snapped a connecting rod, cylinder 7 i believe, went through both sides of the oil pan, chewed up the rod bearing next to it,,i was racing when it happened, and the car just shut off completely,,,when it happened i heard a **** load of grinding...anyways, it looks like my block is ok,,,( only cut the oil pan off) planning of boring to a 383, my question is,, my dad said my pison could have came up and slapped my head,,,is this a common thing? and if it did what kind of damage could have been done. i just barely have enough cash to bore, and buy a forged stroker lower end,,new heads are out of the question..
thanks
-Jason

 

I guess it's possible, but mine did the same exact thing and my heads were fine. I guess it depends when it broke lol

 

Mine were fine too. It hapened at lower speed for me, I herd some clunking and backed off then bang! put a hole throught the pan.
The piston might have touched the head in my engine but did not hit it hard enough to do any thing.

 

There is really only one way to find out for sure. You are gonna have to remove and disasssemble the motor anyway.

 

more than likely the piston hit the head, but although its a pretty big force, its over a large area (low pressure) so the impact probably did not damage anything badly.

 

ya we're taking it apart, just need the $$ first. hopefully the head isn't damaged.

 

Recently pulled apart an LT4 that broke 2 rods @ approx 6400rpm.
It bent 1 valve in each cylinder, but otherwise the heads were fine.

 

I blew up a 383 many years ago.

Totally destroyed a piston.
Broke the cam and the cam tried to go out the back of the block damaging the distributor and flexplate
Bent 2 rods
A bunch of broken or bent pushrods
At least 5 valves are visibly bent. Never tore the heads down to check the rest since I don't need to use the heads. No other damage to the heads though.
Nothing exited the engine and the pan had no holes in it but did have a bunch of dents from something trying to get out.

I pulled the intake and heads and threw the rest into the scrap metal bin at work.

Now when I dropped a valve in my BBC a couple of years ago that was something different. The head of the valve broke off and stuck in the piston. When the piston came up, it punched a hole through the combustion chamber which makes the head a boat anchor. Crankcase instantly fills with coolent from the head. The force put on the piston when that happened caused it to swell or distort in the cylinder and it cracked the cylinder wall. I had the block sleeved and put on a new head plus many other parts and went racing again.

If there's no coolent in the oil then there's a good chance any damage is minor or repairable. It's always a good idea to have the heads pressure checked after any failure like that.

 

Stephen,
Did the same w/ a new Severe duty exhaust valve in my BBC a few years back but my cylinder wall was OK. Still looking for a replacement L-88 head.

 

Well I should have come over here to post instead of the LT1 Tech side.
I just blew my 383 and I Belive it was the fault of the engine builder, but I don't know enough about ARP Nuts and if it is possible for them to 'back off' the bolt under severe conditions.

I am calling ARP to see what they say.

Here is the post
http://web.camaross.com/forums/showt...32#post2769332

 

If they were torqued properly, they should never back off.

The only way they could become loose is if the rod bolts stretched. Properly torquing rod bolts should be with a stretch gauge. Since the majority of us don't have one we do a standard "torque 3 times" method. I even go as far as using red loctite on the rod bolts.

Failed rod bolts usually happens at high rpm with heavy rotating components. The downward force on the piston from compression does nothing. It when the piston is going upward and has that sudden stop at the top. It's the rod bolts that keep that piston from smaking into the head. If all the upward force from high rpm or very heavy parts excedes the strength of the rod bolts, they will eventually stretch. Once they stretch, the clamping force won't be the same on the nut. That's why many high performance con rods use a cap screw design instead of a bolt and nut design. Clamping force is greater with less chance of a failure from a stretched bolt.