How Snug Should My Valve Lash Should Be?

[justinevert]

Going through the valve lash after hearing some ticking. Can get the feeler gauge in there with some effort. Got me to think how much resistance the gauge should have when running between the lobe and top of valve.

I do get play on the rockers when moving them back and forth.

Just wondering if I am doing this right.

TIA, as always.

Justin

[fourtii]

I use the "go,no-go" rule...use the .006 feeler guage first, followed by the .008 second (cold engine) that will get you at .007.

If the rockers have excessive play in them it's possible the bushings and rocker shafts are worn if they have a bunch of miles on them. Also inspect the eccentrics on the rocker by taking them out, you will see the visible wear there.

[c.d.iesel]

a ticking valve is a happy valve - really.

0.006" COLD (go)

0.007" (very tight)

0.008" (no go )

[Simeon]

By the way, the feeler gauge goes between the valve and the eccentric.

Somebody, better at mathematics than me can confirm what the difference in clearance would be measured at the camshaft / rocker interface due to the different lengths between the rocker centre line and the eccentric and the rocker centre line and the rocker pad.

[justinevert]

Oh, two more things I forgot to mention:

1) Brand new rebuilt head, everything but rockers are new

2) Schrick 292, which I have been told needs to have the lash at .008

Sorry for the oversight.

Justin

[Mike Self]

burned valves...

Did you check your rocker arms for wear before re-using? Oddly enough, it seems the shafts wear faster than the rockers. If you run out of adjustment with your eccentrics, I believe Ireland makes oversize (larger diameter) eccentrics to solve just that problem.

cheers

mike

[SteveJ]

.006 and .008. I have those two feelers on a separate ring. No searching or trying to remember values.

Cold motor. Let it sit overnight. Go out in the morning with a cup of coffee and have at it. Once done, you're set for a nice morning drive to 'test' the car.

Loosen the nut on the ecentric, slide the 6 in. Adjust the ecentric with a 2.5mm allen in the adjutment hole. Tighten down the nut. The 6 should slide out with no problem. Then test it with the 8. If you are able to slide the 8 in, then you got it too loose.

I'd recommend ordering up a spare bolt and nut for the ecentric adjusters. Not a common threading- maybe a 5x1.0 as I recall. In all my stash of parts and sorted hardware I had none. I now have two. One in the car and one in my parts stash.

[c.d.iesel]

..."2) Schrick 292, which I have been told

needs to have the lash at .008

Sorry for the oversight "

0.007" (very loose feeler blade)

0.008" (slight drag on feeler blade)

0.009" (very tight if forced)

0.010" (NO-GO in)

[fourtii]

"Brand new rebuilt head, everything but rockers are new" (quote)

Well I'm glad to see everybody agrees somewhat on this thread...here's my question.

Knowing that these engines cruise at high rpm's going down the highway and wear out the valve train early in life. What machine shop would rebuild a head and use the old rockers and possibly shafts, especially when everything is torn apart and all it takes is new parts to do "the job right".

[c.d.iesel]

fourtii - yer Right!

especially when you went and spent

some doe on a Dr Schrick 292 bump stick?

how do you expect to get the improvement with

sloppy worn parts mated with it?

[justinevert]

Let me clarify even further, when I got the head rebuilt I asked the machine shop (who is highly recommended here in the DFW area) to check the parts and he stated that the rockers were in very good shape and not needed replace them. The lobes during adjustment moved very little at suggest gap indicating that as well ( as opposed to the lobes who need to move much more to get to the proper gap).

Hope that clarifies somewhat.

Justin

[jerry]

"What machine shop would rebuild a head and use the old rockers and possibly shafts, especially when everything is torn apart and all it takes is new parts to do "the job right".

if the parts were inspected correctly, i would say the machine shop was DEFINITELY doing their job and had the customer's interests at heart.

it is so much easier to throw things away on 'general principals', rather than evaluate and disposition parts accordingly. in a perfect world, parts should have serviceable limits published.

[02for2]

The M10 motor is supposed to sound a little like a sewing machine because they do not have hydraulic lifters. If you don't have some valve noise, your lash is too tight !

The reason you need to adjust the lash over time is because the valve pounds itself deeper and deeper into the valve seat over time closing the gap between the top of the valve stem and the eccentric. You will always open this gap on adjustment, not close it.

If set too tight, the valve may not close or seal fully resulting in a loss of power and the valves (esp. the exhaust valves) can only shed their heat when they are in contact with the head which is water-cooled. Proper lash adjustment ensures that the valves are in contact properly.

If you have a fresh head w/ new seats, you do not need to adjust the valves for at least 10k mi. - probably more like 15k on a new head (though you should check at 10k). I have found on several cars which have had the head re-done that this lash is set too tight, probably to eliminate valve noise, so whenever having the head done, no matter how reputable the shop, be sure you double-check the shop's work so you don't risk burning a new valve.

Cheers!

[fourtii]

if the parts were inspected correctly, i would say the machine shop was DEFINITELY doing their job and had the customer's interests at heart.

it is so much easier to throw things away on 'general principals', rather than evaluate and disposition parts accordingly. in a perfect world, parts should have serviceable limits published.

_________________

Proud owner of 2570440 & 2760440

and others

C.D. iesel...do you care to comment on this reply, or should I?