I have seen where some people put the feeler guage between the rocker arm and stem to get a real tight fit, while other like the slight drag on the guage. What is the correct way to adjust the rockers? Tight or Slight drag.
When I had my engine dynoed, the dyno guy like the tight fit at .022 cold. The cam card recommends .026. How does tighter or looser affect the power range when adjusting the lash. I know that tighter will make the cam seem bigger, but whats the benefits of using a loose lash. I have not tried the .026 lash and did talk to UDHAROLD and was told I can run the .022 hot with no ill effects.
Thanks:

The correct way is to use a Go, No-Go method.

If the feeler gauge is loose between the rocker and the stem, then the reading is not accurate. It should be a tight fit, and the next size up should not go.

Its really a "feel" thing, but if you do not feel comfortable with it they do make "go / no-go" feeler gauges for setting valves. Each one has a step on it. For instance the feeler gauge for .022" will be .021 at the end and then step up to .023. If the 21 goes in and the 23 will not you are pretty darn close to 22. I think a lot of people get too carried away worrying about the exact gap, as soon as you start the engine and the valve train starts flexing all ove the place, a couple of thousanths eitehr way probably does not matter on the average engine.
Just my opinion,

Just remember the most important thing about adjusting valves is . "a loose valve is better than a valve that is too tight " let em clack and win at the track is my motto ;)

Yes, it's an oilie, feelie thing!! He, He!!

Feelie thing with the feeler gages and warm to hot oil all over you at a good idle!!

But thats the way I learned how to do it!!

pdq67

tight is right . . . you want to make sure you are taking up all the slack in the valve train when setting valve lash.

IMO it is more important to make sure they are all the same than to make sure the valves are all at .022 or .020 etc.

When P&G came out with their new product the "Valve Gapper" (sets the lash with a dial indicator) they went to a race to show how much better your car would run if all your valves were set exactly the same.

They found a big name top fueler (chrysler hemi) and set his valves and the car made a run. Then the car owner took the valve covers off, and without a guage, went through all of the valves tightening some and loosening others. Took the car back out and ran the same as with the valves adjusted perfectly.

Moral, it isn't a big deal as long as the valves don't hang open and the push rods don't fall out.

By the way, P&G is no longer around even though they made a product that set valves perfectly.

John,
that may be true with Top fuel, but in a street strip ride, accurate lash is important.
The little things matter when searching for ET in a street/strip car.

Brian, I agree (wow do I agree!) that a lot of small things make big differences. Experimenting will help you find the differences. It's just that setting valves to factory specs won't.

I always use a go-no go method of adjusting valves. The feeler gauge should be a tight fit. My first solid cam was 4 years ago when I was 16 or 17 and I've been setting them this way every time I adjust the lash. Credit for learning the proper way to set them goes to our old best buddy racer1320.

UPdragracer,

Sorry - I have to disagree with you there. Additional slack in the valve train is NOT a good thing. The cam will take up that slack very quickly which in turn slams or shocks the lifters, pushrods, rocker arm tips, and valves. This is why you ALWAYS set a solid cam on the tight side for break in.

Also - another thing to add to the discussion - Its my opinion that if you vary more than a couple thousandths from the manufacturers specs on lash setting, AND you notice a increase in performance at the dragstrip - you do not have the optimum cam for your combination. Anybody have other opinions on this?

Originally posted by AdamLym:
Additional slack in the valve train is NOT a good thing. The cam will take up that slack very quickly which in turn slams or shocks the lifters, pushrods, rocker arm tips, and valves. Especially with a roller cam! :eek:

Alright this is the way it is when I say loose setting I mean like .002" at the most . I have proven time and time again that a slightly loose valve adjustment will outperform a too tight lash setting {too tight meaning .002" or tighter than spec. setting } get your compression tester out and do a comparison between different lash settings and you will see it change dramaticly
This argument will go on forever because people do not put forth the effort to actually see the what and why's of how this relates to performance

Originally posted by AdamLym:
I always use a go-no go method of adjusting valves. The feeler gauge should be a tight fit. My first solid cam was 4 years ago when I was 16 or 17 and I've been setting them this way every time I adjust the lash. Credit for learning the proper way to set them goes to our old best buddy racer1320.

UPdragracer,

Sorry - I have to disagree with you there. Additional slack in the valve train is NOT a good thing. The cam will take up that slack very quickly which in turn slams or shocks the lifters, pushrods, rocker arm tips, and valves. This is why you ALWAYS set a solid cam on the tight side for break in.

Also - another thing to add to the discussion - Its my opinion that if you vary more than a couple thousandths from the manufacturers specs on lash setting, AND you notice a increase in performance at the dragstrip - you do not have the optimum cam for your combination. Anybody have other opinions on this? Additionally, Ed found 1 tenth in the lash. By buying a cam on the small side, and then lashing the valves to the tight spec, he found a tenth over factory.
If it didnt matter, he wouldnt have found that tenth.
A tenth is a significant gain in my opinion.

Some might find that their goals arent to find every hundreth, and some might be looking for that edge on the competition.

I donno, b/c I find it funny that CC says their Magnum solid cams can be lashed from .015" to .030"!!!!

But to me it is a feelie thing and I just kept messing around until I liked the way it ran AND sounded....

pdq67

While we're on the subject of the Magnum cams I've run two of them and played a lot with lash on both.

When you set lash tighter than the spec on the time card, like going from .022" to .018", the seat timing events get longer, more seat duration, by several degrees. But the higher the valve lift gets the LESS that change in valve lash effects cam timing.

I found that on the SBC Magnum 294S .004" in valve lash makes about 6* difference on the seat, 2-3* at .050" duration and <2* at .200" lift. So IMO you are basically fine tuning your OVERLAP period by messing with the lash, or rocker ratio for that matter, but are making very little change in mid and high lift duration.

When I was running the 282s in my 383 I found the engine liked .018" lash hot the best. But if I went tighter than that it lost 60' time. If I went looser than that my MPH went down. I switched to the 294s and found that it ran best set at .022" lash. Don't ask me why or how, that's just what I found.

As far as lashing the valves goes I dont bother with a go/no go feeler guages... they do work perfectly and for most they are probably the best idea.I go for the feel thing... a feelable drag that is niether loose or tight...Probably the most important thing is to be consistant.

Clearence ramps are not all the same.Some are gentle , and others are aggressive , some are long and others are short.. ect... depending on what the designer was trying to acomplish in that given design... Some designs can tolerate lash changes better than others can.The Crane / CD IR rollers are very aggressive with a very tight lash .010/.012 in that range and cant tolerate more than a couple thou either way... An 097 Duntov has a short fairly rapid intake ramp but a long more normal exhaust ramp... Yet a 30-30 Duntov can tolerate a fair amount of lash change.

I have chased lash all over the place and in some cases there was power to be found and in others there simply wasnt.I would tend to think that if you are finding that small changes in lash from the factory specs are not making much difference then you probably are fairly close duration wise with the cam you have.