PTV checking with VVT cam
10-31-2012, 02:48 AM
#81
Ok cool...so in order to stay efi stock harness and computer i would have to run a vvt cam???just seems like a lot of work to do a cam swap and such....sorry for dumb q.s ....just didnt know about this vvt stuff....
11-01-2012, 10:56 AM
#84
Piston valve clearance, clay method, VVT
Here is the clay method I used for checking PTV clearance using a VVT cam. It isn't all that different from doing it with a nonVVT cam, just a few added steps and for now the use of a sacrificed phaser.
First I locked the phaser to full advance as shown below. I am using a cut-off screw that happened to fit well when combined with a phaser limiter block.
Next, I installed the cam using the dot-to-dot method.
Then I applied approximately 1/4" thick strips of modelling clay to the top of the piston with the piston dry & clean. I pressed them into place so they stuck well to the piston, then sprayed the top of the clay, the valves, and the combustion chamber with WD-40 to prevent sticking.
Next (not shown) I installed two solid lifters for this bore. Then I installed the cylinder head with an old gasket of the same installed thickness as the gasket I intend to use (in this case, the same PN MLS gasket from GM).
I installed my old (nonadjustable) pushrods and rockers, then adjusted them to zero lash using the rocker bolts . Before this can be done the crank must be rotated 180 because when the timing marks are set dot-to-dot, the no1 cylinder is in the overlap phase (both valves partially open).
Finally, I rotated the crank through two revolutions so the valves would make an impression on the clay. The impression left would represent minimum clearance with the cam at full advance, but I care about both full advance and full retard.
I rotated until both the crank sprocket dot and cam sprocket "dot" (arrow) were facing up. This put the no1 valves on their base circle. I made a mark to the cam sprocket tooth nearest the crank dot so I could get it back into position later.
Next I removed the phaser and locked it to full retard as shown below. In this case, I cut off the tip of a 1/4" hex drive philips bit which happened to fit perfectly.
Then I reinstalled the phaser. To do this, I first put the phaser on the nose of the cam without the timing chain installed. This allowed me to rotate the cam by hand to the new retarded position and line up the mark I made on the sprocket. Then I installed the chain and rotated the crank two revolutions.
The resulting impressions in the clay should represent the minimum clearance for both full advance & full retard. I only had to install the heads once - I just had to adjust the cam phasing to get both extremes. Pardon the dirty marks in the clay - the heads still need a bit more cleaning.
Next I used an Exacto knife to slowly and carefully slice through the clay. This gave me a nice cross section. Here is the intake:
And here is the exhaust:
After a search through my boxes, I couldn't find my trusty calipers (!) so I used a steel rule instead. Axial thickness seemed to agree with what I measured before. The advantage of this method over the indicator method is I can also observe radial valve clearance, which I think looks pretty good. The radial clearance was about 3/16" for both valves. Hopefully I can find my calipers and get a better measurement tonight - they seem to have walked off over the last week.
Here is the clay method I used for checking PTV clearance using a VVT cam. It isn't all that different from doing it with a nonVVT cam, just a few added steps and for now the use of a sacrificed phaser.
First I locked the phaser to full advance as shown below. I am using a cut-off screw that happened to fit well when combined with a phaser limiter block.
Next, I installed the cam using the dot-to-dot method.
Then I applied approximately 1/4" thick strips of modelling clay to the top of the piston with the piston dry & clean. I pressed them into place so they stuck well to the piston, then sprayed the top of the clay, the valves, and the combustion chamber with WD-40 to prevent sticking.
Next (not shown) I installed two solid lifters for this bore. Then I installed the cylinder head with an old gasket of the same installed thickness as the gasket I intend to use (in this case, the same PN MLS gasket from GM).
I installed my old (nonadjustable) pushrods and rockers, then adjusted them to zero lash using the rocker bolts . Before this can be done the crank must be rotated 180 because when the timing marks are set dot-to-dot, the no1 cylinder is in the overlap phase (both valves partially open).
Finally, I rotated the crank through two revolutions so the valves would make an impression on the clay. The impression left would represent minimum clearance with the cam at full advance, but I care about both full advance and full retard.
I rotated until both the crank sprocket dot and cam sprocket "dot" (arrow) were facing up. This put the no1 valves on their base circle. I made a mark to the cam sprocket tooth nearest the crank dot so I could get it back into position later.
Next I removed the phaser and locked it to full retard as shown below. In this case, I cut off the tip of a 1/4" hex drive philips bit which happened to fit perfectly.
Then I reinstalled the phaser. To do this, I first put the phaser on the nose of the cam without the timing chain installed. This allowed me to rotate the cam by hand to the new retarded position and line up the mark I made on the sprocket. Then I installed the chain and rotated the crank two revolutions.
The resulting impressions in the clay should represent the minimum clearance for both full advance & full retard. I only had to install the heads once - I just had to adjust the cam phasing to get both extremes. Pardon the dirty marks in the clay - the heads still need a bit more cleaning.
Next I used an Exacto knife to slowly and carefully slice through the clay. This gave me a nice cross section. Here is the intake:
And here is the exhaust:
After a search through my boxes, I couldn't find my trusty calipers (!) so I used a steel rule instead. Axial thickness seemed to agree with what I measured before. The advantage of this method over the indicator method is I can also observe radial valve clearance, which I think looks pretty good. The radial clearance was about 3/16" for both valves. Hopefully I can find my calipers and get a better measurement tonight - they seem to have walked off over the last week.
08-13-2014, 01:08 PM
#86
Reviving this old thread because it is the closest thing I could find to answer my question. So if you have a cam with the wrong core for its phaser is it still usable? Can you adjust the cam a tooth or two to make it work as it should or will it still be off?
Last edited by rindoze; 08-13-2014 at 01:26 PM.
08-13-2014, 03:26 PM
#87
TECH Apprentice
The stock cam gear has 44 teeth so one tooth is 8.18 degrees. There is no problem with that as long as you know how to degree a cam. Just put some new marks on the gear so the next guy won't have problems.
