How To Check Valve Gaps?

[HarvRead]

I have always measured valve gaps with the cam lobe on the heal (that is, with the lobe pointed exactly away from the valve). By this method, I have three tight valves. I took it to the dealer to get them re-shimmed and they are saying "all are in spec.". They check the valves at TDC on the compression stroke, using timing marks. I'm going there tomorow with my own (nearly new) feeler guage and try to resolve this. I'm looking for input from the list, in hopes of avoiding making a fool of myself if I'm wrong!

[jackd]

You do it the way I do.. The high side of the cam is not directly horizontal with the engine. But I don't think it is that critical.

An excessive amount of oil on your gauge will make it drag a little more if you are tight.

Did you think they tight big time?

Is is possible:

that you read the gauge markings wrong
wrote the wrong numbers on your check sheet
measured an intake and measured for exhaust clearances

[dshealey]

I have always measured valve gaps with the cam lobe on the heal (that is, with the lobe pointed exactly away from the valve). By this method, I have three tight valves. I took it to the dealer to get them re-shimmed and they are saying "all are in spec.". They check the valves at TDC on the compression stroke, using timing marks. I'm going there tomorow with my own (nearly new) feeler guage and try to resolve this. I'm looking for input from the list, in hopes of avoiding making a fool of myself if I'm wrong!

You are doing it right. There is a long dwell on the valve closed area of the cams, as the valves are closed for nearly half a crankshaft revolution. The valve lobes can be anywhere within 30 degrees either way of straight out from the valve and still read the same. Besides, there are NO timing marks anywhere on the LT engine. Sure would love to see the dealer point them out to you. :D

[murray]

You are doing it right. . Besides, there are NO timing marks anywhere on the LT engine. Sure would love to see the dealer point them out to you. :D
True there are no Ignition timing marks. There is a reference for TDC if the timing chain cover is removed. The picture I supply depicts the the rotor flange , note the pin at 3 o'clock just to the right is the TDC mark on the crank case. In the shop manual there is another picture page 11.45.

[frankf]

Had the same thing happen to me. Three seemed tight, one very tight. Mechanic says only one is out of spec. He sez if you can get the feeler gauge in no matter how tight it feels then the valve is in spec. I always thought that you can push the valve down a little if you apply too much pressure with the feeler gauge and get a wrong reading that way.

[dshealey]

Had the same thing happen to me. Three seemed tight, one very tight. Mechanic says only one is out of spec. He sez if you can get the feeler gauge in no matter how tight it feels then the valve is in spec. I always thought that you can push the valve down a little if you apply too much pressure with the feeler gauge and get a wrong reading that way.

You are right. Someone should put a dial indicator on a valve and show that mechanic how LITTLE pressure it takes on a feeler gage to open the valve, then he would shut up and not give out such stupid and uninformed "information".

Way too many years ago, we adjusted valves on racing engines by using a dial indicator and larger than required feeler gages. For instance, if you need 0.012", put an indicator on the valve and use a larger gage, say 0.016" and adjust the valve for 0.004" deflection on the indicator. Cannot get more accurate readings than with that method.