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

Originally posted by SvtTour98.5-3:

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Maybe this is something everyone running hybrids w/ 3L valves might want to keep an eye on.

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Originally posted by SvtTour98.5-3:

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Well, Got both heads off tonight and found the problem. I had no compression on #3 cylinder is the reason for the teardown.

Found bent exhaust valve on #3. Also found a bent exhaust valve on #2. Looks like both exhaust valves on #2 & #3 have been making contact. This is the head I removed to get my center mount powdercoated so I started thinking it was something I did.

Then I pulled the Left head off and found that #6 had both exhaust valves making slight contact. The way it was explained to me was that the cylinders furthest from the driven end of the cam are most likely to have this happen to them because as revs increase, that end of the cam (due to drag and twist) becomes slightly retarded from where it should be and is now lagging as the piston comes up on the exhaust stroke. WHAMMOOO! Contact.

Maybe this is something everyone running hybrids w/ 3L valves might want to keep an eye on.

I'll be getting the valve reliefs in the pistons opened up (dished out) a little deeper in to hopefully avoid this in th future. Now all I have to do is order up some new valves and what not.

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Originally posted by warmonger:

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This is NOT a problem if it is done correctly. You shouldn't have to dish the pistons. Also, you don't want to go machining valve reliefs in stock pistons as these pistons are aged in the heat treatment process and you don't really know what it will do to the piston surface. It may be ok but then it may lead to greater rate of heat transfer to the piston body. It also may not have a beefy enough crown to take having four holes machined into them. You can get the later model pistons that have valve reliefs cast into them if this becomes a real issue.
In your case, it was one of three problems that I can think of:

1.) timed incorrectly
2.) bad or worn out timing chain/crank drive sprocket/tensionsers/guides. Any of these can allow too much slack. Also using the wrong tensioners on the chains
3.) machined too much off the heads and there is no longer enough clearance.

You can fix your valves and retime the engine, but use some modelers clay on the piston tops to see what the clearance is.
Let us know if you reused old timing components (not necessarily bad) or if you mixed and matched any components.
Let us know if you had the heads surfaced before installing them, and if so tell us how much was taken off. Hopefully if you did it wasn't some shop with a table sander that just slapped the heads on and then said "that looks about right" and gave them back to you.

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