docc Posted July 14, 2015 Posted July 14, 2015 Soooo, having drunk the Kool-Aid (over-and-over), I know that the valves are to be adjusted "stone cold." But, I'm helping out a forum member with a tune-up and there's no opportunity to let the V11 sit that long. I always like to start the tune with a valve adjustment and fresh plugs (which I also like removing from a cold head). Question is, what to expect checking hot valves? Looser when hot? Tighter? By how much?A couple thousandths? More? How long does it take for the motor to cool down enough to be "stone cold?" Hours? Overnight?
stewgnu Posted July 14, 2015 Posted July 14, 2015 Blimey there's a question! They certainly take a good while to cool down- the head stays warm long after headers and crankcase. I am now very interested to know if there's much of a difference when hot. I am no help here, haa! Sorry!I though stone cold meant ambient temp at least (to ensure some universal 'yard stick')?. But I'd reckon after an hour or so it couldn't make much difference to the home mekkanik.... Oh and
docc Posted July 14, 2015 Author Posted July 14, 2015 I just did mine up after it sat five or six hours. I suppose I could get it up to temp and recheck them for comparison. Unless someone here just already knows . . .
czakky Posted July 14, 2015 Posted July 14, 2015 My SOHC Volvo calls for valves to be checked warm! I just sold a VW Beetle that had push rod adjusters similar to a Goose and I believe if you had to check em warm they were tighter. My concern would be plug removal though...
docc Posted July 14, 2015 Author Posted July 14, 2015 My SOHC Volvo calls for valves to be checked warm! I just sold a VW Beetle that had push rod adjusters similar to a Goose and I believe if you had to check em warm they were tighter. My concern would be plug removal though... Right? I definitely do not want the threads coming out with the plug!
andy york Posted July 15, 2015 Posted July 15, 2015 Cold means ambient temp. Old Porsche's require Cold engine to adjust valves. Rocker arm adjustment VW bugs are to be done cold also.
Lucky Phil Posted July 15, 2015 Posted July 15, 2015 Its always better to remove plugs from a warm head and install in a cold one, for reasons that seem obvious. Well to me at least Ciao
docc Posted July 15, 2015 Author Posted July 15, 2015 Its always better to remove plugs from a warm head and install in a cold one, for reasons that seem obvious. Well to me at least Ciao Wait . . . why?
Welshguzzi Posted July 15, 2015 Posted July 15, 2015 Ambient temperatures are variable - Sweden in winter or North Australia in summer? Could be different by 50 Celsius 1
Kiwi_Roy Posted July 15, 2015 Posted July 15, 2015 Doesn't everyone check the plugs hot after a good fast run?
docc Posted July 15, 2015 Author Posted July 15, 2015 Doesn't everyone check the plugs hot after a good fast run? Good point.
GuzziMoto Posted July 16, 2015 Posted July 16, 2015 I would expect valves to be tighter when warm. How much tighter? Well, you could adjust yours to spec, then run the motor to get it up to temp (that is one of the problems here, what temp is up to temp), then check yours to see what they are warm. I would avoid doing it this way, but I think it can be done.
docc Posted July 16, 2015 Author Posted July 16, 2015 First off, what's the chance of warming the bike up (18 miles riding) to 90˚C (guzzidiag), putting it on the lift and finding the right cylinder at TDC? Here's what I found: intake had loosened 0.002" (to 0.008") and the exhaust had loosened just less than 0.001" (to 0.009ish"). Not what I expected. I'll watch it over the next couple hours as it cools down and see what happens. edit: 40 minutes in my 20˚C/70˚F garage with two fans on the motor and guzzidiag reads 34˚C, valves measure 0.006/0.008. That's a much quicker "recovery" than I expected also. I'll have to check it again later and make sure they don;t keep tightening up as she cools to 20˚C.
andy york Posted July 16, 2015 Posted July 16, 2015 You do have an abnormal beast. Just like me lol the purpose of "valve clearance when cold" is cold metal is smaller than hot metal. Ideally when cold, set the lash, as motor warms up( in a perfect world) valve lash would be .000 If you set the lash when the engine is hot, in theory, you could have 2 or 3 times the desired lash if setting to spec. I suppose you could get it hot, set the lash to .000, but do you really want to take the chance.
GuzziMoto Posted July 16, 2015 Posted July 16, 2015 You do have an abnormal beast. Just like me lol the purpose of "valve clearance when cold" is cold metal is smaller than hot metal. Ideally when cold, set the lash, as motor warms up( in a perfect world) valve lash would be .000 If you set the lash when the engine is hot, in theory, you could have 2 or 3 times the desired lash if setting to spec. I suppose you could get it hot, set the lash to .000, but do you really want to take the chance. I would agree with you in theory, except that docc actually tried it and got larger clearance when warm. Perhaps it has something to do with the difference in push rod material to cylinder material. Or maybe more tests are required.
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now