Quench Question

[perfconn]

How much piston to head clearance can you get by with before you risk detonation ?

[BLSTIC]

Depends on the combustion chamber design and how much it relies on quench/squish for mixture motion. The most detonation resistant engine I know of doesn't even have quench, but it's a 4v engine with a ton of tumble even compared to other 4v heads (and other tricks), so it has more mixture motion than any inline valve engine is going to get.

I'm not an expert on the subject so I don't have much constructive to add apart from that, but those who are will likely need to know what engine/head you're asking about.

[Procharged 434]

I am not sure on Small/Big Block Chevy or Ford, but on a traditional Pontiac engine and chamber design, the highest risk for detonation seems to be in the .060"-.095" window ... I prefer Quench Distance to be in the .034"-.039" area for a high compression, pump gas street engine(block zero deck, or piston .005" above deck, combined with a .039" head gasket.

[perfconn]

SB2.2 head. .043 in hole & .051 gasket = .094 quench

[RDY4WAR]

My rule for safe quench distance is .010-.015" per 1" bore diameter. So a 4.00" bore will be safe with .040-.060" piston to head clearance. Wider than that, you start risking detonation from insufficient turbulence. You can go narrower but then have to consider factors like piston to wall clearance (rock), piston weight and speed, stroke, quench area in the heads, and so on, in order to remain safe.

I would put the thinnest gasket possible on that SB2.2

[perfconn]

Can't.Already at 14.3 compression

[mt-engines]

I've run .130 without signs off detonation

[PackardV8]

How much piston to head clearance can you get by with before you risk detonation ?

As previously mentioned, too many variables; chamber design, intake swirl and tumble, compression ratio, intake closing point, bore diameter, et al.

SB2.2 head. .043 in hole & .051 gasket = .094 quench . . . 14.3 compression

I've run .130 without signs off detonation

Other engines in my experience, anything above .050", even though it lowered compression, would be more likely to ping than if kept in the .035" range.

[juuhanaa]

I've run .130 without signs off detonation

Was it the official Volvo instruction for the turbo to use two head gaskets? Anyway... Ive been wanting to tell you for a long time that youre doing it wrong. Maybe its because the caliber you use for measurement is too big.



-juhana

[Procharged 434]

Also, what I was speaking of above goes, goes for naturally aspirated engines only. Quench Distance is not a concern for me, in a Power Adder engine, due to the extra cylinder pressure and turbulence being introduced into the cylinder. Sometimes, but probably not in all cases, a thinner head gasket that creates a "tighter" Quench, equates to MORE detonation resistance, even though the compression increases. This is due to a more efficient Combustian Process.

[Bigchief632]

With the proper fuel for 14:1, it won't detonate.

[Procharged 434]

If your engine is Naturally Aspirated, and the piston is .043" in the hole, you definitley don't want to cut .043" off the deck of your block. The correct way to do it would be to order a set of custom pistons with a compression height that brings it as close to zero deck as you can get it with your current deck height, and with a dish to get you at the compression you desire. Then have the block decked to acheive your zero deck with the new pistons(so that you only have to cut the minimum off the deck to acheive zero), then run a .040" head gasket for your tight .040" Quench.

[panic]

The idea is that the quench volume, being chilled by surrounding surfaces, burns later than the main charge.

[RDY4WAR]

Can't.Already at 14.3 compression

So? What's holding you back from going higher? Are you trying to make this work on pump gas?

I would rather have 15+ SCR with proper quench than I would 14.3 SCR with improper quench.

[perfconn]

Engine is already together just waiting on intake spacers.I asked the question because I was wondering how the engine will act on dyno if detonating.Pictures of 33.4cc chambers & 4.135 bore pistons.