More lifter preload less vacuum and compression. What is happening?

[Guest joe28704]

Engine: 1952 Buick Super 263 W/ Dynaflow (fresh rebuild).

VL1 Hydraulic lifters installed in a 1952 Buick 263 Super w/ Dynaflow are displaying the following symptoms:

At the lowest RPM I can get the engine to idle at: (around 800rpm)

LIFTER PRELOAD:

2 turns(per “book”)………….6-7 In. Hg Vacuum……….80 psi compression (Min should be 120psi)

1 turn……………………………….10-11In.Hg Vacuum

Zero lash…………………………..14In.Hg Vacuum

.008” lash………………………….17In.Hg Vacuum

.015 Lash……………………………………………………………….125 psi compression. (starter turnover)

 

Vacuum increases towards normal as preload is decreased and good vacuum is achieved with .oo8” lash! I can't figure this out!

 

Any thoughts on what the source of this valve issue is coming from? Lifters pumping up due to slow bleed rate?

 

Data would show  no Vacuum leaks and cylinder compression is in normal range.

 

Lifter preload (set at TDC, on base circle of cam, timing is confirmed good)

 

Allowed time to let valve springs bleed down lifters and return to closed position before going to next valve.

 

To rule out oil viscosity issue on lifters had 15w-20 Rottella Oil initially.  Changed to 5w-20 synthetic, maybe increased vacuum by 1 in.Hg. if that much, nothing dramatic happened with new oil.

 

Timing is confirmed by method set forth in 1952 Buick Shop Manual (Par. 2-17 placing dial indicator on exhaust valve spring cap,

Compressing lifter with ball stud  till solid then rotating engine until spring cap rises .145”, “if timing mark is visible thru timing hole cover then the valve and camshaft timing is correct.” Also when UDC (TDC)  mark on flywheel is on pointer, rotor is pointing to #1 on distributor cap, piston is truly on TDC and both valves closed

 

Any help on describing this phenomenon will be greatly appreciated. Is it valve timing? Lifters not functioning properly(bleed down issue)?

[Beltfed]

Not an engine rebuilder but have done this job many times.  My limited experience is with mostly chevy engines with hydraulic lifters.  With that said, our procedure is 1/4 turn of nut after zero lash, not two turns.  Sounds like your hanging valves open killing your vacuum.  If you are on the compression stroke with both valves closed on the piston number your adjusting, then timing should have nothing to do with valve lash.  Not being a 'smarties pants', but once you establish TDC on #1 you're not adjust all the valves are you?

[Guest joe28704]

Beltfed,

Thanks for the input, no I set #1cyl on TDC then do valves 1,2,4,7,8,11,12,14 then set #8cyl on TDC and do valves 3,5,6,9,10,13,15,16 saves a lot of time.

After reading more of the dynamics of hydraulic lifter operation I believe my problem lies in what is called "lift loss" ; a "shortening " of the lifter due to check ball travel before it checks off flow and lifter begins to open valve. "lift loss" is critical for proper lifter function and valve seating. If check ball travel is too low (low or no "lift loss") this will cause volume of oil in the lower chamber  to "pump up" and EXPAND the lifter(at any RPM) thereby preventing valves from seating. This is what I believe I am experiencing.

The lifters are new supplied by Kanter, I am waiting for their tech people to get back to me so I can share this with them, I believe I may have a case of poorly engineered or calibrated lifters, if I can't document/convince them of this them I'm stuck with my problem. As you can see I have low vacuum all the way 'till zero lash (lifter at full length).

Well see if they concur, Ideally, I think I'm due a different set of lifters to test as I cant think of any other reason that can cause preload setting to so DRASTICALLY effect vacuum/compression (valve seating).

[misterc9]

Will it run all right if you set the valves with lash like solid lifters? Are you sure they really gave you hydraulic lifters ?

[Rusty_OToole]

Are you sure you have the right camshaft? Is it possible you have a solid lifter cam with hydraulic lifters? A hydraulic cam should be very noisy with .008 clearance. If not, you may have the wrong cam, or the wrong lifters.

 

Personally I would rather have the solid lifters.

[Aaron65]

When I first got my '53, I adjusted them incorrectly cold.  The "feel" of zero lash seems different on a straight-8 than a typical V8.  This is a little tough to explain, but at TDC, when the rocker arm is loose (not yet at zero lash), the tip of the rocker (on mine) won't even be touching the valve.  When I hit zero lash, there is noticeably more resistance (because it's trying to open the valve).  That's zero lash.  Go two turns down from there.

 

Maybe you're already doing it that way, but I was cranking mine down way too far before I figured out the feel on that car, and honestly, none of this explains why it will run well with measurable (when running?) hot lash dialed in.

Edited January 3, 2017 by Aaron65 (see edit history)

[c49er]

Are your lifters NOS GM or a quality old stock american made brand?

Or are they "White Box" off shore maybe works or maybe not.

A lot of the offshore parts belong in the recycle bin.

I don't trust any of it anymore...way too many problems with it.

[JACK M]

Two turns past zero seems to be a lot.

However may not be excessive, I am with those that think there may be a mismatch of cam and lifters.

You might find that these need to break in for awhile.

Running a hydraulic lifter at exactly zero lash is totally acceptable in a race engine if they are adjusted every race.

I think if it were me I would go, say a quarter turn, then drive it a bit then start over.

Running at .008 would be a mistake if these lifters are indeed hydraulic.

In hopes that the supplier will have some answers.

 

[JACK M]

Another thought,

Turn the engine to each piston TDC to do the adjustments.

[Rusty_OToole]

I still say .008 clearance on a hydraulic cam should be super noisy because they have no clearance ramps. If the engine runs well and doesn't scare the hell out of you with the clatter you must have a solid lifter cam.

[F&J]

1 hour ago, Rusty_OToole said:

I still say .008 clearance on a hydraulic cam should be super noisy because they have no clearance ramps

Actually, there is a ramp on hyd cams also.  The ramp is very short in height, compared to a solid cam.  On a solid cam, the ramp is sized in height to match the factory valve setting clearances.  The ramp gently takes up the slack between the rocker and valve, before the valve gets shoved quickly.

 

You can tell with a dial indicator, if it is solid or hyd.  You are looking for "rate of climb change" as the valve gets close to start of opening.  Sounds like rocket science to some, but if you test the same lobe quite a few times and can rotate the cam slow/steady, you will see a spot on the lobe, by looking at the dial indicator needle, where the needle hits a spot where the rate of climb increases very noticeably.

 

if the ramp height, is closer to .002-.004, compared to perhaps .010 more or less, the taller one is a solid cam

 

ramp is measured from base circle, needle set to zero, to the exact spot where the rate of rise really jumps up.

 

.

[NTX5467]

Whatever the stock adjustment setting for the hydraulic lifter might be, that adjustment is supposed to be at the center of the lifter's piston travel inside of its lifter mechanism.  There should also be a spring inside of the lifter holding the piston at "full travel", which is compressed as the valve preload is added.

 

The old Chevy hydraulic lifter adjustment spec was about 1.5 turns from zero preload.  Many "performance"  people would run them at less preload for greater rpm capabilities.

 

The base adjustment should be done on an engine at "operating temperature", unlike solid lifters which have "hot" and "cold" specification clearance settings, usually.

 

On a 4-cyle engine, the TDC mark will happen at real TDC and also at TDC 180 degrees later.  Best to actually look at the rocker arms and determine if they are both at the "valve closed" position.  There's also the time-honored way of manually turning the crankshaft and getting the cylinder's intake valve at full-open, then setting the exhaust valve.  When the exhaust valve is full open, setting the intake valve.  Working from one cylinder to the other until all are done.

 

The OTHER messier method is with the engine running.  Starting at the front, loosen the valve until noise is heard, then slowly "adjust" until noise decreases/stops, then about 1/2 turn more preload in 1/4 turn segments.  As the lifter adjusts, that cylinder might miss and then smooth out again.  Move to the next rocker arm.  This can be MESSY as oil is slinging around with the valve cover off the engine.  There might be some "oil stoppers" for the rocker arms, but they might not completely keep things clean.

 

The whole idea of hydraulic "lash adjusters" is to maintain zero clearance between valve system components for quieter and consistently smooooooth operation.  Personally, I like the least preload on the valve train, myself.  For my small block Chevy engines, that usually means no more than 1/2 turn preload, total, with 1/4 being more desired.  The engine just seems to work better at those lower preload levels.

 

As stated, the difference In a solid lifter camshaft and the hydraulic camshaft is the "clearance ramps" on the leading edge of the cam lobe's shape.  That longer ramp is there to help cushion the clearance in the solid lifter valve train.  With the hydraulic camshaft, no real need for those ramps.  SAE has specs of how to measure valve open duration and lift, too.  The aftermarket uses the .050" lift duration specs for the same reason.  Lifters need to match the camshaft design.

 

Another thing which might be happening, possibly, is that the head has had too many valve jobs or poorly-done valve jobs.  End result, the valve seat is "sunk" too far into the port.  This can affect ultimate valve adjustment as the valve stem is too far our of the valve guide.  Valves with stems which are too long would have the same issue!

 

Possibly, the best way to do hydraulic valve adjustment is with the engine running.  Messy that it is, the lifters will be getting full lube pressure to keep them pumped-up.  Get them loose enough to make noise, then adjust them for "no noise" all down the line.  Then go back and add another 1/4 preload to each rocker arm.  See how that goes.  IF things are quiet on a cold engine start-up, leave it there.  IF there might be a little noise, then add another 1/4 turn preload and be done with it. 

 

Sometimes, valve guide wear can cause what appears to be "lifter noise".  In any event, the least preload needed to keep things quiet is probably the best--period.

 

Please advise of your progress.

NTX5467