Can you get a plenum spacer from them, or do you need one? Seems all the pics of them, I see one sandwiched in there....And what size carbs for a 512 reving to 6500?

I made my own out of white nylon 6/6. You can see it between the intake and top plate.

Yep, Indy do them 1/2" part# 440-14-15S $160 according to the price list. I asked Indy about these, they said on a 572 it was worth around 10Hp but only once the rpms exceeded 7200.

That suggests that the plenum is too large for engine (perhaps) smaller than 500".
Has anyone made a turtle or stuffer for this manifold? If carefully shaped, coated, and attached, wood is OK (Grumpy used it).

is that nylon 1/2" thick ?
open or 4 hole ?
how does it compare to a thick, factory type fiber gasket with the bushed mounting holes ?
TIA.

You can buy them from Indy or make one obviously. There was at least 2 diff bolt patterns for the lids. What do you need? That's a question for the person who is engineering the entire engine from carbs to the oil pan. There are many ways to skin a cat and you have some core pieces to make power but the devil is in the details. Hutch, over at the bullet, mentioned one time that two different guys can build a 727 and one will be over a tenth quicker than the other while USING THE SAME PARTS. The engines that make more power than average ones likely have some more engineering incorporated.

We know from testing our engines like more plenum...The more material I remove from their 4500 intakes, the faster my car goes, but never had one of their wedge tunnel rams. Either way, I am planning, if money allows, to put one on with two 750 carbs...

EDIT: Looking back at my conversation with Indy, the 572 wedge motor in question has a 1" spacer fitted. Apparently there was a "small gain between 7200 and 7500" so it might not have even been 10 hp (my memory ain't so good)

I've recently got hold of an Indy, 1/2" one (it's still stateside). The guy took it off his 572 motor as it made no difference at the track. This will be for my 655 motor as I think it may respond to more plenum

It would be helpful if a proportionate relationship could be determined among the relevant factors:
1. engine size (or demand at peak power)
2. plenum volume
3. total carburetor CFM

AIUI, a bigger engine needs more plenum, but tests with a spacer showing no change cause me to question whether the jetting should also change for optimized?
AIUI, larger carburetors can work with a smaller plenum.

50 years ago, Grumpy was working with a SBC, a TR, and dual 660. He said that the highest dyno power would MPH well, but not launch the car: reduce the volume by 10%.

So... plenum volume vs. CFM: is there a number out there, like with 500" @ 7,000 you need X CFM & Y volume, or smaller X & larger Y, but what ratio?
Above a certain minimum volume, the buffering effect (vacuum pulse at the intake valve) reduces the draw at the venturi, and may cause fuel drop-out. What multiple of engine size does this, 100%? More?

Test, tests and tests some more until you know exactly what your stuff wants

Junk that crap and get a tunnel ram in a sea shell. 🤣

So, looking at the tunnel rams for a 400, how do I get the first piece of tunnel ram linkage to fit? The arm that the gas pedal cable attaches to and then transitions to the upper level?

Old pic but pretty much the same deal as now. HTH's

I drilled and tapped the manifold in between the runners for the lower pivot. I made an angle milled spacer block to get it level side to side and to the desired height. In hind sight it didn't need to be angle milled.

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This is a $25 ebay throttle cable. With slight trimming of the threaded barrel, thinner nut, and a brass spacer it fits the stock pedal. Plenty of length to get anywhere. The you can loose all the complexity of the bell crank. Though this isn't a tunnel ram it's basically the same deal.
Doug

With increased RPM and cubes, a motor will want more plenum volume. Biggest thing ive seen is how much it cleans up the air fuels from cylinder to cylinder with proper plenum volume, it no longer has to steal from its neighbour cylinder.

So on a 400/512, what kind of power increase might I see over a typical 1050 and an open spacer.

My experience. 580ci 9.57 @ 142.5 Indy 440-3X, 1" tapered spacer and a Pro Systems modded Dominator. Swapping to an Indy T/R and 2 x 1150 Dominators. 9.51 @ 142.4, no other changes combo wise but car was likely 50lb heavier.
EDIT. it's been almost 2 mph quicker in the 1/8th but this wasn't carried over to the 1/4 for some reason ??

Not sure Cab, fuel pressure fairly constant during a pass (7 dropping to 6 psi by the traps) but a change to a different rear ratio (4:10 - 3.73) has revealed a mismatched converter. I suspect even with the 4:10 rear we had over 15% slip, we now have 20% I didn't have a racepak fitted until this past season which at the same time we switched out to a 3.73 gear. I have a 9 1/2" converter to replace the old 8".