Timing Adjustment
Thread Starter
Mopar Fanatic
Joined: Apr 2013
Posts: 191
Likes: 0
Timing Adjustment
The comp cams 268h xe is broken in, car was overheating checked every possible avenue except the timing. Checked oil and filter for chunks of metal nothing, radiator is good great flow, thermostat is good. Engine is at TDC. It was put there to do the came install the timing chain, etc. Anyone know of what to set it at with the new cam, I was reading 12 degrees before TDC for 68 Chrysler 383, 4 Barrel. I bought timing tape not sure how to do it, have a rough idea but not certain.
Last edited by mrzods13; Apr 17, 2014 at 05:17 AM.
Mopar Lover
Joined: Nov 2007
Posts: 2,424
Likes: 248
You left WHAT at TDC?
1.......There is no guarantee that the crank timing mark is not or ever was correct. You need to use a positive stop to find out
2......If you "threw" the cam in at the "timing mark to the timing mark" this is not installing the cam. You needed to degree the cam. This is a procedure which insures the cam is installed not only to correct for machining errors in the crank, cam drive, cam, and so on, but to position it where you want for performance. GOOGLE "how to degree a cam"
What I mean by the above is, that there is no guarantee that the cam is PROPERLY installed, regardless of the marks on the cam drive. It is common that retard / advance timing drive components are used to move cam timing to get the power curve in perspective.
3......Ignition timing must be recurved, that is, the mechanical advance must be MUCH shorter and faster for a hotter cam. Even a mild cam should be shorter and faster for performance. Advance curves from about 68 through until fuel injection were for smog control NOT performance. A starting point would be about 20 degrees "in the distributor" crank degrees with about 15 degrees inititial advance. That gives you a total advance initial plus mechanical of about 35 degrees. Any vacuum advance, if used, is "on top" (added) to that. There are BOOKS written on this.
You CAN NOT run a 268 cam using a stock factory "smogger" distributor with stock factory advance settings. The engine will be a dog.
1.......There is no guarantee that the crank timing mark is not or ever was correct. You need to use a positive stop to find out
2......If you "threw" the cam in at the "timing mark to the timing mark" this is not installing the cam. You needed to degree the cam. This is a procedure which insures the cam is installed not only to correct for machining errors in the crank, cam drive, cam, and so on, but to position it where you want for performance. GOOGLE "how to degree a cam"
What I mean by the above is, that there is no guarantee that the cam is PROPERLY installed, regardless of the marks on the cam drive. It is common that retard / advance timing drive components are used to move cam timing to get the power curve in perspective.
3......Ignition timing must be recurved, that is, the mechanical advance must be MUCH shorter and faster for a hotter cam. Even a mild cam should be shorter and faster for performance. Advance curves from about 68 through until fuel injection were for smog control NOT performance. A starting point would be about 20 degrees "in the distributor" crank degrees with about 15 degrees inititial advance. That gives you a total advance initial plus mechanical of about 35 degrees. Any vacuum advance, if used, is "on top" (added) to that. There are BOOKS written on this.
You CAN NOT run a 268 cam using a stock factory "smogger" distributor with stock factory advance settings. The engine will be a dog.
Thread
Thread Starter
Forum
Replies
Last Post
a.johansson84
Interior/Exterior Electrical
7
May 27, 2012 03:30 AM
