ram I designed
 
1 Attachment(s)
I designed a new type of tunnel ram. I call it the Real Street Ram. In my dyno testing, it makes more torque than a dual-plane from right off idle. I've attached a graph of the torque curve vs. a dual plane on a stock Goodwrench 350 engine.

The biggest difference from a regular tunnel ram is that instead of having one huge plenum it has four small separate plenums. Only two runners connect to each plenum. I had to do a lot of work to get fuel distribution to be even between the cylinders. We used vacuum secondary 580CFM carburetors, so you can slam the throttle open even at <1500RPM.

Testing so far has been terrific. ****************

Hoping to get some technical discussion going.

68NovaSS 08-27-2011 08:37 PM

This post is borderline classified ad, feel free to use the classifieds here, they're free. :thumbup:

UPandComing 08-27-2011 09:04 PM

yeah lets bring this post in a better direction lol pics? describe the process you used to actually create such an intake. did you use a tunnel ram thats in production and modify it or was this a ground up design? what are the specs on the engine you used as a test subject?

L79vette 08-27-2011 09:18 PM

1 Attachment(s)
I used a Weiand base and designed custom tops for it. Attempting to attach a picture.

OK, that worked.
From the picture you can see how the plenum area is divided into four plenums.

L79vette 08-27-2011 09:24 PM

So I had the idea to divide things up to get better venturi velocity at low RPM. I have a friend who is a hardcore engine builder and has a dyno. We tried a bunch of different schemes to get the fuel distribution right, and then had to do a bunch of carburetor customization to get the carbs to deal with the uneven firing in each plenum.

Tested on a bone stock Goodwrench 350, an 11:1 compression engine with ported L98 heads and a .570 lift roller cam, and the history-unknown-but-appears-to-be-stock-except-for-headers 350 in my 1971 El Camino. The torque graph is off the Goodwrench engine.

NEW INTERIORS 08-27-2011 10:17 PM

Quote:

Originally Posted by L79vette
I used a Weiand base and designed custom tops for it. Attempting to attach a picture.

OK, that worked.
From the picture you can see how the plenum area is divided into four plenums.



Look's like two plenum to me... :mwink:

Front and back makes two..

L79vette 08-27-2011 10:33 PM

Each top is completely divided in half. There are two tops, each of which has completely separated right and left plenums. So there are four plenums all together. Using small-block Chevy cyinder numbering, there is one plenum for #1 & #3, one for #2 & #4, one for #5 & #7, and one for #6 & #8.

When you start thinking about the firing order, you quickly see a big problem we had to engineer around. #5 and #7 fire right next to each other in the firing order. The other pairs have a pattern like bang-rest-rest-bang-rest-rest-rest-rest (for #1 & #3). So you get this weird induction, rest-two-cycles, induction, rest-four-cycles pattern. For some pairs the cylinder under the primary venturi goes after four rest cycles, while for the #6 & #8 pair it is the cylinder under the secondary. So we had to do some major work on the carburetors to get even fueling everywhere. We have screw-in air bleeds, and each venturi has jetting and air bleeds tuned separately. We have 8 wide-band oxygen sensors on the dyno so we can graph what each cylinder is seeing for air-fuel all the way through the pull.

NEW INTERIORS 08-27-2011 10:53 PM

Quote:

Originally Posted by L79vette
Each top is completely divided in half. There are two tops, each of which has completely separated right and left plenums. So there are four plenums all together. Using small-block Chevy cyinder numbering, there is one plenum for #1 & #3, one for #2 & #4, one for #5 & #7, and one for #6 & #8.

When you start thinking about the firing order, you quickly see a big problem we had to engineer around. #5 and #7 fire right next to each other in the firing order. The other pairs have a pattern like bang-rest-rest-bang-rest-rest-rest-rest (for #1 & #3). So you get this weird induction, rest-two-cycles, induction, rest-four-cycles pattern. For some pairs the cylinder under the primary venturi goes after four rest cycles, while for the #6 & #8 pair it is the cylinder under the secondary. So we had to do some major work on the carburetors to get even fueling everywhere. We have screw-in air bleeds, and each venturi has jetting and air bleeds tuned separately. We have 8 wide-band oxygen sensors on the dyno so we can graph what each cylinder is seeing for air-fuel all the way through the pull.


I see them now.... :drunk: I guess I was in the sun to long today.. :sweat: :thumbup:

UPandComing 08-28-2011 03:15 AM

Wow keep us up to date more pics wish i had the resources to do things like that

F-BIRD'88 08-28-2011 03:19 AM

Interesting. Looks like it is air flow limited s the torque at 5000rpm is equal. So it likely does not make any more peak horsepower than the stock manifold even thou it makes more low-mid power.

How does your manifold compare to a out of the box weiand tunnel ram?

timothale 08-28-2011 07:01 AM

spider leg manifold.
 
A few years ago i built a corvair engine for my dune buggy They have intregal intake as part of the head. I machined the manifold part down, added mounting flanges then welded up steel tubing like a set of headers to a box and used a 2 barrel holly truck carb. It would pull the wheels up in second gear.

L79vette 08-28-2011 10:07 AM

Quote:

Originally Posted by F-BIRD'88
Interesting. Looks like it is air flow limited s the torque at 5000rpm is equal. So it likely does not make any more peak horsepower than the stock manifold even thou it makes more low-mid power.

How does your manifold compare to a out of the box weiand tunnel ram?

We're not airflow limited on that engine.
Horsepower peak with the Street Ram was 286, vs. 274 with the Performer.
Where we did get into limitation is on the 350-inch 11:1 roller motor we ran. There the RPM air-gap style intake made 460HP peak vs. 440HP for our setup. We made more power everywhere below 4000RPM. So I'm thinking 450HP is about the limit of engines it makes sense to put this on.

We ran the regular Weiand top with a pair of 390CFM vacuum secondary carbs to give it the best possible chance on the mild engine. Those carbs are over $700 for a pair, so way more expensive than anything you get in the combo kits from Summit or Jegs. Our setup made 42lb-ft more torque at 1500RPM, 23lb-ft more at 2000, and keep making more up to 4000RPM where they crossed over. The regular top made more top-end power, but was mushy down low even with the small vacuum secondary carbs. If you put on the 450CFM mechanical secondary carbs you get in the kits, it would be terrible down low because the venturi velocity would be so bad.

This setup is so eager and responsive on the street. If you coudn't see the dual carbs you would swear it was a single four on a dual-plane.

UPandComing 08-28-2011 11:47 AM

Quote:

Originally Posted by L79vette

This setup is so eager and responsive on the street. If you coudn't see the dual carbs you would swear it was a single four on a dual-plane.


that being said wouldn't it be easier and more economical to just run the single carb dual plain and save the $$???

ssmonty 08-28-2011 12:05 PM

Keep up the good work! Too cool!
ssmonty

L79vette 08-28-2011 03:04 PM

Quote:

Originally Posted by UPandComing
that being said wouldn't it be easier and more economical to just run the single carb dual plain and save the $$???

For sure! But then you don't get the eye candy.
The point of this project was to build eye candy that works well on the street.


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