Stock Intake Manifold Question.

[Arron tate]

Hello All,
Wondering what is the purpose of the two inserts in the plenum of this manifold.
Can they be removed and plunged up ?
If so what would be the expected gain to removing them?
Thanks in advance
Happy Mopar
Arron.

 

[318willrun]

emissions and I've never gained anything by removing them as far as daily running or performance.

 

[rumblefish360]

What he said ^^^^

Those holes in the plenums bottom go to a under intake passage to the center of the cylinder head where in stock cylinder heads, there is a port to allow some exhaust into the intake manifold for first, heating the intake up for cold weather and secondly, in later years like your intake, recirculating exhaust into the intake for emissions reasons.

One should be easy to plug and the other, possibly a bit hard since it probably doesn’t have threads for a plug. The amount gained will be small in most every engine and combination. Something seen on the dyno and ?LOL) probably ever felt but seen at the strip.

I can not comment or power gains and ET or MPH gains, but you should see a most minor something from a non contaminated air and fuel charge.

 

[brian6pac]

Those are for the EGR Valve only and nothing else, after the engine is hot the EGR valve opens and puts exhaust gases into the intake to basically take up space, so less oxygen = smaller bang, = cooling the combustion chamber and reducing oxides of nitrogen, or NOX emissions which are the worst for humans, cancer causing!

 

[Wyrmrider]

also the reason for keeping the long slow closing ramps so you get exhaust dilution at overlap with the cams that were designed before smog but were designed to be quiet throughout warranty period
not optimum for power or mileage or most anything else cheap crutches

 

[70 Buster 340]

A first attempt at an EGR. Uncontrolled .. as modern EGR is. These are a 'jet' that goes to the exhaust heat riser crossover. If you block off the heat riser passage at the gasket location you will defeat the purpose. Those floor jets are an 'oddball' thread and I never found the right plug to put in there.
Block off the heat riser at the gasket and there is a performance gain. Good for racing or you can get away with it in warmer climate areas. The heat riser is good to have for drivability on the street in cooler to cold climate