Competition 24V Cylinder Head - Chop and Port

[sbentz]

As many of you are aware, we run a 24V head that we chopped the intake manifold off of years ago, and build a bolt on intake manifold. Many others have done the same since then. I won't say that they copied us, as it is such a common sense deal, that everyone should do the same in order to really get into the intake ports to work them over and open up #5 and #6 fully.



The real story is that I had a spare head that was cracked in the intake manifold area, and I started whacking at it with a mill to see how i could improve the airflow. Once I had the entire thing cut off, I figured I might as well use it for the race car.



We are doing another head for our new motor, and thought I would put up some photos as it comes together to show how the ports look inside.



I would never do this for a street truck, or anything less that a full out deal. At 80 PSI with a set of twins, porting makes a small amount of difference compared to the cost and time to do it.

 

[Jim Fulmer]

Scott, were you meaning #1 & #6, I've seen recently that they are not hard to reach, just depends on what you do.



Jim

 

[RDLeader]

Scott, can you post a pic looking down into the intake?

FWIW, you may want to run the stop up on the quill to lock it down real good. There's alot of slop in the spindle/quill and locking the lever down rarely locks it good enough to hold. Just trying to save you from making a crash.



Roman

 

[sbentz]

Scott, were you meaning #1 & #6, I've seen recently that they are not hard to reach, just depends on what you do.



Jim

What I really meant to say was that the air flow to 5 and 6 are really shared with the stock cast in intake. Take a peek towards the back of the head, and see how small of a opening there is.

 

[sbentz]

Scott, can you post a pic looking down into the intake?

FWIW, you may want to run the stop up on the quill to lock it down real good. There's alot of slop in the spindle/quill and locking the lever down rarely locks it good enough to hold. Just trying to save you from making a crash.



Roman

I will post some more close up photos as we go. The old mill that I use is looser than, well just say LOOSE! I actually use a 2" end mill for the main work, I was chunking away at one of the ports to test out the roughing end mill. I am building some better holding clamps for the head.

 

[sbentz]

Here is a photo of the rear port and how restricted it is. Remember, the "B" head has 7 intake ports, each end feeding 2 valves each, and the center 5 ports are siamesed, sharing adjacent cylinders.

 

[sbentz]

Here is the front cylinder.

 

[sbentz]

Here is the port layout on the head, notice how the bolts represent the angles feeding each valve per cylinder.

 

[sbentz]

Here is the surface that the intake manifold bolts to. As you can see the pushrod casting bosses are the issue. They are protruding into the air flow, and in order to really clean up the airflow, you need to get clearance for porting, but also larger radius entering #1 and #7 ports.

 

[RDLeader]

Looks good Scott, do you have pics of the bolt on manifold? What size bolts are gonna hold it on?



Roman

 

[sbentz]

The one we have run for the last 4 years are 1/4" NC, allens, every 2" around the plate. i have a different design that I may try with this.

 

[Jim Fulmer]

Dang, I thought the 12V head sucked but wow... ... ..... is it really that bad or am I just missing something.



Isn't it nice to cut up stuff, one thing is for sure these heads 12 and 24's were made for cooling and not racing! Can you imagine the power with a head that would flow twice as much, or that you could match to the C. I. and boost we put out... ... ... ... ... how about a redesigned bare casting... ... ... ... that would be a years budget project.



Jim

 

[sbentz]

Port Photos

Here are some port photos of the 24 V head in ROUGH stages. It is a bit hard to see, the first photo is a pretty stock port, and you can see the rough size, and dull radius entering the ports. The second, is after a bit of rough grinding, and now ready for finish shaping and polish.

 

[sbentz]

Does anone have a good photo of the 12V port entry? I have not spent a lot of time working ont he 12V stuff, and curious how different it looks... .

 

[sbentz]

The famous "bad port" with the water port drilling. This is the feed for #5 rear intake valve and #6 cylinder front intake valve... .

 

[HOSS]

Very cool stuff Scott it is nice to see some one willing to share some of what he has learned. Being a 24 valve guy myself I am VERY interested in this

 

[sbentz]

You know, I debate what to put out and share, vs. what I keep "secret". What I feel anymore is share ALMOST all of it to keep the Cummins ahead of the rest.



It is hard to keep our "hood" locked..... 99% is out for the world to see.

 

[Green Machine]

Nice pic's thanks for the info. Not knowing much about the racing stuff or seeing your ride. have you ever built a new intake instead of welding the stocker back on? Maby feeding from the side instead of the top? With a 3 pipe style intake with the center being bigger to force feed #5?



Thanks

Ron R.

 

[Mark_Kendrick]

Good stuff Steve. Nice to meet you at ATS last week. The dragster is a really nice ride. I don't think anyone other than your son fits. . just ask Mike :-laf:-laf.



I wonder how much difference it will make with boost and EGT #s. I suspect boost will drop a lot and egts to match somewhat proportionally.

 

[sbentz]

Nice to meet you at ATS last week.



I wonder how much difference it will make with boost and EGT #s. I suspect boost will drop a lot and egts to match somewhat proportionally.

Mark, wish I would have had more time to talk to you at ATS. About the time we got to talk, some big green Ford on the dyno filled the whole damn building with smoke, and chased us all away. Must have been that darn MADDOG fellow. I am interested to see what you are doing with your turbo stuff, and hear more about what you though about our setup.



Clint and I are planning a complete different tubo setup for our new engine. rather than going the same way that everyone else is going, we are thinking about doing something a little different. The twin setup and wastegate we run now (as most of you out there have seen, pointed to and laughed at) is so simple that most people think will not work. Well, it does. And for reasons that most people don't even notice. Things are not always at is seems.



The new cylinder head is much more agressive than the one we have on the car now. In addition, I am planning on doing some cam testing to see if we can build some HP on the top end. On the 7. 98 run, we went flat at 1000 ft. due to being conservative on gearing and tuning. I was more concerned about putting on a safe but slightly fast run, than throwing the kitchen sink at the tune-up. Oh well.



I do think that the EGT's will get back in line a bit, currently too hot at 2500+ degrees F. The 12 and 24V heads are not know for air flow, so any improvement should make gains. If all goes well, we should see some real HP this year.