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Project Survivor: 1968 AMX |
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DAMX
AMC Apprentice Joined: Nov/13/2017 Location: Silicon Valley Status: Offline Points: 195 |
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Posted: Dec/16/2017 at 2:22pm |
Project Survivor: The 1968 AMX that lasted through time and the Santa Rosa Fires The Car: It is a rough "patina" 1968 AMX Tahiti Turquoise with a 390, M12 transmission, and nearly stock except for a aftermarket steering wheel, headers, and interior sprayed black (A child of the 70's). The rear end had been replaced with a 3.54;1 Twin Grip at some time, but that is an AMC part. It was known to have some run/motor problems at the time of purchase including a mystery knocking noise that would come from the motor from time to time. I never witnessed it. It was also but a few blocks away from the total destruction of the Santa Rosa Fires. the car was actually licensed & insured! It was the only car I looked at that did. This was a major selling point, and lack of rust was another. The car survived time and the fires. The Trek Home: The car was 138 miles from my home, and I was going to drive it back. The former owner said it wouldn't make it, but AAA requires the car to fail before towing. I started the trek not knowing when the hook would be needed, but hoped it wasn't to be on a bridge crossing the SF Bay. I didn't want to be "That Guy" that caused all that traffic. I filled the tank and headed out. In about 40miles the fuel gauge started working and showed the fuel to be getting low, as poorly as the car ran & a 3.54:1 gear it was possible it was getting ~2mpg. I pulled off the freeway for fuel and low and behold I was only able to get 2.5 gallons in. What a relief until I tried to start it. The motor would barely crank, and I spent some luck there and got it started. It was found later the real problem is starter heat soak from the headers. The greatest thing happened on the journey in bumper to bumper Bay Area Traffic people were really digging this old patina AMX! I even had a couple in a Prius roll down the window to tell me how much they loved the car. I couldn't have been more shocked if the motor had fallen out! The last 60 miles were in the dark, and I checked the lights before departing, so that was okay. The dash lights didn't work, but that didn't matter as the none of the gauges worked anyway except for the phantom fuel gauge that drifted in and out. The previous owner had a oil pressure, water temperature, and tachometer which saved a lot of stress on the Trek. The oil pressure was excellent 40-60psi, the water 180-185F, and the tach gave me an idea of my speed. Maybe the motor was just running poorly? I hoped, but that story later. I figured it may have been just loaded up, so about 10 miles from home I hopped on it and mountains of black smoke billowed out the back & it pinged like mad so I eased off some. I tried 2 more freeway tuneups and the motor started running better. Things were starting to look good. Then generator light started slightly glowing the last 5 miles, but over a few more hills & I will be home. It made it and I let a good friend who followed all the way in my other car take the car around the block as a thanking gesture. After that I tucked it away in my garage. It was quite an event. Actually a big relief to have it home! The troubleshooting would start the next weekend. The Build Plan: I want a great running driving street AMX that I can easily cruise and take on long distance trips, but I will occasionally Autocross & go to the Drags. The race stuff is much less important to me as I am a retired NASA Racer and Autocrosser. I have 4 Championships and 2 Track records to my name, and I am done with Competitions. It was a great run, but now it's done. This is my Racing Retirement Toy. I wanted a good "patina" car because I don't want the car to be too nice to be comfortable. Rock chips will just add character, and door dings won't be a huge disaster. This car will only see a trailer if it breaks. To implement this plan I would like to: 1) Improve the freeway cruising. 2) Have nice smooth motor operation. Nothing radical. 3) Tighten up the suspension a bit, as I am not a fan of the 60's soft sloppy feel. 4) Make the interior more comfortable (change the seats), and clean it up some. 5) All the little electrical items working (gauges, turn signals canceling, locks, etc...) Regards Don |
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69BBB3904spAMX
AMC Addicted Charter Member Joined: Jun/29/2007 Location: San Jose, CA Status: Offline Points: 2761 |
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Don, welcome.
The South Bay AMX/AMC Club has a very informal meeting the last Wednesday of every month at 7:00 PM at the Round Table Pizza on Calaveras Blvd in Milpitas. Next meeting is Dec 27th. Feel free to join us and bring some pictures. |
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37 Ford Tudor 60 hp V8 flathead, all original, never restored
69BBB3904spAMX 70 Camaro 1st car 74 Hornet Hatch 6 cyl floor/auto 2007,2008,2009 PT Cruisers Aluminum Deck Car Trailer |
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DAMX
AMC Apprentice Joined: Nov/13/2017 Location: Silicon Valley Status: Offline Points: 195 |
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Hello All,
There has been some progress: The running problems, and the Mystery Sound have been found. 1) The coil used was not compatible with the early Pertronix ignitor. This was causing the missing. 2) The hesitation was caused by a dried out accelerator diaphram. It dispensed about 2 drops. 3) The Mystery Sound was a broken piston in cylinder 5. 4) Many of the plugs were damaged from the piston & ring pieces migrating all over the place. The Story: I changed the plugs, and found many of the ground straps bent, and one severely in cylinder 5. I put a 750dp I had laying around on with good accelerator pumps. I swapped the coil and set the timing. It was 15 degrees over advanced. this was likely done to cover up the hesitation trouble. The car runs pretty well, and now I know it has a Twin Grip! I have 2 stripes on my driveway now. After seeing the plug damage in cylinder 5 I ran a compression test. 1,3,5,7,2,4,6,8 =160,160,140,160,170,165,170 170. 5 is low, so let's try some oil. All cylinders rose 5psi except 5 which didn't rise at all. Seems like a valve, so I put the head to take a look and the piston in 5 looks different. About 60 degrees of top ring land had been blown off! The Mystery Sound was the pieces of ring and piston migrating through the motor. I also found evidence of nitrous being run before. It still has the 5/16" fuel line, so we know what happened. The other odd thing was the pistons were over .050" in the hole and massively dished out. I bet the compression was about 8:1. More bad news: The pistons are .060" over! AMC say .020" maximum overbore. A Santa Rosa AMC expert says to get the block sonic checked and if it passes hone it and put a new piston in. I remove the block and get it inspected and a few cylinders are worn .005". No hone allowed here. I hit a big decision point: Do I dump the original 390 for a 360, or resleeve the original block? After consulting with my AMC Guru it would be bad Karma to put a 360 in the place of a 390. He has a 401 standard block, but I would need to change the heads and get new rods, and then the headers, intake, and flexplate would no longer work. I decided to have the shop resleeve the block to standard. This is a wild one right out of the gate! With all that is going on I'm forced to make the decision on dropping the rpm on the freeway. I have 2 options: 1) Have the crank modified to the later version and put a TH700r4 in with a Novak adapter. No turning back. 2) Easiest & cheapest. I have a 1968 AMX 2.87:1 differential in good shape. Bolt in and go! I'm not pulling the motor later to modify the crank. Option 1 is the right thing to do, but the financial shock of the motor job is putting me in Rambler Mentality. If the crank gets modified I can no longer put the M12 back in. It is Option 1 OR 2. It forces 2 big aspects of the project to hit at once! All I can say is Wow! Regards Don |
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1970390amx
AMC Addicted Joined: Jul/11/2008 Location: colorado Status: Offline Points: 3314 |
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Use a 2004R
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1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box |
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DAMX
AMC Apprentice Joined: Nov/13/2017 Location: Silicon Valley Status: Offline Points: 195 |
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Why? Is it an easier swap? Regards Don
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1970390amx
AMC Addicted Joined: Jul/11/2008 Location: colorado Status: Offline Points: 3314 |
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The two 700r4 swaps into am AMX have had the floor near the 2/4 servo with major work to it. One was cut and moved over and one was beat severely with a hammer to gain clearance for the servo cover. The 2004r is a smaller transmission. I put one in a american with few problems. Some people think the split from 1st to 2nd is to large of a split for cars.
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1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box |
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DAMX
AMC Apprentice Joined: Nov/13/2017 Location: Silicon Valley Status: Offline Points: 195 |
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Noted. Thanks for the information. Easier is better. The reason I wanted the TH700r4 was for the lower first gear, but it doesn't sound worth it if I have to do massive beating to the transmission tunnel. Thanks!
Regards Don |
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