I need some helpful advice - I bought a rebuilt stock 2007 5.7 Vortec MPI long block from a reputable builder and installed it over a year ago. Put 40 hrs on it all last summer without issue. Did the 10 hr break in oil and then changed to Mobil 15w50 . 40 -45 psi oil at idle and 55-60 psi at cruise

Now beginning this season, Im cruising at 3500 rpm for about 15 minutes then engine makes a pop/bang noise and I reduce to idle and its running ruff and popping, so I get towed back to ramp and then home. I pull the valve cover and intake and I find #7 intake and exhaust pushrods bent. Visual inspect lifters. Can not find any reason.

I replaced the pushrods, do compression test, all looks good, put back together and go boating. Within, 25 minutes of cruising again, pop/bang noise and tow back to ramp. Pull apart and again #7 pushrods on both intake and exhaust are bent. This time I inspect the roller tip rockers and their bases and notice they are both discolored from heat build up and the pivot ball is scored up. The roller tips also look marked up from wear. Also the top of the stem of the intake valve has some wear. The other rockers and valve train on this cylinder head are not discolored at the pivot/ball joint. It appears to me that #7 rockers are not getting enough oil.

Can anyone tell me their thoughts on this and what to check or try?

Pushrods typically bend to something hitting valve or valve seizing in guide.

Btw: not uncommon for comp roller tip rockers to heat up/discolor/fail/ due to their lubrication issues. They suck. See (search) my previous rants on them.

hydro lock ?

I refuse to use roller tip rockers due to all the ones I have seen with that exact problem. dont know why they have these problems but I would rather use a standard stamped rocker over a roller tip.

does it have self aligning rockers or guideplates?

There are no guide plates on these vortec heads and I don't believe these 1.6 ratio roller tip rockers are self aligning.

1.6 roller tip rockers? Did they elongate the pushrod holes in the head? Usually with the Vortec heads, if you switch from 1.5 to 1.6 ratio, you have to elongate the holes in the head so that the rockers / pushrods do not bind against the slot in the head. Did you see any wear on the side of the pushrod where it goes through the head??
Just a thought, it could be many things.

The rockers have to be self aligning if there are no guide plates.

The early Vortec heads were known for the guides being too tight and hanging valves open under heavy load. The Chevy dealer used to bring me heads to open the guides up by .001" But it would be rare for it to be the same ones and the fact that only two rockers are getting hot is strange. Comp had a problem with the real early roller tip rockers having the oil hole drilled wrong and they would do that but that was a long time ago.

I have never been a big fan of 1.6 rockers on small blocks. I would rather get the right camshaft to begin with.

Unfortunately you are probably going to have to pull the head to see what is going on. Hopefully the engine came with some type of warranty ?

I agree with BillK. You need to pull the head and watch #7 as you rotate the crank to see whats happening. I initially wondered about oil not getting into the rods, but that's not the case after reading the through the thread. I'm betting the rod might be off sized compared to the others. You got a push rod length checker tool?