Frankenplenum

[LGAFF]

I actually thought about doing this completely with high temp panel bonding epoxy...still might

[LGAFF]

Mocked up some 1/2X1/2 and checked hood clearance, good so far

[rkreigh]

I remember some of the early 415 had the drop plenum mod that was supposed to be worth 10-15 hp on the big 415. I believe raising the runners and adding more volume will help and is a better way to go, but not enough to be worth much more than 15-20 hp

kirchoffer spent a ton on a box ram on his big 421 and it didn't seem to work nearly as well as I would have thought. it had a pretty big "plenum box"

with the "s turn" in the LT5 intake, I prefer the the ITB option. now that OBX has a 1300 setup for the LS1, use that as a starting point and cast up or fab some new base plates for the LT5

I spoke to graham about this and much like the lotus "caliope" stacks they used on the race car this a 4500 up mod, and low rpm thottle response can be a bit abrupt and hard to control the big "stacks" can really kill low end torq so you need some gears to get it rolling

my LPE has the crazy "bifurcation" manifold where they saw in half to do a better job of porting

they did a nice job of dressing the welds and keeping it straight

so, if we "scrap" the manifold and go ITB why not go the extra mile and raise the port? I saw an old ford where they filled the bottom of the port with epoxy and ground away the port roof and used thick billet "plates" recessed into the head

this provides a very high velocity straight shot with a low profile crab style ITB

tuning would be a challenge to be sure as you get LOTS of airflow with little throttle movement and the car will really jump!!

I thought about putting an ITB on the old LS1 in a C3 for sex appeal

the OBX stuff is beyond cheap and looks to be of good quality

nothing like the inglese but still very nice! borla does this stuff too

as small as it is, you could 3d print" the adapter manifold to make the ITB work with the LT5 head and it would likely be strong enough to work just fine

sounds like fun!!

[cvette98pacecar]

Originally Posted by rkreigh

I remember some of the early 415 had the drop plenum mod that was supposed to be worth 10-15 hp on the big 415. I believe raising the runners and adding more volume will help and is a better way to go, but not enough to be worth much more than 15-20 hp

kirchoffer spent a ton on a box ram on his big 421 and it didn't seem to work nearly as well as I would have thought. it had a pretty big "plenum box"

with the "s turn" in the LT5 intake, I prefer the the ITB option. now that OBX has a 1300 setup for the LS1, use that as a starting point and cast up or fab some new base plates for the LT5

I spoke to graham about this and much like the lotus "caliope" stacks they used on the race car this a 4500 up mod, and low rpm thottle response can be a bit abrupt and hard to control the big "stacks" can really kill low end torq so you need some gears to get it rolling

my LPE has the crazy "bifurcation" manifold where they saw in half to do a better job of porting

they did a nice job of dressing the welds and keeping it straight

so, if we "scrap" the manifold and go ITB why not go the extra mile and raise the port? I saw an old ford where they filled the bottom of the port with epoxy and ground away the port roof and used thick billet "plates" recessed into the head

this provides a very high velocity straight shot with a low profile crab style ITB

tuning would be a challenge to be sure as you get LOTS of airflow with little throttle movement and the car will really jump!!

I thought about putting an ITB on the old LS1 in a C3 for sex appeal

the OBX stuff is beyond cheap and looks to be of good quality

nothing like the inglese but still very nice! borla does this stuff too

as small as it is, you could 3d print" the adapter manifold to make the ITB work with the LT5 head and it would likely be strong enough to work just fine

sounds like fun!!

Ron, I could not agree with you more. The OBX ITB is one of the sexiest pieces of equipment that I have seen to date. With the fuel lines on top of the ITB it opens up a lot of room to reconfigure the current IH and build a new plenum.
One of these years I am going to be done with all my LT5 and I am going to install one of these on my 98PC

[FU]

Just an idea.......

https://www.youtube.com/watch?v=t7ils9Ir7EM

[XfireZ51]

Something like this.

[Tony Davila]

Has anybody ever thought of putting a bifurcation into the runner up into the plenum open area? Making the length of the runner individually longer just like a Tune Port intake. I wonder if it would give more bottom end.

Just wondering.

[cvette98pacecar]

Originally Posted by XfireZ51

Something like this.

Dom, Do you still have the Cross fire plenum?

[XfireZ51]

Originally Posted by cvette98pacecar

Dom, Do you still have the Cross fire plenum?

Robert,

No I don't. Haven't had it since I bought the ZR. Should be fairly easy to come by if you want one.

[batchman]

I've wondered what goes on inside the plenum, is post #52 stock inside?

I would think there could be some merit in taking an approach found on SHOs and late four-valve 4.6s: differing runner lengths for the 2 valves.

Adding something like a french cut exhaust tip on 1st, 4th, 5th and 8th runner one side, maybe 3-4", with the opposing one offset to the other valve. Hope I'm describing this reasonably.

Just a thought,
- Jeff