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Type I, Type II and Group 19 camshaft |
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PHAT69AMX 
AMC Addicted 
Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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 Posted: Mar/19/2024 at 2:03pm |
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Part 2 of 4 - Viva AMX ! Car Craft Clone S/S AMX AUG 1969 by JERRY MALLICOAT page 51 : "... Our first step was to take the stock 390 AMX engine, rated at 315 hp, and put it on the dyno. In this way we would know what we had to work with, thus establishing a base line to evaluate the forthcoming modifications. Horsepower-wise, this engine just didn't have it. Maximum power was at 4000 rpm, with a meager reading of 256 ponies. The stock exhaust manifolds are worthless from a performance standpoint, as the engine could not breathe above the four grand figure. Also, the stock hydraulic camshaft floated the valves at 5200 rpm. Setting the total advance from 32 degrees to a high of 37 degrees had no effect on the horsepower readings. The engine was then removed from the dyno and completely disassembled, miking all clearances in the process. "
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Steve_P
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Charter Member Joined: Jun/28/2007 Status: Offline Points: 3808 |
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Posted: Mar/18/2024 at 7:59pm |
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I've said this is a lot, but there's a 1969 Car Craft article and a 100% stock 69 390 dyno'd at something like 260 HP at the flywheel. This engine was pulled from a car bought from a dealer and is the same Edelbrock dyno that showed the SS AMX engine at ~500HP- which was kept secret for decades and finally shared.
There was also an article in a High Performance Cars, or a sister magazine, that looked at actual flywheel HP rating based on weight and quarter mile stats for stock cars and then it refactored the HP. Just about all of the factory muscle car engines were overrated, including the 390 AMC; the hi po 350 chevys were blatantly overrated, etc. Some of the special 427 Chevys were underrated. The only underrated standard engine that I can recall was the 340 mopar, but I'm sure there were a few more. But only a small percentage of the overall evaluated were underrated. The HiPo Cars engine in their 68 test 390 Javelin was stock when delivered. This was the AMC engineering test mule for a 390 in the Javelin and was given to HPC for the purpose of the magazine series. It was chassis dyno'd and 1/4 mile tested when stock, and then after each series of mods. The car was then sold by HPC after the articles concluded.
Edited by Steve_P - Mar/18/2024 at 8:02pm |
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ccowx
AMC Addicted
Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Posted: Mar/18/2024 at 1:08am |
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Oldman,
Just as an FYI, my car consistently does 14.1/14.2 at 101/102 with a best of 13.77@102 mph. With my fat posterior on board and a real weight and time done on an NHRA certified track that calculates out to about 290-300 hp at the rear wheels. I would expect that to be about 380-390 crank HP in old days terms, given drivetrain losses and rolling resistance. To be clear, that is a car equipped as follows: 1970 390/4 speed Javelin, stock bottom end(cast pistons, .030" over, stock crank. flywheel, etc), Group 19 cam and kit, untouched 291c heads, R4B, Holley 780, Mallory dual point type YC, Thorley's, 2-1/4" exhaust, Torq links, 4.10's, Twin Grip, F70-14 Polyglas GT tires. About in line with your expectations. Chris
Edited by ccowx - Mar/18/2024 at 1:13am |
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Oldman
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Joined: Mar/17/2024 Location: Hawaii Status: Offline Points: 9 |
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Posted: Mar/17/2024 at 2:22pm |
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Next year test supercars 70 and 1/2 they admit the car is "AMC build an evaluation machine packed with all the goodies"..... dealer installed 4.10 gears... page 84 is the test results 14.1 at 95 MPH, IMO that is more than the listed 4.10 gears, that is a dyno tune and a 302 degree cam. Cheating? Maybe the big three would say so, but AMC says the dealer is an extension of the factory and the 302 degree cam is the "factory cam".
I've list IMO, I owned, worked on and raced as a young many many AMC engines and once again based on performance test and my own experience, any AMC anything "stock" going quicker that 14.5 had the "stock" 302 duration cam. I had 3 different Gremlin Xs, my bro's best friend had two AMX, and my sister had a Scrambler.
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Oldman
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Joined: Mar/17/2024 Location: Hawaii Status: Offline Points: 9 |
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Posted: Mar/17/2024 at 1:48pm |
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I grew up with AMCs, it is my opinion that any 390 that was clocking 14.5 or better had the dealer installed 302 degree cam, even that cam was small vs many factory cams. AMC treated the dealership as an extension of the factory, even though NHRA did not buy that, it did not stop AMC to treat and market dealer installed parts as factory parts. The 390 cam one or two is just two small for performance. It is the same specs (within reason) as any other 2 bbl engine AMC, Olds, Chevy, ford, Mopar and no 2 bbl cam is going quicker than mid 14s or high 14s.
Above listed 240 net installed engine HP for a 390, with tune I could see 260 net hp, 280 BHP, (not the 315 listed) the cam is WAY to small. Heck the cam is small even for the 304 as I put one in my Gremlin with heads, factory 4 bbl and Holley 650, headers side exhaust as an "upgrade" and I think I got like a .1 of a second 5 to 10 HP over the stock 2 bbl cam. I have several Car Test, Supercars Annual magazines where the author had a AMC 390, many dyno runs many builds, from memory he gets the car tunes it and jokes about it being completely worthless to test the car with a stock cam, from memory it put out 190 dyno wheel HP tuned stock cam. Drops the cam into the car and picks up like 40 HP or more and the car drops into the low 14s. Supercars Annual 69 page 61 the actual blurb for the test as everyone just quotes the results. this is Cars magazine so most / all cars tested are dyno tuned or "tweaked". " to try to even fend of the our javelin against the other pony in this section we asked the AMC dealer to install of the over the counter goodies".... 302 degree cam, 4.10s... 14.32 at 95 MPH. Anyway it has been years, but at least I know now why the AMC 390 cam either version was useless and the 401 cam was at least equal to the basic 4 bbl cam from most other OEM. |
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Trader
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Joined: May/15/2018 Location: Ontario Status: Offline Points: 6917 |
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Posted: Aug/01/2020 at 2:07pm |
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That's "visual" of cylinder #2 intake and exhaust. Just trying to show how tightly packed the lobes are.
Between those machine squares with the cam in v-blocks is approximately 1.418" and the lobe small diameter is 1.392". Never seen an AMC cam like it, or any V8 cam for that matter. Should add, that measuring with a dial indicator the intake and exhaust open and close as per the "cam card" posted within a degree and @0.050" I get 262 degrees intake and exhaust. I don't have a 1" travel dial indicator or a lathe large enough to hold the cam, so cannot provide more exact numbers. Edited by Trader - Aug/01/2020 at 9:45pm |
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Heavy 488
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Joined: Apr/27/2019 Location: In the Status: Offline Points: 3557 |
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Posted: Aug/01/2020 at 1:45pm |
It doesnt say video, it says visual.
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ccowx
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Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Posted: Aug/01/2020 at 1:39pm |
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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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Trader
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Joined: May/15/2018 Location: Ontario Status: Offline Points: 6917 |
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Posted: Aug/01/2020 at 1:31pm |
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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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ccowx
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Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Posted: Jul/31/2020 at 9:39pm |
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Of course not, this is an intellectual debate between us polite Canadians!
 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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ccowx wrote: