killed the motor on a road course

[1977and2010]

That sucks. One thing I've learned the hard way is that our valves will bend if you fart on them. I guess that's a trade off for being light weight. I replaced several myself.

[Reelgrinder]

Something was obviously going on before the chain broke. How on earth will you determine if it was just a bad motor from factory with some tolerances off like crank end play, or main caps not straight that could lead to bearing material scaring up all the internals. Or maybe a bad cam install, to long of push rods, wrong preload on lifters.. is it possible that the cam was bad and clear connecting rods probably not since it wasn't stroked..

I would think that you would see some type of problem when the factory cam was pulled if it was a bad motor from factory. .

Are the bearings ok in the rockers?

[CWI]

Originally Posted by alaskacamaro

drivetrain warranty is bye bye the moment you internally modify, such as a cam, LTH's and tune..

OP, did you replace all the internals in your cylinder heads with the cam and upgrade the oil pump?

Drive train warranty doesn't go away entirely with internals. My first cam went in at 10K miles and the driveline gave up at 36K miles. Warranty covered it. Maybe just my awesome dealer?

[CWI]

Looks like time to stroke it. You said you had a stock timing chain? The extra load of 660 springs probably had an effect there.

Most of us have gone with the Katech C5 chain and LS2 chain tensioner. The LS3 chain and tensioner don't have a good reputation on modified engines. The LS2 tensioner isn't really a tensioner. It does not take up all the slack in the chain. It rather prevents chain slap reducing vibrations and preventing the chance of jumping a tooth. It has no moving parts to break either. More of a guide than a tensioner.

Check the hardened tip on all of the valves. When I replaced my cam and lifters at 75K miles, the tips of all the exhaust valves were cracked in excess of .025" down the stem. I replaced all of them. I use AFR valve springs. My first set had 45K miles on them and they had only lost an average of 5 lbs of spring rate. I replaced them anyways. Cheap insurance against PTV contact.

Excellent time to build what you want if you have the resources. I have the $ for more, just not the time. Good luck.

Also a perfect time to upgrade the trunion bearings if not already done. Mine started failing at 55K miles ultimately leading to the lifter failure at 75K miles.

[Firefighter]

I say go LS7. Or at least that bore and stroke so it'll rev like the devil.

[Reelgrinder]

Yes good insurance on the c5r chain.. but a broken chain not gonna cause all that scoring in the cam and other parts.. it's going to bend some valves and and tear up a piston or 2..

I hate for anyone to have trouble but would like to see caused the grinding.

[VADER SS L99]

I don't see how a chain caused those marks on the cam and lifters either. You might have experienced the same failure many of us have. What oil was used for your road race events?

Also, those recommending a LS7. I hope you don't mean a stock LS7 as those are not very reliable. No way would I use a stock LS7 unless I knew for a fact GM would warranty it even for track days and even then as soon as the warranty ran out I would have the weak points fixed in that motor.

[h018871]

Originally Posted by CWI

Excellent time to build what you want if you have the resources. I have the $ for more, just not the time. Good luck.

I've got time and no $, do you want to adopt me? hahaha

[h018871]

my dealer changes the oil for $15. I get it changed right before and right after each event weekend.

I'm still not sure what broke the chain
I am sure that the cam lobe wear is the same as many have been experiencing for the past few months. it is a comp cams core and was installed July 2013. I think mine lasted longer than other folks though and to be honest, I did not notice any loss of power so they were not worn as bad as some.

I had myself convinced that the cam was stuck because the chain was still on the cam gear and I couldn't move the cam by hand. I guess the spring tension and bent valves were too much for me to rotate the cam. I will go back with the katech c5r chain this time.

[SuperchargedStealth]

Originally Posted by h018871

my dealer changes the oil for $15. I get it changed right before and right after each event weekend.

I'm still not sure what broke the chain
I am sure that the cam lobe wear is the same as many have been experiencing for the past few months. it is a comp cams core and was installed July 2013. I think mine lasted longer than other folks though and to be honest, I did not notice any loss of power so they were not worn as bad as some.

I had myself convinced that the cam was stuck because the chain was still on the cam gear and I couldn't move the cam by hand. I guess the spring tension and bent valves were too much for me to rotate the cam. I will go back with the katech c5r chain this time.

Just reading this and had some thought. They chain may have broken from too much tension or because it caught one of the sprocket teeth. How do they look?
The cam and lifters, at first glance look like oil starvation, but after reading your build, I see that you had a oil pump. The only thing I can think of is that the rockers were over-torqued putting too much pressure on the pushrods.

[h018871]

interesting theory regarding the rockers. i'll make sure that we discuss this

the sprocket teeth looked fine, in this picture you can see one of the broken links sitting on the main bearing boss, just above the crank

[SuperchargedStealth]

Originally Posted by h018871

interesting theory regarding the rockers. i'll make sure that we discuss this

the sprocket teeth looked fine, in this picture you can see one of the broken links sitting on the main bearing boss, just above the crank

Something happened before that. I see metal shaving on the block, so there was metal fatigue somewhere. When you discuss the rockers, keep this in mind, and I'm going off the torque specs I got from TSP, who built my motor. Since they are hydraulic lifters, there's no need for a feeler gauge like there was with older motors. I recently replaced some pistons and needed specs on everything. The torque on the rockers is on 22ft/lb. How do the cam bearings look?

[h018871]

I forget which bearing this was, the rear I believe.

we tore the motor down on the floor of a friends garage, hardly sanitary conditions. I think what you are seeing is sand or dirt. there was not that much metal (steel) anywhere.

it was easy to see that metal was in the oil especially on the front main journal, I suspect it was coming from the cam lobes and lifter rollers.


SCStealth: a question for you. if the oil pressure is high, will it make the hydraulic lifters act like solid lifters? put another way, could the hypothetical "too much load from the lifters" be caused by oil pressure? if so, how much oil pressure would cause it?
I'm thinking this way because many years ago, I shimmed a SB chevy oil pump spring and the hydraulic lifters would never quiet down and the motor would stumble when you tried to adjust them as if they were hydraulic.
not sure if that is clear.............

[h018871]

crankshaft
~ 22,000 miles on the cam and ~25,000 on the motor