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Type I, Type II and Group 19 camshaft

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Trader View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2020 at 3:57pm
I used an online calculator to reverse obtain the other per-tenant information:
Your amc GR19? has an Overlap of 98.00 degrees and has in Intake Duration of 302.00 degrees. The Exhaust Duration is 302.00 degrees. Your Lobe Separation Angle is 102.00 degrees. The Inlet Cam has an Installed Centerline of 105.00 degrees ATDC. The exhaust cam has an Installed Centerline of 99.00 degrees BTDC.

Very radical cam, but the numbers work.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2020 at 5:10pm
Trader, do those values hold true even if you are looking at advertised duration instead of at .050"? 102 lobe center seems very very narrow, I was under the impression that the Group 19 cam was more like a 110 or 112 center. 

It is a fairly radical cam for it's day, though it is old tech. I have one for years. It tends have low vacuum due to the large overlap, but the lift and duration is otherwise moderate. It has gentle ramps which gives it a lot of overlap and therefore very rough idle etc. The duration at .050" is around 224 degrees and the lift is moderate. I find it acts like a bigger cam than it is, and the overall power is good but not great. It has nice mid range scavenging properties though, especially when paired with a set of proper tuned headers. A modern cam would likely give better idle and low end properties with equal or better WOT power, though it was pretty good for it's time. 

Chris 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2020 at 6:38pm
The values hold true and at 0.050" it's 266. I have one of these also. It has a pink or orange dot and white dot on the back with a red paint blotch interior.
Yes it calculates out to have very poor vacuum, I would not think it could idle below 1300 RPM, but at high RPM runner, approx 3200 to 7300 RPM.
Speculate this was the Trans-Am cam that they would have to document somewhere with other factory parts.

The other factory cam I have with 0.47x" lift (worn) 110.5 LCA, 266 duration, white/red stripe would be more like I would expect for the Gen 2 performance cam. I choose it for purchasing an off the shelf cam that was the closed grind for my own 401.
Thanks Greyhound, your chart made that quite easy. 
Though I have to admit I was disappointed that Lunati listed a cam with 0.484" lift and came with 0.494" lift. The extra lift made no difference on my build except draw HP and stress components. Works fine, but what is advertised is what you should expect.


Edited by Trader - Jul/31/2020 at 8:47pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2020 at 8:33pm
I think something has gotten a bit crossed, the duration at .050" is not 266. I also will dispute that the LC are 102, I have never heard of that narrow a LC on any V8. Not trying to be argumentative, but those numbers are not quite passing a sniff test with me. I also have some contradictory information. 

FYI, I can say the characteristics are rough, but not quite as much as you mention. I have my idle at 850, with 11" of vacuum. It pulls from about 3200 but it should be shifted at around 5500-5800. I would not run that cam and valvetrain to 7300, let alone an otherwise stock AMC short block. It is well paired with an R4B and a set of old Thorley headers. 

Thanks!

Chris 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2020 at 9:17pm
Originally posted by ccowx ccowx wrote:

I think something has gotten a bit crossed, the duration at .050" is not 266. I also will dispute that the LC are 102, I have never heard of that narrow a LC on any V8. Not trying to be argumentative, but those numbers are not quite passing a sniff test with me. I also have some contradictory information. 

FYI, I can say the characteristics are rough, but not quite as much as you mention. I have my idle at 850, with 11" of vacuum. It pulls from about 3200 but it should be shifted at around 5500-5800. I would not run that cam and valvetrain to 7300, let alone an otherwise stock AMC short block. It is well paired with an R4B and a set of old Thorley headers. 

Thanks!

Chris 
I agree, but I did notice that the Group 19 is apparently ground 3 degrees retarded from the figures in the one paper. The intake and exhaust centerlines aren't listed for the Group 19, but they would have to be opposite from all the Wolverine cams listed. Without going back to look at the Wolverines, I think all but one or two are ground with 5 degrees advance. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2020 at 9:26pm
Hi Chris, not trying to be argumentative either. 
There seems to be a lot of legitimate documentation from the period and physical evidence of it. Trying to sort this out for an article based on fact, I believe nearly impossible.
Take all the know "facts" and known "documentation" and known "physically existing" is a PITA to say the least.
Writing the known and the odd existing of the period would just show AMC was doing a lot of R&R at the time and some other's In furture!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2020 at 9:39pm
Of course not, this is an intellectual debate between us polite Canadians! Wink

Seriously, I have a cam ground from very old masters that I am pretty sure are the original Group 19 cam. It is listed as 224@.050 and 110 lobe centers. We did a big debate on this subject a year or two back and there was some discussion that it might be 112 centers and we may be off a degree or two at .050, but this is pretty close. The Fireball and the WG-992 are also in that ballpark. I will not die on this hill, as my data is only 90% certain, but I can not imagine specs as radical as you suggest. 

BTW, You mention the racing cams. They did not use the Group 19 cam for racing, but I do have some listings from various race teams that might give you some idea of what they did use. 

Thanks!

Chris 

PS: I do have what I am fairly sure is a Group 19 cam, but unfortunately the place I live does not have any shop with the ability to measure it accurately. 


Edited by ccowx - Jul/31/2020 at 9:41pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2020 at 1:31pm
I was all over this cam today and it's as close to that 401 spec sheet as you can be. Maybe a visual will show you how radically this cam is:



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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2020 at 1:39pm
Video of what? Not being a smartaleck, but I have two still pics here. 

Here is a discussion of lobe centers. Not a super technical or precise one, but I found it in 3 minutes of looking. Note that these guys are saying that 106 is very radical, so you can see why I am skeptical of a derived value that gives 102. 


Thanks!

Chris 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2020 at 1:45pm
Originally posted by ccowx ccowx wrote:

Video of what? Not being a smartaleck, but I have two still pics here. 

Here is a discussion of lobe centers. Not a super technical or precise one, but I found it in 3 minutes of looking. Note that these guys are saying that 106 is very radical, so you can see why I am skeptical of a derived value that gives 102. 


Thanks!

Chris 
It doesnt say video, it says visual.LOL
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