milling a cumbustion chamber in a 24v head?

We are almost finished with this 12v head and i guess you could say it now has a chamber. However the main reason was to unshroud for bigger valves. We should be ready to flow the head soon. Here are some pics of the chamber. Jimmy
 

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1/2TONCUMMINS said:
We are almost finished with this 12v head and i guess you could say it now has a chamber. However the main reason was to unshroud for bigger valves. We should be ready to flow the head soon. Here are some pics of the chamber. Jimmy
Click to expand...

your missing two valves :lolly: :stab:
 
What does the swirl chamber say after milling the chambers into them? Does it change much?

Edit: what about the squish?
 
ok, that's what I thought we were talking about... I thought someone was implying to just mill down the entire section flat and leaving the rest of the deck raised LOL

looks good
 
1/2TONCUMMINS said:
We are almost finished with this 12v head and i guess you could say it now has a chamber. However the main reason was to unshroud for bigger valves. We should be ready to flow the head soon. Here are some pics of the chamber. Jimmy
Click to expand...

That looks amazing:woohoo:

Did you guys use a Mill to do it or did you just spend a long time with the head on a bench with a die grinder? Looks awesome
 
machined.png
 
Is that a ridge around each valve and the injector hole stayed raised while you cut everything else down .060"? Looks like some prime hot spots especially around those valves.
 
Gaskets only come so thick. They also move the injector farther away from the piston.
 
Unschrouding the valves is barely acceptable. Making the squish volume larger is absolutely the worst way of reducing the compression. You want the volume in the combustion chamber ie. the piston. Reshaping the entrant lip or making the bowl wider. In optimum situation there would be no other squish area but in reality there is some. Keeping it to the absolute minimum is the key. Flycutting the pistons for more lift or larger valves increases it and reduces the compression. Opening the valve are makes the valves flow more at low lifts so it also has some benefits. Thicker gaskets and machining the piston tops lower or the head in a similar manner are absolutely the worst you can do for your engine. In some points it is needed but thats only when all else has been done without reaching the desired compression ratio.
 
rockjeep73 said:
Gaskets only come so thick. They also move the injector farther away from the piston.
Click to expand...
X2. The tighter you can keep your squish and the nozzle tip to piston distance, the better. You'll make less smoke for the same power level and won't wash the top of your cylinders down at high injection durations. Lower CR the right way and machine the piston.

As for the chamber milling, that's really pretty and all, but it kills the squish. Why not lower the valves to unshroud them? Put new seats in and install them so the face of the valve is flush or just protrudes the bottom of the head. There's your low lift flow increases. Use slightly longer valves or machine the spring pad seat down if you're already on the edge of coil bind for the valve springs. Mill valve pockets in the piston accordingly to maintain P2V clearance.

Granted that's a bit more work (especially if a 24v), but from my experience with vw tdi's (which share the basic valve and injector layout with a 12v), little details like that make a huge difference. I can't tell you how many car's I've worked on that people threw the thickest head gasket to lower cr and it ran like crap. Yeah, some were really fast, but all smoked like a train. All the burn patterns on the pistons are always over half on top instead of mostly in the bowl like they should be. After I have the pistons machined and correct hg installed, they always run much better with less smoke without any other changes.

I know smoke vs hp levels don't really matter on race vehicles, but it's something that I think deserves some consideration for a vehicle that sees street use. The favorite pastime of cops in my town is to bust dumb farm boys with huge injectors and stock turbos for smoking. $85 for the offense and $25 for every second until it clears.

Just my $.02
 
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Whitbread said:
As for the chamber milling, that's really pretty and all, but it kills the squish. Why not lower the valves to unshroud them? Put new seats in and install them so the face of the valve is flush or just protrudes the bottom of the head. There's your low lift flow increases. Use slightly longer valves or machine the spring pad seat down if you're already on the edge of coil bind for the valve springs. Mill valve pockets in the piston accordingly to maintain P2V clearance.
Click to expand...

if u start changing head gasket thickness (not too bad) and or valve depth you start changing spring installed hieght, rocker arm geometry and push rod length. not many ppl take this into consideration.
 
DEEZELRAM114 said:
if u start changing head gasket thickness (not too bad) and or valve depth you start changing spring installed hieght, rocker arm geometry and push rod length. not many ppl take this into consideration.
Click to expand...

agreed. the more you sink the v.j. the more your geometry will change. also, losing life of the head for future freshen ups.
if the customer wants the area by the injector milled flush we can. that area is so thick around there.
we'll throw that sucker on a flowbench soon to see swirl & #'s.
 
getblown5.9 said:
Is that a ridge around each valve and the injector hole stayed raised while you cut everything else down .060"? Looks like some prime hot spots especially around those valves.
Click to expand...

as far as the ridges, the area that isn't machined by the valves if thats what you mean, is the stock valve job. we don't have the final v.j in the head yet.

there isn't really anywhere for hot spots because of the unshrouding or cnc milling removing the material.
 
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