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Billet cylinder head

Billet cylinder head

Billet cylinder head


I am looking for advice on material selection.  I am designing a one-off prototype aluminum cylinder head for a 2.4 litre, liquid cooled 4-cylinder inline four stroke engine with pushrods and two valves per cylinder.  The OEM cylinder head is cast iron. The OEM engine block is cast iron, as well, and has wet sleeves.  No nitrous/turbo/blower operation is planned.  The idea is to have the head machined from billet aluminum.  I am planning to copy major dimensions from the original head and improve on the ports and combustion chambers.  
What would be a suitable alloy for this application?  Availability and cost are of course factors.  What are some of the not so obvious things to consider on this project?  
Thanks very much!

RE: Billet cylinder head

The only man I ever knew that was crazy enough to do "one off" cylinder heads was killed this summer in a dune buggy accident in Idaho.  If memory serves, he ended up having the heads cast at a local foundry and then finish machining them.  They were for a Fiat 850 based sports racer from the early 1960's.
I know of several billet heads for a hemi drag engine.  The thing had three plugs per cylinder.  Not exactly what I would think could be "streetable".


RE: Billet cylinder head

Ive looked into this and as Pat said, water ways are the problem, by the time you have made yourself enough tool access points in order to remove sufficient material around the combustion chamber you have weakened the head alot.
If you skimp on machining then you end up with hot spots which as you know is'ent good either.
I take it your using alloy for its improved heat transfer properties over cast Iron?
Do you intend bumping the compression ratio to take advantage of this?

If you are going ahead and have worked out a milling plan that your happy with in order to give you adequate cooling above and around the combustion chamber then you need to get some 6061 billet, it welds well too which may be of benefit to you as I feel you will need to close up/plate any mill access points which, when finished will end up as flange faces etc...

You will also need to take it to a t6 temper, Im sure your aware of that.


RE: Billet cylinder head

My heart goes out to the fellow who died driving his dune buggy.
Thank you Brian for confirming that 6061-T6 will work.  Yes, compression will be bumped to maybe just under 11:1 to compensate for the greater heat loss and to allow operation on pump premium gas.  Losing weight, ease of machining and design changes are factors that make me look to (billet) aluminum.  
I agree with Pat and Brian that the coolant jackets are the trickiest part, and I came to the same conclusion that trying to make it a one-piece design would leave me with a lot of hot spots.  This is not a flow-through design, i.e. intake and exhaust are on the same side of the head.  So at this point the multiple piece design seems like the only feasible one (although structural concerns remain).  However, I found a number of examples of billet heads, and from the photos I'm not sure how they incorporate the coolant jackets.  I would appreciate it if you could review the links and let me know how you think they've done it.



(about 1/4 down the page)

(Discussion and test by David Vizard of billet SB Ford head made by Ultra Pro Machining.  Photos have unfortunately been deleted.)

RE: Billet cylinder head

Oops, I just saw that on the KRE site it says that they might make water-jacketed casting from the billet heads later, nevermind.  Looks like these heads have no water jackets.

RE: Billet cylinder head

Ive been through all this over the last few years with regards milling a head out of billet, its a lot of machining, and Im still not convinced a perfect water way can be machined to provide correct cooling around plug, exhaust port, base of intake port, and above the combustion chamber without weakening the head considerably.

A multi piece head could be done of course but that involves many setups on the mill and errors are more possible.

I went to all the trouble of cutting up a 16v cylinder head just to see exactly where the waterways were and their size etc, once I had this done there was no doubt in my mind that the only way I could get these same waterways in my own head which Im designing and building was to cast it from A356, and to be honest, 4 months into it, Im glad I did go the casting route.
If you want pics of these cutaways let me know, itll give you an idea of their complexity and coolant contact area.


RE: Billet cylinder head

The plastics moulding industry uses Berilium copper inserts or isopipes to extract heat from difficult areas where waterflow is critical but difficult.


These need to have one end inserted into the hot spot and a reasonable proportion of the other end exposed to water flow.

A lot of drag race billet heads are used with methanol fuel that does not require nearly so much cooling as a petrol fueled motor. It also only has to endure a short heat cycle like about 10 seconds or less.  

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