How does quench area change affect same compressio

[Joseph Upson]

In communication with Mahle piston Co who is assessing my setup and has so far revealed to me that the Ford 5.4L engines naturally aspirated and supercharged run a .135 quench. I was also told that the 3900 may actually be a non quench engine and that the increase with the stroke and piston change may actually be a good thing. I'll update here after they look over the specs I've sent.

[SappySE107]

There is a difference between turbulence on the intake/exhaust stroke and turbulence in the compression stroke. Modifying the chambers is for flow and combustion. Valve angles are flow only. Polishing is combustion only (reflect heat, look pretty for the consumer).

You cannot take apart the stock .070" thick MLS head gasket and shave the middle piece down. You can, but then we would have an epic fail thread on this site and I am sure you don't want to start that off.

[Joseph Upson]

There is a difference between turbulence on the intake/exhaust stroke and turbulence in the compression stroke. Modifying the chambers is for flow and combustion. Valve angles are flow only. Polishing is combustion only (reflect heat, look pretty for the consumer).

You cannot take apart the stock .070" thick MLS head gasket and shave the middle piece down. You can, but then we would have an epic fail thread on this site and I am sure you don't want to start that off.

Actually I had already suspected that might be a problem and considered sandwiching 4 of the thinner outer sheets together for each side instead but that would take my compression ratio far beyond what I'm trying to achieve. Hadn't checked with anyone about it yet but I see no obvious problem with that working were it not for the compression ratio unless there's a possibility the thinner additional layers can be blown out. With corrections to the specs in a compression ratio calc the changes plus the mistake in the crank are offsetting and near dead even at a final 9.8:1 with the stock gasket but I want at least 10 plus.

[SappySE107]

Why are you bothering for .2 compression if you don't care about quench? You are just asking for problems with your ideas of modifying a MLS head gasket. Cometic can probably make a 3900 gasket since that is what they designed them on to begin with.

[Joseph Upson]

Why are you bothering for .2 compression if you don't care about quench? You are just asking for problems with your ideas of modifying a MLS head gasket. Cometic can probably make a 3900 gasket since that is what they designed them on to begin with.

I never said I didn't care about quench, I prefer it, but because OE specs appear to defy quench I may settle for non quench to avoid unnecessary expense that can be used for balancing the assembly.

[86FieroSEv6]

You wanna know a little secret? I hate MLS head gaskets with a purple passion. It's damned hard to get my local machinists to give me the surface finish I want for proper sealing. There's just too much of that "good enough" going around. When it comes to high performance, I prefer steel shim with stainless wire o-ring. A little pricey at first, but done and done right it creates an impregnable gas seal. Second choice for me is dead soft copper, or depending on the engine maybe even aluminum. If I'm not pushing it too hard I'll go with graphite. For production work, I use Fel-Pro blue stripe permaseal. I had these in a '91 'retta GT and stomped on it every chance I got with zero failure. In the final analysis, as long as you use the recommended surface finish (and for God's sake use a surface comparator gauge) and good fasteners with maddeningly accurate torque processes you shouldn't have any problems.

[Joseph Upson]

You wanna know a little secret? I hate MLS head gaskets with a purple passion. It's damned hard to get my local machinists to give me the surface finish I want for proper sealing. There's just too much of that "good enough" going around. When it comes to high performance, I prefer steel shim with stainless wire o-ring. A little pricey at first, but done and done right it creates an impregnable gas seal. Second choice for me is dead soft copper, or depending on the engine maybe even aluminum. If I'm not pushing it too hard I'll go with graphite. For production work, I use Fel-Pro blue stripe permaseal. I had these in a '91 'retta GT and stomped on it every chance I got with zero failure. In the final analysis, as long as you use the recommended surface finish (and for God's sake use a surface comparator gauge) and good fasteners with maddeningly accurate torque processes you shouldn't have any problems.

The nice thing about the MLS gasket is what appears to be a pro sealing substance in an outline fashion on the gasket. I intend to use head studs and figured that the outer layers of the gasket which I never bothered measuring but may be close to .010 thick would do the trick. I had also intended to use some spray on head gasket sealant for the middle surfaces. I'll do some more investigating first. I definitely want higher than the stock compression ratio but at the same time I don't want to add a headache. I really need to go ahead and beat on the stock engine and wait a few months before installing the forged motor since I just put the stocker back in the car and didn't get a chance to test the upgrades and cam degree in before leaving.

[Joseph Upson]

Why are you bothering for .2 compression if you don't care about quench? You are just asking for problems with your ideas of modifying a MLS head gasket. Cometic can probably make a 3900 gasket since that is what they designed them on to begin with.

I was concerned about the ability of an industrial machine shop to plain as well as insure consistency in thickness and surface texture of the middle gasket were I to attempt to have it shaved, but why do you believe using a couple of layers of the thinner outside portions of the gasket would not seal/work with the thicker middle section removed with a proper head and block deck surface? I'm asking because I've seen some pretty thin MLS gaskets and copper gaskets offered for other engines ofcourse with turbo applications, I don't know so I'm asking.

[ForcedFirebird]

If you want to get technical, there have been engines that didn't use head gaskets, but that was with like-kinding materials on the head/block, and an impecable sealing surface (they were hand-lapped).

Quench is a tricky thing. I have seen .020", but that was a big block in a mini-truck, detonation and rod stretch were less important in such a comparatively light vehicle. As betterthanyou said, with a quench that wide, you are basically making your entire bore part of the chamber, and I would be most worried about any sharp edges in that area becoming a glow plug - bad mix when talking about boost. A lot of stock motors have in the upper .050's and even as much as .065 in some cases, but does that really mean it's ideal, or maybe did the manufaturer try to keep tooling costs down by intermingling parts between more than one specific platform?

[Joseph Upson]

If you want to get technical, there have been engines that didn't use head gaskets, but that was with like-kinding materials on the head/block, and an impecable sealing surface (they were hand-lapped).

Quench is a tricky thing. I have seen .020", but that was a big block in a mini-truck, detonation and rod stretch were less important in such a comparatively light vehicle. As betterthanyou said, with a quench that wide, you are basically making your entire bore part of the chamber, and I would be most worried about any sharp edges in that area becoming a glow plug - bad mix when talking about boost. A lot of stock motors have in the upper .050's and even as much as .065 in some cases, but does that really mean it's ideal, or maybe did the manufaturer try to keep tooling costs down by intermingling parts between more than one specific platform?

You missed the earlier post regarding Fords 5.4L both naturally aspirated and supercharged having a factory quench height of .135 which makes it essentially a non quench engine. The 3900 has a stock quench height of about .094 stock so as the tech from Mahle indicated it is probably a non quench engine from the factory. The point is these are factory engines with what any small block chevy guru would tell you is bad news quench wise until you tell them GM made it that way from the factory and it runs 87 octane with 9.8:1 compression and nothing close to detonation.

My concern was with going considerably beyond what is already high but is probably not a problem at all from what I've discovered, however I want higher compression, an .020 gasket would raise my compression near 10.5:1 and still leave the piston about .1xx from the head amounting to a slight change from the stock overall setting.

[ForcedFirebird]

You missed the earlier post regarding Fords 5.4L both naturally aspirated and supercharged having a factory quench height of .135 which makes it essentially a non quench engine. The 3900 has a stock quench height of about .094 stock so as the tech from Mahle indicated it is probably a non quench engine from the factory. The point is these are factory engines with what any small block chevy guru would tell you is bad news quench wise until you tell them GM made it that way from the factory and it runs 87 octane with 9.8:1 compression and nothing close to detonation.

My concern was with going considerably beyond what is already high but is probably not a problem at all from what I've discovered, however I want higher compression, an .020 gasket would raise my compression near 10.5:1 and still leave the piston about .1xx from the head amounting to a slight change from the stock overall setting.

Joseph, I have known you to be far more intelligent than most and what you are doing is comparing apples to oranges. While, yes, the quench might be zero, but have you ever closely examined Ford's design in comparison to GM's? They accomplish the same thing, but in a different manner. With GM, you have a dish with a flat ring around it on the piston and a fast-burn chamber, Ford has zero quench, but closer inspection of the piston will show you that it actually gets closer to the head near the dish...

see post # 10 on a Ford forum I visit (I have a 6.8l V10 and a 4.6 2v in my personal trucks)...

http://www.ford-trucks.com/forums/870132-some-391ft-rebuild-questions.html

and for a quick reference...



Now take a look at the chamber design (post #178 )...

http://www.ford-trucks.com/forums/824138-99-2v-dynod-12.html

Have you measured the actual clearancs on the 3900 to confirm the fast burn chambers are in fact zero quench?

[86FieroSEv6]

When I want to be quenched, I drink iced tea. Just make sure there is adequate valve to piston clearance with a skosh extra to allow for rod stretch and put the bastard together already. Unless you are putting this thing into trophy competition and need that last .0001 for the win against the dude with the rust bucket 67 Nomad that's been kicking everybody's ass, I just wouldn't sweat it.

[Joseph Upson]

Joseph, I have known you to be far more intelligent than most and what you are doing is comparing apples to oranges. While, yes, the quench might be zero, but have you ever closely examined Ford's design in comparison to GM's? They accomplish the same thing, but in a different manner. With GM, you have a dish with a flat ring around it on the piston and a fast-burn chamber, Ford has zero quench, but closer inspection of the piston will show you that it actually gets closer to the head near the dish...

see post # 10 on a Ford forum I visit (I have a 6.8l V10 and a 4.6 2v in my personal trucks)...

and for a quick reference...


Now take a look at the chamber design (post #178 )...


Have you measured the actual clearancs on the 3900 to confirm the fast burn chambers are in fact zero quench?

I appreciate the input but the Ford 5.4L quench height of .135 is from a Mahle piston tech not me and since he mentioned the supercharged engines also I believe he's also referring to modern engines (Ford Lightning for example). I assumed there are differences between manufacturers engine and head designs but quench science does not change as a result meaning that beyond a certain point it's no longer quench although design characteristics may counter adverse effects.

I guess that's why he chose to share that information regarding my concern with high quench height and high compression together on an engine that is just beyond the most commonly accepted range of .060 or less. Understand that my quench height is in excess of .150 as a result of the crank offset which is .050+ more than stock and respectively extreme despite the compression of about 9.8:1 that results.

Remember I want higher compression #1 to justify H-beam rods along with possible high boost pressure. I also want as much efficiency as I can build into the engine which again begs appropriate quench height. I've read up on a good bit of this and that's why I'm not dismissing it so easily. In addition to the turbulence of compression forcing the mixture to the center of the chamber in a smaller area there is also a cooling effect on the piston due to better heat focus and transfer in the chamber. The .050 additional quench could be just enough to destroy the current detonation resistance the stock engine has at 7 psi, and no intercooling on mid grade fuel and that's a sacrifice I don't care to make as it appears I'll be able to run high compression and double digit boost with the intercoolers performance without water/meth use. 10 psi and 11:1 compression on premium fuel should be doable that's why this is so important and why I'll be figuring out how to go about tightning the gap.

If I put the heads on with no gasket at all I'd still have nearly .100 quench height so a thin head gasket will but at best only get me close to original.

Is it me or are there others having problems with the new site reply window jump scrolling while typing and relocating the cursor to a location different than intended.

[bszopi]

Re: text box fix

To fix the cursor jumping, goto your settings and select to use the standard editor, not the WYSIWYG editor. Forgot off-hand exactly where the setting is...

Sent from my Devour using Tapatalk

[geoffinbc]

I did not see any pistons mentioned. What ones are you using? Have you bought pistons yet? You could easily have forged pistons made to correct your quench and compression problems.