AFM valves, VLOM, VVT and high output oil pump

[mckpaul]

I have a 2010 Tahoe with a 5.3 that has AFM and VVT. I have a lifter issue on a non AFM cylinder, and I'm about to go down the road of new lifters.

I understand the lifters (AFM lifters in particular) have been updated, and if I replace all the lifters with updated lifters I also need to make sure I get an updated VLOM too.

I know the lifters and VLOM as well as the variable valve timing depend on correct oil pressure to operate properly. The truck has 129,000 miles, so while the lifter work is being done I was thinking about a new oil pump as well.

I know there are higher volume oil pumps available (additional 18%?) that are 'recommended' for high mileage engines.

So here are my questions..

Do the newer updated lifters and VLOM need the higher volume oil pump or are they designed for a standard oil pump?

(I don't want to put a higher volume oil pump if it may eventually lead to VLOM seal leakage or something else later if the parts are not built to operate at a higher oil pressure)

Are the updated AFM lifters more dependable than the original ones? Did they get the bugs out? Did the updates on the VLOM help?

Will the VVT system be happy with a higher volume oil pump?

 

In a nutshell, I don't want to do the AFM bypass, just want to make everything stock and operating properly. But I know the AFM setup has a history of being problematic. I don't want to make a change (such as higher than stock volume oil pump) if it may cause issues down the road.

If the lifters and VLOM were not updated and I had to go back with the original stock equipment, I think I would lean toward deleting the AFM as a preventative measure, but hearing the lifters and VLOM have been updated makes me want to just replace with updated parts and hope the updates make for an improved AFM system.

 

Thanks,

Paul

[Doug_Scott]

If your current oil pressure is good, no need for a high volume pump.  High volume pumps are for "loose" engines.  Engines built with large clearances for example.  You cannot push more volume through passage that is already so full of oil its under 40 pounds per square inch pressure. If GM wanted a high volume pump installed to compliment their updated lifters they would have one available and there would be mention of it in a TSB. 

 

High volume pumps were never intended for production street engines.  They are used to provide sufficient flow of oil in an engine running large clearance main and rod bearings.  A high volume pump will be able to fill those large clearances with enough oil it will have oil left over and that means oil pressure. If it can't supply enough oil you will have low pressure. 

 

High volume pumps are misunderstood by most.  Once you see oil pressure, you are supplying (flowing) the highest volume possible.  Trying to push more oil simply increases the pressure without anymore volume. 

[Jsdirt]

IF you plan on keeping this engine any length of time, do yourself a huge favor - sell what you have for parts, and buy a long block.

 

You'll thank me later.

 

The longer I own one of these engines, the more I hate them ...

[Doug_Scott]

39 minutes ago, Jsdirt said:

IF you plan on keeping this engine any length of time, do yourself a huge favor - sell what you have for parts, and buy a long block.

 

You'll thank me later.

 

The longer I own one of these engines, the more I hate them ...

I see Bill Mitchell is making cast iron small block chevy blocks that are machined to accept LS engine top ends. Kind of the best of both worlds. 

[mckpaul]

Thanks for the replies. Going from a 2003 Tahoe with a 4.8 to the 2010 Tahoe with the AFM 5.3, I'm seeing a lot of differences.

The  oil pressure on the '03 always hovered around 40 psi. On this newer one It concerned me at first seeing it drop to near 20, even in rare instances it will drop just below 20 briefly. I don't have a 'shop manual', but I did find in the Chiltons where it referenced 3 minimum pressures at 3 RPMs and I'm well above them, and from the posts I've read the lower pressures I'm seeing on the 2010 are normal.

 

Doug your comments are right along the lines I was thinking. There is a ton of info out there on these engines and thousands of products, but about 80% of what's out there is based on mods and upgrades and speed and horsepower etc., and after reading a bunch of that you can forget you're looking for info on your bone stock daily driver.

 

Jsdirt, I've actually considered a long block, for a couple of reasons, one being cost, the other being time. To go back stock updated AFM, by the time I buy a set of more expensive lifters (half being AMF lifters) and new VLOM, and probably a cam (not so comfortable tearing in assuming the cam is OK and then find out it's not and delaying the job) and all the gaskets etc., I will have probably spent near the same amount of money as I would have spent on a long block.  And if I choose to do it myself, swapping out the motor would probably be faster than doing surgery on mine. While I've done that kind of work in the past, I don't do it often, so I'd be a lot slower at a tear down and build back (especially when pulling the cam) than a swap out.

 

It just rubs me the wrong way to think a minor misfire at idle (on a non-AFM cylinder) that consistently throws a code can initiate such a major repair. And before you go there, already changed/moved/swapped/replaced plugs, wires, coil, injector, intake gasket, crank and cam position sensors, knock sensors, checked for manifold gasket exhaust leaks on cly 5, checked compression, vacuum, injector pulse with a noid light, coil output with a  spark check light, swapped complete 4-coil pack from bank 1 to bank 2 to eliminate the possibility of that little coil wiring harness on the 4-pack assembly (it has factory splices in it),  watched the cyl 5 rockers rock and pump oil with valve over off and engine running, changed the valve springs on cly 5 checking freedom of valve movement while the springs were off, anything I could think of that would cause a cylinder specific misfire at idle with a constant count you can see on a scan tool. My next move is to install a used ECM that has been programmed with my vin and flashed with the latest software hoping that maybe my ECM isn't controlling the pulse width of the injector or something. On top of the misfire, I'm down to about 8 or 9 miles per gallon with sluggish response about 70% of the time on the low end around 10-30mph range. I changed the O2 sensors, and both secondary sensors are pretty much following the primary sensors on the scan tool, and I have new y-pipe/cats I'm going to put on tomorrow. I'm looking at the VVT valve and activator with a raised eyebrow wondering if they're screwing with my timing, but not getting any codes other than P0305.

 

So Dirt I'm with you, I love the Tahoe but the longer I own this engine, the more I hate it.