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Ongoing Problem: Engine Stalls When Put in Gear |
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WhatISit
AMC Addicted Joined: Aug/07/2017 Location: Phoenix, AZ Status: Offline Points: 0 |
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That’s the cam specs |
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19611 |
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1978+ model 904s and 998s could be had with lock-up. Most were lockup from 78 on, but not all. AMC may not have got lock-ups until 79 or 80. Even then, CA six cylinder cars (at least for 78) didn't get lock-up converters nor did high altitude and HD models (from Allpar site, specifically referring to Chrysler products, but AMC would have been similar).
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Frank Swygert
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amx2bfast
AMC Apprentice Joined: Aug/07/2013 Location: middlesex nc Status: Offline Points: 217 |
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The thumper cam is meant to sound like a race cam but has very little low end power. Generally will not create enough vacuum for power brakes. What stall converter are you running? You may need to get a higher stall so it can idle without a load. Probably need something in the 2800 - 3000 stall range to make it work.
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1975 gremlin
1973 javelin 1976 pacer wagon |
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auag85201
AMC Apprentice Joined: Sep/26/2017 Location: arizona Status: Offline Points: 138 |
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with that cam and an automatic trans you will have a hard time getting it to idle in gear
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WhatISit
AMC Addicted Joined: Aug/07/2017 Location: Phoenix, AZ Status: Offline Points: 0 |
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Yeah, I’m pretty much accepting at this point that the cam’s too much for my setup. I can make it work, but it’s still not going to be perfect, and it’s probably not going to have very good street manners.
According to the cam specs and the rest of my setup, Hughes gave me a 2500 RPM stall converter. I don’t know the details exactly, but I’m pretty sure the engine has 9:1 compression. I think comp cams could stand to update their information a little bit on the Thumpr. I’ve been reading everywhere that this cam is more aggressive than advertised. I could stand to have a 2800-3000 rpm converter and 10:1 CR. We spent about two more hours today tuning the carb and setting the timing. Best we can manage is about 1100-1200 RPM in park, and 750-800 in gear. |
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Boris Badanov
AMC Addicted Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4209 |
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Nice mid range cam. IMO to late on the intake closing timing for a 9:1 motor hooked to an automatic. IMO (again) you would need a very loose converter for that to work. There are few bandaids that can make it more drivable. I would use a racing type electronic ignition with a start up ignition retard. Then eliminate all advance in the distributer, lock it in at 34-36 degrees. Retard to start, full advance for driving. |
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Gremlin Dreams
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tached_out
AMC Nut Joined: Feb/08/2008 Location: Vancouver, BC Status: Offline Points: 328 |
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What did you set the timing to? Glenn
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16591 |
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Bernie70AMX
AMC Apprentice Joined: Mar/16/2008 Location: Pennsylvania Status: Offline Points: 80 |
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Do not know your heads but I would check valve lash first could be open. Just sounds like to me cam problems. If lobe is gone ( like a small block chevy ) you are beating a dead horse and going nowhere.
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Bernie70AMX
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Boris Badanov
AMC Addicted Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4209 |
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It's simple, too much cam for the compression ratio in an automatic equipped car.
A butt load of initial timing may make it work. It looks they are getting close. |
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Gremlin Dreams
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