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Header Hack |
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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I found a set of 3" x 2-1/4" header reducers with a pretty gradual taper, cut off the 3-bolt flange, and ground off the nasty zinc plating.
Once the reducer is in place (and without the 3-bolt flanges) there's plenty of ground clearance. The 2-1/4" reducers tie in to the original H-pipe with some mandrel bends and flex pipe. The connection between the header and the new piping to the h-pipe is made with a stainless band clamp. Here's the passenger side header coming together. The initial test fit showed the collector needing to move up 2" and the forwardmost elbow needing to move up 1.5". So I mounted it to the test head and built up wood to indicate where the original header boundaries were, then marked the new collector location and added spacers to show me where the elbow limits needed to be. Then it just takes some cutting and such to make it all it. On this side one of the middle tubes fit up good, one (#8) had no hope, and the other two were close. I was able to clamp the two close tubes into alignment and tack them, then heat the tubes cherry red with the torch to relieve the stress. The #8 tube needed some extra bend and twist to aim it away from the starter, and then a replacement tube with a section of mandrel bend at the end of it was grafted in. One thing to note is that I did have to grind a little clearance into the mini-starter gear housing and grind a little off the block as well. That allowed me to clock the starter motor one more hole towards the engine and away from the header. At this point I can install and remove the header easily with the starter in place. I'd have to remove the header to get the starter out, but that's pretty easy. |
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1968 AMX 390 w/T5
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White70JavelinSST
Supporter of TheAMCForum Joined: Aug/08/2012 Location: Minnesota Status: Offline Points: 4867 |
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I'm likin it Chris.
The welds are pretty too ! |
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70 Javelin SST, second owner, purchased 1972
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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Thanks! This is a fun project and is really making me see why it's so hard to get a good set of headers. There's a lot of obstacles to miss.
On the drivers side I still ended up grinding a little off the strut rod bracket and putting a clearance dent into the header tube to make sure it doesn't hit. I'm not too worried about a few dings in the headers after watching the Roadkill episode where they dyno test the headers with all the dents in them. No big deal there. I still need to add the O2 sensor bungs to each side. One will get a plug as I only have one sensor, but at least it'll give the ability to swap the sensor between sides if needed. Once that's done they go back to sandblasting, and then get paint. I'm going the cheap route in every way with these, so they'll get PlastiKote aluminum high heat paint like the hookups did. I've had good results with it over the years, and found that I can cure the paint pretty well with a MAPP gas torch. If they work out well they may get real Jet Hot some day, but I want to make sure the relatively short tubes perform well enough before spending that much on them, and there's still a chance that mods will need to be made to them as well for clearance, etc. |
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1968 AMX 390 w/T5
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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I finished the O2 bungs and got them sandblasted again, then finally painted them. I'm using Plastikote HP-14 aluminum high temp paint. Two light coats, then wait an hour, then cure it with a MAPP gas torch. Final cure will come from running the engine.
This paint has worked really well for me in the past. |
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1968 AMX 390 w/T5
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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Well I finally have the exhaust done. Here you can see how the band clamps worked out. With the Wilwood pull slave on the drivers side I ended up with the O2 sensor on the passenger side. You can also see the heat shields I made out of a big chunk of heat shield material I nabbed off a Corsica. At the tightest spot there's only about 1/2" of clearance, so I may have to tweak these a little depending on how the floor tends to heat up. The lowest point of the headers is about level with the bottom of the bellhousing. |
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1968 AMX 390 w/T5
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304-dude
AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9081 |
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Real nice work! Tucked up pretty well.
If you get too hot on the floor, use an aerogel sheet between the heat shield and body. I plan on using a lot of aerogel on my custom exhaust through the cold air duct / ventilation part of the kick panels and cowl, for through the fender output to side exhaust. Though, being a dropped suspension on my build side exhaust would not work without frame mods, thus my odd idea. |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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White70JavelinSST
Supporter of TheAMCForum Joined: Aug/08/2012 Location: Minnesota Status: Offline Points: 4867 |
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Nice Work Chris.
Curious here, how did you route the tailpipes? What mufflers are you using and can you make a video so we can hear the exhaust note? Awesome work ! |
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70 Javelin SST, second owner, purchased 1972
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Scene One
AMC Addicted Joined: Jan/13/2014 Location: Friedens Pa. Status: Offline Points: 699 |
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Wow very nicely done!!
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