Valve clearance Under spec?

[Theron]

I have a 89 Corolla 4A-F with 30,000 mile on the engine. I have some noisy valves so I'm doing a valve lash adjustment and the readings I'm getting are under spec. Valve lash has not been done on this 230,000 mile rebuilt cylinder head, so the lifter shims have never been replaced.

Why would the clearance be under spec. I would think that the clearance would be over spec if anything.

Here is my intake valve clearance:
#1 .006 (0.15mm) / .005 (0.13mm)
#2 .005 (0.13mm) / .007 (0.18mm)
#3 .005 (0.13mm) / .007 (0.18mm)
#4 .005 (0.13mm) / .005 (0.13mm)

The stock intake spec's indicate (cold): 0.15-0.25 mm (0.006-0.010in.) Correct me if I'm wrong, but doesn't the shim wear down as the engine wears? which would give me MORE clearance. Should I replace the shims???

Here is my Exhaust valve clearance:
#1 .006 (0.15mm) / .006 (0.15mm)
#2 .011 (0.28mm) / .009 (0.23mm)
#3 .013 (0.33mm) / .006 (0.15mm)
#4 .006 (0.15mm) / .005 (0.13mm)

The stock spec for Exhaust valve clearance (cold): 0.20-0.30 mm (0.008-0.012 in.)
Now on #3 .013 is what I expect from valve chatter, but this is the only one out of 16 valves!

I have not yet measured the thickness of the shim.
Should I go ahead and replace the shims out of spec????

[new echo owner]

Do you have any other problem besides the valve noise?

Valve clearance can actually decrease sometimes due to wear to the valve seat and valve face.

N.E.O.

[Theron]

Oh OK that makes sence. Could that one Valve thats OVER spec be making that noise?
Another problem is I have been getting lower mpg ever since I've switched carbs to a Weber 32/36.

[Donald]

Originally Posted by Theron

Oh OK that makes sence. Could that one Valve thats OVER spec be making that noise?
Another problem is I have been getting lower mpg ever since I've switched carbs to a Weber 32/36.

One valve out of tolerance could make noise, but yours doesn't seem to be bad enough to be heard.

I would say change them.
First, measure them and see if some could be swapped into different positions to get the right gaps, then buy the ones you need. If you have the Toyota manual, there is a chart with shim thicknesses and part numbers in it.

[verlaryder]

Originally Posted by Theron

Oh OK that makes sence. Could that one Valve thats OVER spec be making that noise?
Another problem is I have been getting lower mpg ever since I've switched carbs to a Weber 32/36.

Yes that one loose valve could make a tapping noise that varies with engine rpm. The tapping should be audible when the engine is both cold and warm (if not, then the source of the noise might be something else besides the valves).

Yes you should get all the clearances within the middle range of the factory specs if possible to restore top engine performance and smoothness.

The cause of your valves getting out of specs could be delayed or neglected preventive maintenance service or engine modifications or both as they both cause abnormal valvetrain wear. Or, in your case of a rebuilt head,
if the rebuilder ground the valves too much then they will tend to need more frequent readjusting of the valve clearance. Well maintained, unmodified, never overheated 4A-F's and 4A-FE's don't have problems with the valve clearances getting out of spec.

Weber Carbs = richer fuel mixture = lower fuel economy.

[eage8]

Originally Posted by verlaryder

Weber Carbs = richer fuel mixture = lower fuel economy.

actually with the weber 32/36 it should be: better design + not being 20 years old = better fuel economy...

I'm not sure why would would be getting worse gas mileage... did you make sure you capped everything off properly? I delayed putting on my weber 38 due to all the stuff I'm going to have to cap/block off. I might get some block off plates made for some of them... I do have the California model 4AF though.

[new echo owner]

Originally Posted by Theron

Oh OK that makes sence. Could that one Valve thats OVER spec be making that noise?
Another problem is I have been getting lower mpg ever since I've switched carbs to a Weber 32/36.

Too much clearance in one valve can make some noise; however, only you can say whether that is the cause of your noise or not. What have you done to isolate the source of the noise? If valve clearance is indeed the source of your noise, its location would have been pretty close to the one that is out of spec.

I am not familiar with the Weber 32/36, so I can't really say whether it will affect your fuel mileage or not. One question though, was it come set up for your particular vehicle already, do you need to do some fiddling to work with your particular application. There are also other factors that may affect fuel mileage.

N.E.O.

[Theron]

The head + engine was rebuilt about 4 to 5 years ago so its a little hassy to exactly what I did. The head was put in the machine shop to install valves + guides + whatever they do with a valve job and machine the surface. Its possible that the valve face was machined down a little, so that could cause low clearance. The valves have always sounded loud. I'm going to go ahead and replace shims that need it and see if that quiets things down.

Hey eage8 I also have a rx-7. Its a 85 and what I currently am driving while I work on the corolla.

As with the Weber causing worse millage. I was getting about 25 average / 30 at best Hwy and now 23 or 20. Hopefully adjusting the valve lash will help the mileage a little. I also might have to use different jets, although the mixture and idle speed screws are in spec of the Weber instructions.

[new echo owner]

The idle mixture and idle speed can be within spec, but doesn't have much affect on fuel mileage. The main jet on the other hand will, if it is running a little on the rich side.

The valve clearance you have wouldn't have affect you gas mileage that much; might try advancing your timing a little bit and see if that helps, as long as the engine is not pinging you should be fine.

N.E.O.