I have been in the process of getting a new upgraded cam installed in my '13 Z06. A few weeks ago my engine builder gave me the bad news that my oil pump was scored and probably should be replaced. So went down that rabbit hole, no more GM pumps, so my only option was the Katech track pump for $1,700. Got that and just took it to him today, he then says come on back to where my engine is, well this guy is really thorough and he motions me over to where my heads are on the work bench. You guessed it, the heads I had "fixed" 6 years ago had every valve guide trashed. Some were 6+ thousandth's of wiggle. So guess I dodged another bullet. I don't know how much longer it would have gone before it dropped a valve. Whew. He recommended I change over to roller rockers because the geometry on the stock rockers just doesn't work. Anyway just ordered a set of TSP shaft roller rockers ( they are not on their website have to ask for them) to go with all the other parts. So far a simple cam shaft upgrade has been way more expensive than planned, however it is surly better than a aerated block. Should be done in a few weeks IF I don't have anything else that needs replacing.

 

So who did the head work? "Fixed" stock castings are not a guarantee as the geometry doesn't change.

 

Wiggle = Approx. 2x Valve Guide Clearence

 

The same shop did the head work with upgraded trunions.

 

Sooooo.. name the shop???? So other's can be informed perhaps?

 

I have no issues with the shop or their work. If I wanted to blast them I would. You can see clearly when actuating the rocker across the tip of the valve the rocker tip going completely across the valve tip putting too much side load on the valve.

 

To the OP, you said heads "fixed" 6 years ago, but how many miles and how was the car used; road racing; 1/4 mile, roll racing, half mile, standing mile, etc.

 

Can you detail what was done to "fix" the heads; new or reused OEM int/ext valves, stainless steel ext valves, heads ported, valve guide material, stock cam or aftermarket, and probably most importantly, stock GM rockers or aftermarket roller tipped and brand, etc?

It appears to me that the GM OEM slider rocker design along with the geometry issue with the LS7 heads if not machined perfectly seems to be a critical component of valve train failures and should necessitate the mandatory replacement of the GM rockers with a roller tipped one whether the heads are being reworked or bone stock.

As I have stated previously, at this point in the life cycle of these LS7 engines and knowing what the issues are now with the LS7 valve train, I, personally, would strongly consider replacing the GM heads with NEW aftermarket LS7 non GM heads, several of which are offered by vendors on this forum. I guess I have learned over the years sometimes with most things in life that the motto of "if ain't done twice, it ain't done right" can often be avoided just by doing it right the first time, mining all the fine details, X2 learning from my mistakes.

 

Assuming the shop that did the head work previously used stock valve guides. If so, not surprising that they are worn out again.

 

Not so sure about assuming the stock GM valve guides were used since there are many documented cases of valve issues with NON GM stock LS7 guides, as well.

That question AND the rocker type, stock GM rocker slider (side forces on the valve) or aftermarket roller tip rockers, are becoming a very relevant factor, as well, now that much time has elapsed with "fixed and refixed" heads showing issues.

 

OP, the chewed up oil pump may be due to higher levels of Titanium in the oil. People sometimes assume that comes from the OEM Ti intake valves or aftermarket Ti retainers. In my case, I was concerned that it came from the TI connecting rods rubbing each other on the crankshaft journals, so I had the bottom end redone with forged steel Con rods and an improved forged crankshaft in addition to the Katech oil pump and added baffles in the oil pan. Has your engine builder checked to bottom end to see if the Ti rods have rubbed thru the protective coating?