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Discussion Starter · #1 ·
How tight of a quench area can be safely used on a 7M? I've read as tight as 0.035, but that is really tight with stock rods.
 
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Discussion Starter · #2 ·
Wow, that sounds tight. I've usually read 0.050" clearance as about minimum on a blueprinted street driven engine.

It depends a lot on your piston to cylinder clearance, since the pistons can rock side to side a bit. The benefits are rather small running it very tight, compared to the disastrous outcome once the piston hits the head.

I'd shoot for about 0.060".
 
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Discussion Starter · #4 ·
My pistons (flat-type with cut-outs) are 33.45mm tall (from rodbolt center to top of piston)
...they are almost level with the deck (not measured, just looked at).

Were you thinking of using domed pistons?

//Nielsen
 
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Discussion Starter · #5 ·
Actually ED_MA61 has his set at 0.035 running 10:7 commpression with stock rods. We were thinking .045ish but if I could get a little tighter that would be better. Most mass produced engines have a clearance of 0.060 maybe even more. But with my commpression I'm inviting detonation. It also fights of detonation at lower engine speeds. Provided my cranking pressure isn't to high(hence my other thread). The tighter quench will make my engine more efficient. Also reducing the quench I can reduce my timing gain some low/mid range torque. Plus 2-4hp:) The results are small but still a gain.
 
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Discussion Starter · #6 ·
NielsenRacing said:
My pistons (flat-type with cut-outs) are 33.45mm tall (from rodbolt center to top of piston)
...they are almost level with the deck (not measured, just looked at).

Were you thinking of using domed pistons?

//Nielsen
No they are flat.
 
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Discussion Starter · #7 ·
Ideally you want it so the piston just barely brushes the cylinder head, at the highest RPM. To get it that close, you need some amazing machine work and precision when setting it up.

Of course once the engine wears out a bit, watch out! Really the gains are couple of HP at the expense of having all your nice engine parts go to a scrap pile.
 
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