Old-timers secrets for setting valve lash
Discussion
Hi,
Last night I re-set the valve lash for the second time in a month because I'm an idiot and used the wrong dimension the first time... This is my first engine with solid tappets (a Ford 351C) and I'm still trying to figure out a foolproof procedure for setting the lash the first time.
This is a more time-consuming process than I think it ought to be because I can't consistently set the lash to where I would like it to be - I have to use a sort of trial-and-error. Tighten down the roller rocker and check lash... Too tight? Loosen it up. Too loose? Tighten it up. Measure again. Loosen. Measure. Tighten. Measure. Tighten again. And so forth.
Is there anyone out there who has been living with a solid-tappet engine for years and has found a method for setting lash in 5 minutes that allows you to set the lash you want instead of measuring the lash you have acheived to see if it is in spec?
TIA
Last night I re-set the valve lash for the second time in a month because I'm an idiot and used the wrong dimension the first time... This is my first engine with solid tappets (a Ford 351C) and I'm still trying to figure out a foolproof procedure for setting the lash the first time.
This is a more time-consuming process than I think it ought to be because I can't consistently set the lash to where I would like it to be - I have to use a sort of trial-and-error. Tighten down the roller rocker and check lash... Too tight? Loosen it up. Too loose? Tighten it up. Measure again. Loosen. Measure. Tighten. Measure. Tighten again. And so forth.
Is there anyone out there who has been living with a solid-tappet engine for years and has found a method for setting lash in 5 minutes that allows you to set the lash you want instead of measuring the lash you have acheived to see if it is in spec?
TIA
I think that the setup is the same one you are familiar with and describe. There is an allen set screw in the middle that tightens down the roller rocker, and the lash is set by the outer nut.
I set the desired lash with the out nut, then, while holding this nut in place, tighten down the set screw in the middle. The problem is that I don't think I can tighten the set screw sufficiently just using an Allen wrench, as I can tighten the outer nut somewhat. So I back off slightly the allen nut, then tighten down the outer nut (which tightens both nuts) hoping to return the allen nut to its previous location. This is somewhat of a trial and error process, and I end up repeating it a half dozen times until I finally get the lash I am looking for.
If I had a diagram, this would be so much easier to explain, so thanks for your patience.
I set the desired lash with the out nut, then, while holding this nut in place, tighten down the set screw in the middle. The problem is that I don't think I can tighten the set screw sufficiently just using an Allen wrench, as I can tighten the outer nut somewhat. So I back off slightly the allen nut, then tighten down the outer nut (which tightens both nuts) hoping to return the allen nut to its previous location. This is somewhat of a trial and error process, and I end up repeating it a half dozen times until I finally get the lash I am looking for.
If I had a diagram, this would be so much easier to explain, so thanks for your patience.
Thanks for the suggestions... For posterity, I think I found an easier method when I set the other half last night.
I determined how much clearance is lost when I snug everything down by tightening the outer nut (0.006"), add this to my desired valve lash, and set them by hand to this. Well, I tightened the set screw with the Allen wrench to this spec. Tightening the outer nut by wrench brought them right to final spec, every time. All 8 valves, exact lash, first time. Much less frustrating than the trial-and-error method, and a lot quicker.
Once again, my engine makes that beautiful "clack clack clack" that sounds like a 5.8 liter sewing machine and I'm a happy camper.
I determined how much clearance is lost when I snug everything down by tightening the outer nut (0.006"), add this to my desired valve lash, and set them by hand to this. Well, I tightened the set screw with the Allen wrench to this spec. Tightening the outer nut by wrench brought them right to final spec, every time. All 8 valves, exact lash, first time. Much less frustrating than the trial-and-error method, and a lot quicker.
Once again, my engine makes that beautiful "clack clack clack" that sounds like a 5.8 liter sewing machine and I'm a happy camper.
Mr2Mike said:
I think that the setup is the same one you are familiar with and describe. There is an allen set screw in the middle that tightens down the roller rocker, and the lash is set by the outer nut.
This dosen's sound like any setup I have ever seen. Generaly the screw is used to set the clearance(lash), and the outer nut is used to lock the screw in place. If this is the case then you ned to understand how tightening the locknut affects the clearance. Normaly as you tighten the locknut, the clearance increases slightly as the screw is forced hard against it's threads. In order to get the correct clearance after tighening the lock nut, you need to set it very slightly tight.
Mr2Mike said:
I think that the setup is the same one you are familiar with and describe. There is an allen set screw in the middle that tightens down the roller rocker, and the lash is set by the outer nut.
This dosen's sound like any setup I have ever seen. Generaly the screw is used to set the clearance(lash), and the outer nut is used to lock the screw in place. If this is the case then you ned to understand how tightening the locknut affects the clearance. Normaly as you tighten the locknut, the clearance increases slightly as the screw is forced hard against it's threads. In order to get the correct clearance after tighening the lock nut, you need to set it very slightly tight.
That's how valves are adjusted on at least Ford V-8s, dont' know about other US engines... I've had two different brands of roller rockers, and they both function like this.
You turn the outer nut which increases or decreases valve lash, and the inner set screw holds it in that setting.
The snag is that you can't snug down the set screw sufficiently just using an Allen wrench - you need to tighten the outer nut which also tightens the inner nut, but since the outer nut controls lash, you change the setting when you tighten it. The trick is to make sure that when you tighten it down, you end up with the lash you want.
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