yeah, i know, its the wrong forum.
i think a buddy of mine just got taken for a ride.
he's got an 85 ram, LA 318 (i guess), 2 bbl carb, auto, with about 250k.

something happened the other day and he had it towed to a shop. i don't know if the timing chain was just loose and slapping, or if it actually slipped or broke or what.

so the shop determined that it needs a timing chain and they do that. then its still not running or not running right, so they pull the heads and do a valve job, replace push rods, rebuild carb, etc, and they get it running.

its got 250k so i don't doubt that it needed all that, and probably a lot more, but here's whats bothering me...

the shop showed him a bent push rod and told him that the timing
chain slipped, and the piston hit the valves and bent the push rods.

i'm calling BS on that, because i don't think the 318 is an interference engine. is it ?

by the way, timing set, valve job, carb rebuild, probably a tuneup but not sure. - $1800.

 

That is prolly more than the truck is even worth...

 

It is possible , Since the timing chain does control valve action. Im a marine mechanic , and Volvo penta had a issue , on their belt timing chain four cylanders , the pulley would rust , causing the belt to slip and their timing would be off causing piston hitting the valve and causing serve damage.

 

crank gear is connected to the cam gear by the timing chain, correct? ( I think there's a song in there somewhere.)

So if the gear or chain slips (more like breaks) then the cam and crank run out of sync and the valves could end up being fully extend when the piston hits TDC, it's possible I guess. With a stock cam it'd have to be a helluva slip, but I guess it's possible.

 

It is in the realm of possibility. Imagine the crank and pistons turning while the cam is stationary during the time you're coasting to a stop. $1800? What's a few more skins after that?

 

http://cgi.ebay.com/ebaymotors/1985-...spagenameZWDVW

 

I never knew the 318 to be an interference engine, but I might be wrong.

 

I've never heard the 318 was an interference engine either. I've heard of non interference engines having this happen when you have a timing jump combined with weak springs in the valve train...so that's a possibility I guess.

Did they put all new valves in the head? Seems to me he should have a collection of a couple valves since if one or two did hit a piston, surely it damaged the valve.

 

What is an "interference engine" as opposed to a "non-interference engine," and can you give me examples of both? To me, all overhead valve, piston engines have the potential to mate pistons and valves. Unless you're talking about a flat head, turbine, or Wankel rotary.

 

In an interference engine, a valve at it's fully extended position will hit the piston at tdc, so basically, if your timing jumps, you risk a valve hitting a piston. Non interference, the valve fully extended will never touch the piston.

Seems like most of the newer cars with overhead cams are interference motors, small block chevy is too I think.