less oil to rockers than I thinks ideal

[grumpyvette]

Good morning, Grumpy. I've got a question about a 1995 LT1 engine. I've built several (50+) engines over the years but I'm having a problem that I can't seem to figure out. Two years ago I built a killer LT1 for my Impala SS. When I built, on the initial startup, even after priming it, I noticed that the oil took a long time to reach the rockers. I drove to St. Louis (500 mi) and the car was a little noisy but not too bad. It's been getting noisier all the time and I still have very little oil to the rockers.

The rockers are the Comp Pro Magnums steel ones. I made a mistake and used a Melling high volume/high pressure pump. When I start the car I have 80 PSI and when it's hot I have 45 at idle. I'm using stock LS7 lifters. I had to change them because of a tranny problem. I screwed up on the shift points while programming and over revved in second. One of the original LS7 lifters came apart. No engine damage luckily. I also have hardened pushrods /guideplates, and I've tried 2 different sets of springs. Beehives and some that are supposed to work with my cam.

I guess my question would be what could cause the slow oil flow to the rockers. I even went so far as to change out the rockers with a set of shaft mounts that I had lying around because I thought the bearings may have shit the bed because of low oil flow. It was still noisy.

I didn't drill and tap the oil galley plugs on the front of the block and was wondering if one of those popped out would I still have the oil pressure I do now? I've never seen this before and am ready to pull the engine but I thought Id ask if you have any ideas before I do.

My cam has pretty steep ramp rates and around .580 lift and duration in the 242 range. I'm running a Dragonslayer crank, Oliver rods and Mahle pistons. Lloyd Elliot did the porting. I have 11:1 compression and don't get any knock count with my current tune. I'm just lost and don't get it. Never had this problem before.

Thanks

obviously I can,t be sure without some testing but as you state it sounds like theres limited oil getting to the rockers and you certainly have the oil pressure and flow rates so that indicates a blockage or the lifter adjustments too tight,yes Ive seen engines where the staked in front steel, pressed in plugs in the lifter gallery plugs blew out, but that normally results in a significant drop in oil pressure, so I don,t think thats the cause, here as a first test ID strongly suggest doing an oil change and use 10w30 oil and a wix or pureolator oil filter, then adjusting the rockers at idle just the same way you adjust flat tappet hydraulic lifters IE back off the rocker nut till it clicks, then tighten it just to the point the click stops then add an additional 1/4 turn pre-load

if that cures it you know its mostly having the pre-load to tight on the rocker adjustment which is VERY VERY COMMON on hydraulic roller lifters

now you can also have a valve train geometry issue or condition where the rocker geometry doesn,t allow the holes in the lifter, rocker and push rod to fully line up and that can limit oil flow to the rocker
OR the cam bearings may be installed incorrectly

 

[Indycars]

Grumpy said:
obviously I can,t be sure without some testing but as you state it sounds like theres limited oil getting to the rockers
and you certainly have the oil pressure and flow rates so that indicates a blockage or the lifter adjustments too tight,
as a first test ID strongly suggest doing an oil change and use 10w30 oil and a wix or pureolator oil filter, then adjusting
the rockers at idle just the same way you adjust flat tappet hydraulic lifters IE back off the rocker nut till it clicks, then
tighten it just to the point the click stops then add an additional 1/4 turn pre-load.

How does the pre-load effect the oil flow volume ??? Maybe at some point it starts to cover up the oil
passage in the block ?

Is it a linear relationship or does it only restrict at some point, say from a 1/2 turn on ?

 

[grumpyvette]

BUT GRUMPYVETTE? HOW WILL ADJUSTING THE LIFTERS EFFECT THE OIL FLOW TO THE ROCKERS?

your far from alone , with that question,most guys don,t realize that the cam lobe lifting the lifter compresses the oil under the lifters push rod seat and that lifter push rod seat moving down into the lifters body forces oil up the push rod as the lobe lifts the lifter, naturally the distance the seat can move from its fully extended location it reaches on the cams base circle when oil pressure fills it to the lowest point the push rod seat reaches as its compressed is reduced if the pre-load has already moved the lifter seat part way down into the lifter body, the threads on the rocker stud control the distance the lifter push rod seat is pre loaded , on most lifters theres about a .060 total potential distance the lifter seat moves, as the cam lobe takes up valve train slack on the lobes clearance ramps.the greater the preload the lower the oil volume thats forced up the push rod as the lifters seat is compressed, a bit of math will show you you could reduce the oil flow to the rockers by over 50% with a significant difference in the lifter preload
KEEP IN MIND if theres a valve train geometry issue the hole in the push rod on either end may not seal correctly to the rocker oil feed hole or lifter seat and if that happens youll get little or no oil flow up thru the rocker, this normally occurs if the push rods bind on the guide plates or the push rod length is wrong

one little known bit of engine trivia, the thread pitch on the rocker studs is a known value, and therefore you can use that info to get a close approximate lash clearance.
THAT INFO IS GOOD TO KNOW WITH ADJUSTING LIFTERS

ok, HOW you ask?
if the rocker studs have a common NF thread theres a pitch or number of threads per inch, now obviously youll need to carefully verify what the thread pitch, and the clearances are with a feeler gauge on your engine, while its not running and take into account the rocker ratio but lets assume
3/8" 24 Threads Per Inch
7/16" 20 Threads Per Inch
Threads per Inch Distance per 1/4 of a Full Turn
24 .0104”
28 .0089”
32 .0078”
36 .0068”
40 .0063”

 

[Indycars]

Grumpy Said:

that the cam lobe lifting the lifter compresses the oil under the lifters push rod seat and that lifter push rod seat
moving down into the lifters body forces oil up the push rod as the lobe lifts the lifter, naturally the distance the
seat can move from its fully extended location it reaches on the cams base circle when oil pressure fills it to the
lowest point the push rod seat reaches as its compressed is reduced if the pre-load has already moved the lifter
seat part way down into the lifter body


Ok, I still don't understand, no matter how many times I read your statements or how much I Google it. From the
statement above, the valve would NOT lift as high as it should because the lifter is compressing since some oil is
flowing out of the lifter and up thru the pushrod.

So where am I going wrong ???

 

[grumpyvette]

I,M not sure I under stand your question, the threads concern is with lack of significant oil flow rates at the rockers not valve lift, now your correct that some potential early valve lift is lost due to the lifter seat receding, into the lifter body several thousands of an inch, as the lobes clearance ramp takes up the valve train slack and forces the oil out from under the lifters push rod seat. as the oil under its forced up the push rod to the rocker but the receding lifter seat distance is both minimal and partly compensated for by inertia as the lifter runs over the peak of the lobe where its mass momentarily trys to resist the valve spring,but all the oils forced out of the area under the lifter seat on the cams early lobe ramp,as the lifters compressed, thus holding the valve open longer than it would if it exactly followed the cam lobe with out that inertia, or preload ,plus you might want to consider that the oil under the lifter seat actually lifts the valve higher than its supposed to go by design as the lobe takes up slack in the valve train,as its there mostly to take up any slack in the valve train and cushion the impacts between components to reduce noise, and provide a self compensating adjustment in the valve train for heat expansion/contraction, as the components change dimensions under the raped thermal changes a running engine endures during the start up process

 

[Indycars]

My questions all started with the statement; "the greater the preload the lower the oil volume that's forced up the push rod as the lifters seat is compressed,"

Assuming Zero pre-load. If the lifter is compressed when lifting the valve, then the valve must be opening less. You said, "on most lifters theres about a .060 total potential distance the lifter seat moves," If the lifter can compress up to 0.060", then (1.5 x 0.060=0.090) 0.090" at the valve sounds like a VERY SIGNIFICANT loss in valve lift.

Sorry if I'm not making any sense with my questions ! Just a second I will be right back......I see a brick wall I can bang my head on, that should help. :?

 

[grumpyvette]

I think the problem is one of perception, on what your dealing with, no mater where the lifter seat starts out at the pre-load you've set (1/4 turn-3/4 turn) the lifter seat is bottomed out in the lifter body well before the time the cam lobe has reached peak lift, as by that point all the oil under the push rod seats been forced up the push-rod, or bled out on the lifters internal clearances, in fact almost all the oils forced out as the cam lobes clearance lobes take up the valve train slack.
lets assume were dealing with a cam that has a lift of .540, the pre-load has a minimal effect on the very early valve lift as the slack in the valve train is compressed but the effective valve timing after the cam lobes clearance ramps have taken up that slack is very minor or non-existent, especially with the fast bleed lifter designs like the crane and rhoads design hydraulics.
changing the lifter pre-load you've set (1/4 turn-3/4 turn) has zero effect on max lift, and minimal effect on valve timing past the point the valves off its seat by about .100 simply because the increased inertial loads and valve spring pressures are forcing the few trapped CC's of oil out