I upgraded the cams in the Westfield in summer of 2007. The resulting power increase was pretty profound, but over time it seemed less so. Yes, the car was still very quick, but it just didn’t seem to have quite the same level of urgency I remembered those first several months. It also failed smog twice (2009 & 2011) after passing within a few months of cam installation, so I suspected that the power loss might be real, rather than a simple recalibration of my butt dyno. Compression and leak down tests revealed no issues, so valve timing was the next logical culprit. Given a check of valve clearances showed some were out of spec, and I had an oil leak that required a closer look, I decided to pull the engine to address.
Now setting valve clearances on a Duratec is a complex affair thanks to their mechanical, non-adjustable design. A small inverted bucket (i.e. tappet) sits over the valve spring and its base forms the fixed, mechanical interface between the top of the valve stem and the cam lobe. The buckets come in different thicknesses and are selected to achieve optimal valve clearance. To adjust the clearance, you first need to measure it, then remove the bucket to get the base thickness measurement that is stamped to the inside (3.xxx mm), and then calculate the new thickness required to get the clearance within spec. The buckets are available with base thicknesses that come in increments of ~.02 mm, so the final setting is never exact, but should be within the accepted range (0.09"-0.011"/0.09"-0.012" intake/exhaust). Given that measuring and changing out these buckets requires cam removal, and by extension, resetting cam timing, this was also an opportunity to correct any discrepancies in this area.
After removing the crank pulley and front timing cover, I noticed that the adjustable cam gears weren’t where I left them in ‘07 – i.e. they had moved and with that movement, had altered the cam timing. A quick check revealed that the specs were significantly out of whack. Kent recommends exhaust timing is set to 110 deg before TDC, and the intake to 105 deg after TDC, yet measurements showed these were at 116 and 95 respectively. Now to be fair, the timing was most likley altered when the front pulley was removed (it’s not keyed and instead relies on a friction fit), but the delta between the two settings cannot inadvertently change during that process, and it too showed a big discrepancy, so cam timing is indeed out.
The good news is that I appear to have found the source of missing horsepower and increased emissions. The bad news is that it reveals the torque wrench I originally used to torque the clamping bolts isn’t very accurate at the required 12 ft-lbs setting. Suffice it to say I am buying a new torque wrench to handle all fastening duty under 20 ft-lbs, and investing in Loctite.
Now setting valve clearances on a Duratec is a complex affair thanks to their mechanical, non-adjustable design. A small inverted bucket (i.e. tappet) sits over the valve spring and its base forms the fixed, mechanical interface between the top of the valve stem and the cam lobe. The buckets come in different thicknesses and are selected to achieve optimal valve clearance. To adjust the clearance, you first need to measure it, then remove the bucket to get the base thickness measurement that is stamped to the inside (3.xxx mm), and then calculate the new thickness required to get the clearance within spec. The buckets are available with base thicknesses that come in increments of ~.02 mm, so the final setting is never exact, but should be within the accepted range (0.09"-0.011"/0.09"-0.012" intake/exhaust). Given that measuring and changing out these buckets requires cam removal, and by extension, resetting cam timing, this was also an opportunity to correct any discrepancies in this area.
After removing the crank pulley and front timing cover, I noticed that the adjustable cam gears weren’t where I left them in ‘07 – i.e. they had moved and with that movement, had altered the cam timing. A quick check revealed that the specs were significantly out of whack. Kent recommends exhaust timing is set to 110 deg before TDC, and the intake to 105 deg after TDC, yet measurements showed these were at 116 and 95 respectively. Now to be fair, the timing was most likley altered when the front pulley was removed (it’s not keyed and instead relies on a friction fit), but the delta between the two settings cannot inadvertently change during that process, and it too showed a big discrepancy, so cam timing is indeed out.
The good news is that I appear to have found the source of missing horsepower and increased emissions. The bad news is that it reveals the torque wrench I originally used to torque the clamping bolts isn’t very accurate at the required 12 ft-lbs setting. Suffice it to say I am buying a new torque wrench to handle all fastening duty under 20 ft-lbs, and investing in Loctite.
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