View Full Version : Interference engines

07-29-2015, 09:35 AM
Hi all long time

The crankshaft broke in my 1992
The motors line bore was checked as OK during assembly. The crank was turned 10/10, the motor only had about 5000 miles on it. The car had sat for a several years I fixed the brakes, new rack, tires and various other things and gave the car to my daughter. According to her it broke on the highway she says just cruising along
My machinist still has the build sheet from the last go-around and I have a seasoned crank that he says just needs polishing. He can balance the new crank to the existing rod/piston set using his build sheet. I know this is probably a bad idea but to save some time & money I would like to just replace the crank without dissembling the top end I haven't pulled the motor out yet so I don't have all the facts but I do have a question.

Are our (Stock) 3.8 motors Interference engines or not ?

07-29-2015, 10:16 AM
I don't believe they are, but if the crank broke, all bets are off, since the piston could potentially go further up in the bore and make contact with the head. Also trying to snake the crank in there without pulling the rods and pistons is going to be very difficult. For the little added expense, it would be worth it to just pull the heads and send them to be checked out to make sure there is no damage. Also having the crank bore checked again is a good idea since the crank broke. It would really suck to get the whole thing back together only to find another problem that will require pulling the motor back out again.

07-29-2015, 05:22 PM
I can verify they are interference engine, floated valves and blew my last motor up. That being said I agree with Mikey not worth the risk and need to see what the problem is. While I personally believe it was just fatigue, the heads/valves need to be checked and piston tops.

At this point what's the extra cost of head gasket and new bolts

XR7 Dave
07-29-2015, 07:30 PM
Yeah, absolutely has to come apart. Generally all modern engines are interference with very few exceptions.

08-03-2015, 08:39 AM
Yea I guess that's the right thing to do. I'm just getting lazy in my old age.