Pistons above block

[Reese92tsi]

I'm in the middle of a stock rebuild (6 bolt) and I've got what I think is an issue/problem. It appears that the pistons are slightly above the block surface. On a block that hasn't been resurfaced where do the pistons normally sit in relation to the block surface? What is the crushed thickness of a stock head gasket? What is the best way to measure the amount of piston protrusion?

 

[BogusSVO]

http://www.dsmtuners.com/forums/cyl...heck-piston-deck-clearance.html#post152107571

I normally see the pistons .005-.007 below the deck surface, on a 4g63

Most composite HG are about .040 crushed.

 

[SmoochDarling]

Rod bearings are torqued up and the clearance is in spec?

 

[Reese92tsi]

Rod bearings are torqued up and the clearance is in spec?

Yes they were torqued to 38 and the clearances are between .0015-.002

http://www.dsmtuners.com/forums/cyl...heck-piston-deck-clearance.html#post152107571

I normally see the pistons .005-.007 below the deck surface, on a 4g63

Most composite HG are about .040 crushed.

Thanks

 

[YZFR1]

I had my block surfaced .004" and the wiseco's sat at about .018" the last time i check them.

If you want to be sure where you stand just get some clay from the nearest store crafts section (note: don't use mother's car care clay )and some solid lifters or washers. Take measurements without the headgasket to give yourself some room for error. This is the only measurement i care more about damage control than accuracy. Here is what mine looked like with the cam gears being straight up VS. the tightest LSA:

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Remember, the best time for the contact to happen is not at TDC but when the piston is chasing up the exhaust valve and when the intake valve is chasing down the piston!

This is how i measured my priston to deck height:

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[Reese92tsi]

Great post!!

Could you describe your method of measuring the piston to deck height in more detail? Thanks

 

[YZFR1]

Sure thing.. btw, that straight edge might look expensive but i was able to score it new for 35 shipped on ebay. It looks and feels pretty solid though, i love handling that thing for some reson . Not sure if that seller is still there though.

The procedure itself is rather straight forward, find the true top dead center with the dial gauge. Personally, i prefer needle gauge vs electronic for doing that. Lay the straight edge and note the gap between piston and deck with feeler gauge. After, you would want to account for the piston rocking and take another reading while pressing down on the opposite side of piston. You would be surprised at the difference that would make. Also make sure all bolts are torqued to spec with minimum ammount of oil on the journals to help get more accurate reading.

Maybe someone else more experienced than me could chim in with some more pointers.

 

[Reese92tsi]

Hey guys whats the uncompressed thickness of a stock headgasket? It looks as if the pistons are above the block by about .008 and the head height is about 5.183 so I may need a thicker head gasket. I have a new ITM composite head gasket and it measures .067 thick which seems to be thicker than a stocker (unsure of whether the ITM and the stocker have a similar crushed-uncrushed differential though). If this gasket is truely considerably thicker than the stocker I may not have to buy an MLS.

 

[miliman13]

Revival. Any one know if there is such a thing as a composite thicker head gasket? As in thicker than the crushed .040 ?