Is the Lincoln LS 3.9L an Interference motor??

Nope it isn't. An interference motor uses belts instead of timing chains which our JA motors use.
 
I stand corrected. So then is the JA motor an interference motor? I thought interference engines pertained to some 4 and 6 cylinder engines?
 
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I don't like being wrong so I did a little research and it sounds like all overhead cam engines are interference motors and push rod engines are non interference. Is that correct?
 
Skidsmint said:
I don't like being wrong so I did a little research and it sounds like all overhead cam engines are interference motors and push rod engines are non interference. Is that correct?
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No - varies.
 
I asked cause i found a Lincoln LS that i was told had a bad timing chain and i was just curious what kind of damage i was looking forward to. The Trans was good and i was going to part the rest.

I kinda got confused on all the back and forth...

you said the 3.9L is an interference motor?

Also... does anyone know what to look for to be certain ( besides opening up the upper end)

Thanks for all the responses :)
 
many members have had bent valves, piston damage - however, the was one guy (caqn't remember his name) that broke his timing chain and said he was able to replace it and the motor was fine... now I don't know if he looked for damamge or simply restarted the engine and it ran...

the rule of thumb is not weither it's a timing belt or chain but usually naturally aspriated high compression engines are - since they have to have a very tight combustion chamber (the piston comes way up the cylinder) so there is no clearance for valves to be open at that same time.
 
Skidsmint said:
I don't like being wrong so I did a little research and it sounds like all overhead cam engines are interference motors and push rod engines are non interference. Is that correct?
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Nope...wrong again.
2.3 liter ford, used in the SVO mustang has an overhead cam, timing BELT and is NOT an interference engine.
 
Is that because it has a lower compression ratio of only 8.0:1?? If the pistons were changed out and the compression was changed to 10.0:1 then could it be considered an interference motor? I don't claim to know everything but I do like to learn from my mistakes :D
 
depends on how much more the pistons move up into the combustion camber. If the piston at fully up can hit a valve at fully down then it's an interference engine.
 
Quik LS said:
the rule of thumb is not weither it's a timing belt or chain but usually naturally aspriated high compression engines are - since they have to have a very tight combustion chamber (the piston comes way up the cylinder) so there is no clearance for valves to be open at that same time.
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Exactly.

"Interference" referes to whether the piston at TDC will interfere with the valves when open. This has nothing to do with whether is OHC or OHV or whether it uses a timeing belt or chains. It has to due with compression ratio and valve lift. The more compression the closer the piston will come to the head and the more valve lift the more the valve will stick out into the combustion chamber.
 
Actually, the piston in an AJ engine is a complete flat crown design. There may be very small valve clearance cuts. The combustion chamber is a pent roof design. There is virtually no squish.

It's not uncommon for a broken valve to intrude into a combustion chamber in such a way as to have contact with a piston, so EVERY engine can be looked-on as potentially 'interfering'.
KS
 
cammerfe said:
It's not uncommon for a broken valve to intrude into a combustion chamber in such a way as to have contact with a piston, so EVERY engine can be looked-on as potentially 'interfering'.
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Yeah, but that's a broken valve, not a broken timing belt or chain. When you're talking interference or non-interference, the valves are presumed intact; it's the stopping of the cam(s) that leaves them in a position to be hit (or not) by the pistons.
 
386Motoring said:
I asked cause i found a Lincoln LS that i was told had a bad timing chain and i was just curious what kind of damage i was looking forward to. The Trans was good and i was going to part the rest.

I kinda got confused on all the back and forth...

you said the 3.9L is an interference motor?

Also... does anyone know what to look for to be certain ( besides opening up the upper end)

Thanks for all the responses :)
Click to expand...

So...
Plan on parting out an LS?
 
Are you in CA? If you just need a Transmission, I have one sitting in my garage collecting dust. It needs new shift solenoids. They come in a pack and are easy to replace. From the dealer, they're $375. I hadn't planned on selling it.
 
drag214 said:
Are you in CA? If you just need a Transmission, I have one sitting in my garage collecting dust. It needs new shift solenoids. They come in a pack and are easy to replace. From the dealer, they're $375. I hadn't planned on selling it.
Click to expand...

The problem i'm having is that the transmission shop said if they take mine apart and the valve body is damaged then i have to pay a fee for that along with the cost of finding a new transmission. I'm just worried about it cause my trans went out with no warning at 87k miles and the fluid was burnt although i had just had a synthetic flush at 75k miles. I've been looking for a used transmission but most of them have more miles then my own had. At the cost of buying a transmission i could get almost a whole car and part it out. I know there is enough demand for these to make it worth my time.

If anyone is selling a transmission that works please let me know. I'm ballin on a budget. The idea of spending 1800 on a trans scares me to death just to think that it may happen 6 months from now :( I'm a single dad and stuck driving a pickup truck all the time now.
 
SoonerLS said:
Yeah, but that's a broken valve, not a broken timing belt or chain. When you're talking interference or non-interference, the valves are presumed intact; it's the stopping of the cam(s) that leaves them in a position to be hit (or not) by the pistons.
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Who 'presumes intact'? Is there a formal definition? I've never seen one!

Please read what I wrote. The piston is a flat top and no 3.9 piston I ever saw even has valve reliefs. The combustion chamber is a classic four valve pent roof. The valve would have to protrude beyond the chamber in order to hit a piston, and factory lift figures make that unlikely.
In order for contact to happen, the most likely scenario would include broken valve-train pieces and not just a timing miss-event.

It IS fairly common to pull the valve-stem/keeper interface through the factory retainer, and 'drop a valve'. This inevitably causes a crash.
KS
 
cammerfe said:
Who 'presumes intact'? Is there a formal definition? I've never seen one!

Please read what I wrote. The piston is a flat top and no 3.9 piston I ever saw even has valve reliefs. The combustion chamber is a classic four valve pent roof. The valve would have to protrude beyond the chamber in order to hit a piston, and factory lift figures make that unlikely.
In order for contact to happen, the most likely scenario would include broken valve-train pieces and not just a timing miss-event.

It IS fairly common to pull the valve-stem/keeper interface through the factory retainer, and 'drop a valve'. This inevitably causes a crash.
KS
Click to expand...

I felt smart until i read this.....

Does this mean that its possible that a broken timing chain would cause valves to break?

I'm waiting on a response since my search uncovered nothing. I'm ready to buy this Lincoln with a bad timing chain. I need my lS back :(
 
nope - Ken was making the comment that it is more likely a broken valve fell into the cylinder and caused damage than that the valve hit the piston head from the cam being out of time (because of a broken timing chain).
 
Quik LS said:
nope - Ken was making the comment that it is more likely a broken valve fell into the cylinder and caused damage than that the valve hit the piston head from the cam being out of time (because of a broken timing chain).
Click to expand...

Quick LS.... and a quick responder. LOL

Thanks for the info guys.
 
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