U-flow horsepower limitations

[Walken100]

Ok, I'm out of commission for a couple of days (don't get old) and I have question that I've been considering a bunch. What are the U-flow cylinder head limitations from a horsepower standpoint. This is NOT directed only at the 300. Of course that's what I've been working on so that's where the question comes from but the question is more than that.

2 scenarios a head for a 300 application (don't limit yourself to an oem head for discussion):

1. 500 NA horsepower limit (stock block and crank). Can a U-flow get you there. For me the only limitations is flow, CSA and possibly intake manifold options. But am I missing something?
2. Max NA horsepower application? Honestly, to me its the same limitation with the addition of intake manifold design options (you are going to have to make a manifold).

The real reason for this question is that I'm exploring things I can do that help a U-Flow head specifically. I'm thinking more in the chamber than the ports but......

Thanks in advance for entertaining my curiosity

 

[pmuller9]

1. 500 NA horsepower limit (stock block and crank). Can a U-flow get you there. For me the only limitations is flow, CSA and possibly intake manifold options. But am I missing something?

If we limit the stock block and crank to 7000 rpm you would have to make 375 lb ft of torque at 7000 rpm to get 500 hp.
At 6000 rpm it would take 437 lb ft of torque.
I don't see that happening with the present available U-Flow head castings.

You would need a High Port U-Flow head where the ports are at least .650" higher than the present U-Flow heads.

 

[Walken100]

If we limit the stock block and crank to 7000 rpm you would have to make 375 lb ft of torque at 7000 rpm to get 500 hp.
At 6000 rpm it would take 437 lb ft of torque.
I don't see that happening with the present available U-Flow head castings.

You would need a High Port U-Flow head where the ports are at least .650" higher than the present U-Flow heads.

I definitely am starting to understand the limits of the current head. I'm curious about the limits of a U-flow head in general as compared to a cross flow. Ie, what makes a cross flow head so much better?

 

[pmuller9]

I'm curious about the limits of a U-flow head in general as compared to a cross flow. Ie, what makes a cross flow head so much better?

If all the ports are on one side of the head, then the horizontal port dimension is limited by the length of the head.

Secondly, in order to limit the common wall overlap between the intake and exhaust ports to minimize heat transfer from the exhaust ports to the intake ports, the exhaust ports generally sit lower than the intake ports which handicaps the exhaust port flow.

The U-Flow head dictates an inline valve configuration with little room for variation although valve canting is still possible.

 

[aussie7mains]

If you look at heads for the old Holden six (very similar to chevy inline) then the irving or Jzed head shows the way:-http://www.jzedholden6.com.au/products.html
And the Irving which preceded the jzed:-https://www.headstuddevelopment.com.au/hsd-irving/

The secret to power is a downdrafted intake port, the non crossflow design is less of a liability than you might think.
All of these engines achieved 100bhp per litre with pushrods, but it takes a well developed engine to do this. IMO its easier to get something more modern like a Barra and small turbo to do it. Power = torque=bmep=VE=breathing!

 

[Walken100]

the non crossflow design is less of a liability than you might think.

That's what I've been thinking. The cross flow has some packaging benefits but...

IMO its easier to get something more modern like a Barra and small turbo to do it. Power = torque=bmep=VE=breathing!

Don't disagree. This, for me was a effort to better understand NA technology relative to a U-flow head.

Or alternatively is there something else a U-flow head likes beyond flow and area.

 

[Walken100]

If all the ports are on one side of the head, then the horizontal port dimension is limited by the length of the head.

Size matters.....

Secondly, in order to limit the common wall overlap between the intake and exhaust ports to minimize heat transfer from the exhaust ports to the intake ports, the exhaust ports generally sit lower than the intake ports which handicaps the exhaust port flow.

The tech discussions on this topic vary greatly. I was concerned with what you have outlined but without a "magnitude of impact" information I suspect for anything short of an unlimited no holds barred application it matters but I also suspect that is beyond 500 HP.

The U-Flow head dictates an inline valve configuration with little room for variation although valve canting is still possible.

This was the one that I landed on after watching some discussions from Darin Morgan. But then I ran into a discussion (without measurements) on the benefit of U-flow to swirl and overlap flow. I have strong doubts about improving overlap flow over a correctly designed cross flow head but the swirl and combustion efficiency discussion caused me to think about detonation resistance. This also got me thinking about what does that chamber what to leverage any potential overlap flow benefit (however slight)

I'm not going to lie, I started a conversation with my machine shop on canting the valves a bit.....

 

[pmuller9]

If you are going to cast a new U-Port head, significantly raising the ports on the U head can increase the intake port flow rate over 300 cfm.

 

[Walken100]

If you are going to cast a new U-Port head, significantly raising the ports on the U head can increase the intake port flow rate over 300 cfm.

Definitely not the plan but I was thinking that 300 CFM is not a stretch with a correctly designed U-flow cylinder head.

 

[pmuller9]

Definitely not the plan but I was thinking that 300 CFM is not a stretch with a correctly designed U-flow cylinder head.

If you have a sacrificial head, use a hole cutter and come in just short of the valve cover directly into an intake bowl.
Sleave the hole and blend it into the bowl and the short turn radius and see what it flows.

 

[Walken100]

If you have a sacrificial head, use a hole cutter and come in just short of the valve cover directly into an intake bowl.
Sleave the hole and blend it into the bowl and the short turn radius and see what it flows.

Once I finish my work on the Promaxx head I'm going to play with my practice head. There is no way that I can see the stock head getting to 300 CFM. More importantly there isn't enough material to support an adequate CSA to support a significant increase in horsepower (RPM). But thats not going to stop me from playing..... The items I'm super curious about are reshaping the chamber around the intake and exhaust, raising the port and substantially widening the short turn. Gonna take a bunch of hucky puck but it will be a fun learning exercise. I've just have to keep the project on track in the mean time.

 

[pmuller9]

If you insert a pipe as shown in the picture in post 10 and have it stick out above the head, you can have a plate across all six pipes to bolt the custom intake flange to.
Then epoxy the former intake openings and use the head on an engine.
You may want to epoxy the small water jacket violation at the top of the port before installing the intake port pipe.

 

[Walken100]

If you insert a pipe as shown in the picture in post 10 and have it stick out above the head, you can have a plate across all six pipes to bolt the custom intake flange to.
Then epoxy the former intake openings and use the head on an engine.
You may want to epoxy the small water jacket violation at the top of the port before installing the intake port pipe.

Now you are just egging me on.....

 

[pmuller9]

Now you are just egging me on.....

Yes I am.
As a side note, the intake port should still be closer to rectangular (Not perfectly Round).

 

[pmuller9]

Now you are just egging me on.....

I would encourage you to modify one intake port on your practice head as shown in post #10 with a pipe insert and flow bench it.
The biggest obstacle with the stock head is the 78 degree port angle and the short turn radius angle, not so much with the CSA.
Straightening out the port and short turn radius will do wonders for flow.

 

[Walken100]

I would encourage you to modify one intake port on your practice head as shown in post #10 with a pipe insert and flow bench it.
The biggest obstacle with the stock head is the 78 degree port angle and the short turn radius angle, not so much with the CSA.
Straightening out the port and short turn radius will do wonders for flow.

Once I'm ready for the build I plan on continuing to play with the head.

 

[Walken100]

Straightening out the port and short turn radius will do wonders for flow.

Not sure if you are following my porting thread but by raising the port cross sectional area .5" I went from 230's to the 250's in CFM. So I'm in total agreement with your statement. Additionally the promaxx head has a taller short turn. Still trying to leverage that..