Interference or not (92 sunbird 3.1)

[belome]

OK,

I've spent half the morning researching if the 92 3.1 is an interference motor or not. It seems that half the web thinks it is an interference motor, the other half doesn't. (even dedicated GM V6 sites disagree)

Who is right?

My roomie has a 92 sunbird with 180k. It quit at 80mph on the freeway. He coasted to a stop. I pulled the oil filler cap off and had him roll it over with a flashlight shining on a rocker. Sure enough, it wasn't moving.

I looked at a service manual and it appears to be a pretty large PITA to change the timing chain. According to it you need to drop the oil pan which requires the motor to be lifted up.

Any words of encouragment or discouragement? I really don't want to tear into it, but he is a pretty good roomate... If it is an interference motor, thats the best excuse I can come up with to not do it.

[RidgeRunner]

http://60degreev6.com/forum/viewtopic.php?t=2658

A recent discussion here pretty much came to the conclusion that it's interference.

[belome]

Wow, it just seems like nobody 'really' knows. This guy in the link claims he had valve damage. I just called the local dealership and GM's official stance is that it is a NON-interference engine and there should have been no valve damage.

I guess the questions isn't as cut and dry as I figured it would be.

[geoffinbc]

WTF. Well I know where there is a 3.1L (alum head) Im gonna pull the chain and turn the crank over with the valves at full lift. I will bring everyone a conclusion.

[belome]

I think the fact that the 3.1 came in so many different configurations is why I can't seem to get the same answer from different sources. Until I read about the guy with the 91 with valve damage I was convinced that the pushrod version was non-interference and the OHC one was... Throw in the fact that they had a iron head and aluminum head version [I think right???] and now I'm just more confused than I was when I started looking.

I plan to check out the front valves and see if they are fooked. It is easy to get to that valve cover, but the one on the back seems looks to be a real PITA. I figure since he was going 80mph when it broke the chain, if there is a problem with the valves, it ought to be pretty evident by looking at the front set of them.

[robby1870]

I dont see how a pushrod COULDNT be an interference motor. I mean, think about it.....

[belome]

I mean, think about it.....

Ummm... I'm thinking... still thinking...

There are plenty of pushrod engines out there that are not interference engines. It really has nothing to do with 'what' makes the valves move, it simply comes down to piston and valve design.