Crossflow CFM

pmuller9 said:
If for some reason you do not need the .040" over ACL pistons and don't want to use them, then you would get another set of pistons from Autotec/Racetec.

It doesn't matter if the 200 rod and ACL pistons are a hard-to-get combination, since the Molnar rods and aftermarket pistons are available.
The Molnar rods are almost as long as the 200 rods and are stronger. (6.21" versus 6.27")

ACL pistons are a high silicon alloy piston that is fine for NA use but not for power adder applications.
Here is a statement from their own publication.

"ACL Performance pistons are NOT intended to replace forged pistons in applications where output isgreater than 100 BHP/litre or in turbocharged and supercharged engines. However they are ideal for engine builders wishing to obtain moderate increases in power and speed from otherwise standard engines for street or off road use."

Autotec/Racetec forged pistons would be far better for supercharger use.
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So it sounds like I should sell those for a chunk of change and get the molnar/racetec combo, gotcha. I plan to beat the hell out of this thing, and doing this would allow that, I underatand that now. I was a little worried about that when I saw cast aluminum pistons.

Just went through Racetecs catalog, looks like it would have to be a custom forged piston. You know what these typically cost? Its the 'custom" word I dont like lol. The closest I saw was a chevy 305, but thats fairly bored over to make fit.
 
StarDiero75 said:
So it sounds like I should sell those for a chunk of change and get the molnar/racetec combo, gotcha. I plan to beat the hell out of this thing, and doing this would allow that, I underatand that now. I was a little worried about that when I saw cast aluminum pistons.

Just went through Racetecs catalog, looks like it would have to be a custom forged piston. You know what these typically cost? Its the 'custom" word I dont like lol. The closest I saw was a chevy 305, but thats fairly bored over to make fit.
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They are indeed custom pistons.
You would fill out the custom order sheet.
I can help you do that if needed.
The Autotec 4032 alloy forged pistons were about $650 a set but prices keep going up lately.
The Racetec 2618 alloy forged pistons will be more but I don't think you will need to go that extreme.
 
pmuller9 said:
They are indeed custom pistons.
You would fill out the custom order sheet.
I can help you do that if needed.
The Autotec 4032 alloy forged pistons were about $650 a set but prices keep going up lately.
The Racetec 2618 alloy forged pistons will be more but I don't think you will need to go that extreme.
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Nothing on the piston form will change, except bore with oversizing, right? I guess I can get the form filled out and ready.
 

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Another thing with the MPFI that looks like it will suck is the injector locations. Any buyable intake on the market has tiny runners and almost no room for injectors. They have to be angled 90° to the intake which isnt super efficient. I cant mount on the bottom b/c of the distributor... Do I just suck it up and angle it like that? Or should I just stop whinning and stick with the sniper? The sniper will support draw-thru. Can it be mounted sideways?
 
I asked the Holley techs about using the Sniper throttle bodies as side drafts and the answer is no because the annular discharge ring needs to be horizontal to work properly.
 
pmuller9 said:
I asked the Holley techs about using the Sniper throttle bodies as side drafts and the answer is no because the annular discharge ring needs to be horizontal to work properly.
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Thats stupid. They shoulda designed it better haha. So I'll plan on finding a sideways throttle body that will support 890cfm, the roots charger, plan on just doing 90° injectors, and roll with the aussie speed intake. i got this.
 
StarDiero75 said:
Ok so I'm gonna be limited on valve size then, now does this come from the bore size or the valves are too close together in the head? I'll definitely have to see once i get it. Are the valves inherently short like the log heads where they aren't designed for much lift? I'd really like to keep the multiport efi it has on it. This will give me the best fuel distribution. To make this easy to drive with my power goals, its definitely going to have to be boosted, ok thats alright. The cam i have, would that be bad for a blower?

Thats perty impressive any other mods like a cam or anything? Or is it just a blower? I remember yoy showed me this engine and told me to get a 200 or a 250 aussie, thats why im in this mess now hahaha.
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Ok Ive checked one of my crossie heads, it has 1.84/1.54 valves, I think you could get 1.9/1.6, it will be tight and IMO no gains to be had. The inlet port is very nicely shaped and comes down almost verticaly over the back of the valve, possibly a tiny bit of blending behind the valve seat, but even that I doubt you would get far. The exhaust is very nice as is. A bit of chamber work might help, it depends on which head you have. Dont forget these alloy heads have good valve seat inserts in them from the factory, Ford here sold a LOT of cars set up for LPG, and they need good valve seats. The inlets are silicon bronze I think, the exhaust steel of some sort, but they last a long time even in taxi service. IMO these heads are quite superior to the 250-2v head, and they are lighter and bits are far more available.
 
aussie7mains said:
Ok Ive checked one of my crossie heads, it has 1.84/1.54 valves, I think you could get 1.9/1.6, it will be tight and IMO no gains to be had. The inlet port is very nicely shaped and comes down almost verticaly over the back of the valve, possibly a tiny bit of blending behind the valve seat, but even that I doubt you would get far. The exhaust is very nice as is. A bit of chamber work might help, it depends on which head you have. Dont forget these alloy heads have good valve seat inserts in them from the factory, Ford here sold a LOT of cars set up for LPG, and they need good valve seats. The inlets are silicon bronze I think, the exhaust steel of some sort, but they last a long time even in taxi service. IMO these heads are quite superior to the 250-2v head, and they are lighter and bits are far more available.
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Do you think the lack of gains is b/c of the chamber size limiting airflow? What about just a larger exhaust valve to help get the air out? Is there anything to be gained with just that? Oh I know the crossflow is way better. Thats why I'm looking at getting one now. You mentioned it a bit ago on my 250 2V build, now here we are lol.
 
IMO the lack of gains, is because Ford did a good job on the design. I wouldn't bother with any exhaust work, its good as they come. As to improvements to the chamber, there is a variety of chamber shapes, it depends on what you get, the two Ive got and the one in my car are all fairly open chamber heads, You might get a bit out of it, but you will run under the gasket area before you get far. The valve seat inserts are right up against the chamber walls as they are, so not much scope there. The intake port itself is 36mm, you might be able to enlarge it 1-2mm, but whether this would make much difference I couldnt say. The intake on the 250-2v head is bigger, and is generally considered too big for the relatively small valve it has, the exhaust is awful, and you cant do much with it. The crossflow alloy head is a much better proposition on most fronts as we have discussed before, and now days its heaps easier to find and tonnes cheaper. Ive paid as little as $100 for a whole engine which turned out to be a 200 and good standard bores. The only better engine is the SOHC AU engine or the barra, unfortunately the Barra is a big heavy thing, its a ripper engine, too big for my car, ATM they are cheap down here, you can get a whole car for $1000, the engines can get as low as 250, they do not blow up and last forever.
 
StarDiero75 said:

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I meant screw, but what about a roots like this? Opinion?
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Look at both the Compressor maps and flow charts for the Eaton M112 supercharger.

A roots supercharger is very inefficient.
The M112 has a max rpm of 12,000 and is limited to about 10 lbs of boost.
It also has a VE of 85% at 10 lbs of boost.

If the engine will run to 6,000 rpm that means the M112 is limited to a 2:1 drive ratio.
At a 2:1 drive ratio and an 85% VE it will only produce around 7.7 lbs of boost even if the engine only has a 85% VE.
Beyond 5000 engine rpm, the Thermal Efficiency drops below 60% making a lot of heat in the airflow going into the engine.

There is a reason why all the early generation of Eaton superchargers are inexpensive.
 
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pmuller9 said:
Look at both the Compressor maps and flow charts for the Eaton M112 supercharger.

A roots supercharger is very inefficient.
The M112 has a max rpm of 12,000 and is limited to about 10 lbs of boost.
It also has a VE of 85% at 10 lbs of boost.

If the engine will run to 6,000 rpm that means the M112 is limited to a 2:1 drive ratio.
At a 2:1 drive ratio and an 85% VE it will only produce around 7.7 lbs of boost even if the engine only has a 85% VE.
Beyond 5000 engine rpm, the Thermal Efficiency drops below 60% making a lot of heat in the airflow going into the engine.

There is a reason why all the early generation of Eaton superchargers are inexpensive.
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This makes so much sense now. Yeah I see these pretty cheap all over the place. Alright, I'll go back looking for the twin screw. Are there any particular junkyard cars that might have something that might be good to use?
 
StarDiero75 said:
This makes so much sense now. Yeah I see these pretty cheap all over the place. Alright, I'll go back looking for the twin screw. Are there any particular junkyard cars that might have something that might be good to use?
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Sprintex, Whipple, Kenne Bell, Opcon, I have the Sprintex S102 on mine. These have a maximum rated rpm of 14000, but I know of some driven much higher. I run mine right to that limit. I have seen 18psi on mine, and i think it could go higher.
 
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