Setting Valve Lash

[55blacktie]

I've read as many opinions about setting Valve lash as which brand/weight of motor oil to use. There doesn't seem to be a consensus, even among professionals. The cam card for my aftermarket camshaft says that the lash should be .022, which is .003 looser than what Ford recommended (.019). I assumed that both numbers are for normal operating temperature. Here's the dilemma: some say to increase cold lash; others say to decrease cold lash. Personally, I would much prefer setting the valve lash on a cold engine. I certainly don't want to set the lash on a running engine. Setting the lash on a hot, non-running engine? Unless you're Speedy Gonzalez, there most certainly will be an engine temperature drop by the time you get to the last valve. Although I expect to get various answers (or none), should cold lash be looser or tighter than hot lash? By how much? In the meantime, I'll check to see what Gil Baumgartner said.

[Rusty57]

I have done a few experiments with the accuracy of valve lash as well as the “hot or cold” debate. By no means are the results statistically significant nor can I claim accuracy to the .0001”.

What I have observed is that neither issue is worth loosing any sleep! Using a flat feeler gauge will at best get you a range of .002”. Even when I set at a valve at a certain clearance with “moderate” drag I can always push the next larger size in and there will be slight drag on the next smaller size.

The thermal expansion rates for steel and cast iron are very similar. A big factor is how hot you really get the engine and all of the components. Thinks of all the parts that change dimension due to heat: camshaft and lobes, pushrods, rocker arms, valve stem, head, and block. Do you really think the clearance is the same after letting an engine run 1/2 hour versus a 6 hour drive?

My most experience with “hot or cold” is with overhead valve inline 6 cylinder engines with cast iron block and head. I set the valves cold and then drove the car for about 20 minutes. When I checked the clearance hot there was not enough difference to justify reseting the valves. I did the cold setting and checked the hot setting with the engine not running. It took less than 5 minutes to check the hot settings.

My experience is that I can’t get as consistent a setting with the engine running. So my preference is to set valves on a cold non-running engine.

I would recommend that you use your cam manufacturer’s recommended setting. I expect that the cam has more lift and duration so the lobe profile is more aggressive. The larger clearance ensures that the valve will close. Remember that when the engine is running you are dealing with the dynamics of motion of the valve and rocker arms as well as friction and inertia in all the moving components.

[ward 57]

According to the shop manual a preliminary cold adjustment should be 0.020. Run the engine until fully warm then check to 0.019.
Thanks to the CTCI Thunderbird circle chapter and their tech tips here is a method that worked great for me.

[55blacktie]

I just watched Tim McMaster's (Y-Block Guy) Valve Lash Adjustment Video, Part 1. Although the recommended lash for a stock Y-block in good condition is .019, Tim said that he likes to set them at .015 to quiet them down. He uses .020 for an engine that is equipped with an aftermarket cam.

I'll probably use the camshaft manufacturer's recommendation of .022. On a cast-iron block & head engine, I don't think the difference in hot & cold lash should be more than .001-.002.

Thanks!

[ward 57]

Well they should know their own product. You can always tighten up a bit if too noisy after everything is broken in.

[ICON 1956]

I have done a few experiments with the accuracy of valve lash as well as the “hot or cold” debate. By no means are the results statistically significant nor can I claim accuracy to the .0001”.

What I have observed is that neither issue is worth loosing any sleep! Using a flat feeler gauge will at best get you a range of .002”. Even when I set at a valve at a certain clearance with “moderate” drag I can always push the next larger size in and there will be slight drag on the next smaller size.

The thermal expansion rates for steel and cast iron are very similar. A big factor is how hot you really get the engine and all of the components. Thinks of all the parts that change dimension due to heat: camshaft and lobes, pushrods, rocker arms, valve stem, head, and block. Do you really think the clearance is the same after letting an engine run 1/2 hour versus a 6 hour drive?

My most experience with “hot or cold” is with overhead valve inline 6 cylinder engines with cast iron block and head. I set the valves cold and then drove the car for about 20 minutes. When I checked the clearance hot there was not enough difference to justify reseting the valves. I did the cold setting and checked the hot setting with the engine not running. It took less than 5 minutes to check the hot settings.

My experience is that I can’t get as consistent a setting with the engine running. So my preference is to set valves on a cold non-running engine.

I would recommend that you use your cam manufacturer’s recommended setting. I expect that the cam has more lift and duration so the lobe profile is more aggressive. The larger clearance ensures that the valve will close. Remember that when the engine is running you are dealing with the dynamics of motion of the valve and rocker arms as well as friction and inertia in all the moving components.

I totally agree with Rusty 57. When adjusting mine I follow his exact procedure. I have the P&G Valve Gapper. It's a great tool to help adjust precisely. If you can't find the P&G You can also use this Remote Starter Switch and feeler gap gauges. This is used by quick start and stop increments.

[DynoDan’55]

I see you have the camera switch. Have you tried setting lash while running? My unit was long stored assembled (with the spring compressed), so the gauge bounces too much now for an accurate reading. I usually set cold and add a thousandth for the exhausts.

[ICON 1956]

I tried using the camera switch too much bounce. I also used the remote starter switch along with the feeler gauge. I found that using P&G technique gives me a better reading without the cable.
https://www.google.com/search?q=p%26g+v ... Z2V4g,st:0

[MarkR]

To answer your question….. Dennis Hackenberger in Anchorage is a lifelong Y block guy easily on par with McMasters, Eaton and Mummert. Owned a drag racing machine shop and still builds hot rods from scratch in retirement in that shop. Just ask Ernie Phillips, the Tbird drag racer from Tyler Tx. Dennis rebuilt his worn out 312 in 3 days when Ernie broke a wrist pin driving his 57 bird to see me in Anchorage from Tyler. Ok, enough about Dennis.

He sets a stock Y block (rare for him) 17 cold 19 hot. I can certainly understand Tim going 15 to quiet things down. With the great set up you’re building I know you want to get right. I don’t think 17C or 19H are your numbers.

[Rusty57]

Great comments and definitely on subject!

Note that my comments were relevant to an overhead valve engine with pushrods and rocker arms and a cast iron block and head. It is a different discussion if any of those parts are aluminum. An overhead cam engine adds more intrigue to the discussion.

There will be many opinions about which clearance is appropriate. Remember that the real reason that there is any clearance is to ensure that the valve closes in a solid lifter engine. Theoretically no clearance is needed but we all know that is an unrealistic solution. As a side note I find it interesting that you set no clearance in a hydraulic lifter engine. There is enough force in the valve spring to move the plunger in the lifter and make sure the valve closes.

With respect to the actual setting I can understand someone wanting to reduce the clearance. The engine responds as though it has a “bigger” cam. Less clearance means that the valve opens more and is open longer. The result typically will be a little more top end power but a loss at the lower end. If you watch Engine Masters you will see episodes where they test various clearances. Their dyno results do confirm those results. The actual numbers are pretty small. For example they might record a less than 1% horsepower gain at 6000 or 7000 rpm in a wide open throttle single pull dyno run. I’m pretty sure not much of that scenario translates to us and the way we drive these classic TBirds. I also know that a 1% power gain is not worth a burned valve to me.

We all know the consequences of too much clearance. In addition to a noisy engine there is more shock load on the valve train components.

This thread reminds me that I need to get back on my “to-do” list for our ‘57. I got sidetracked with other projects and did almost nothing to it over the winter. One of my tasks is to polish valve covers and check the valve clearance while I have them off. I also want to check oil delivery to the rocker arms. The valve train will be noisier if there is not enough oil to the upper end.

[55blacktie]

There have been recommendations for more lash on the exhaust side because it runs hotter, but this seems to be an exception. In just about all cases, the lash is the same for both intake and exhaust. I don't think .001-.002 will make a significant difference, but .004 (or more) might. I prefer not to have them too tight or too loose, but finding the sweet spot might require some trial and error.

Thanks, again, for your comments.

[Rusty57]

55blacktie,

I agree with your assessment that .001 - .002" is not a concern but variations up in the .005" range might be.

I did see one video regarding Comp Cams that really caught my attention. The recommended clearance for both valves was .030" with a special high lift cam. Their "guru" felt that was too much so set them at 024" and did a baseline dyno run. He then set the clearance down to .012" and did another dyno run. Peak horsepower was up about 6 at 5900 rpm (367 vs 361) but down about 4 hp at 3500 rpm.

That is a big lash change that I would not be comfortable with long term on a street engine.

I also have found it interesting that the Ford recommendation for the Y-blocks is the same setting for intake and exhaust. I do not ever remember setting both clearances the same for any other engine. My understanding is that the larger cold clearance on the exhaust was to accommodate the greater localized thermal expansion due to the greater heat on the exhaust side. I have seen a few older shop manuals for other engines that would specify a greater cold setting for the exhaust with the recommendation to check it again when hot to confirm that the clearance was the same as the intake.

I think your plan to do a bit of trial and error is a good approach. I would not hesitate to start with the stock setting for the intake (.019") and the cam manufacturer's recommended setting on the exhaust (022"). I think that .022" on the intake will be pretty noisy.

Let us know what you learn.

[55blacktie]

Ted Eaton (eatonbalancing.com) posted on y-blocksforever.com this morning. He said he uses the same lash for intake & exhaust on the initial startup, but then opens the exhaust side .001-.002.

I don't want noisy, but not too tight either.

[Jimntempe]

We just did a "tech day" here and a long-time mechanic showed how he sets the valves. He did it with the engine running. When he was done, I checked the clearance and it was right on the spec, 0.019. The interesting part relative to this thread is that at the start he found that most of the valves were very close to zero clearance. They had been set by whoever rebuilt the engine 30,000 miles prior. Whether they were at near zero all that time or they changed over time no one knows but if anything, I would expect the clearance to increase with mileage. So my presumption is the engine has run 30K with near zero clearance. It sounded good and the owner say it always runs good. No evidence of any burned valves, no odd noises, ran very quiet. What I noticed while he was making the lash adjustments was when he loosened the adjustment too much (I would guess by perhaps 0.003 too much) I could start to hear the valve clatter. When he tightened it back into spec it quieted back down.

Based on this engine seemingly getting along fine with any lash between near zero and the spec of 0.019 I would not be too worried if I was anywhere between 0.015 and 0.019 when I set them. If I had a slight clatter at 0.019 I'd also not worry about giving it another 1/16 turn if that quieted it down.
I think someone here posted the Walt Knuckles method (engine off) of going to zero lash and then backing the adjustment nut off 1/4 turn to get it to 0.019 . I watched the mechanic at the tech day and it looked like the difference between when he started with them at near zero to when he got done, he was loosening them right around the 1/4 turn.

[55blacktie]

Apparently, there's only .001-.002 expansion on iron block & head engines. Some lash is necessary to ensure that the valves completely close.

According to Ted Eaton, some aftermarket cams have "aggressive'' profiles; those cams tend to perform better at lower rpm without losing anything at the upper rpm range. However, they can be harder on the valve train , depending upon how aggressive they are, and can be noisy. The Comp Cams Xtreme Energy cams are known to be aggressive. Ted said that camshafts that have a closer advertised duration and duration @ .050 tend to be aggressive and noisy. A tighter lash is usually recommended by the manufacturers to quiet them down. A good example would be a cam with an advertised duration of 254 but 228 @ .050. An advertised duration of 254 is considered small; 228 @ .050 isn't.