[Wilka_SS]

Just installed a custom speced boost cam from tsp with tsp cnc heads decked 5 thou with standard PAC 660 springs and retainers. Cam spec is 635/635 227/239 on a 115lsa, vvt is locked at zero. Standard ls7 lifters and ls2 trays, I do have tsp LT roller rockers increasing my ratio to 1.82 over the standard 1.8. I measured pushrod length using the comp cams 7702 tool. I have 50 thou preload on intake and 70 thou on exhaust, and ended up with 7.825 push rod length. My question is with the rocker ratio change putting my lift at 641.9 am I getting piston to valve under high load or am I losing control of the spring because of the increased weight of the roller rocker? I asked texas speed and they said I should have no issues but looked at a cam from cam motion with similar lift and slightly different duration and it requires pistons with bigger valve reliefs or knotching or (flycutting) of factory piston. I've double checked my exhaust and motor mounts, haven't found anything loose. Verified knock is still there with e85 and is rpm related.
Car only has 18 degrees of timing in it and me and my tuner both agree to not add anymore until the knock is sorted. I will add I removed baffles inside my valve cover because I found the roller rockers hitting the valve cover but can no longer find witness marks on the valve cover. Consulted with tuner and got my valve events from texas speed and adjusted soi and eoi tables accordingly to the cam. Any feedback is appreciated. Fixing to switch back to stock rockers with che trunions and see if the roller rockers are my problem. Just seeing if anyone else ran into this issue before.
I found on a c6 forum where someone had a similar issue after 6000 and his btr 660 springs couldn't handle the weight of the roller rockers at redline, swapped to stock rockers and never had another issue.

Any suggestions or feedback is appreciated.

[KingLT1]

I doubt it's the roller rockers...they should actually be less noisy then a slider type OE rocker with a cam.

Imho .050 isn't enough preload for a LS7 lifter. You should be between .070-.090. LS7 lifters have over .200 travel, ideally you want to be in the middle of the plunger travel or slightly less.

I wouldn't of used LS7 lifters to begin with. Morel 6504 or ultimately the Johnson 2110 for replacement drop-in lifters would of been my choice.

[Wilka_SS]

Originally Posted by KingLT1

I doubt it's the roller rockers...they should actually be less noisy then a slider type OE rocker with a cam.

Imho .050 isn't enough preload for a LS7 lifter. You should be between .070-.090. LS7 lifters have over .200 travel, ideally you want to be in the middle of the plunger travel or slightly less.

I wouldn't of used LS7 lifters to begin with. Morel 6504 or ultimately the Johnson 2110 for replacement drop-in lifters would of been my choice.

That would have changed pushrod measurement a lot. I know 50 is the oem spec of the lifters which is more or less what I was aiming for, with standard length pushrods I had them nearly maxed out. I'm scared either the weight of the rocker is making the valve train uncontrollable after 6000 or its hitting the valve cover and I can't see where. My map kpa falls off which is normal for high rpm and goes from 102 to 98 kpa which my tuner says is just an intake restriction. I have a lt5 throttle body to ported msd to the cnc tsp heads.

[Wilka_SS]

Originally Posted by KingLT1

I doubt it's the roller rockers...they should actually be less noisy then a slider type OE rocker with a cam.

Imho .050 isn't enough preload for a LS7 lifter. You should be between .070-.090. LS7 lifters have over .200 travel, ideally you want to be in the middle of the plunger travel or slightly less.

I wouldn't of used LS7 lifters to begin with. Morel 6504 or ultimately the Johnson 2110 for replacement drop-in lifters would of been my choice.

I went from the standard 7.850 tsp 3/8 pushrods to 5/16 ends to btr 7.825 after measuring in full 5/16 to reduce valvetrain weight and was told the 3/8 was overkill even with my future plans of a d1sc

[KingLT1]

Originally Posted by Wilka_SS

That would have changed pushrod measurement a lot. I know 50 is the oem spec of the lifters which is more or less what I was aiming for, with standard length pushrods I had them nearly maxed out. I'm scared either the weight of the rocker is making the valve train uncontrollable after 6000 or its hitting the valve cover and I can't see where. My map kpa falls off which is normal for high rpm and goes from 102 to 98 kpa which my tuner says is just an intake restriction. I have a lt5 throttle body to ported msd to the cnc tsp heads.

That is for OEM lifters not LS7. Buy the correct length push rods to get the lifter pre-load where it needs to be across all valves. .050 on the intake and .070 on the exhaust isn't how I would setup my valve-train. Stepping down to 5/16 was a mistake as well.

[Wilka_SS]

There is no inbetween 7.85 and 7.825, I'd need some kind of stupid precise custom pushrods. I'm thinking of just going back stock rockers with che upgrade.

[KingLT1]

Originally Posted by Wilka_SS

There is no inbetween 7.85 and 7.825, I'd need some kind of stupid precise custom pushrods. I'm thinking of just going back stock rockers with che upgrade.

so put the longer 7.85 push rods on the valves that are only .050 preload, that will put them to .075 and the others .070 with the 7.825 with the shorter push rod. Much better then being .020 different and the lifters will be in the correct preload range across the board. lighter push rods do nothing for valve train stability. 5/16 will flex and act like pole vaults with that cam and valve spring setup. It would be different if they were shorter like LS stuff where you can squeak by with 5/16.

[Wilka_SS]

that's the thing when I did have standard length with the roller rockers, it still knocked, worse than it does now.

[KingLT1]

Well I guess the next step would be to put the stock rockers back on and see if it goes away.

[Wilka_SS]

Originally Posted by KingLT1

Well I guess the next step would be to put the stock rockers back on and see if it goes away.

Yeah my trunions come in tomorrow, knew it was too good to be true to have roller rockers.

[KingLT1]

yes reverting back to stock rockers is probably the best solution even though I have confidence I could make one of these engines run fine with them....js. Just need to desensitize the knock sensors more. We had to do it back in the 90's for the 4th gen LT1 when running roller rockers. I know you said that you did, but without seeing your tune it's hard to say if it's enough or on the threshold of too much.

[Wilka_SS]

Originally Posted by KingLT1

yes reverting back to stock rockers is probably the best solution even though I have confidence I could make one of these engines run fine with them....js. Just need to desensitize the knock sensors more. We had to do it back in the 90's for the 4th gen LT1 when running roller rockers. I know you said that you did, but without seeing your tune it's hard to say if it's enough or on the threshold of too much.

We already had them desensitized because of headers as you need to with almost every 6gen with headers but then he did it an additional 2 times and said it was to the point if anything mechanical happened it wouldn't pick it up, and I cant tell if the valve is actually floating or if its the roller rockers just making noise with increased rpm

[Wilka_SS]

Nobody really has roller rockers on these cars so its kinda hard when to judge, I had almost 6.8 degrees of KR even with them desensitized. I thought I had combated it for awhile but now its knocking even 2-3 shift and 3-4 in the same rpm range from like 6300 6500 all the way up to 6800, we were shifting it at 7 until we saw the knock was a real thing.

[Wilka_SS]

Now that we have the knock sensitivity back to where he had it pre cam I get like 11.3 knock