I am always open for opinions
I wont cut the deck. Basically I was contemplating running a thinner gasket to get back some quench, thats all
When it comes time to build the next version, I'll be sure to use pistons that get where I need with only the mildest of clean ups to the surface
Knowledge of the effects of quench is new to me, ironically, other sources put it from "absolutely critical" to "you should do it" This site is awesome for its "no BS" approach. I do appreciate it too. Thats sorta how I work
As far as mine, it ran good before, so I am sure it will do well again, next build I'll focus on quench, but I am not going to for these pistons, my guess is that they are the problem, not the block.
Thanks again
Quench question
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Yes I was referring to when they are in tune.MadBill wrote:Not really. The cam, intake and exhaust are 'out of tune' at low RPM, and there is reverse flow after BDC.
We have different definitions of compression then. If we are adding mass to, and/or raising pressure in, a constant or shrinking volume, then I believe compression in fact is taking place. What other definitions of compression are there?At high RPM they are in tune and the flow continues well after BDC, which is why the valve is left open, but there is no 'compression' to speak of until it closes.
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Re: I wasnt clear
The way I see it even with 0.105" quench distance you still have quench. If this distance is measured at engine assembly the actual running quench distance will be at least 0.020" less. Installing the thin gasket and getting the quench down to 0.085 at assemble is an advantage if the engine can handle the additional compression. With a 0.020” gasket and steel rods at running speed and temperature the quench distance will be around 0.065"; not ideal but better than 0.085". With the piston to head that close togeather air/fuel mix will be moving out of the quench area into the combustion chamber cavity so the advantages of quench will be realized. Felpro makes a rubber coated steel shim for the SBC that works with aluminum heads. It might be available for your engine.Unkl Ian wrote:Too much clearance eliminates any benefit from the "quench" area.
.105" down to .085 won't make much difference, because .085 is
still too much.
My427stang wrote:or once you get beyond a certain point, does no quench = no quench and just run my Felpro .040 gasket because either way I have no real quench
I agree with Shawn on this one, the objective is to pack (compress) as much in the cylinder as you can and close the intake valve at the right moment before reversion takes place.Shaun wrote:Yes I was referring to when they are in tune.MadBill wrote:Not really. The cam, intake and exhaust are 'out of tune' at low RPM, and there is reverse flow after BDC.
We have different definitions of compression then. If we are adding mass to, and/or raising pressure in, a constant or shrinking volume, then I believe compression in fact is taking place. What other definitions of compression are there?At high RPM they are in tune and the flow continues well after BDC, which is why the valve is left open, but there is no 'compression' to speak of until it closes.
If the induction dynamics are working to perfection at the 'tuned' RPM, and the engine has huge TBs/carbs, good manifolding and great flowing heads, the cylinder pressure might be 3 psi above atmospheric pressure and thus by your definition 'compressed' when the valve closes at around 90 degrees ABDC. In the next 90 degrees (if the spark plug doesn't fire) the pressure will rise to maybe 350 psi. That's what I mean by compression in this context.
Thanks for clarifying Billl, I am aware that the large majority of compression takes place close to TDC (exponential rise in pressure as it approaches), but I see as anything along the path to peak compression, as compression, not just the final stages where it gets very high. Cheers and have a good week ahead.MadBill wrote:If the induction dynamics are working to perfection at the 'tuned' RPM, and the engine has huge TBs/carbs, good manifolding and great flowing heads, the cylinder pressure might be 3 psi above atmospheric pressure and thus by your definition 'compressed' when the valve closes at around 90 degrees ABDC. In the next 90 degrees (if the spark plug doesn't fire) the pressure will rise to maybe 350 psi. That's what I mean by compression in this context.