Checking lash with valve cover off?
- Thread starter MT63AFX
- Start date
Gene Fiore
Famous Member
I can see where you might do that with a hydraulic cam but there's no way you could adjust valve lash on a solid lifter cam with the rockers moving...that's my 2 cents.
Gene Fiore
Famous Member
So how do you measure valve lash with a feeler guage when the rockers are moving? Seems like it would be difficult.rbohm":3uoyb4co said:
Gene Fiore":v8am5txa said:
It's not easy from the start, but it's doable. Sliding the feeler gauge under the rocker arm while running ensures all rocker arms are set at the same temperature. Using a box wrench does not stay on the adjuster nut during the whole time, so a simple tweak either way is enough to check again with the feeler gauge. Probably can get them all adjusted in a 1/2 hour or a bit more. Simply warming up the engine to OT will allow downstream rockers to cool as you slowly work/adjust, plus bumping the engine around takes time which allows more cooling. Some have figured the growth or changes in the lash between setting them hot and setting them cold and will just set them cold, RodC.
I used to set my idle low on my old 138 Vaxuhall I6, and shove the 13 thou in, and the bolt was tightened with an open ender (aint nobody got time for dat box spanner sh!+), and set with a flat head screw driver. GM engines were designed to be clearanced at idle. Ford don't use the same stone age simple screw like the Ford Kent 1500 and 1508/1594 and 2262 Vauxhall engines did. Cork gasket was reusable, and never a problem unless you squeezed it more than 50 percent of its original unclasped depth.
http://www.classiccar.co.nz/articles/ho ... rances-230
http://www.classiccar.co.nz/articles/ho ... rances-230
Although it can be done, I'm not certain why you would set lash that way with either solid or hydraulic lifters. As far as temperature, there's not going to be a significant change in the valve train as you go from #1 to #6. It just doesn't cool off that fast that it makes much difference. Besides, you can always warm it up and check again from the other direction.
It's easy enough with a solid lifter to set the lash, cold or hot. If you do it with the engine running, you may not get consistent results. All you could hope to accomplish would be to insert the feeler gauge and listen for the ticking to go away. But at that point you wouldn't know for sure if it was just right, too tight, or still a tad too loose. Too loose and you lose lift, too tight and the valve isn't going to seal and transfer heat properly. The result could be lost power or burnt valves.
You actually only have to rotate an inline six crank two revolutions to get all the valves in a position to be adjusted. Start with #1 at TDC and adjust #1 intake - #1 exhaust - #2 intake - #3 exhaust - #4 intake - #5 exhaust. Then turn the crank until #6 cylinder is at TDC, and adjust #2 exhaust - #3 intake - #4 exhaust - #5 intake - #6 intake - #6 exhaust.
With hydraulics you have a preload range, usually up to .100" and sometimes more. With them you simply tighten the adjuster to zero lash then add another 1/2 to 3/4 turn to add some preload to the lifter. If your adjuster is a 3/8-24 thread, then you know exactly how much preload you put on. For example, 3/4 turn is exactly .03125" of preload. (BTW, this is not the case for stud mounted rockers. That math is slightly different).
Just turning until they get quiet with the engine running, might get you inconsistent results.
It's easy enough with a solid lifter to set the lash, cold or hot. If you do it with the engine running, you may not get consistent results. All you could hope to accomplish would be to insert the feeler gauge and listen for the ticking to go away. But at that point you wouldn't know for sure if it was just right, too tight, or still a tad too loose. Too loose and you lose lift, too tight and the valve isn't going to seal and transfer heat properly. The result could be lost power or burnt valves.
You actually only have to rotate an inline six crank two revolutions to get all the valves in a position to be adjusted. Start with #1 at TDC and adjust #1 intake - #1 exhaust - #2 intake - #3 exhaust - #4 intake - #5 exhaust. Then turn the crank until #6 cylinder is at TDC, and adjust #2 exhaust - #3 intake - #4 exhaust - #5 intake - #6 intake - #6 exhaust.
With hydraulics you have a preload range, usually up to .100" and sometimes more. With them you simply tighten the adjuster to zero lash then add another 1/2 to 3/4 turn to add some preload to the lifter. If your adjuster is a 3/8-24 thread, then you know exactly how much preload you put on. For example, 3/4 turn is exactly .03125" of preload. (BTW, this is not the case for stud mounted rockers. That math is slightly different).
Just turning until they get quiet with the engine running, might get you inconsistent results.
To each his own, but yeah the heat bleed off takes a good while before you have to be concerned with the engine cooling down affecting lash. Also, most feeler gages aren't heat treated, and sticking them between the valve tip and rocker with the engine running can ruin a set and a .018" feeler gage becomes a .016" or thinner without you knowing it. Plus, most people's "feel" of what they are trying to gage isn't accurate because of the gage being pinched repeatedly with it running either.
