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MattyBrown's CAM RESULTS!!! Check 'em out!!
https://slantsix.org/forum/viewtopic.php?t=44951		 Page 1 of 2
Author:  MattyBrown [ Thu May 12, 2011 8:01 pm ]
Post subject:  MattyBrown's CAM RESULTS!!! Check 'em out!!
It's been a long long day of turning my degree wheel, graphing, calculating. I'm tired! But I can finally post some specs on my camshaft. I'm hoping someone out there will be able to tell me what to make of them!

The following information recorded from valve retainer with ZERO valve lash:

INTAKE Highest Point: 105.5 degrees
Counter-clockwise .050: 71 degrees
Clockwise .050: 142.5 degrees

That should put my Intake Centerline at: 106.75 ATDC That's great news, it appears I am NOT off a tooth.

EXHAUST Highest Point: 246.5 degrees
Counter-clockwise .050: 213.5 degrees
Clockwise .050: 284 degrees

That should put my Exhaust Centerline at 248.75 (rouchly 112 BTCD). Anyone have an opinion on that?

Next, I mapped out the following graph. All information on the graph was recorded from Valve Retainer with rockers set to ZERO lash.

Image

If you would like to see the graph LARGE, so you can read the numbers, here's the URL: http://www.eternitycomplex.com/largegraph.JPG

So this is where things get interesting. It seam the highest point of my intake is about .390 but the highest point of my exhaust is about .401. Would that be normal for a stock cam? I went back and checked to make sure the dial didn't slip or anything and it didn't. Other than a .001 margin of error, I would say that the highest point of my intake and exhaust are .010 different.

My next step, at Doc's suggestion, was to check the valve timing at some varying lashes. Here are the results:

ZERO LASH
Intake First Opens: 57 degrees BTDC
Intake Closes: 275 degrees (95 ABDC)
Duration: 332 degrees

Exhaust First Opens: 55 degrees ATDC
Exhaust Closes: 76 degrees ATDC (not a type-o)
Duration: 381 degrees (seems extreme!)

.006 LASH
Intake First Opens: 22 degrees BTDC
Intake Closes: 257 degrees (77 ABDC)
Duration: 279 degrees

Exhaust First Opens: 77 degrees ATDC (103 BBDC)
Exhaust Closes: 61 degrees ATDC
Duration: 344 degrees

.020 LASH
Intake First Opens: 10 degrees BTDC
Intake Closes: 229 degrees (49 ABDC)
Duration: 239 degrees

Exhaust First Opens: 123 degrees (57 BBDC)
Exhaust Closes: 25 degrees ATDC
Duration: 262 degrees

.050 LASH
Intake First Opens: 3 degrees ATDC
Intake Closes: 31 ABDC
Duration: 208 degrees

Exhaust First Opens: 38 degrees BBDC
Exhaust Closes: 5 degrees BTDC
Duration: 213

WHEW!! So what's the scoop? Anyone got an opinion on this cam? Is it stock (for a '72)? Did I just go through all this work for nothing? Haha. If I did, it's okay, it's been a fantastic learning experience. I notice that the Exhaust durations seem to be a lot longer than the intake durations. Would that be normalized by setting the lash .010 off (as in STOCK).

I look forward to hearing what everyone thinks. THANKS!!!!

-Matt
Author:  ceej [ Thu May 12, 2011 8:23 pm ]
Post subject: 
The events happen at roughly the correct locations for a stock cam.

I don't have the lift numbers for that cam. You measured on the top of the rocker adjusting nut? There may be some variation due to that. The nut travels in an arc, and not all rockers are created equal. Measuring directly off the lifter would be more accurate, but even so, sounds like an OEM cam or an OE regrind to me.

CJ
Author:  MattyBrown [ Thu May 12, 2011 8:44 pm ]
Post subject: 
Hey CJ, no, I measured off the metal retainer part at the end of the valve spring. Did not touch the rockers.

I just took specs for the Intake at .010 lash.
Opened around 20 BTDC and closed around 74 ABDC with a duration of abou 274. That puts the intake and the Exhaust (at .020 figures above) within a reasonable proximity I figure. I'm definitely starting to see that it could be a stock cam. Hopefully someone will come along who can confirm.

-Matt
Author:  WagonsRcool [ Thu May 12, 2011 8:50 pm ]
Post subject: 
If your lift is at the valve as you said then it sure does sound stock. I think gross lift was .430" or so but rockers sure aren't exact to spec.
Good job!
Author:  Charrlie_S [ Fri May 13, 2011 3:23 am ]
Post subject: 
I do "plots" like that for every cam I install. It is really interesting to see the differences, between two different cams, with similar "advertised" specs.
Author:  Dart270 [ Fri May 13, 2011 3:30 am ]
Post subject: 
Looks stock. Congratulations on enjoying learning a new skill! That is worth every minute.

Lou
Author:  Doc [ Fri May 13, 2011 8:47 am ]
Post subject: 
Great job collecting all the data... yes looks like it's a "stock" cam that needs a little more advance... I would try 4 degrees.

Here is a list of stock cams that will be helpful.
DD

http://www.dutra.org/dutraorg/pictures/ ... -specs.jpg
Author:  MattyBrown [ Fri May 13, 2011 11:34 am ]
Post subject: 
Thanks everyone and thanks Doc for providing that list, although it does cut off at '69. Would you happen to have a pic of the 70's cam info?

Let me just confirm this: A '72 stock cam most likely would have had an intake centerline of about 106, right? Right now I just want to rest assured knowing that my cam is stock and it is timed as such.... should be able to get it running halfway decent!

I'm still a little hazy on the art of installing cam bushings to advance the cam but it is something I will look into because I have heard from others as well that the stock cam usually performed better with a slight advance.

Thanks again!

-Matt
Author:  MattyBrown [ Fri May 13, 2011 11:53 am ]
Post subject: 
By the way, does anyone have any recommendation for where I should set my timing (via distributor)? Ceej recommended about 10 degrees advance if I remember correctly and I feel like I've seen a lot of people mention that as a good place for timing on a slant. However, I do want to be careful not to focus only on performance, MPG is important too. I drive A LOT and great distances. What you all think??

-Matt
Author:  SlantSixDan [ Fri May 13, 2011 6:01 pm ]
Post subject: 
Quote:
Thanks everyone and thanks Doc for providing that list, although it does cut off at '69.
The cam listed starting in '67 for the (export only) 225 2bbl setup, p/n 2264582, is the one that was used on all slant-6s from '71-'80.
Author:  MattyBrown [ Fri May 13, 2011 11:30 pm ]
Post subject: 
Ahh, okay, thanks for clarifying that, Dan. It's interesting to see how many variations there were to the cams during the 60's. Do you, or anyone else, have an opinion on what the best stock cam was? I'm also curious for a bit of back story if anyone knows why any of the variations were made throughout the years.

Did the use of the 2264582 from '71-'80 have anything to do with emissions? Does it's use correlate to the decline of factory specified Slant horsepower in the 70's?

-Matt
Author:  SlantSixDan [ Sat May 14, 2011 8:05 am ]
Post subject: 
Quote:
Ahh, okay, thanks for clarifying that, Dan. It's interesting to see how many variations there were to the cams during the 60's.
Not that many…just three stock cams: the one with 232° intake duration used '60-'64 on 225s (advanced 8° in '60) and '60-'65 170s, the one with 240° intake duration used '65-'70 on 225s and '66-'70 on 170s, and the one with 244° intake duration used '67-up on export 2bbl engines and all domestic production in '71-'80.
Quote:
Do you, or anyone else, have an opinion on what the best stock cam was?
Definitely the 244° item.
Quote:
I'm also curious for a bit of back story if anyone knows why any of the variations were made throughout the years.
In the late 1950s when the slant-6 was being developed, very mild, very conservative cams were the norm on low-RPM 6-cylinder engines with 1bbl carburetion. As Chrysler engineers (and those of their carburetor suppliers...) gained more experience with the slant-6, they developed the camshafts for improved performance and driveability. The 244° cam started life as a marine item in conjunction with 2bbl carburetion, then was extended to roadgoing 2bbl applications; its increased duration and lift let the engine breathe better.
Quote:
Did the use of the 2264582 from '71-'80 have anything to do with emissions?
Yes; because it has greater overlap (26°) than the previous two cams (16° for the 240° cam and 8° for the 232° cam), the 244° cam reduced NOx emissions. Its increased duration and lift still meant better breathing, but this was largely moot on the road because as the camshaft was evolving to allow better breathing (and therefore higher RPM), final-drive ratios were getting taller so the engines were operating in a lower RPM range. This is a little backwards; the early cars with 3.23 and 3.55 rear axles would've done better with the later 244° cam, while the later cars with 2.76 and 2.45 rear axles might've liked the early 232° cam better.
Quote:
Does it's use correlate to the decline of factory specified Slant horsepower in the 70's?
Not as such, no. The cam timing would certainly have something to do with this; I don't have year-by-year published specs on valve events at my present location so I can't point directly to changes that were made, but the general wisdom (supportable or not) is that the nominal factory cam timing grew more and more retarded over the years. Whether this was supposed to be the case or not, in actual practice the less-than-super-durable cam sprockets and timing chains and the sloppy "almost kind of sort of near the right place" indexing of the cam and crank sprockets means most of the later engines were running with retarded cam timing right off the end of the production line or soon thereafter. The main drop in rated horsepower had nothing to do with the engine configuration; the rating system changed to give lower, more accurate numbers. See here for details.

Later on, in the late '70s to early '80s, the engine really was strangled with smaller carburetors, a meeker cam with the switch to hydraulic lifters in '81, more restrictive exhaust systems, higher-volume EGR, and slower ignition advance curves in an effort to squeak it past tightening Federal emissions type-approval tests without spending the money that should have been invested to modernise the combustion chamber, fuel-inject it, and otherwise bring it up to date.
Author:  MattyBrown [ Sat May 14, 2011 6:19 pm ]
Post subject: 
Thanks, awesome info Dan! I really appreciate such a thorough response. You have a way of not just delivering facts, but actually encouraging understanding with your answers. In conjunction with the older thread you referenced, I've learned A LOT. Thanks for taking the time.

-Matt
Author:  DonPal [ Sat May 14, 2011 6:22 pm ]
Post subject: 
Matt plots a total intake duration of about 330 crankshaft degrees at zero lash. Respectively he shows 240 at .020 lash which is double the normal lash.

His stock cam has a possibility of being a 244 deg intake duration based on Dan's definition of a 71 & up cam.


In order to understand the rating of 244 intake duration where does the 244 intake duration show up in Matt's plot?
Author:  ceej [ Sat May 14, 2011 6:35 pm ]
Post subject: 
Factor lash and allow for measurement error. Pretty darn close though.

CJ
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