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Re: Advancing camshaft
[Re: fast68plymouth]
#2758432
04/01/20 01:53 PM
04/01/20 01:53 PM
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Joined: Jan 2003
Posts: 3,122
Auburn WA
Dave_J
master
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master
Joined: Jan 2003
Posts: 3,122
Auburn WA
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Not V8 but when Shelby did the 2.2's for 1983 he found the stock cams were too retarded after he milled the blocks 0.030". So he had Chrysler make a Shelby spec cam sprocket to advance the cam 9 degrees to re-centerline it due to the belt pulling the cam into retard with the deck mill. When I threw the degree wheel on it it was 5 degrees advanced. I did use the Cam advance keys to set it at 8 degrees total and it ran stellar.
Years later working on a fairly stock 2.5 in a Shadow ES 5 speed. I removed Balance shafts. I had a measured 10:1 comperssion, and a 240/252 0.460" lift DC cam. I played with Cam keys but ended using the stock key and slipping the timing belt 1 tooth advanced, that was 9 degrees per tooth. Before I advanced the cam and 'Granny' shifted at 3500 RPM it got 32 MPG. Advancing the cam 9 degrees, that car had gained so much bottom and mid range power but nothing up above 5,000 RPM. Again, Granny shifting it then got 41 MPG. This was a daily driver for commuting 82 miles a day.
But back in the 1980's playing with a dead stock 318 with a Performer manifold and 600CFM Holley we ran a 360 2bb cam. It was strong and with a 74 Dart Swinger and 2.76 gears gave 20 MPG. Then we put a 4 degree advanced chain and it boosted the BUTT DYNO a lot and when babing it, it got the best of 25 MPG but avareged 23 MPG.
Retired, US ARMY 1973-1994
ASE mechanic, Electrical 1994-1997
Retired GTE/VERIZON/FRONTIER 1997-2015
Posting cheap tech help (CRAP) here since Nov 97, 1000's of posts, some may be good.
03 Suzuki Burgman 650(Burger King) Scooter
65 Formula S Cuda
78 Little Red Express Truck
98 Buick Regal (wifes car)
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Re: Advancing camshaft
[Re: fast68plymouth]
#2758454
04/01/20 02:40 PM
04/01/20 02:40 PM
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Joined: May 2005
Posts: 2,107
Apollo, PA.
B1MAXX
top fuel
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top fuel
Joined: May 2005
Posts: 2,107
Apollo, PA.
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All kinds of cams, engines. The one I remember it helping was a cam with a lobe sep angle of 112. I’ve never done it....... and don’t think I would....... but it would be interesting to know the whole combo on something where that worked. little chevy 355 cubes brodix track 1's as I recall long time ago, Nova 5.13's at say 2800...lots of fiberglass ect. transbrake with chip removed.I want to say we even moved the rockers 1.7's to the exhaust to make it work. now I try to put everything in at 106, or as close as possible, where the valve to piston clearance works out.
Last edited by B1MAXX; 04/01/20 02:55 PM.
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Re: Advancing camshaft
[Re: B1MAXX]
#2758465
04/01/20 03:06 PM
04/01/20 03:06 PM
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Joined: Aug 2003
Posts: 43,913
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,913
Bend,OR USA
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You really need to know if people talking about advancing the cams are talking about crankshaft degrees or camshaft degrees, correct  I always use crankshaft degrees when talking about advancing camshafts but people some don't  The first camshaft I had to degree to get the motor to run halfway decently was a 392 hemi in a V drive flat bottom ski boat, I didn't know about cam timing and degree checking off of the lifters instead of the valves at that time or about lobe separation angles.  I do now  The cam was a Sig Erson solid roller cam for ski boat racing and it was ground 8 crankshaft degrees retarded from 110 LSA on the intake lobes, they recommended running the intake lobe center at 108 and when I finally got to checking it properly it was installed at 118 ILC  They insisted it was anything but their cam being ground wrong, they wouldn't replace it with one ground correctly  I ended up using the LSA method to get it where they wanted it by using offset keys on both the cam and crankshaft  The only good thing that I learned form that is how to use LSA for cam timing verification and cam installing off of the intake lobes BTW, I always verify the exhaust lobes to make sure the cam is ground on the LSA the cam card says it is If it is a 108 LSA grind and installed at 104 after top dead center on the intake lobes on the crankshaft the exhaust lobes should be in it at 112 before top dead center to be ground correctly I have seen more than one cam ground wrong on the LSA from several different cam companies  I never bought another Sig Erson cam after that one though  Never, NEVER install any cam by aligning the dots and ASSUMIMNG it is installed straight up, always verify  OP, I've installed and ran and raced a bunch of motors and check all the cam timing and tested a bunch of cams in different motors advanced, straight up and retarded, none of the Mopar V8 motors like straight up or retarded, they all like the cams advanced at least four crankshaft degrees None of them liked or ran faster or made more power advanced more than six crankshaft degrees  IHTHs
Last edited by Cab_Burge; 04/01/20 03:09 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Advancing camshaft
[Re: Cab_Burge]
#2758470
04/01/20 03:19 PM
04/01/20 03:19 PM
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Joined: Jul 2008
Posts: 215
portland, ct
Since1822
OP
enthusiast
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OP
enthusiast
Joined: Jul 2008
Posts: 215
portland, ct
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You really need to know if people talking about advancing the cams are talking about crankshaft degrees or camshaft degrees, correct I always use crankshaft degrees when talking about advancing camshafts but people some don't The first camshaft I had to degree to get the motor to run halfway decently was a 392 hemi in a V drive flat bottom ski boat, I didn't know about cam timing and degree checking off of the lifters instead of the valves at that time or about lobe separation angles. I do now The cam was a Sig Erson solid roller cam for ski boat racing and it was ground 8 crankshaft degrees retarded from 110 LSA on the intake lobes, they recommended running the intake lobe center at 108 and when I finally got to checking it properly it was installed at 118 ILC They insisted it was anything but their cam being ground wrong, they wouldn't replace it with one ground correctly I ended up using the LSA method to get it where they wanted it by using offset keys on both the cam and crankshaft The only good thing that I learned form that is how to use LSA for cam timing verification and cam installing off of the intake lobes BTW, I always verify the exhaust lobes to make sure the cam is ground on the LSA the cam card says it is If it is a 108 LSA grind and installed at 104 after top dead center on the intake lobes on the crankshaft the exhaust lobes should be in it at 112 before top dead center to be ground correctly I have seen more than one cam ground wrong on the LSA from several different cam companies I never bought another Sig Erson cam after that one though Never, NEVER install any cam by aligning the dots and ASSUMIMNG it is installed straight up, always verify OP, I've installed and ran and raced a bunch of motors and check all the cam timing and tested a bunch of cams in different motors advanced, straight up and retarded, none of the Mopar V8 motors like straight up or retarded, they all like the cams advanced at least four crankshaft degrees None of them liked or ran faster or made more power advanced more than six crankshaft degrees IHTHs Cant thank all of you guys enough for posting your knowledge to help me out. As always, much appreciated. I wish I did this much research when I was in school lol. Learn a lot here
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Re: Advancing camshaft
[Re: Cab_Burge]
#2758475
04/01/20 03:38 PM
04/01/20 03:38 PM
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Joined: Jan 2003
Posts: 14,545
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,545
So. Burlington, Vt.
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If you use a typical 9 way timing set, you can get within 1deg of where you want the cam installed........ no matter how far off it is.
Those sets can go +/- 8*, which is 1* past the 1/2 way point to the next tooth over.
So, if you’re more than 8* off...... move the the timing set over a tooth, and come at the c/l from the other side.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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Re: Advancing camshaft
[Re: Cab_Burge]
#2758477
04/01/20 03:45 PM
04/01/20 03:45 PM
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Joined: May 2012
Posts: 1,918
South Bend
John Brown
top fuel
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top fuel
Joined: May 2012
Posts: 1,918
South Bend
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Some of the car companies (Ford specifically) moved their cams around by changing the crank and cam gears and not the cam. 1970 429 Ford cam gears when used on 75 or up 460's turn trucks that won't spin the tires on wet grass into trucks that will smoke the tires on any kind of pavement. That kind of retarded camshaft also effects gas mileage in the worst kind of ways. Sold many many earlier style timing sets to Ford car and truck owners after explaining the difference to them and never had a complaint from any of them.
July 19th should be "Drive Like Rockford Day". R.I.P. Jimmie.
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Re: Advancing camshaft
[Re: lewtot184]
#2758550
04/01/20 05:40 PM
04/01/20 05:40 PM
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Joined: Jun 2016
Posts: 920
Washington
hemienvy
super stock
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super stock
Joined: Jun 2016
Posts: 920
Washington
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This may help understanding cam advance and intake centerline.
When the rod and the crank throw are perpendicular, this is the point of maximum piston acceleration.
Some would argue this is also the point of maximum draw/pull on the intake mixture, although this point
is not quite an exact mathematical relationshp, but it's probably not too far off.
For most engines, the crank throw and the rod are perpendicular at approx 70 degrees ATDC to around 76 degrees ATDC,
depending on rod length and total stroke of course. 70 degrees in a "short rod" motor, 76 degrees in a "long rod" motor.
This is A LOT earlier than 100 degrees ATDC, which is considered pretty advanced for intake valve centerline.
The hidden question is: Should the intake valve be at max lift at the point of max piston acceleration for max breathing ?
Because of this, it should not be surprising that advancing the cam, i.e., the intake centerline, generally shows
up as higher torque output of the engine (in a given RPM range). It also shows how much of a compromise cam design
really is, they are not AT ALL ideal, but, it's the best we've got.
*********************************
Edit: Replace the phrase "piston acceleration" with "piston velocity". The degree numbers are correct, everything else
is correct. I can't believe I made that mistake.
Last edited by hemienvy; 04/01/20 07:23 PM. Reason: more info
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Re: Advancing camshaft
[Re: hemienvy]
#2758575
04/01/20 06:24 PM
04/01/20 06:24 PM
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Joined: Oct 2007
Posts: 4,219
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,219
New York
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Another argument: a short rod has significantly faster piston acceleration ATDC, and initiates vacuum at the intake valve curtain earlier (for which Vizard has made a good case as not merely useful but indispensable).
It also has slower motion ABDC, and captures a greater percentage of the stroke at the same point of cam & crank rotation than a long rod. Will show higher CCP and stop reversion at lower RPM.
Boffin Emeritus
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Re: Advancing camshaft
[Re: B1MAXX]
#2758605
04/01/20 07:30 PM
04/01/20 07:30 PM
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Joined: Jan 2003
Posts: 10,155
Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,155
Frostbitefalls MN (Rocky&Bullw...
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I have to think that the overlap events have more influance on power when a cam is moved than closer to max valve lift. Getting that. Intake charge moving through the intake valve at low lift is pretty important. To me it reminds me of the importance of 60ft and 330 ft times. They are the base of a great ET. Bad 60 or 330 numbers can't be compensated for.
Look at a 440 with unported iron heads. It responds to a lot of advance AND overlap because of the poor heads.
Last edited by gregsdart; 04/01/20 07:33 PM.
8.582, 160.18 mph best, 2905 lbs 549, indy 572-13, alky
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