If your checking head clearance put pressure down on piston.to all that run low clearancesDo you push up on the piston from underneath when you check?
Nitro Nub
Nub;to all that run low clearancesDo you push up on the piston from underneath when you check?
Nitro Nub
Accucheck Is Most Accurate to check squish with.to all that run low clearancesDo you push up on the piston from underneath when you check?
Nitro Nub
marty, in your opinion, how accurate is the measurement obtained, by measuring with the engine assembled? it seems that it would take into account any variations in liner position and head also, by having them torqued down. not doubting anything, just trying to learn the best, affordable way to get accurate results, for the average boater. your setup in the link is very nice, but out of the reach of a lot us us.
Plastiguage will get within about .002-.003". Most of the measurements that you will get will show the clearance MORE than it actually is because the piston is being squeezed a ton at top dead center because of the taper in the liner. This makes the piston NOT get all the way to TDC.
The piston is either under "compression stroke" or "power stroke" when its near TDC,, at what possible point
is the piston going fly "up" that additional .002 or .003". That .003" play would mean .006" rod clearance wouldn't
it? why would you have that much?
JW
Plastiguage will get within about .002-.003". Most of the measurements that you will get will show the clearance MORE than it actually is because the piston is being squeezed a ton at top dead center because of the taper in the liner. This makes the piston NOT get all the way to TDC.
The piston is either under "compression stroke" or "power stroke" when its near TDC,, at what possible point
is the piston going fly "up" that additional .002 or .003". That .003" play would mean .006" rod clearance wouldn't
it? why would you have that much?
JW
When the engine is running, the metal expands and the fit of the piston to the liner is much looser. The tighter that your engine is, the more difficult to measure accurately the head clearance cold.marty, if you have a solid, non flexing rod, and a piston the same, what gives, not allowing the piston travel? the crank pin makes a full revolution, moving the crank pin through tdc. if i can turn it through a full stroke by hand..... you make it sound like a physical impossibility? the same lost motion you mention, doesn't this affect squish, while running, no matter how carefully measured on the bench? help me understand.....
that makes more sense to me. the increased taper when cold can and will affect measurements. how much "fudge factor" is involved in the on the bench vs running parameters? static squish, compression and squish/quench velocity is all affected by these differences, isn't it? or, is more of knowing what a specific measuring style will yeild? ie- your measurment says .006 squish, and mine (assembled) says .008, as long as we measure consistently, and changes are based on our OWN measurements, does it really matter? in these very technical discussions, it is good to be on the same page, but for most of us, we are changing things based on our measurements. and, while testing at the pond, some measuring procedures can be difficult. i know this kinda flys in the face of "good shop procedures", but i'm trying to relate a lot of this info to us common folk :lol: :lol: . don't mean that in any bad way, in either direction, just that a lot of folks don't have the access to the facilities, or the skill to use them. having been an auto tech for 30 years, i understand the measurements, and how to measure them, just not the same as you, or (probably) as precisely. thanx for what you, and others have taught me thus far, and thanx, in advance, for helping me understand more.
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