[ace.cafe]

It will be possible to order the head with standard rocker ratio and use it with the hitchcock cams if I remember correctly. Would this combination be of any advantage?

I don't know what the lobe lift of the Hitchcock cams are.
Our max lift at the valve is .600". I think the smallest rocker ratio we can get is 1.5:1. So probably .400" or lower lobe lift is allowed with lower ratio rockers.

I do know what the duration of the Hitchcock cams are. I don't see any advantage to using lower ratio rockers just to use those cams. I think the stock cams with 1.7 :1 ratio rockers would be better.
Rocker ratio almost always trumps lobe lift, unless you are already at max rocker ratio, because it isolates the majority of increased moving mass inertia on the valve side of the rocker. Cam lobe lift increases moving mass inertia on the entire valve train. With rocker ratio, all the mass of the tappets and pushrods and half of the rocker itself continue to operate at the relatively lower speeds of the stock lobe profile. Only the masses of the valve/spring/retainer, and half the rocker are subjected to higher speeds.   This is a big advantage when controlling the valve train at higher rpms with the valve spring.

The only time to consider cams in this platform would be for more duration when reaching for a higher rev limit. This would require other changes, such as bigger throttle body or carb, and more flxibility to move the rev limiter up the rpm range. In a higher budget racing application, we could envision needing longer cam duration. I don't think it will be needed for the intended street application within the PC-V rev limiter potential.

[KD5ITM]

Do you have a website that gives all the information about the head

[ace.cafe]

Do you have a website that gives all the information about the head

No, not at this time. I have a Yahoo Group which has most of our stuff, and a full open discussion forum.
We are not a catalog type outfit, and our custom work does not lend itself to little snippets of info and a price tag. We make things to order, based on the application. This billet head is as close to a retail product as we have ever done, and it isn't really even available yet. The first production is closed, and I will call for a list of interested buyers when we are ready to do another run.

Pretty much everything known about the head is found right here on this thread.
There is no possible way that I could put everything in this thread into a sales blurb on a web page. If you have any specific questions that have not already been covered here, or that you didn't understand, just ask me and I will be happy to explain.
 

[Otto_Ing]

Im looking at the GT head pics and wondering; the pushrods are not perpendicular to the rocker axles. Is the rocker bearing made to withstand some axial load? ...maybe it is just the pic that looks bit extreme?

[ace.cafe]

Im looking at the GT head pics and wondering; the pushrods are not perpendicular to the rocker axles. Is the rocker bearing made to withstand some axial load? ...maybe it is just the pic that looks bit extreme?

This is correct.
The pushrods are not perpendicular to the rocker axles.
The rocker bearing is made to withstand much more axial load than could ever be presented in this application. It is extremely common that the pushrods are not perpendicular to the rocker axles. Most American cars are made this way. Not unusual.
However, that is the reason why there are shaft mounted rockers in there, and not stud mounted rockers.

Just for the record, these rockers are the same rockers made for Pro Stock drag racing big block Chevy racing engines with  more than one inch of lift, and about 1200 pounds of spring force, turning 11000 rpm at the drag strip. These are not just "any old rockers".
 

[xpertmachinist]

Tom,
The head looks great, but one of the best feature of your design is the rockers. Very clean and professional - with room to be tweaked if someone would dare;It is just boss set up!

[ace.cafe]

Im looking at the GT head pics and wondering; the pushrods are not perpendicular to the rocker axles. Is the rocker bearing made to withstand some axial load? ...maybe it is just the pic that looks bit extreme?

Otto,
Also, I might point out that the pushrods are not going to be vertical either. Some of that angle is going to be taken up in the pushrod which will come up on an angle from the tappet. So, all the side thrust is not going on the rocker axle. Some of it is shared as side thrust on the tappet guide. The pushrod/rocker impingement angle is not severe.

[Otto_Ing]

I'm not worried, it just looks unusual to me. Most ohv engines I've seen the desing tends to be as perpendicular as possible. But I've not seen many american engines....maybe a reference picture?

[ace.cafe]

I'm not worried, it just looks unusual to me. Most ohv engines I've seen the desing tends to be as perpendicular as possible. But I've not seen many american engines....maybe a reference picture?

[Otto_Ing]

I see most of the angle goes in the tappets. So the holes for the pushrods in the head will not be straight or have the required clearance.

[ace.cafe]

I see most of the angle goes in the tappets. So the holes for the pushrods in the head will not be straight or have the required clearance.

This is the best shot that I have of the pushrod tunnel area. It was from an earlier machining stage, but it shows the wide clearance area pretty well.

[Otto_Ing]

Well, can't wait to see this head on my bike.....till than I keep looking at the pictures and asking annoying questions 

[Farmer_John]

if you keep asking, I won't have to start...

[Otto_Ing]

New confusion; on the stock head there is a bolt just before the sparkplug hole, I don't see a hole at that place in your pics only the tap for the plug?

[ace.cafe]

New confusion; on the stock head there is a bolt just before the sparkplug hole, I don't see a hole at that place in your pics only the tap for the plug?

Yes, it's there. The photos just are taken on angles that don't show it. Our head doesn't have as much cut-out there around that area, but the stud hole is there, and provision to get a socket on it. The spark plug will need to come out to torque the head nuts.

I have a meeting tomorrow with a machine shop to discuss various matters, including some ideas about getting castings done, and also for some small parts that I have been wanting to do. I don't know what will come of this meeting, but we shall see.