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Divider for intake manifold?
https://slantsix.org/forum/viewtopic.php?t=55660		 Page 1 of 1
Author:  lgu32 [ Sun Jun 22, 2014 1:05 am ]
Post subject:  Divider for intake manifold?
Most of the V8 intake manifolds are built for 2 separated groups. Four cylinder each. If the firing order is 18436572, then cylinders 1, 4, 6 and 7 are in one plenum and the rest in the other.

This is also possible to do for slant six. There is already a manifold for 2 carburetors (or throttle bodies) but seems to be doable for other hiperf manifolds like Clifford.

If anywhere I assume here someone has tested this already. Did it grow up the low end torque noticeable? Did it reduce anything at high rpm?

I have 2 port throttle body and I just get thought if it do this to get some more performance for the rpm range I am mostly using.
Author:  SlantSteve [ Sun Jun 22, 2014 4:21 am ]
Post subject: 
I built an Australian 265 ci Hemi engine using a divided plenum intake. The engine was a very mild build. I dynod it using a long runner intake which is very similar in design to the hyperpac intake on the slant six engines. I ran it both with a plenum divider and without,we used a variety of carbs and exhaust manifolds. To cut a long story short the divided plenum made a noticeable amount more torque but lost around 10 hp.the torque also dropped off very quickly as the rpm climbed... From memory it made something like 220hp with the long runner and about 208 with the divider. I wanted to continue to experiment with trimming the divider to provide a little more "sharing" between the sides of the intake,but I had to pull the engine because my friend at the time needed his dyno for his customers. I ran it in a 1970 Valiant with a 465 holley carb and long tube headers and it was a torque monster....but it did feel flat as the rpm climbed,so I trimmed the divider a little and it did help get a little top end back and flatten the torque curve,which made it pretty nice to drive.The long tube headers were streets ahead on the dyno compared to a stock iron exhaust and also a factory dual outlet exhaust,the long tube mandrel bent headers left them in the dust...well,scrap bin actually...I always thought the plenum was really too small for a true dual design intake and trimming the divider helped to compensate. I ended up selling the engine and trans and now run a small block with an overdrive in the same car. Hope this helps!
Author:  DusterIdiot [ Sun Jun 22, 2014 6:58 am ]
Post subject:  Midrange...
On a short ram manifold, it wouldn't make much difference, other than allowing a person with true dual exhaust to tune the engine like a "V" engine (front 3 cylinders and rear 3 cylinders)...I've done it to a hyperpak intake and it did help tuning and it made better mid-range torque, while still retaining the intake's ram tuning at higher rpm (large plenum with 24" runner lengths).

It will change the reflection wave characteristic in the longer runner manifold, but not sure you will get any large gains from the ram tuning with a dry manifold/EFI.
Author:  emsvitil [ Sun Jun 22, 2014 3:41 pm ]
Post subject: 
Quote:
I built an Australian 265 ci Hemi engine using a divided plenum intake. The engine was a very mild build. I dynod it using a long runner intake which is very similar in design to the hyperpac intake on the slant six engines. I ran it both with a plenum divider and without...............
Use a butterfly valve (square choke valve might do it) as the divider.

It's closed at low rpm, then opens at high.

You'd need to experiment with when it opens, and if it should open gradually or all at once.
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