For a 416+ cube stroker making 500hp +/- 50 Which is better from a performance stand point? The dual opening, snorkeless '71 unit? Or does the trap door '72 unit flow more?
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'71 vs '72 340 Air Cleaners
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We cut the 72 open like the 71
DionR
Well-Known Member
I thought the '72 had a trap door and vacuum canister on the PS. That looks like a '73 or something?
like I said we cut them off and opened it up like a 71
mcodecuda
Senior Member
The vacuum canister for the trap door would be underneath the air cleaner so you wouldn’t be able to see it. The most cost effective way to do this would be to start with an air cleaner without the trap door.
The best air cleaner I found for a 4150 carb is a K&N with the K&N top. sealed to the hood with a Mopar snorkel scoop. That sucker left the air to be forced in and still utilized a filter. Still have it and won't be using it or the scoop on the new car. Its just a conversation piece now . But it did work very well. We'll be using the taller after market snorkel mounted to a one piece nose for more forced air and just a sealed hood pan on a 4500 series carb.
If your looking for more air my recommendation would be to cut and old top plate as we did in the last picture
If your looking for more air my recommendation would be to cut and old top plate as we did in the last picture
DionR
Well-Known Member
You can see the canister on mine well enough.
Not saying he didn't cut his off, just that the canister isn't hidden.
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DionR
Well-Known Member
My gut says it is a wash.
This is based on the guess that while the trapdoor opening is probably a larger opening, it draws from right off the top of the intake. So the '71 unsilenced air cleaner might (just a guess) draw less air, it will draw (marginally) cooler air.
I say buy both and take them to the strip and try them back to back. My bet is you will see little to no difference between the two.
But it is just a guess.
Its for a class racer. I have the opportunity to build either a '71 or '72 car so Im weighing the pros & cons of each year.
Well one thing I have to say is the 72 and newer 340 360 air cleaners Killed the performance on every car I used them on. Not only do they suck less air, They suck hotter air. These restricted air cleaners were all about keeping the cars quiet. Why do you think the 69 and earlier breathers were called unsilenced. If your car came with that style and you want original appearance then leave the elephant nose in place. I am putting the factory 70-71 style on my Demon. Not because it breaths better, But because that is what it came with.
DionR
Well-Known Member
I'm confused. The '72 air cleaner was very different than the '73 and up and technically was "unsilenced" when the trap door opened.
Not arguing that it didn't suck hot air and kill performance when compared to the '71, only that it wasn't the same as the '73 and later ones that only had the snorkel.
This is the style we cut the tubes off of that I pictured above in post #2. It was a 400 air cleaner. If I was to use the trap door style I would prop it open or weld it shut and cut holes in the front side as we did in that post . Unless I was looking for original .
when you say class racing, do you mean like Stock Eliminator? The 340 HP rating for 71 and 72 is significantly different, right, so that might make your choice easier...
Factory Appearing Stock Tire (FAST) which is way different then Stock Eliminator.
Head & exhaust manifold castings are the same '71-'72. Intakes are also basically the same. Any internal modification is allowed. (Compression & valve size being the biggest difference in performance between stock '71 & '72 340s which Im allowed to change).
DionR
Well-Known Member
If you aren’t required to run a ‘71 TQ, I would build it as a ‘71. Just because I like the look of the ‘71 better. 
Dartswinger70
Well-Known Member
I seem to recall the trap door was for emissions or drivability not so much performance is that correct? something about letting warm air in or something? people think it is a performance air cleaner I'm not sure that was the original intent but it is a 1 year only piece right before the strict emissions started showing up.
DionR
Well-Known Member
I think you are thinking of the plate in the snorkel that closed and caused the engine to draw warm air off the exhaust manifold during warm up (I think?).
The trapdoor was setup to be pulled closed by vacuum and only open when vacuum dropped enough and the spring forced it open, like at full throttle. Pretty sure it was intended as a performance thing, just not sure drawing air right off the hot intake was the best idea.
Dartswinger70
Well-Known Member
Ok, makes sense. I actually have one of these setups, Intake, TQ and air cleaner Its just that my car is a 70 Swinger 340 not correct for my car but its nice having parts I suppose.
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