So I have had LS7 lifters in my L31 since I ran the Ramjet cam in it. Recently swapped to the GM 357 HP SPO 350 cam. Since the SPO cam/LS7 lifter swap I have had an oiling issue under sustained throttle/rpm. I actually noticed it after the LS7 lifters went in with the Ramjet cam but at the time had assumed it was just a bad sending unit. I ended up hurting #1 slack side (the insert on the cap) rod bearing insert from oil starvation. Upon tear down the crank was still in good shape, so I replaced the rod and main bearings as well as the oil pump and added a milodon windage tray in place of the stock GM tray. I put a 5qt pan on it in place of the 4qt and never realized that GM used a longer tray with the 5qt pan. I now have rock solid oil pressure, 70-75 psi even at sustained higher rpm. I had assumed the upper end lifter noise I was experiencing prior was from the low oil pressure. At approximately 4,000 rpm after about 4-5 seconds the valvetrain suddenly starts sounding like someone has backed all the rockers nuts off a good 2-3 turns. It is obvious slack in the valvetrain. I am running 1.6:1 self-aligning full roller rockers on screw in studs, the Vortec heads have had the pushrod holes opened up to 1/2" and have LS6 Springs/Comp 787 retainers. Currently scratching my head because I have used LS7 lifters in other 350 builds and have not run across this issue. What am I overlooking?

 

Did the valvetrain actually back off or was it lifters just collapsing/bleeding doen?

Could there be too much lifter to lifter bore clearance, losing oil pressure at the lifter

 

Lifters are just collapsing with RPM.

Engine is fairly low mileage and the problem did not show up until the lifter swap. Wouldn't a clearance issue there also show up as low idle oil pressure?

 

What valve springs? Set up at what height? What retainers etc.?

 

Yeah you would think but not sure

I never had an issue with ls7’s but i have heard of some bad sets

 

LS6 springs, Comp 787 retainers, shimmed to a 1.8" installed height on 0.100 longer than stock valves. Pushrod length was checked.

 

Reason I ask is with the stock high volume/high pressure pump it was idling 40 psi and running 70 psi down the road. I had a new mellings stock volume, high pressure 454 pump laying around and threw it in it. It idles 60+ psi hot.

 

Reason I ask is with the stock high volume/high pressure pump it was idling 40 psi and running 70 psi down the road. I had a new mellings stock volume, high pressure 454 pump laying around and threw it in it. It idles 60+ psi hot.

 

Valve guides arent worn?

Thats alot of oil pressure imo what weight oil?

 

0w40

Heads are low mileage 906s that actually had valves sticking from the guides being too tight. They have about 10K on them since the guide clearance was corrected.

My buddy has a big cammed 6.0L with Caddy race lifters and his truck idles at 60 psi and pegs the 80 psi gauge at WOT. Runs 0.600+ lift on them. Beginning to wonder if its just a bad batch of Delphi crap LS7s.

 

It doesn’t sound like typical ls7 performance to me for such a mild setup. But i would be curious on how the stock lifters did in that setup

 

One of the roller wheels locked up with ~30K on this engine and wiped the 215/220 comp cam I was running in it. It came out, came apart, all the oil passageways were roded out, was completely cleaned, and put back together. I replaced the radiator and oil cooler lines too at that time.

Poor engine has not made a 20K mile stay in its home without something coming apart yet.

 

Man that sounds like something else going on but not sure what.

 

I know you said ""LS6 springs", but... "LS6 springs" seems to cover LOTS of ground these days.

Where did they come from? What are their MEASURED seat and open pressures last time they were checked?

Your cam is pretty mild, wouldn't expect it to be too radical for much of anything in the LSx engine realm of springs, where everything is a notch or 2 higher even in its stock trim than the old SBC. Still, your description sounds ALOT like valve float. Might even be worthwhile just pre-emptively striking, maybe a set of 1218s or the like, set to no more than 1.800". Especially if you have some such or know somebody you can get them from without having to buy new.

 

Did the old cam have any lobes that show marks on the closing side of the lobe? Or did any of the other lifters have marks on the rollers?

 

If I am reading this correctly, you ran these very same LS7 lifters with both the Ramjet and the SPO cams. So I have had LS7 lifters in my L31 since I ran the Ramjet cam in it. Recently swapped to the GM 357 HP SPO 350 cam. Since the SPO cam/LS7 lifter swap I have had an oiling issue under sustained throttle/rpm. I actually noticed it after the LS7 lifters went in with the Ramjet cam...
Now you think you are having oil starvation issues at high rpm. 2 thoughts here:
1) did any of your cam bearings walk out of position? This would cut off or restrict oiling to its following main and then rod bearing.
2) Do your lifters sit in the same positions in their bores as before? If that recessed portion on the side of the lifters (I'll call it the oil flow band) should get either too high or low in their bores, then you are then losing oil pressure and flow to the mains.

 

How was the length checked? With .100" longer valves the best valvetrain geometry will have the contact nowhere near the centre of the valve. It will tend to run off of the exhaust side of the valve tip. If you settled on using the (very poor) witness mark method and didn't observe how wide the contact mark was and how it changes as you advance the length of the pushrod, chances are you've wiped out the guides. Max width of the mark itself should be less than .030" for a cam your size.
This isn't to say that this is your problem, but it will a problem in and of itself.
Speaking from expensive experience.

 

sounds like an oil control or oil starvation issue and the rod furthest from the pump going out. By any chance one of the front lifters was the one that locked up? How is the oil control in your heads? All rod, main AND CAM bearing tolerances spot on? Distrubutor o ringed or not? Return passages all smooth and open?Does your block have a 1/8npt port on the front above the timing cover so you can hook up a gauge there? The oil pressure is at it's lowest there being last in line.

 

Lot's of good suggestions all ready. But I'm kinda skeptical of having poor lifter pre-load that becomes noisy only above 4000rpm - though it is possible.. I'm kinda thinking the SA rockers - if that's whats your using - can't handle the job and you need some correctly clearanced guide plate using standard rockers (non-SA). That or possibly the installed height is wrong.

Hey thanks for sharing that SP350 357 cam. First time I've heard of it and it looks like a drop in cam for vortec heads with stock springs. Or a GEN II LT1. Wish that was out earlier. Sounds like a LT4 Hot Cam little brother.

 

Should have mentioned, its got guide plates, screw in studs and 1.7 non self align rockers.

 

Could your oil pump pickup be too close to the bottom of the pan, which would supply enough oil at idle, but be restricted at higher rpms?
It's more likely something that was done/changed during the cam swap, but I'm just trying to cover all the bases.

 

Any results?

 

Wow, 1.7 rockers! Did you check them for clearance with the spring retainer and the rocker stud. You need to check them for the full lobe cycle - up to max lift and back down to base circle. A unbent paper clip works though there is a spec for this - check Cranes w/s tech.

 

Exactly....