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#1
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Exhaust Difference - '73 Formula
I have been looking at new stock exhaust systems for my '73 Formula 400 and see 2 different options. Most exhaust I see is listed as either "70-'74 Ram Air" or '70-'74 Except Ram Air".
What is the difference? It seems like the application is not entirely accurate as I was under the impression that the only difference by '73 was the air cleaner. Even though my car has the Ram Air(air cleaner) option, am I to assume the exhaust I want is the one listed for non ram air? Also, are the classic industries, classic exhaust, or any of the other lower priced options acceptable? Gardner was recommended to me. But they were expensive even before things went completely bonkers. FYI - It must be stock style exhaust. Every 2nd gen I hear that isn't OEM style exhaust just sounds wrong to me. It will be a while before I need exhaust. But, no heat in the garage and a hatred of working barehanded in the cold means winter is pretty much just for research and parts acquisition here in Iowa.
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"What the hell's wrong with freedom man? That's what it's all about." (Billy) "Oh yeah, that's what it's all about alright... but talkin about it and bein it, that's two different things." (George) Easyrider |
#2
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I believe they are distinguishing between the exhaust manifolds and their outlet point.
1970 Ram Air III and IV, along with 71-74 round port cars, had a unique exhaust manifold outlet point, that required different headpipes.
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keith k 70 Trans Am RA III / T400 / Lucerne Blue / Bright Blue 70 Trans Am RA III / M20 / Lucerne Blue / Sandalwood 70 Formula RA III / M21 / Lucerne Blue / Bright Blue |
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#3
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Ports
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#4
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It’s about the exhaust manifolds. SD, RA3and 4 all have same exit points. So all could use the same downpipes
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#5
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Quote:
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RA downpipes/headpipes wont reach the mounting flange on log manifolds. Non RA downpipes would hang down like headers when bolted to RA manifolds. Clay |
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#6
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On RA manifolds, "D" or " O" port I recommend the oil filter offset kit that was developed for '69 but fits perfect for second gen cars and gets the oil filter away from the manifold. It is almost touching it without the adapter.
Having used a bunch of exhaust systems, I will only run Gardner, but I have heard people speak well of Waldron exhaust. Don't ask about " Dronemaster" . Pypes required a few mods and tweaks, and sounded tinny to me. Every engine sounds different too.
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"The Future Belongs to those who are STILL Willing to get their Hands Dirty" .. my Grandfather |
#7
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In '73 Ram Air is basically just RPO WU3. fresh air inlet.
Only cars originally having RA manifolds were SD cars. Even a 455 T/A had the logs ( non SD).
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"The Future Belongs to those who are STILL Willing to get their Hands Dirty" .. my Grandfather |
#8
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In addition to the great advice above, it's worth noting that the d-port cars with log-type exhaust manifolds (regardless of displacement--350 to 455) had 2-inch diameter head pipes. The over-axle pipes were 2.25", however.
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#9
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I believe that as far as stock replacement exhaust kits are concerned the "Ram Air" versus "non-Ram Air" are all about the headpipes;
As mentioned earlier the exhaust manifolds for cars with RA exhaust manifolds require a tighter and lower connection point.
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1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
#10
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Thanks for the help!
__________________
"What the hell's wrong with freedom man? That's what it's all about." (Billy) "Oh yeah, that's what it's all about alright... but talkin about it and bein it, that's two different things." (George) Easyrider |
#11
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'73 & '74 Formula Firebirds with the 400 4-bbl & 455 4-bbl D-port engines could be ordered with Ram Air hood induction and both these engines had standard exhaust ('log') manifolds, so would use the "Except Ram Air" exhaust system (specifically the regular duty head pipes).
I included a couple pics of Ram Air equipped 455 D-port Formulas for examples. Dennis Last edited by SD455DJ; 01-14-2022 at 07:03 PM. |
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