erick_e

UPDATED 27 NOV 12 WITH ACTUAL VALVE GUIDE CLEARANCES FOR COMPARISON

So I finally broke down and bought a dial gauge and valve spring compressor. I still need to measure the guides on my car, but thought this may be a good reference for those wanting to check theirs.

I'm building a new motor for my 09Z, and have a new set of LSX-LS7 heads. These are almost identical to the OEM LS7 heads except the deck is thicker, they are not CNC ported by GM, and they have PSI or PAC springs, I forget which. They have the same valves and valve guides.

I measured both intake and exhaust valve guides and this is what I found.

Both intake and exhaust have the same movement .003"

I also noticed that the exhaust valve has the part number etched on it, along with the "EDIVAL 05-08" which I assume is the maunfacture date, but I don't know what/who EDIVAL is.

Also, for those of you interested in measuring your guides, I will considering renting these tools to help recoup some of my costs.

RFZ

to get actual clearance you need to measure stem diameter and guide diameter..subtract stem from guide measurement


with the method you used you should have about .0015 or so clearance ...with the wiggle measurement of .003 that you got

Mark2009

Edival is an Argentinian company that produces valves. They were bought by MAHLE (who also makes LS7 valves for GM) in 2007.

http://www.mahle.com/MAHLE/en/News-a...-March-21-2007

AzDave47

I think some of the WCCH builds measured .002 using the above method although they looked for less. I'm not sure if GM told the dealers to replace the heads if the wiggle was .008 or some other similar number.

hoefi

Using this method, one will typically get a measurment "larger" than the stem-bore method.

AzDave47

I'm not certain of that given the number of measurements done with the heads off and clearances of .0160 or more going against a max. spec of .0037 and a target clearance around .0012

Dirty Howie

Thanks for posting this important info. Hopefully other will in fact borrow your tools


DH

RFZ

the wiggle method of measurement gives you about 2x the actual clearance... it can be more than 2x depending how far away from the end of the guide you take the measurement....

erick_e

I'm going to try and find a small bore gauge to measure the actual clearance. Since GM is apparently measuring the guides on the vehicle, I wanted to post these as a reference for those who want to have something to compare their measurements to.

I also made a few more measurements, and will post them soon.

erick_e

This is the valve around .850" lift

And This is the valve around .850" lift

I also inserted the valve upsidedown and measured the clearance



And I took a video of the valve movement.

http://www.youtube.com/watch?v=IlFOicej64A

AzDave47

Not good, what are the miles on the head and was the LS7 stock?

erick_e

These heads are brand new LSX-LS7 heads...

AzDave47

I think GM looks for max of .008? (or was it .002) measured this way? and you're at .010

erick_e

In my first post they measures .003" which is how they would be measured on a vehicle with the valves seated on the valve seats. I was just trying to show how much that clearance is magnified with valve lift.

Mark2009

From what I've read here the max is 0.008 and the measurement is taken just above the valve guide with the valve only about 0.010 off its seat.

The 0.010 measurement shown here, with the valve 0.850 off its seat, is meaningless.

Mark2009

Altho definitely budget items, I suppose they would work well enough to determine any gross wear:

http://www.amazon.com/KD-Tools-3771-...pr_product_top

You can also find half-ball and full-ball gauges, but since we suspect an oblong/ovoid wear pattern in the guide those would not give you a representative measurement.

Edit: Mmmm, just found a single Starrett gage for $30 bucks

http://www.starrett.com/metrology/pr...ing-Gages/579A

erick_e

You are correct, I was just trying to show how the clearance is magnified as the lift is increased.

The important thing to note about that measurement, is that the valve is still fully inserted in the valve guide. Meaning the valve is still extrnding out from the top of the guide.

Johnjan

Those measurements are irrelevant. Measure the bore in three places, measure the valve stem diameter and subtract the numbers. End of story.

Mark2009

No, the clearance was not magnified as the lift is increased... the reading was magnified as you moved the measurement point away from the fulcrum (the valve guide itself).

Think of a playground teeter-totter (see-saw)... if you measure the board movement an inch away from the pivot point (fulcrum), you'll get one reading. If you measure the board movement four feet away from the pivot point, you'll get a much much greater reading. However, the movement of the board is unchanged.

In the case at hand, the best approximation of the actual valve guide clearance is to take the measurement as close to the valve guide as possible (as Chevy reportedly specifies). Otherwise geometry is going to introduce measurement error. The valve lift at that point should be irrelevant (I suppose Chevy says to take the measurement with the valve only slightly off the seat is to eliminate any error introduced by contamination of the valve stem).

Mark2009

That story only has a happy ending if you remove the heads and find excessive clearance needing rework. If you remove the heads simply to check the clearance, and find the clearance okay, then you've done a lot of work for essentially nothing (except perhaps peace of mind).

What the OP is trying to do, to benefit us all, is to validate the Chevy 'shadetree' method that has been floating around which allows one to get a reasonable approximation of the valve clearance without having to remove the heads. IMHO this is a good thing.