Early fox body dual exhaust conversion questions

voshson

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Jun 14, 2020
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I'll apologize in advance, this has probably been asked a thousand times, but here I go anyway:
1983 GT conv, t-5 trans. car is totally stock.
I want to put a true dual exhaust set-up on it. I know I'll need the dual hump trans cross member. I want to keep the stock manifolds for now, and retain the heat riser for the holley.
This is where I'm getting lost. Do the stock manifolds in the 83 use the same pattern as an 86? Meaning, can I use a 86 and up off road pipe and it will line up with the manifolds?
 
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7991LXnSHO

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Since no one else has jumped in, let’s chat. What does your car have for manifolds? Can you share pics of the manifolds?

I think my 79 had cast iron exhaust manifolds, and I updated them to E-7 (87) factory headers when I switched to to dual exhaust. I had a talented old exhaust guy run duals “for off-road use” without the double hump crossover. I planned on switching, but he ran the other pipe without it hitting or hanging down in the way.
 

voshson

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Jun 14, 2020
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Thanks for the reply. It still has the original manifolds. I have it on the hoist now, just to check it out, so I'll get some pics tomorrow.
.
I went ahead and just ordered the dual hump member, and a mount. This stuff is dirt cheap compared to my challenger project!
I wanted to retain the heat riser, because of the carb, but maybe I'll ditch that idea.
 

Mustang5L5

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I’ve done it on an ‘85. The pass side manifokd with the riser has a unique collector shape that required me swapping it out to an 86+ OEM hesder to mate to an 86+ h pipe.

drivers side was untouched. No idea if 83 manifolds are the same, but back then stock 86-93 headers were $25/pair
 

7991LXnSHO

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For what I am thinking about for you, pictures from the top will be better. I am interested in the heat riser since it also seems to be a concern. A good exhaust shop can make the dials (edit : duals) you need if the headers are a different length.The cost of a custom system with a H pipe was not worth trying to hassle fitting pre bent Walker exhaust pipes myself.

I am trying to remember what I did on my 79 to make the combo close to stock looking and functional. (I refuse to admit the number of decades involved.)
Is the heat riser a stamped steel box that connects to the manifold bolts and the flex tube that goes up to the bottom of one filter snorkel on the 83 GT? Right before I switched to dual exhaust, I also went with an Edelbrock 4bbl intake, the 4bbl EGR spacer, a Holley 1850-2, and the GT dual snorkel filter housing, including the fender CAI bellows and inner fender connectors. I do not remember if the “heat box” was From the 79 or later GT.
So I basically had the same top equipment, eventually on an E-7 roller cam, long block. (Not so fast now, but pretty zippy at the time with posi in the 7.5” diff.)
I know I bought the flex hose for a heat riser and had it attached to something on the exhaust. I do remember not much trimming or fabrication, some VHT paint, and no big problem.
I am sure I swapped the upper intake before the exhaust, so the heat riser box worked with the 79 and 87 exhaust without any big hassle (for someone handy with tin snips and duct work type sheet metal.)
I hope this gives you ideas. I do not think you have to keep your stock exhaust to have your car warm up on cold mornings, but a pic of the heat riser you are talking about would sure help.
 
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