Hydraulic roller lifters tick only under crankcase vacuum

[BILL-C]

We recently built a mild street/roadrace 331 cid sb Ford engine with drysump oil system. For the first time we used a retrofit hydraulic roller cam and howards retro hydraulic roller lifters.While running on dyno we noticed the lifters were very "ticky" while running with 10" crankcase vacuum but would instantly quiet down to acceptable level the instant the valve cover breather cap was removed . It would literally take 2 seconds to go from very ticky to ok. Has anyone else come across this issue? I really want to run a sealed crankcase. Having a breather on valve cover will cause the drysump tank to be extremely foamy and potentially messy.

[PRH]

Be interesting to see if the manifold vacuum at idle changes with the clacking vs not clacking(breather open).

[BillK]

Are you fairly certain that it is the lifters making the noise ? What kind of valve covers and how much clearance to the valve train ? I am thinking way outside of the box that the valve covers are flexing enough under vacuum to hit the rocker arms if the clearance is not much to begin with ?

I just cant imagine any reason for crankcase vacuum to affect lifters. Even if the oil was getting aerated for some reason I would think it would take longer than 2 seconds to calm down.

Is the oil pressure the same with the cap on or off ?

[BOOT]

WAG did you check the lifter to bore clearance?

[BILL-C]

Are you fairly certain that it is the lifters making the noise ? What kind of valve covers and how much clearance to the valve train ? I am thinking way outside of the box that the valve covers are flexing enough under vacuum to hit the rocker arms if the clearance is not much to begin with ?

I just cant imagine any reason for crankcase vacuum to affect lifters. Even if the oil was getting aerated for some reason I would think it would take longer than 2 seconds to calm down.

Is the oil pressure the same with the cap on or off ?

Plenty of room on the valve covers. They are custom built tall cast covers with lexan windows. Oil pressure is 1 psi more with cap off. We can visually see that the oil flow out of rockers does not change with cap on or off. No visual oil aeration inside heads or tank.

[BILL-C]

WAG did you check the lifter to bore clearance?

Lifter bore clearance measured .0016-.0017 with sunnen bore gauge.

[PRH]

If you’re fairly certain the noise is from the lifters themselves, then it would mean that vacuum is somehow affecting the filling of the pressure chamber at the bottom of the lifter.
If the manifold vacuum was higher while the lifters were clacking, it would be somewhat confirmation that the noise is the plungers collapsing to some degree, acting like a variable duration lifter at low speed and reducing the effective duration.

[PackardV8]

We recently built a mild street/roadrace 331 cid sb Ford engine with drysump oil system. For the first time we used a retrofit hydraulic roller cam and howards retro hydraulic roller lifters. While running on dyno we noticed the lifters were very "ticky" while running with 10" crankcase vacuum

Where is the makeup air supply limiting valve? Would be interesting to put a temporary adjustable valve and gradually close it to determine at what vacuum the clicking begins.

but would instantly quiet down to acceptable level the instant the valve cover breather cap was removed. It would literally take 2 seconds to go from very ticky to ok. Oil pressure is 1 psi more with cap off. Has anyone else come across this issue?

So oil pressure to the lifters remains essentially the same.

Lifter bore clearance measured .0016-.0017 with sunnen bore gauge.

Does that seem loose to anyone else? However, since it's fed dry sump, no matter how much is escaping, there should be plenty of pressure; speaking of which, what does the gauge show and from where is it tapped?

[In-Tech]

I'm betting it's the valving in the lifters, yes the clearance to bore is a bit high but I doubt that is the problem. Nothing to do with it being a ford but I just fought this problem on a 347 and lifter replacement was the cure, what sucked(no pun) was I had to do multiple replacements one at a time till problem was solved. Mine was OE type and not tie bar like yours. I did find that the little trick of trans fluid to clean the valving helped as well as higher viscosity did too.

[mag2555]

If the lifter bore clearance is on the loose side then once the oil gets hot enough my bet is that the vacuum is sucking the oil film out from between the lifter bore and the lifter OD.
Proving this might be done by lowering the vacuum level in small amounts to see what hg it takes to make it noiseless.

[allencr267]

All 8 & similar & constant sound/s?
When replacing the cap, do they all do their noise thing at once or progressively, starting at the end of gallery?
good luck

[V12MECH]

What type of oil are you using? Some type of break-in formula, or a straight synthetic race oil? If a 10-40 wt. Maybe trying 5-30 , or vise versa , a different brand may have an additive formula that may help as this would be a quick thing to cross off your list.

[Kevin Johnson]

WAG

I am assuming the pump stages are driven by some manner of drive belt. When you place them under greater load (drawing partial vacuum) the oil intake at the inlet points around the engine is irregularly pulsed at greater amplitude.

This would create a larger torsional vibration which would then be transmitted through the timing chain to the camshaft and the roller lifters. I am further assuming that they do not tolerate this well.

A possible way to reject this hypothesis is by examining the spark scatter on a scope as it should also be affected by virtue of the distributor gear drive.

Good luck.

[BILL-C]

The tightest I have ever seen a lifter bore clearance in an iron block without bronze bushings without seizing is .0013. Ive seen plenty of lifters stick in bore at .0014 clearance in race applications. Most engines I have measured are at .0016 to .0018 from factory. Lifter bore clearance is not loose. Oil is Shaeffer conventional 30 wt. The change from ticky to quiet happens so quickly that by the time the suck sound from popping off valve cover cap stops ,the valve train has gone totally quiet. Dry sump pump is belt driven off of a conventional drive mandrel bolted to damper. Camshaft is driven by a good quality double roller chain with .003 endplay and Torrington roller bearing thrust washer on upper gear and a roller thrust plate. Very traditional and proven parts and clearances here. Block is a new Ford motorsports boss 302 block. One more odd thing to throw out there is that the new comp cam had a base circle of 1.060 .This is more like what you would see on a large solid roller. Most mild hydraulic rollers have closer to 1.3 ish base circle. Initially we were going to use oe style lifters, but with small base circle the lifter flats were starting to come out of factory dogbones on base, so we had to go to link bar style lifters. No, the oil bands are not getting exposed. Comp says they are totally out of the larger base circle cores and don't know when they will be available, so we have to make this work.

[Kevin Johnson]

... Dry sump pump is belt driven off of a conventional drive mandrel bolted to damper. Camshaft is driven by a good quality double roller chain with .003 endplay and Torrington roller bearing thrust washer on upper gear and a roller thrust plate. Very traditional and proven parts and clearances here. ,,,

... For the first time we used a retrofit hydraulic roller cam and howards retro hydraulic roller lifters. ...

There are all sorts of dampers and they are tuned for different engine combinations and rpm. When one presents a theory it is good form to suggest an empirical way to reject it versus a gedanken or thought experiment. Spark scatter that closely associates with the release of vacuum would be interesting. Try an adjustable valve and see if the relationship is present.