9.260 Deck height effect on compression ratio
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Teching In
Joined: May 2016
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9.260 Deck height effect on compression ratio I am getting ready to have some machining done on a LSX block. Boring/honing for sure. My LSX block has 9.260 deck ht, 20 thousands over stock blocks. Everything I have read says if your going to build it to typical build specs and use typical parts designed for 9.24 deck height I should have it machined to 9.24. But if I am planning on building to achieve forced induction compression ratios, does this still apply?
I tried to figure out what my compression would be or more importantly how much effect the .20 ci volume would have on lowering the ratio, but I am not confident in my math. I think I figured that it would add 42.5 cc to the cylinder volume if punched to 4.065 and slightly more if I do 4.125. (Its obviously no big deal to have it cut down but I don't like to machine away metal if not needed)
I would be running CNC ls3 heads. I think these are 70cc. I haven't bought a rotating assembly yet so that is still open. Is it viable or possible to leave the deck alone and run higher compression pistons, or is this not practical or give me too low compression? Thats assuming the deck finish will be good enough to leave alone. It looks pretty good to me but haven't done any checks.
I tried to figure out what my compression would be or more importantly how much effect the .20 ci volume would have on lowering the ratio, but I am not confident in my math. I think I figured that it would add 42.5 cc to the cylinder volume if punched to 4.065 and slightly more if I do 4.125. (Its obviously no big deal to have it cut down but I don't like to machine away metal if not needed)
I would be running CNC ls3 heads. I think these are 70cc. I haven't bought a rotating assembly yet so that is still open. Is it viable or possible to leave the deck alone and run higher compression pistons, or is this not practical or give me too low compression? Thats assuming the deck finish will be good enough to leave alone. It looks pretty good to me but haven't done any checks.
Piston Deck The Piston QUENCH is MORE important on SC engines.
I would "spec" .025"
I can supply the CORRECT RacTech piston.
I can supply the Crankshaft and Forged Rods.
Lance, BTW, at great price !
I would "spec" .025"
I can supply the CORRECT RacTech piston.
I can supply the Crankshaft and Forged Rods.
Lance, BTW, at great price !
Thread Starter
Teching In
Joined: May 2016
Posts: 34
Likes: 1
I was off one digit in my calcs! (.020 instead of .20)Thats why it didn't make sense. Can you explain what piston quench is and how it relates in this situation? I want to be as informed as possible and not rely completely on a machine shop for info and knowledge. (And also when I get to the parts ordering I will look you up Lance).
Piston Squish/Engine Operation OK, many here state "Quench has little power effect on SC engine operation".
Thus I will pass on that, don't agree, using another instance.
I will provide two reasons of benefit, there are more :
1. Most SC engines have a lower compression ratio, hence a lower combustion gas temperature BEFORE the Spark Instant.
The action of Squish, the term states a "pushing" of mixture generally into the center/plug area, adds heat to the pre-combustion gases.
This is MOST important when the engine is throttled, when there is VERY LOW cylinder pressure.
This effect has a great influence on BSFC with the ability to run a higher AFR, good for fuel consumption reduction.
2. The Quench (Squish) area runs at lower temperature, the crown/head area that is in close contact.
This effect is VERY good for top ring land life, the area that pre-ignition is born.
The old story "HP sells engines, Torque wins races"
Lance
Thus I will pass on that, don't agree, using another instance.
I will provide two reasons of benefit, there are more :
1. Most SC engines have a lower compression ratio, hence a lower combustion gas temperature BEFORE the Spark Instant.
The action of Squish, the term states a "pushing" of mixture generally into the center/plug area, adds heat to the pre-combustion gases.
This is MOST important when the engine is throttled, when there is VERY LOW cylinder pressure.
This effect has a great influence on BSFC with the ability to run a higher AFR, good for fuel consumption reduction.
2. The Quench (Squish) area runs at lower temperature, the crown/head area that is in close contact.
This effect is VERY good for top ring land life, the area that pre-ignition is born.
The old story "HP sells engines, Torque wins races"
Lance
