Factory heads which one for 440 hi po street

[moparjohnny]

Which one was the open chamber heads?close chamber give off more emission,so give me your experience or opinion. Car will be a torque flite with a little shift kit,3.55 gear,mild cam. 67 coronet.

 

[RustyRatRod]

906, 902, 346, 452 are the popular open chamber choices. It's arguable which one is best.

 

[HT413]

Just curious, but why do you care about emissions? I give off more emissions just from my open crank case breathers in one romp around town than my Camry probably does in a month. And i run 906 heads lol.

 

[Hemirunner]

If both heads are on a complimentary combo and tuned correctly, it shouldn't be a distinguishable difference in emissions.

 

[Budnicks]

cylinder heads 101

A closed Chamber head will give a slightly higher compression ratio than an open chamber head design & if the quench area is properly spaced/sized, you have the proper thickness & material of head gasket & you tune the ignition & carburetor properly, camshaft if you have good sealing, rings {where the top piston-ring is located, what type/style material of rings used etc.} & valves, with a good round cylinders, properly honed & sealed rings, with a good multi-angle performance type valve job, flat mounting surface areas, with the proper length/style of push-rod & lifter pre-load, it really shouldn't make a real big difference on a street motor, at all, even for emmissions... Cylinder head Port design, size & flow characteristics, camshaft choice/size, overlap or lobe separation, amount of lift... also the style of intake manifold, dual or single plane & exhaust manifold choices cast iron HP's or headers, the carburetor choices, are far more important issues, to get the best bang for your buck... than just either open or closed combustion chambers... there are a ton of threads about cylinder heads & articles everywhere on the WWW... IMHFO I would highly suggest that you do some serious reading & research... There are quite a few great books too, one for example is, written by Mopar Performance, Mopar Engines 9th edition #P5249704, another is by MP "Big Block B/RB Engines" #P4876825 or many, many more, also like the one below, all have some good/decent tips & hints, or parts combos/suggestions... like my signature line says...

 

[moparjohnny]

bud, you are outstanding when explaining this stuff in the terms that you do,can feel the your knowledge and experience with this stuff and i am taking notes from you,you always give a great explanation and leave me with purpose and drive and your knowledge to proceed with your directions. thanks

 

[kansas connections]

squelch true will not effect emmissions much . the reason for a tight area or squelch area is to create turbulance in the combustion chamber wich helps control detonation , one reason modern cars can run higher compression on s***y gas is they have a tight squelch area to force air fuel mixture and cause turbulance in chamber. something can be said for open chamber heads will flow better around the valves by eliminating the shrouding of the closed chamber.

 

[Meep-Meep]

Actually, too tight of a quench area will contribute to higher HC emissions. This is because the flame front can't get in that space to burn all the fuel. I believe the open chamber head was developed for this reason - to get the flame front in to burn everything - but at the expense of compression. Quench is good, and one of the perks of a wedge design chamber, but it must be done properly.

It is also a fact that putting the top compression ring higher on the piston reduces that small annular clearance around the piston head, thus reducing the volume of fuel that can't be sufficiently burned. This is also why the hypereutectic alloy was used to make pistons in the later years because the stronger alloy allows for a higher ring placement. My 78 440 block in the green Bel has huge bore chamfers (responsible for a .4 point of compression loss) and I believe this was done to open up that area around the piston head to try and get the flame front in to burn all the fuel. Burning all the fuel in the chamber is a pretty darn good idea to make power. You just need to increase the compression ratio while not destroying the dynamic of the chamber. Late model engines do this very well.

- - - Updated - - -

The 906 head was the first "emissions" head and I believe is one of the best production heads to use next to the closed chamber 915. Both have the same intake port shape. The popularity of the later heads only came from the need to supply the masses because usable 915 and 906 heads were disappearing. Sure the flow in CFM can be equal between all the iron heads but I think the magic is in the WAY the mixture flows around the corner into the valve pocket. Of course the hemi solves that problem!

 

[Budnicks]

Actually, too tight of a quench area will contribute to higher HC emissions. This is because the flame front can't get in that space to burn all the fuel. I believe the open chamber head was developed for this reason - to get the flame front in to burn everything - but at the expense of compression. Quench is good, and one of the perks of a wedge design chamber, but it must be done properly.

It is also a fact that putting the top compression ring higher on the piston reduces that small annular clearance around the piston head, thus reducing the volume of fuel that can't be sufficiently burned. This is also why the hypereutectic alloy was used to make pistons in the later years because the stronger alloy allows for a higher ring placement. My 78 440 block in the green Bel has huge bore chamfers (responsible for a .4 point of compression loss) and I believe this was done to open up that area around the piston head to try and get the flame front in to burn all the fuel. Burning all the fuel in the chamber is a pretty darn good idea to make power. You just need to increase the compression ratio while not destroying the dynamic of the chamber. Late model engines do this very well.

- - - Updated - - -

The 906 head was the first "emissions" head and I believe is one of the best production heads to use next to the closed chamber 915. Both have the same intake port shape. The popularity of the later heads only came from the need to supply the masses because usable 915 and 906 heads were disappearing. Sure the flow in CFM can be equal between all the iron heads but I think the magic is in the WAY the mixture flows around the corner into the valve pocket. Of course the hemi solves that problem!

well said meeps

 

[67Satty]

There's a nice-looking pair of 346s on eBay right now:

http://www.ebay.com/itm/Dodge-Chrys...Parts_Accessories&hash=item4ac275f325&vxp=mtr

I think 346s are pretty much the same as 906s. For years I read on message boards about how the open-chambered heads are junk and/or your car will be a dog that detonates unless you run close-chambered aftermarket aluminum heads. So I was ready to be diappointed by my stock, unported 452s which was all I could afford but I've been pleasantly surprised. So I'd say, unless you need sub-12 second performance, regular old stock, unported open-chambered factory iron can get the job done for a street cruiser or something in the mid-12 to 13 second range.

Of course with that said, I will be putting some aluminum heads on my 440 as soon as time and funds allow because I want to go as fast as possible and my 452s have their limitations. But right now I'm still having too much fun to start taking things apart.

 

[Cranky]

Tight quench is usually better. Most say .040 minimum for clearance issues but I've run as tight as .019. It just depends on your combo. As for emissions? My cars may pollute but how often are the driven? Eddycate yourself for what you want to do and study up on quench etc.
http://www.forbbodiesonly.com/moparforum/showthread.php?12581-Quench-explained&highlight=quench

 

[RustyRatRod]

Keepin um tuned will go a long way towards bein green.

 

[Budnicks]

Keepin um tuned will go a long way towards bein green.

Amen to that brother, also a nice hot ignition box/module, hotter coil & ultra-low ohm resistance spark plug wires, along with proper heat ranges of plugs, to help burn all the fuel better, a hot Multi Spark ignition & firing thru long dwells, like 20+degrees helps too {like MSD or the Chrome CEI Module}... a properly sized/style & well tuned carburetor/induction &/or fuel system helps a ton also, for emissions....

 

[fatecaptured]

Not to be a dumbass. But, if emissions are are concern? Why not throw some good ol catalytic converter's on there to burn up the crap before it dumps emissions into the atmosphere??
Not that I will ever worry about it, both my mopes are emissions exempt