Installing MAC headers on a 93 F-body By Bobby Moton Introduction: I just finished installing a set of MAC headers and MAC catalytic converter onto my 93 Trans AM and thought I would try to expand on the very UN-detailed instructions provided by the MAC corporation. First and foremost this project is not for the faint of heart or people with a blood pressure problem it might kill you. The install itself is pretty simple it just the little pain in the asses you run into along the way. With all that said it is something an average do it “yourselfer” can do, if you’ve changed plugs and wires on these beasts you have the ability to install headers The instructions from Mac are barely ¾ of a page long so hopefully this will explain things better! Supplies: Needed- 1. Oil and filter 2. A vast assortment of extensions and swivels 3. WD 40 or liquid wrench 4. Anti seize compound 5. High temp silicon sealant spray 6. A couple of cases of ice cold beer and Band-Aides Recommended- 1. New plugs and wires (I used NGK TR-55 gapped @.050 and Taylor’s Spiro Wires, which fit in the stock looms) 2. New O2 sensors 3. New serpentine belt 4. Stage 8 fasteners, the Allen heads make them easier in spots 5. New dipstick tube (hard to get out the old one without mangling it) 6. GM exhaust gaskets or copper ones the FelPro 1406 WILL NOT WORK!!! Aside from tools, which my toolbox is not the best stocked, and ramps (Rhino ramps work good with our low cars) this is all you really need. Getting Started: First when you receive the headers, look on the back of the passenger side of the header on the top there is a AIR about 7/8 wide on the back there maybe a much smaller tube coming out. If you have that look on the back of your stock manifold and see if anything goes into it. It is the EGR hookup for the 94-95 I don’t think the 93’s use this (first time you recognize the oxymoron of MAC “true-fit”). Mine didn’t I had it cut off and welded up at an exhaust shop. Also check and make sure everything is in the box MAC is notorious for leaving items out, I think they were supposed to come with plus for AIR tubes if your not using them mine did not come with those. STEP BY STEP: Removing the stock manifolds 1. Get the car up in the air pretty high but, realize that you are going to have to do a lot of stuff from the top as well the Rhino ramps I used were just about perfect. 2. Soak down the bolts to the CAT and Y-pipe bolts, AIR tube fittings, and exhaust manifold bolts, I mean soak the hell out of them!!!! 3. Go to bed. 4. Next morning after the bolts have soaked a good long time, remove the y-pipe and cat. I think most of the bolts are 15mm and some of the smaller are 14mm. It’s a bitch because the bolts have rusted for a while. 5. I started with passenger side it is the hardest so I figured get it out of the way! 6. Disconnect battery (make sure you know the code to the stereo!) 7. First remove the alternator, the belt tensioned is loosened with a 14mm socket and the alternator bolts are 15, 14, and I think a 13. The little bolt connected to the alternator is a 7mm. 8. Disconnect the AIR tube on top of the manifold towards the back. 9. Remove the starter two bolts hold it in 14 or 15 mm. The bolts on the power wire and solenoid wire are 13mm and 5mm. Remove the O2 sensor, be careful if you plan on using them again. 10.While your down there drain the oil and take off the oil filter. 11.Remove the manifold bolts the first need a deep well 15mm socket for the bolt holding the alternator bracket and the rest are a 14mm socket. Some you get from top some you get from bottom. 12. Now wiggle the manifold out I got it out from the top. 13. Driver side is cake, unbolt the EGR AIR tube and the six manifold bolts and it practically drops out on its own. 14. Then remove the dipstick one of the hardest parts of the whole damn job!!! I used a combination of vice grips, flathead screw driver, and a hammer. Be creative, I’ve blocked this one out. It comes straight out finally but mine was mangled hence the recommended new one $6.50. 15. Remove spark plugs and if your going to replace wires now is the time to do it. ( the passenger’s side is a pain in the ass, I could do a write up on that alone!) USE THE STOCK WIRE LOOMS they will work!! 16. Congrats... that’s all for the hard stuff!!! Installing Headers: 1. Again, starting with passenger side put the header in from the bottom It might take a little creative jiggling and shifting but it works. I did mine first with that tube on the back that’s when I realized that I had nothing to go into that tube after I installed the header. One of the reasons I recommend cutting the tube off and welding it makes it much easier to get in. 2. First but the little fitting thing in the AIR tube fitting bevel side up and get the AIR tube threaded in, I did not do this and went through HELL!!! The MAC instructions don’t say anything about that fitting I had to learn the hard way... 3. Install the gasket in-between the head and header and get one bolt in kind of loose. This way it holds the header up and you can play with the gasket and bolts. This is also where it helps to have the stage 8 bolts you can use and Allen head socket and extensions to get them started. 4. Tighten the bolts from middle out evenly you got to go from top to bottom to do this. They are supposed to have a finally torque of 30 ft/lb. if you can get a torque wrench in there more power to you. I just tightened the hell out of them!! 5. Tighten the AIR tube real tight. 6. Install the spark plugs and wires, making sure they do NOT touch the headers or they will melt. 7. Install O2 sensor and starter, then the alternator all in reverse order easy stuff at this point. 8. Drivers side, first there is this big rubber thing above the oil filter housing pop the rubber thing off and there is a sensor plug of some kind disconnect it move it to the side. 9. Bolt the back piece first, this is a real PITA to get in and started take your time it does fit. Then spray the end of the front piece with high temp silicon gasket stuff and slide clamp over back piece and fit the front piece on (you’ll see what I mean). 10.Put the fitting in the AIR tube bevel side up and tighten. 11.Install spark plugs make real sure no wires on this side are touching manifold mine are pretty damn close! 12. Install the oil pressure sending (the sensor that is resting against the headers) unit you have to play with it for a while to get the rubber heat shield over it, 13.Install the O2 sensor and oil filter. Installing Y-pipe: True-fit my ass, not even a CLOSE-FIT!!! This part is really frustrating because you’ve been through so much already the bolts are 11/16 all I can say is push and pull till they get in. I actually got them in all pretty loose and drove it to the exhaust shop and had them tighten it all. It’s a lot easy under a lift with an impact wrench with the correct swivel extensions. Plus if you are using the stock cat you need to get it welded to the Y-Pipe or the fitting MAC provide to bolt it up. You can drive it to the exhaust shop with just headers and Y-Pipe it will be loud as hell!!! (don’t do this is winter when its really cold then you could hurt something) Problems: The problems I ran into, I tried to explain in the instructions. First, that extra fitting the guy I bought them from said that maybe there are early 93’s and late 93’s some do some don’t, whatever. If you don’t have anything connecting to the back of your passenger side manifold and there is a tube in the back of the header, cut if off and have it welded shut!! Manifold bolt broke into head!! This one really sucked but the LT1s use have the spacing on the manifolds wider on the outside than normal small blocks. Lucky for me Chevy drilled tapped holes in the head for the old style locations. I used the header gasket as a template and drilled a hole in the flange of the header and used the other hole in the header. This will only work on the front and back of the heads but (whew), a lot easy than taking the head out and having the bolt removed!!! That sensor resting against the header, is your oil pressure sending unit, you may have to relocate this by simply adding a piece of wire to it and extending it, so it may be attached out of the way somewhere else under the chassis. The big problem on the passenger side header is that I did not do the AIR tube before installing the header, it will not line up after the fact. Thought what the hell cut it and patch it with some high temp hose, wrong it blew the hose after 5 minutes of driving. Luck is I know a great exhaust guy who was able to patch it will metal and weld it in the tight space. Spark plugs, yeah there easier than stock but still not easy had to use an open ended wrench on the spark plug socket for most of the passenger side. The y-pipe, just take it to shop and let them tighten it is too hard to get to the damn bolts and it doesn’t want to line up properly a very poor fit I hope you get better. I just got it in there pretty good and had them tighten it! COSTS: Header- MAC TRU-fit (LOL)- $424.00 shipped from muscle motors, only place that had them and to Jacks credit I called him for help and deliver times and he returned my calls promptly even on the weekends. He didn’t however credit me for the 1406’s that do not fit, or the welding I had to get done to the header. Jack if you ever read this the 1406’s DO NOT WORK they are for the old style small block, whatever! Cat- Mac Bolt on (LOL) -$206.00 shipped higher prices Jack charges the 3% Credit card charger to customer don’t know if he should be doing that. Dipstick- $6.50 GM, a must have Gaskets - $13.00 GM, again 1406’s do not work Plugs- $15.00, NGK’s tr55 (.50 gap) Wires- $55.00 custom fit Tailor’s from summit Stage 8 bolts- $30.00 from Summit O2 sensors - $62.00 for both GM $75.00 at exhaust shop for custom AIR patch tube and tightening of Y-Pipe and cat and welding my Flowmaster exhaust pieces up. New belt - $19.00 GM Grand total: $905.00 for Headers and Cat. Final thoughts: Would I do it again???? Hell yeah she is much quicker and meaner and will be even better with cam and heads!!!! I just wish I knew all this stuff before hand!!! Hope this helps out and again a disclaimer this is just my car, others could be different and if you follow this and something wrong happens it is not MY FAULT. If you have any questions ask me at the 93 Bulletin board (http://pub26.ezboard.com/f93fbodymessageboardfrm4). I’m 93TAWicked1 and I check the forum regularly.