Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec 3L troubles

Originally posted by SvtTour98.5-3:

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Ok, so my guy over at Dart started work on the heads last night (finally!!) and we think we found the problem.

On the cylinders that were making contact, the valve seats weren't cut deep enough. From the lowest to the hightest on the exhaust, we found .050" variance on the exhaust and .025-.030 variance on the intake for valve height from the deck. We're figuring that the valves have always been making contact since the motor was built two years ago but I may have a spring that's a bit week allowing them to interfere a bit more and bend. We'll check spring rates before reassembly.

So he started with a 5 angle valve grind and set them all the same. Then tapered the tops of the seats a bit more. Continuing on, he did a bit of bowl work to continue unshrouding the valves. He's going to be working on these hopefully this week.

He's guessing maybe around 10 more ponies from the work he's doing but we'll see.

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Well, I don't think I'd be happy with the valve seats being cut so different, but I don't see that causing the contact.

You see, the installed height of the valve may change but the rocker assembly can not push the valve ANY close to the piston than the calculated amount of lift unless there is a problem with the pivot point being higher than it should, rocker arm ration has changed, or valve stem length has changed.
I also find it hard to believe that this cylinder had float and others did not.


The only other possibility is deck height, a problem that would move the whole valve train assembly closer to the pistons, or some portion of it if it wasn't even. Did you measure the deck height????

I suspect that the heads were decked by hand on a sanding belt and they may not be decked evenly. This would make one side of the head thinner than the other and the net result could be interference on one side of the head while not on the other side.
If the wedge-shaped effect was enough, there could be all four valves in the cylinder on the end touching and maybe only one or two in the middle cylinder touching and the head would still seal.
This may not be the case at all, but see if there is a pattern in the interference. Look and see if you can see more evidence of contact on one side of the head or if it is evenly disrtributed.

I just don't buy the argument on valve installed height problem causing it, at least not by itself.