Thoughts On Engine Building

[rob83ke70]

hey

I've been poking around the wide wide web for a little while, and I haven't really come up with anything conclusive. I'm going to be building another K motor, in all likelihood another 4k, which will be going in a ke11. I have a set of 3k-b twin carburettors and manifold sitting on the shelf in the house, and I'm intending on using these, which brings me to my questions:

 

I know a 3k bigport head has bigger ports than a standard 4k, and a smaller combustion chamber (higher compression ratio). I haven't come across anything conclusive about the valves. Does a 3k bigport head have bigger size valves than a standard 3k/4k cylinder head? I'm told the combustion chamber is a "canted oval" instead of a "wedge" as well, what exactly does a "canted oval" look like? basically, is it a huge drama to machine a 4k head to 3k bigport specs? what exactly are the specs, what exactly do I need to get machined?

 

I have the twincarb manifold sitting next to a single carb manifold on the shelf and I can see that the ports are noticably bigger :D I would assume the exhaust ports would be bigger as well. I'm more than likely going to have to get a set of 4:1 extractors made as well, as soon as I work out the correct length.

 

Seems like a bit of trouble to go to, but based on how kylie's 4k turned out, its definitely worth it to put a lot of thought and planning into how it will all go together.

 

Robert.

[rob83ke70]

anyone know the size of the valves in a 3k bigport head and/or the size of the valves in a normal 4kc head?

 

the tosco manual says 37mm and 30mm for inlet/exhaust valve diameter but i'm assuming this is larger than a 3kb?

 

Robert.

[Felix]

36mm intake

29mm exhaust

 

They are the same for all motors, except K (1077cc) which has 34mm intake, and 28mm exhaust.

note. I'm not sure on 7k sizes.

 

The valve sizes stated in the tosco manual are aftermarket tosco (preTRD) parts.

Edited May 26, 2009 by Felix