Indy 400-I4 t ram mod

A well known Mopar shop told me their is a mod for this tunnel that is worth some ET. You remove the plenum divider and add a 1/2" plenum spacer. Has anyone here performed any mods on this t ram with good results. Was told the mod was good for 2 tenths in their car. Post pics if you have any. Thanks

Always heard the Indy hemi tunnelrams had very small plenums and almost all combos benefit from a 1/2" or taller plenum spacer. I imagine the wedge tunnelrams are in the same boat.

Going to try this, having a 9/16 phenolic spacer machined up very soon.

I fabbed up some 1/2" thick anti-reverson plates for under my carbs and also 1/2" thick delrin/nylon insulator/spacer for my tunnel ram. If you look closely it is the white portion between the intake and top plate. I made several and tried none and up to 4 spacers on dyno with no significant power or torque improvements over not having any. Choose to just use the one to help keep the top plate and carbs cooler.

I understand the plenum divider needs to be removed as well. Requires some welding.

What does that manifold look like inside?
How big is the plenum?
What size carbs did they use?

I removed mine as shown here. I didn't remove as much as I originally intended due to my lack of welding skills causing repeated cracks when cooling. The divider is hollow and requires about 1 1/2" of fill weld. (I'd suggest finding a good welder)


As for how much it helped or hurt, I have no idea as this is a new build waiting on parts.

I also made a 1/2 nylon spacer with a flat 3/8 top plate so the carbs could be shifted forward a little.

Hmmm my TR seems to be different as mine has no divider.

I've seen some older ones that don't have the divider. They also seem to have more symmetrical runners...although that may be at the expense of throttle bore to runner entrance alignment.

Do you have a side view or down runner picture?

Pic

No divider on mine (IIRC)

That's what mine looked like before. I'd like to see that view from rebel's

This is mine as cast. I measured the port from the point it starts to form the port, to the size at the flange base, its 3x larger at the plenum.

Removing the divider alone increases plenum volume. Really depends on the cid of the engine its going on. I've done it on a Hemi manifold. Didn't back to back test it though.

It seems Indy re-designed them. Not exactly sure which way round chronologically, I think maybe the later T/R's have less bolts for the top ?.
It seems my memory is incorrect, mine DOES have a divider. Date on the photo's are from roughly when it was purchased and kindly sent by Todd Marsh (Sasquatch) many moons ago.



Hmmm....useful to know. Probably won't make any difference then, my carbs are hanging in the breeze anyway.

I will talk to Indy today to get their opinion as well. I need to order the spacer from them anyway. If i cant find a professional welder for this, can i just epoxy it?

Those runners look quite a bit different than newer models. It would be interesting to hear Indy's thinking on what the various changes were intended for.

I don't think I'd trust epoxy. it would be solid epoxy for about a 2-3" span between the groups of runner. There would be pretty substantial expansion and contraction with different materials during heating and cooling i would think.

an interesting thing i learned was that the plenum volume (poured) was approx. 20+ cu.in. more in the M1 tunnel ram intake i'm using on my current engine vs. the modified Indy intake.

I spoke with Wilson Manifold about the Indy T ram yesterday. They said full on drag motors like plenum volume. The extra volume makes the engine pull harder thru mid to high rpm. The divider like in my t ram is there for better fuel/air distribution. Without it, the fuel/air bounces from one end to the other of the plenum creating poor distribution. They suggested to me for my mostly street combo to not increase the plenum volume, but to add a couple anti-reversion plates as those alone may help with poor distribution. I may try the 1/2" lid spacer anyway just to see along with anti-reversion plates.

The only way YOU will learn about YOUR parts is to test them
I 've seen very knowledgeable racers spread misinformation intentionally and through them misunderstanding their parts
For instance on BB Mopar timing covers and stock balancer, do NOT mix early balancers with later (1966 and later) timing covers or vice a versus Doing that will make your ignition timing off by around 10 degrees
The early timing covers have the zero mark on the top of the straight timing tabs, the later curved tabs have it in the middle of the tab, around 10 degree difference

I use a 71 400 cover and with my ATI damper it is dead on 0 at TDC. Just checked it and more accurate than i thought it would be.

Good work
Never ASS U ME anything stock is correct

Being that the 400 is a different stroke than the 511, you would think it would be off. Maybe just got lucky there?

Why is that?

Longer stroke would push the piston to the top quicker.

Crankpin to keyway location remains the same no matter what the stroke is.

Ok, maybe im thinking it wrong. Just thought with longer stroker top dead center would be different. Always learning.

My tunnel ram looks just like that inside but I and blended it all over.

Not really, RPM is RPM, the longer the stroke the more distance traveled, correct
Stroker motors suck in more air and fuel than short stroke motors do on the same stroke RPM hence the more power they make. Thye have more ring travel per RPM so maybe they wear out the rings quicker per mile traveled also

As I understand it, piston speed is increased and thus piston acceleration. On a theoretical 3.50 stroke and a 5.00 stroke motor, the piston will arrive at TDC at the same time if they were at the exact same RPM. (And that they started in the same place etc etc)
The piston will accelerate quicker away from TDC on the 5.0 stroke motor, it also decelerates quicker to arrive at BDC.
You need good pistons for a big stroke crank