Why Would Someone Do This To A Plenum ?

[Mike T]

This plenum was in my spare parts and I understand the attempt to radius the rear of the plenum but I don't get the thought process behind reducing/flaring the intake side. Does anyone know why they may have done this? My plan is to cut all of this stuff back out but would still be interested in knowing this was done.

 

[pacecarta]

looks like an attempt at what hemco did and that was to reduce the flow to the rears which in stock form makes the 5-6 leaner than the rest

 

[Mike T]

looks like an attempt at what hemco did and that was to reduce the flow to the rears which in stock form makes the 5-6 leaner than the rest

I agree with you on the rear of the plenum but did you notice the changes to the entire border of the intake manifold side of the plenum. Was a hemco made like this also?

 

[Pronto]

Stealth Hemco. Better ones have an aluminum plate welded in.

 

[StageII86]

Man, not that it would matter for function much, but a few more minutes with the stone, followed by a few more with a cartridge roll would sure make a huge aesthetic difference there. That thing looks like the surface of the moon.

 

[Mike T]

Man, not that it would matter for function much, but a few more minutes with the stone, followed by a few more with a cartridge roll would sure make a huge aesthetic difference there. That thing looks like the surface of the moon.

The port work is not very good and the plenum is very thin in some areas already. I may clean the JB weld (or whatever that stuff is) out and weld it up. Believe it or not the plenum came off of a fairly quick car owned by an older guy who had been around these cars for a long time . He has passed so I can't ask why he necked down the lower base portion. I am still puzzled as to what it's intended purpose was.

 

[StageII86]

Often times the quickest Turbo Regals ain't the cleanest or prettyist.

 

[sweetv6]

This Is mine

 

[earlbrown]

. He has passed so I can't ask why he necked down the lower base portion. I am still puzzled as to what it's intended purpose was.

It's to kinda let the air 'stall'. That way all the molecules can take a break, regroup, get to know each other a little, then head into the lower manifold a little more evenly.

The layout of the throttle body, plenum, lower and ports lends it's self to spraying the rear cylinder with air and starving the fronts. Sticking a shelf in there allows the upper plenum the opportunity to act more like a plenum and less like a flow device.

 

[Mike T]

Thank's Earl for the great information. This confirms my thought that this was not just some random thing he did to the plenum. A few months before passing he told me that his car was the first north eastern car in the 11s many years ago.

 

[Howling Mad]

The plenum on my stock motor and my new motor has the back filled in. It ran great...

 

[turbofabricator]

By adding meat to the back of the dog house it redirects airflow to the middle of the plenum. Good move on the cheap. Execution could have been more professional but probably wouldn't have made a difference.

 

[Mike T]

By adding meat to the back of the dog house it redirects airflow to the middle of the plenum. Good move on the cheap. Execution could have been more professional but probably wouldn't have made a difference.

I had came across the modification to the rear before but not the base area. In the photo below the area marked in red is material that was added by the previous owner. Earl's explanation makes sense as to why the shape of this area was changed but I wonder if it really worked.

 

[earlbrown]

I never said it was right.... I just said that's what they were trying to do

 

[LEGACY_GN]

I have a plenum identical to that. Wonder who did them all.

 

[Mike T]

I have a plenum identical to that. Wonder who did them all.

This one came off of a very clean Limited that had a stage motor in it. It was a one owner car from the NE located in Boston and somewhere in New Hampshire for a while. From what I gather it was a group of friends that did all of the work on this car and some others. My guess would be that it was made by someone local to them. Interesting that you have one also maybe the plenums were some sort of experiment.

 

[Hot Air]

Seems to me that this would smooth out the flow to approach laminar conditions. Sudden change in direction does not tend to create laminar flow. I like what I see from a flow standpoint. Flow distribution is another separate discussion.
Conrad

 

[gsgnnut]

hot air you are correct. The added radius smooths out the air flow ( more laminar) and reduces turbulence, especially under boost. This ensures more even distribution to the runners. never thought my industrial ventilation engineering studies would ever paid off, but theres endless automotive applications!

 

[1952ray]

looks like an attempt at what hemco did and that was to reduce the flow to the rears which in stock form makes the 5-6 leaner than the rest

Who in the hell is this (old ) ass hole. Must be someone who trolls this forum to give neg. feedback

 

[pacecarta]

heres what i found searching my ratings
BOP4ever rated your post

Old in the thread Why Would Someone Do This To A Plenum ?.