lol the chevy engine things funny.... i see 350s break down in a month as much as a SBF. and i see them go 200k just like SBFs.... no difference its just a mix of luck and a good build.... you had a good build so sadly the bad luck overcame it
Yes, every intake valve is stuck part way open as the bent stem has then hung open, pic is only one I took of heads but the other looks identical.
ok, its the broken rod that has me a little puzzeled. maybe it hydro-locked that cylinder with gas or coolant. then everything went down hill from their.
It is quite possible, I admit I am still at a loss as to what event lead to what, I can only go by what I expereienced from the drivers seat which was immediately upon firing of the engine it made all the banging noise, I responded by shutting it down as quickly as I could, now as I stated prior I had just done some work on the car(nothing to do with internal other than a t-stat) prior I had driven the car approx. 5 miles from my sons to my house, was not running it hard and parked it, after it cooled down I completed the work and then the failure happened upon start, I make the assumption that the valve hitting the piston caused the failure based on the scoring of piston top, all pistons show hit marks but #8 shows hit marks around the top of the piston as if it was trying to rotate, also the rod as seen in the pics is a twisted break, not a snap, I would love to know definitively exactely what the initial cause of the failure was, one thing that was mentioned was about the cam bolt being tight.....when we assembled the engine it was torqued with the proper bolt and washer and loc-tite, however when I removed it I can't honestly say it was as tight as it should have been due to my haste in getting it apart I had a 1 ft. 3/4 ratchet with socket I used to break it loose so maybe there is merit there.....as to hydrolok I don't know how the cylinder could have been full of fuel, why would the others not have been? I'm open to all possibilities this is #8 piston you can see the dotted marks around the piston showing it rotated against the valve whereas all other piston merely had marks in one place, also it's the only one that broke...I dunno
Please do give your opinion on what broke the rod then, I want to know , I'll gladly take any additional photos up close of any part(s) you need to make a diagnoses
I'm not really sure either. Was there any coolant in the cylinder when you removed the head? I'm basing my opinion on the fact that the connecting rod is substantially stronger than a valve stem and the bend in the valve is relatively minor. Right now I'm with Bryant, gas or coolant are the only things I know of that could bend a rod like that. Was the rod bearing cap and rod bolts still intact? Maybe the rod was somehow damaged prior to this incident and it was just "it's time to go".
There was no coolant in the cylinder, I just removed the connecting rod from the crank and it was tight and spinning freely, I'm going to take some pics up close here shortly........but here is the thing, why the broken pin on cam letting all vavles hit the pistons, and furthersince they all are stuck open if fluid was in a cylinder it had a path out? I could see this being one answer if it wasn't for the cam getting out of degree and allowing intake valves to open as pistons made TDC, pics coming shortly
maybe the connecting rod let go first. That caused that piston to hit a valve. That Valve hitting a piston may have caused the cam to shear the pin and then causing the rest of the valves to hit. It's all speculation but I feel like there's a missing piece to this puzzle.
Here is all I know to offer, notice in the pic of the #8 cylinder the corresponding outter head bolt holes that goes into the water jackets tou can still see the RTV as well as in the holes on the head to prevent leaks, also both head gaskets were intact, I inserted a pic of the #8 crank journal, the cam bolt, washer, eccentric used and while it may not show well the bearings are in excellent condition as is the #8 cylinder wall...I can turn the crank freely by hand as it sits right now
I would love to know what caused what but would a rod breaking and letting the piston hit the valve cause enough shock travel through the valve up to the rocker arm back down the pushrod through the hydraulic lifter creating enough bind to shear off the pin and let the timing gear rotate? seems like there are several paths there to give way first to me...but then again I have never had or seen a failure like this
One more thing, I know some probably question "well, I bet he was dogging the car when it tossed it's load", on my life I sincerely was not, I had done exactely as stated, now I have buried my foot in it on more than one occasion and if I had been rodding it and this happened I would have no problem admitting it....I would then be wanting to know why the motor couldn't take be run since that's what we built it to do and there is a fellow local who is spraying a 250 shot right off the line on stock 302 rods and hasn't had them fail yet so I would have questions, the only thing I could have done wrong was got the distributor off when I re-stabbed it, but would that cause this....I've never known it to?
