I was told by a pretty experiened engine builder that i shoild almost be bleeding when i am done checking/setting lash, even on a roller tipped motor. He said “no way am i going to begin to compress a 500-600-700 + pound spring by trying to insert a feeler gauge in there. So, if the next size up goes in there , no matter how hard i try, lash is too loose. Plain and simple, he said. I’ve been doing like that ever since.

Sorry Charger, I disagree. when you start to compress a valve spring you are not compressing the full poundage. To move it .005 only takes a few pounds. Think about it full open pressure is 500 lbs. To start compressing is very slight.

Not talking full open pressure, seat pressure but that is still 200 or better, Im in agreement with the man above your post. Sure, you could drive a feeler gauge in there with a hammer, but not by your hand, at least not mine. I have also checked with the next size gauge to check my work, if it wont go, what I did was right.

My take is, if you do it the same everytime, your results will be as accurate as you can make them. Also I was told to slide the feeler gauge in at a right angle to the roller tip wheel, not parallel to the rocker. The wheel turning will make you think its looser than it really is. Ive tried it both ways and do the right angle checking.

Comp guys are the same way EO/IC is the way I have always used with some pretty big sticks

This was a story told to me several years back by a very experienced Comp Cams employee that, before he retired, worked a lot with Super Stock racers.

"Don’t use that chart. Do it like this: Look at one cylinder…rotate the motor by hand….set intake lash when exhaust rocker starts to move. Continue to rotate and set the exhaust when the intake rocker goes all the way down and is about ¾ of the way back up. You can do anything from your Chrysler to a Subaru to Ferrari that way and always be right. I was at the national event in Columbus one year with a very famous Chrysler Super Stock racer (to remain un-named) and was sitting on his trailer door shooting the breeze as he was running the valves before dinner. I watched as he did the Chrysler chart thing. When he was done, we ran through them again using the approved method I listed above. Some of the settings were .004”-.006” different. The next morning he went about .03 faster than the prediction. The ones in error made the settings too loose and not only lost performance, but if the desired settings were on the loose side anyway, for performance, the risk was there to fail a valve or lifter by making too severe."

Rocker shaft, cam, and pushrod flex. Check it your way, then check the intake again as the exhaust valve is starting to open, the intake will loosen up for the reasons I mentioned before.

That's the part that varies, the technique like Jim said. I have watched the Top Fuel guys and they generally drag the feeler gauge through sideways with both hands....the key word being "drag" rather than push in.

technique and consistency mean more to me than the actual method. I always do the exhaust cracked open/ intake closed thing. I never trust my first pass on big rollers and always go thru them twice. find a method that works for you and your parts. I've found that doing frequent lash adjusting is more related to human error/inconsistencies than parts problems, but having a good maintenance schedule can nip problems in the bud.

From what I’ve seen...... the user technique and feel have at least as much influence on the actual lash as the method being used.

I was at another shop helping another builder sort out a combo on his dyno.

We had made a few pulls and checked the lash since it seemed a bit noisy to me.
It was his build, his shop, his dyno....... so I ran the starter button and he did the adjusting.

After he was done I checked a few myself.

I like there to be a lot of drag on the feeler gauge....... he didn’t do it that way.

I could stuff a blade about .005” thicker in there than if I had done them.

This was not a cam that used a particularly large lash setting.
The card called for .020, and I could jam a .024-.025 in there.

We made a few more pulls...... still noisy.

Went thru the valves again, only I set them the way I like it.
He looked at me like I was crazy when I was jamming those blades in there.
(He liked a very light smooth drag. It took him forever to do each valve...... and get it juuuuust right)

Noticeably quieter operation after I set them....... and picked up some power too.

In that particular case, the motor didn’t really respond favorably to the smaller net duration that came from the looser lash setting.

Sometimes they do....... sometimes they don’t.

(Open pressure - closed pressure) ÷ lift = spring rate in lbs. per inch. Lbs. per inch at the valve × rocker arm ratio = spring rate on the cam, tappet, pushrod, adjuster.
Example: 800 lbs. open - 300 lbs. closed = 500 lbs., ÷ .800" lift = 625 lbs. per inch deflection rate; with a 1.7:1 rocker arm the cam etc. sees 1,062.5 lbs. per inch.
Depressing the adjuster .010" requires 10.625 lbs. of pressure.

When you mic a crank do you tighten it like a c clamp?
Doug

This is a neat discussion. Um, I always did the TDC both valves deal. I can now see checking the intake under exhaust loading, as they overlap, but no need to check the exhaust under intake load because that doesn't happen.

I think what I will do is check a couple intakes this way, chaInge my setting spec, then go back to the TDC method.

That's the way I was taught by my Dad many years ago, with a slight drag when pulling the feeler gauge through.


Tim

remwmber that all pairs of lifters for a cylinder are seperated by a lifter from the other bank.

I've always found feeler gauges I've had to be slightly undersized if you mic them up

Obviously different methods are working well for most. So IMHO it boils down to your combination of parts and preferance. You can get away with a lot when using solid lifters and low spring pressures and modest duration. Sounds to me like those pro stock cams are quite rigid and can also tolerate some deviation. I understand they run less duration that most would think.
My deal is a stock size cam core with a .510 lobe on it, which limits the base circle. So it flexes, and the ramps are 30 degrees (yep!) Long on each side of the lobe before reaching the .050 lift point. Due to the profile and ramps Jones said no more than .002 lash change in either direction. That and needing to keep an eye out for valvetrain trouble forces me to be as accurate as possible.
One question- what do the cam companies say is the proper "feel" for setting lash? I shoot for a modest drag, light enough that i can't feel anything with a .001 smaller gauge.

are you concluding that while ignoring seat pressure? sum of forces.......

I’m going to say that if you set them to say, .020”...... and I checked them..... I would say they were .002”-.004” looser than that.

I’m just looking for repeatability, more so than being absolutely exact on what the actual lash measurement is.
I like it where you basically can’t get the next larger blade in.

If it want to try a looser setting, I use a thicker blade.

I’m def not saying my way is better, but after 30 years of playing with that stuff on the dyno, that’s what my system has evolved into.

Greg that is true but it still won't help counteract any flex in the rocker shaft. On a set of paired rockers it may make little or no difference. I believe the first time I read that it was on here from Monte Smith, I then checked my rockers to see what it did. I don't recall the number but it was pretty surprising when I checked it with my Erson W2 rockers, however the Erson Rockers had a dinky shaft that was almost floppy compared to the Harland Sharp rockers I run now.

Since a hemi has separate rocker shafts for intake and exhaust would there be any push rod flex at TDC?