Piston to head clearances

SoDak24valve

SoDak24valve

Never Enough
Joined
Aug 17, 2010
Messages
334
I know that everything says that a person needs a minimum of .030 clearance between the pistons and the cylinder head. But if a person was to cut deep enough valve reliefs where a person didn't have to worry about piston to valve clearances how tight could a person run with the piston to head clearances. I guess if anyone would have any real insight to how much the piston grows height wise that would be great.
 
Wow, they do make different injector washers which have a different heights. Anyways with out something as that, which had been thought of like injector height, back to the simple question to people that have put a motor together before how tight of clearance could someone run for piston to head with deep enough valve reliefs to not worry about piston to valve.
 
dmax runs .020-.025 and .0015-.002" PTWC factory... MAHLE race cast piston spec is .002-.003 most run PWTC around 4-5 on comp engines or losser
really depends on which engine use and how loose you build it... main/rod/PWTC clearances.. the looser they are the more quench you need to keep things from contacting... valve reliefs not included...

as for efficiency/power
i unintentionally did a test, long story short.. went from .040 quench to .030 and picked up 3mpg and 10mph on a 5% grade in my 99 hotshot with an avg gross weight of 24,000lbs and nothing else changed..



as for valve reliefs................ how big of a cam you plan on running? how much piston protrusion 0" +.015" +.030", in the hole? what are the HG thickness options?
 
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There are thicker and thinner injector seals, I got shipped thicker seals and it didn't seem to idle good, but I was running a .010 gasket plus seals that were almost twice as thick.
 
I have .025 piston protrusion and I would like to run a standard mls gasket which measures .044 I know that only gives me .019 of piston to head, and the reasoning behind the thin head gasket is I do not want to drop the CR lower then I have to. I will have to check clearances on the rod bearings the crank was just polished so it shouldn't be to far off from factory. If it comes down to it I will just mill the pistons for the added clearance before I go to a thicker gasket.
 
SoDak24valve said:
If it comes down to it I will just mill the pistons for the added clearance before I go to a thicker gasket.
Click to expand...
milling the piston (5-20grams off a piston) would put the engine more out of balance than it it already is... OEM balances's sucks but still balanced...

engine already out and in building stages?
 
Yes engine is in the building stage and far as piston having weight taken off that would be minimal compared to the rest of the weight reduction that was done to the crank and rods. The last part of this motor is the pistons pretty much this is for my drag truck so it really wont be a dd at all.


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malibu795 said:
dmax runs .020-.025 and .0015-.002" PTWC factory... MAHLE race cast piston spec is .002-.003 most run PWTC around 4-5 on comp engines or losser
really depends on which engine use and how loose you build it... main/rod/PWTC clearances.. the looser they are the more quench you need to keep things from contacting... valve reliefs not included...

as for efficiency/power
i unintentionally did a test, long story short.. went from .040 quench to .030 and picked up 3mpg and 10mph on a 5% grade in my 99 hotshot with an avg gross weight of 24,000lbs and nothing else changed..



as for valve reliefs................ how big of a cam you plan on running? how much piston protrusion 0" +.015" +.030", in the hole? what are the HG thickness options?
Click to expand...



1/2 point in compression?

Skeptical_87506e_127195.jpg
 
when fuel consumption is 75% of my operation expenses when i was running hotshot..... going from ~9 to ~12mpg @ $4.00 diesel IS noticeable. going from 55 to 65mph on a grade.. is noticeable as well. i went from 16.5 to 17.0

its been proven over and over compression IS power and effciency IF the hard parts can handle it..
 
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