would a valve clearance that hasn't been adjusted cause a decrease in MPG?

if the valve are tight, would it cause a rich condition? or a lean condition?

 

Bringing something back from the dead, but I would love to know an answer to this old question as well. I had my 2004 adjusted the first time last year, valves were loose, compression check was good, but since the adjustmentd my city mileage has dropped by around 2 mpg but highway is fine. I also have more frequent low RPM shudder (but no stall) when going into idle and coming to a stop (you know where it drops to 600 rpm but doesn't stall). This use to only drop to 600 RPM during warm up, when it's idling then drops down to 600 RPM then back and never again. Now I'll get that shudder more often while driving.

I'm going to have this checked again, but it would helpful to know what kind of symptoms can one experience from too tight valves? Is there a particular sound the muffler makes? (I can't tell if mine is sucking in paper or not to see if I burned something since last year).

Lastly, I've been trying to find this for over an hour, but I cannot find Billman specs on 2004 intake (is it .08?), I understand exhaust is .010.

thanks guys, would really appreciate some feedback.

 

If they're within specs the valves will work normally. I go by the specs on the hood, which is slightly over the lower end, I've noticed that throttle response is better when it's right on the money. I haven't noticed any change in mpg I get about 200 miles between fillups. I put in 9 gallons and haul ass 1/3 of the time.

 

2000-2005 .008IN and .011EX.
2006-2009 .008IN and .012EX. (Drive by wire)

 

Where's a good place to buy the bent feeler gauges?

 

I got mine (latest one) from Amazon:


http://www.amazon.com/Stanley-Proto-...ey+bent+feeler

 

Would still love an answer to understand this better. Just had a valve adjustment done Sat to .009 intake and .011 exhaust and it feels much smoother for my city driving compared to before which the mechanic said was tight, tighter then the .008 spec (ouch). Compression testing was 225 all around so all is ok.

But I've noticed such a substantial difference in performance, would I notice one if I go from .009 to .008 and .011 to .010?

 

No you won't, because if you look at your hood it says clear as day that valve clearance is .009(.23mm) and .011(.25mm) +-2mm so it's fine where it's at. As long as it's in range you'll have ideal performance, out of spec you won't.

 

Hi, I'm not disputing the spec range, I have looked at that sticker for 11 years, and yes I did notice a difference going looser in the valves.

I understand I am in spec, I want to understand what happens to the performance when it's tightened or loose. The spec has a range, I am right in the middle, so what happens when going tighter or looser? There's a plethora of threads talking about the specs, no one discusses the symptoms or performance of the valves tight or loose. Everyone knows tight valves burn, but what do you get out of it on the road?

thanks

 

I understand I am in spec, I want to understand what happens to the performance when it's tightened or loose. The spec has a range, I am right in the middle, so what happens when going tighter or looser? There's a plethora of threads talking about the specs, no one discusses the symptoms or performance of the valves tight or loose. Everyone knows tight valves burn, but what do you get out of it on the road?

thanks
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Here's a few items to consider. Valves need to fully seat to prevent burning. Valves need to fully seat to maintain good compression. Loose valves have large gaps, don't burn and seal the combustion chamber during the compression stroke. However, with a tighter gap, the valve lifts off of the valve seat further than with a large gap; sort of like having a slightly higher lift cam lobe. The higher lift adds power (maybe too little to measure) until the lift is so high that the valves don't seat, the engine loses power and subsequently the valves burn. So the issue is finding the sweet gap that maximizes lift without burning valves. Billman has noted a preferred gap for DBW engines to enhance longevity.