Topic: K7 combustion chamber Q?

[Don R]

 I recently read the 77/78K has a bigger combustion chamber than early K's, how does that compare to the early K?
  A similar question was recently asked about the F2 head, if I used 10.25/1 Wiseco's in 65mm, how much compression reduction would there be? A wild ask guess is close enough.
 

[PeWe]

I bought an ugly 392 head with good fins. It should be ported anyway. Most guides really bad, all ex and 2 in. All replaced. Bigger valves.

The chambers were between 22.5-22.9cc

Someone had tampered with it so I do not know if chambers had been smaller. Head height as stock, not milled.

392 mark is upside down.



Look like residues of a Honda sticky head gasket.



Chambers 23.7cc after restore and porting as ordered. Here with 72mm gasket 33.5/28.5mm valves.


Drilled the 2 stud holes for oil with 9.5mm drill. HD studs are 8mm so not much left for flow.
Maybe more 392 heads are like that.

[scottly]

IIRC, the K7 has an approximately 24cc chamber according to my rough measurement, the early chamber was reported to be 22cc, and the F2/3 was reported to be 28cc.

[Don R]

 Thanks, I had forgotten the last two K models may have 392 heads.

[PeWe]

A burette and a piece of clear plexi with 2x  5-6 mm holes will help you to find out.

Very useful to measure chambers, verify volumes and if equal.

I use a 25ml version
Head is resting on a valve cover with cam holder bolt mod that levels it.

[Don R]

 Once upon a time I had a graduated syringe, I do have lexan left from our dragster windshield too.

[Don R]

 I noticed that CycleX made mention of using these 392 heads with 12-1 pistons to make a little more sane compression ratio. My thought exactly.