Cylinder head material

[Metal_slicer]

I was considering making my cylinder head from brass but what about the valve seats? Will I need to insert steel valve seats or will brass work ok?

 

[Brian Rupnow]

Brass will work okay. All of my i.c. engines have brass valve cages.---Brian

 

[Cogsy]

Brass valve seats work just fine. Many model engines run with brass valve cages/seats in aluminium heads.

Edit : Dang it, Brian beat me while I was typing! What he said.

 

[Silvergoose]

What are the pros and cons on using bronze as a head material.

Thanks

 

[gbritnell]

Unless you only want a piece of shiny brass for the head why not go with iron or aluminum. With iron you don't have to make separate valve cages and guides, just machine them into the head. With aluminum I would suggest making either a valve cage assembly or separate guides and seats.
gbritnell

 

[Brian Rupnow]

George--I have no doubt that you are correct in what you say.---However, on my first two or three i.c. engines, I had horrible problems getting the valves to seal. It was so bad that I had to redo my valve cages a couple of times. If I had been using an iron head without cages, I would have had to scrap a far more complex part than a simple valve cage.---Brian

 

[Metal_slicer]

Ok brass it is. I have another question regarding the valve seats: it seems 60deg cutters are everywhere to be found and anything else is hard to find. What do you guys use?

 

[Cogsy]

When you are set up and cutting the valves you use the same setup to machine a valve seat cutter, then mill some flutes in it on the mill and your valve seat angles will match perfectly.

Here's a link to a couple of pictures LINK. It's basically just a valve blank with a few grooves in it. The 'stem' keeps the cutter perfectly aligned and you just need to turn it by hand and it cuts a beautiful seat.

 

[Silvergoose]

I have another question. Why machine the valve angle the same as the seat angle, such as 60 and 60 degrees? Why not machine the valves at 60 degrees and the seat at 59 degrees? this would insure a positive sealing surface? This would allow wear to occur without a loss in cylinder pressure.

Thanks

 

[Cogsy]

I would assume that (at least in this scale with very thin valve seats) the 1 degree difference would mean extremely thin line contact of the valve and would very quickly wear the softer seat to match the valve angle anyway. So there may be no benefit but added complexity. We only cut very thin seats anyway.

 

[Goldflash]

about 80% of the heat generated by combustion is absorbed through the cylinder head ( mainly because in OHV engines the exhaust gas flows through the head ) Thats why Aluminium is used these days for cylinder heads as it has a higher rate of conduction and heat dissipation. I prefer aluminium. valve seats can be Bronze with Aluminium Bronze being a good choice.

 

[Metal_slicer]

When you are set up and cutting the valves you use the same setup to machine a valve seat cutter, then mill some flutes in it on the mill and your valve seat angles will match perfectly.

Here's a link to a couple of pictures LINK. It's basically just a valve blank with a few grooves in it. The 'stem' keeps the cutter perfectly aligned and you just need to turn it by hand and it cuts a beautiful seat.

Oh nice! I like that idea. Thanks for the link.

 

[tornitore45]

What is a valve cage? I know of valve guides with integral seats and ports but never heard of cages.

 

[Metal_slicer]

What is a valve cage? I know of valve guides with integral seats and ports but never heard of cages.

Inserts that can very in design: