Manager Forum

Anyone know if the 3.9 V-6 will bend valves when the timing chain or gears break?

Truck towed in. Customer said he put in a new water pump and while running up to temp the engine made a rattle sound and cut off. Would not restart. Pulled valve cover and had no cam action. He then installed a new timing chain and gears. Now it cranks like a honda with a busted belt. He assured me the the marks were lined up and even pulled it all down a second time to be sure. Pressure tested cylinder 1 with 100% leak down thru intake.

I checked and couldnt find any mention in any service manuals.

I looked too. Found nothing conclusive.

This is a pushrod motor. That's what usually bends. Pull the valve covers yet? You can loosen the rockers on cylinder one. That'll set the valves closed. If it still leaks, there's a problem with the valve sealing. If not, maybe timing is off.

Yank the valve cover, remove rockers or loosen enough to twist off of valves. Lat a straight edge across the valves and you'll be able to see if the valves are bent. If the stems are staggered the valves are bent. Clattering noise is the key here and it sounds like Jo Jo wound up the engine so much it stuffed itself. No rev limiter on this one (i think) so i would look further and this may have grenaded so look at the pistons for deep smiles, if there are any they'll need to be replaced and then look for metal inthe oil pan. May be better off doing a r&r. Be carefull and cover yourself. We really don't know how much of a beating this took but we do know once you commit to this you own it. In the past i've found that people at the level of doing their own repairs like this will usually return with a ticking noise or other issue once you've repaired it. May turn into a nut twister.

Pulled right side valve cover last nite after I posted (easiest to get off). With #1 at TDC all 3 exh. rockers sloppy loose. I like the idea off pullin all the rockers and using a straight edge. Thats next step I guess. Just couldn't remember one of these being a "bender". Thanks for the tips guys!
On a side note the father is a pretty good customer. The son is outta work and was tryin to save himself a buck. Thats how I started out fixin cars. And now I is a mekenik!

Jeff @ Able Auto wrote:Anyone know if the 3.9 V-6 will bend valves when the timing chain or gears break?

I checked with my machine shop and he said absolutely they are an interference engine. Will bend valves.

Sorry I didn't get back and post last night. Pulled the heads, found all exhaust hanging open. Pistons show contact on all cylinders from both valves. All push rods bent. Odd enough the piston dings are very minor. Machine shop picked up last night, called this morning. Both heads are cracked in the areas between the valves. Customer Ok'd the reconditioned heads. Tried Alabama cylinder head, not avail. gonna get em from CQ. Thanks folks for the tips and help.

I use Clearwater Cylinder Heads in Clearwater, Florida. Good price, 3-5 day deliver and good quality.
(800)572-1963

Just for s&g's look at the lifters and make sure the retainers are there. I've had the experience of bent push rods popping the retainers and missing it until i've put it back together. I would get a good sense of how it was running from the customer. I'm not saying it's going to happen but this person may expect it to run like new and be a faithful "it wasn't running like this before". The smiles in the pistons may be small but i always make sure the top compression ring isn't jammed. If i'm remembering correctly isn't this intake one of those that the gasket on the bottom plate leaks and causes idle issues? Make sure the fuel rail is clean and IAC is free of crapolla. Good luck.

Thanks Steve for the insight. Yes it is the "plated" intake. I will check the lifters closely. Thanks again everyone!