School me on hydraulic lifters….

[forcefed86]

Are Hyd. Lifters basically “pumped up” 100% during WOT operation? Could excessive oil pressure cause valve train issues on hyd lifters? Say 120+psi?

First, this is a GM 5.3 LS motor, not a buick. Same rules apply I’d think. And I always come back to my buick crowd for basic engine information.

I shimmed my oil pump relief with a couple washers (old school SBC tendencies got me again!) and pressure is pretty excessive. With 5w30 oil I see around 83+ cold startup, 55 warm at 850 idle. 80psi gauge pegs out WOT. My issue is the motor just stops making power around 6k. It does not breakup, power just drops. (10 mph slower in ¼ than last year) Seems to do great up to that point. Same top end last year would pull strong to 6800 or so. Cams a small 215/215 @112 .565 lift. Springs are a 130lb installed, 318lbs open. Rated to .600 lift. (again ran same setup with no issues last year). Maybe 1000 miles on these springs. They are single beehives.

It's not the plugs(or gaps), wires, coils, boost leak, AFR, timing issue.... etc It doesnt' sound like valve float, but I'm wondering if the excessive pressures may be causeing an issue here...


I plan to pull the shims I installed no matter what. But do you believe this could be my issue with the power nosing over?

 

[Mike Licht]

Valve springs are going away IMO.

 

[bison]

I would say you likely have valve float. What lobes are you running and why would you only use 130lbs on the seat? For what you're doing id want as much spring pressure as possible and I'd select the springs based on the coil bind limit and work backward from coil bind. I'd want every bit I could get for an application like yours .

 

[Chuck Leeper]

My LS has 150 seat, and 440 at .620. When I talked to Bullet cams, and to Manton, they both said that I should be OK up to about 20+psi boost.
After that, Mark at Bullet, said that I may need to "step up" on the springs. I'm using the LS7 lifters, Manton p rods.
I'm w/ Mike/Brian... Not enuf spring.
What kind of boost R U pushing?

 

[bison]

With the availability of really good almost drop on springs these days I'm very surprised at the number of engines that are under sprung. With a low lift application like the OP has adding a lot more pressure is very easily done

 

[notacarlo]

Google spring less valve train. I agree with Mr. Licht on this one.

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[forcefed86]

First thanks for all the input!

I've floated some valves in my day and I could almost always hear it.... I'm going off what others including myself needed as far as springs go with the same or very similar cams. These are the PAC1218 drop in beehive springs. Same springs I ran last year with a .560 211/230 @121 cam to 6800 without a problem (24psi+). These are not aggressive grinds. They are very mild isky "truck cams". Many run them with more aggressive cams than mine over 6k without issue. I run an OE valve train so I didn't want to over spring the motor and end up with bent push rods either. Why run a .640 lift spring on a .560 lift cam?

Not saying this isn't' my issue, just explaining why I ran them and thought they would be fine. I was mainly wondering about the lifter "over pumped" theory. Sounds hokey to me. I'd think a lifter would already be pumped up to max at WOT with less pressure. even at 12lbs the power just drops after 6.

I did order a set of stronger pushrods 7.35" (oe is 7.4") as suggested by isky. I will try these with the oil pressure reduced first. If I still don't see an improvement i'll grab the stronger spring or shim these. Either way i'll report back

thank you!

 

[Razor]

Oil pressure is not your issue. Unless oil isn't getting to the lifter.