AT REST
Finally got to dismantle my brother's expired 3.5 EFI engine out of his 86 RR. The story goes he was towing a trailer at his normal pace in the country and a loud clatter resulted. He drove it home at a much slower pace and finally diagnosed a broken crank because of excessive front pulley movement. I thought the block might therefore be OK but closer inspection shows its all for the scrap heap. The second and third main bearing caps split in two and pulled out one bolt hole in the block. All the bolts were still at full tension. Amazing it ran at all...
I will keep the pistons and accessories but if anyone wants a block to cut up just come and get it.
Well I have never seen that in a 3.5 beforeWe had a 360 Chrysler do it years ago. Just made a dull clunk noise. Saved the block luckily.
Your brother was very fortunate he made it home by the looks of that. He must rev the pick handles out of it as I haven't killed my 3.5 yet and it runs at 4000 rpm wile towing.
Master
I've heard of the crank breaking when supercharged, but never normally asperated
AT REST
Must have been a rare weakness or slow growing crack, he didn't usually push over 4000. He wasn't the only owner of the RR of course, had about 200K on it when he bought it.
Not like me as a lad, I broke a crank in a P76 at 5000rpm and it made a seroius mess of the block, the front pulley broke off and skittered down the road 100m or so. That was exciting.
Master
Never seen that in a 3.5, once had a break just aft of the rear main in a 318 chrysler installed in a dodge d5n, think it might have had something to do with the driver rather than the motor though
AT REST
I'll tell him what the forum thinks... should amuse him.Originally Posted by Jhonno
ChatterBox
I understood it wasnt uncommon when you had issues with cross fire due to poor plug leads.
Master
What do you reckon broke first - the caps or the crank?
if the caps went south i can see the crank breaking real easy.
AT REST
You could be right, one of the first things I did when big bro bought it was to replace the ignition amplifier and plug leads. The Lucas originals had caused the LPG to explode repeatedly for the previous owners. To the extent they sold it with the LPG disconnected.
With the new Bosch amp it ran perfectly for 50,000km but the damage was already done.
AT REST
I reckon he would have noticed main bearing rumble/low oil pressure if the caps had broken. The broken crank knocking could easily have hammered the caps apart. Just think of the torsional loads on a crank being smoothed by the flywheel and counterweights.
Yep, crank broke first. It was a typical fatigue crack after all, those shell-like tide marks are a dead giveaway.
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