Valve to piston contact pix

[exhaustfumes]

[exhaustfumes]

i am 98% sure the reason my 2.7 engine locked up at start up was a jumped timing chain. the only evidence i can see of this is in this pic....see the small shiny arc, at the bottom of the piston crown? sprayed some solvent on the carbon on piston, that's why it looks like the LaBrea tar pits. when i removed all my rocker arms, the engine would spin fine.

now, if all of my timing chain parts LOOK good, where do i start replacing parts? i already have hyd. tensioners, and the ramps look fine. the gear teeth look OK too. just do the chains, or replace the tensioners? anyone have suggestions on t-shooting hyd tensioners?

don't want to put it back together until i am comfortable it won't happen again.
thnx..joe

[lateapex911]

No pic....at least visible to me...but if your pistons have marks, it would be a lucky miracle that teh valves didn't get bent...at least a little. Are you redoing the head and valves?

Was the engine apart before? If so, remeasuring the chain end distance is in order.

Did you look at the timing of the cams before opening up? How far off were they?

[exhaustfumes]

jack-

it's got 185K, so someone has been in there before, but i have no records.
how do you measure the chain length??

thnx..joe

[2.7RACER]

Where is the piston dome, left or right?
It's hard to tell from the picture.
Number 4 cylinder. Dome should be to the left.

[exhaustfumes]

yes, it is number 4 (cylinder just behind fan on passenger side.).
and the dome is towards the left in the pic.
i did not check the timing prior to ripping into it.
what else could cause piston to valve contact?? i hadn't messed with the valve adjustment, the rocker wasn't seized, and the psiton/con rod seem to all move properly.

thnx..joe

[Elombard]

Over rev?

[lateapex911]

Too bad you didn't measure before opening. Valuable evidence is lost. Which makes it hard to determine the actual incident.

Some possibilities.
-Bad tensioner..
-lost tensioner oil pressure
-misalignment of cam gears, or loosening of same.
-overrev, esp on downshift
-old valve springs revved to redline
-broken or weak valve spring.

Is it JUST this cylinder??

You really need to inspect the head and valve very carefully.

That said, this is one of those, "while it's out" deals.

I'd send the heads off to Ollies or CE, and do the pistons and cylinders etc. Cams need to be checked, and possiblyy replaced. As its a 2.7, there is a laundry list of things to go through like studs, etc if they haven't been attended to.
At 185K it's probably due....

If you need a good wrenc, Rick Deman is near(ish) you in the Tarrytown NY are, and has a great reputation. He IS busy though, so plan on that.

If you want to do it yourself, measure everything, get a good workshop manual if you don't already have one, and get Bruce Andersons book, at a minimum. Pick up some accurate measuring devices, and set yourself up an area with a lot of space and the cleanliness of an operating room.