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I just adjusted my valves for the first time. Had the truck, 1980 stock 1.8 minus air pump for five years 22,000 miles. #1 and #2 intake valves were .001 too tight, all the rest were on. .006 being the right setting. Soooo...Dividing 6 into 1 gives a rouded up 17 percent. In a perfect world with a stock 80HP motor how many Horses did I gain? I can feel it in the seat of the pants. When I give it the gas going up hills the speedometer goes to the right (or at least holds it own) and the temp gauge doesn't. Compared to the last hundred times when I went up the same hills and had to downshift or start in a lower gear. 98,440 miles on truck.

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1980 4x4

While 17% of 80 HP is 13.6 is easy enough to figure, I don't think it works that way. with the valves set too tight, you were losing more air and fuel mixture than you should have. Metal valves on a metal seat will always leak a little. If the valve doesn't close completely, you will lose a lot more.

I have no idea what the valve lift is on a stock motor but I'll take a wild guess and say 0.250

This means that when you were .001 too tight, you were lifting 0.251 (.001 of extra lift).

After adjustment, you reduced the valve lift by .001, from 0.251 to 0.250

So you reduced the amount of air/fuel by 0.4%. Since it was only 2 of 4 cylinders, after adjustment, you reduced the power by 0.2%.

If the motor's about 80 hp, then you reduced the power by about 0.16 hp, or about the same as a hefty sneeze.

I think that what you felt in the seat of your pants was the satisfaction that comes from turning wrenches on your own truck.

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You went there in that?!?!

No, it doesn't work that way. With the valves too tight you would be getting more lift. The problem is that after the cam lobe rotates away, you would still have some lift. It would reduce power, the same way a burned valve does. Of course, with any overhead valves, they are closed in the upper position, and lift is a measure of how down they go when they open.

I doubt you felt a difference of adjusting a valve by .001. You might be over thinking

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Certified pilots, looking down on people since 1903.

Normal valve clearance is .006", His were at .005", so he adjusted them by .001"

The valves were still closing fully, with .005" to spare. So there would be no blow-by like a burned valve. The only effect is that it would be like an infinitesimally higher lift higher duration cam.

My point is that it's not a 17% difference, it's a 0.2% difference. And in the wrong direction.

So Luvrv8's right. It's not enough to make any noticeable difference, in the seat-of-the-pants or otherwise.

Still a fun exercise though, as long as we're grading on a curve.

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You went there in that?!?!

THEY TOLD ME THERE WOULD BE NO MATH!!!!

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OK, I'm over it. Where's the beer?

I encountered similar hp gains after a recent valve train adjustment, but after much excitement my wife pointed out we were going down the hill, not up.

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'75 body with '82 diesel running gear
My build thread.

The intake valves were .001 too tight in two cylinders meaning they werent closing completely correct? .001 of .006 is almost 17%. 20hp per cylinder two cylinders off. Even if off power by only 5% on these two cylinders it would be a two HP gain. .006 isnt that much to begin with. I should have done a compression test before and after. I told my wife after I was done what the results were and said "I dont think it will make any difference." but I think I could have gained 6 HP. From 74 to 80. The funny thing is most of you snobs shop out your work and dont have a fucking clue.80.

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1980 4x4

OK, I'll try this one more time:

When the valve's properly adjusted, after the valve closes, there's .006" between the valve stem and the rocker arm. You could tighten the valve by up to .006" and the valve would still fully close. It's only after the valve is tightened to less than 0 clearance that the valve doesn't fully close, because the cam would then be holding it open. So anything between .000" clearance and .006" clearance will allow the valve to fully close.

On your truck, before you adjusted the valves, you had .005" between the valve stem and the rocker arm. YOUR VALVE WAS FULLY CLOSING.

If you think about it, when that cylinder's at TDC, you can rattle the rocker arm, even at .005" clearance. That means the cam is not pushing on the valve at all, and the valve is closed.

Adjusting the valves by .001" did nothing. Whether you like the answer or not, it's the right one.

Maybe something else happened while you were in there to make the truck run better. Perhaps the distributer got bumped (You can gain an easy couple of HP by advancing the timing a few degrees. I run mine at 12 degrees.) Or maybe your plug wires are getting weak and moving them kept one from shorting.

Personally, I've owned my truck for 25 years, modified every part of the drive train and most of the body, and never shopped out any of it.

In any case, if you're happy with your truck then I, and I'm sure most of the other clueless snobs like me, are happy for you.

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You went there in that?!?!

I misread the original, thinking it only had to 0.01, not off by that much. In such a case, when the engine was warmed up, the clearance would go down and the valves might not close completely. I have to agree that any gain in power from a minor adjustment wouldn't happen.

I assumed from you statements you were pulling our leg.

Regarless if you have two valves so far out of adjustment that the motor is not running right it's safe to say your valve seats are getting worn, causing the valves to bury into the head which is why your valve lash is decreasing unevenly on your motor. (re-read that last part)

I've built/tuned motors on the dyno and track and can assure you adjustments of .001" (one thousand of an inch) will produce little to no gains.

With that said it's been real quite here so it's nice to see some chatter.

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Almost forgot, it's possible you gained 17% power from a simple repair, but it wasn't from changing valve lash .001". Did you replace any vacuum hoses, PVC valve, ignition timing or change dist vacuum from ported to manifold. Now these are things that could make a noticeable difference in power while asending a large hill.

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I farted in my truck one time and gained 8 MPH.

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Certified pilots, looking down on people since 1903.

DAMN!

This seems like it was a fun thread and it sucks I missed most of it. A real math problem right after I just finished my first Algebra class.

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In life there is the "Way things should be" and then "There's the way they are".

2005 Silverado 3/4T Crew Cab
1981 Luv 2WD
1979 Luv 4x4 Currently going through Open Heart and Cosmetic surgery
1995 Roughneck JetBoat
1981 Luv parts trk

I have to say that I am sorry for the last line of my last post. It was out of line and regretful.

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1980 4x4

After giving the truck some rest. Got a new 1992 F-150 I have to admit that the power gain was minimal, but when you are dealing with 80 hp max anything is noticed. Thanks to all for the entertainment and insight.

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1980 4x4