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Type I, Type II and Group 19 camshaft |
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Posted: Jul/29/2020 at 12:24pm |
Hi! This should be a quick one. I am trying to settle a debate on camshafts for 1970 V8's. The type 1 camshaft was installed in all 360's and 390's (up to sept 26th, 1969) had 266 duration and .457 valve lift. After that, the 390's got a type II cam, with a bit more duration and lift, but the 360's stayed with the type I, correct?
Someone has some incorrect information that the type II cam was the Group 19 unit with 302 duration and .477 lift. I am positive that this cam was not installed at the factory in anything. Does anyone have the specs for the type II camshaft in later 1970 390's? Thanks! |
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16611 |
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Just a guess, and from reading on this stuff, but Im thinking that when AMC came out with the Machine, that had the 340 HP 390, and the bigger cam was for that
The 302 cam wasnt factory.
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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This is a fact check for an article going in a magazine, and much as I enjoy the many AMC myths, I am trying to set it straight. Somehow they got the Group 19 specs in there as the Type II cam. I am hoping to get the right specs for that one. I agree, the Group 19 was never in anything from the factory.
The new cam was introduced in September ,69, I thought the Machine was a bit later than that? Either way, that cam was desperately needed because the Type I was a total pussycat in a 390! I am hoping to provide the correct specs for the type II for this article. Thanks! Chris |
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6884 |
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I am assuming you want paper documentation and not a camshaft. There are several grinds of 3180259, an AMC blank as far as I know. The one I have sitting on the bench has other paint markings and 0.496" lift.
I posted, asking before: http://theamcforum.com/forum/3180259-rv-cam_topic97293.html It is the largest lift from a factory cam blank I have ever come across.
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SC397
AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5476 |
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I think that you are correct.
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Sonic Silver
Supporter of TheAMCForum Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7950 |
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One thing that I will say about the factory 401 camshaft. I sent an NOS one to Cam Motion about 40 years ago to be read by their Cam Doctor machine. They sent me a printout that showed 207/208 duration at .050 and .456-.458 lift on 114 degree lobe centers, with 4 degrees ground in advance (110 and 118 centerlines). I have no direct information on the Type 2 cam, but have always wondered if it wasn't the 401 cam, since it had the same lift. I have never seen a cam with only 196 degrees at .050 have .457 lift with 1.6 rockers.
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SC397
AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5476 |
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Here is some fun stuff from one of the cam drawings.
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mramc
AMC Addicted Joined: Jul/12/2007 Location: United States Status: Offline Points: 3220 |
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OK, The group 19 cam was a period crane fireball cam shaft. It has 302 duration listed and I'm not sure of the duration. The type II camshaft your talking about is the white stripe or Rebel Machine camshaft . Off the top of my head it I recall correctly the cam was listed as a 296 /302 duration. Note back in the day they only used base circle on camshafts , there was no at 50 thousands measurement. So it a lot like comparing apples to oranges , one camshaft cam with 302 degrees would be radical, and anothers would be mild as milk. that is why they started the @ .50 thing. The stock cams of the late 60s and early 70's were the very mild 266, and into the emissions era a lot of stock cams were 262 or 264 degree cams. Really milk toast cams. There is a whole section on this topic some here on this forum including the SAE report from AMC on the Rebel Machine and the Camshaft posted in it's entirety. It listed in the SAE document BUT AMC used the Rebel Machine camshaft in the last 2 quarters of 1970 and the first quarter of 1971. AMC listed no change in horsepower but desktop dyno puts it at an extra 25 Horsepower. LRDaum
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LRDaum
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WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5799 |
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Since I am on a bit of a manual quest at the moment, I can post the following excerpt from the 67-71 parts manual:
As you can see, the Group 19 camshaft has a different part number to any of the standard production camshafts. Type 1 to type 2 is a production change based on engine sequence number, so it would appear that all 390's built after that got the type 2 camshaft and it is not specific to the Machine. Also note that the 1970 390 type 2 camshaft is the same as the 71 401 camshaft. The 71 TSM lists the lift at 0.286", intake duration as 296.25 deg and exhaust duration as 303.5 deg. Note that the 71 304 and 360 camshafts are also dual pattern and differ from the earlier camshafts. |
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I've finally given up drinking for good...........now I only drink for evil.
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Thanks guys, we can all take a bow for helping to dispel the many myths of AMC! I will pass this along!
As for the milk toast camshafts, you are correct. I drove my car for a few months with the stock cam, but a Group 19 version certainly woke it up. Thanks again! Chris |
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