Sunday, April 15, 2007

Chamber reshaping work, major session!

Possibly the most effective giver of ecomony, torque, low speed torque/power, driveability. However this is not easy work! VERY delicate.

It took me 10hrs to "de-pocket" all the valves, roughly shape the chambers on each cylinder and finish one chamber completely! Tomorrow probably another 4hrs to finish the buffing and cleaning up the other chambers.

Problem is shown above the valves need to be open 2.5mm before they flow from the entire seat area, as 1/3rd of the valve is pocketed by the poor head shape. Also ALL the seats are poorly recessed/deeply recessed into the chamber, this absolutely slaughters low valve low flow, the closed to 2.5mm area, even at full life the awful recesses cause turbulence and cain flow potential. Ideally the valve seat inserts could do with being 1mm higher in the chamber...this is a fault on all K heads.
Even at 3mm lift the valve is only just starting to get past the pocket seen above on the right side, even then its still totally bad for flow as gas cannot leave the valve and throat cleanly...This pocket follows the valve movement with a 0.75mm gap till its 2.5-3mm open...1/4 of overall lift!...

Key to my work is opening out this area and all round the valve, removing the recess seat by polishing out the chamber.
To do this work I need some blank valves that sit very low down in the seat, waffer thin tops so they just cover the seat but don't protude from it, this allows me to grind directly over the seat and axe the recesses. I made some blanks from some old valves from my triumph head, just stuck them in a drill and worked them against a running bench grinder, this made the stems 6mm and axed the heads down. After about 30mins I had suitable items to begin the work.

First stage shown above is de-pocketing the areas I mentioned on inlet and exhaust valves...Exhausts just as important! and grinding out the majority of the recessed seats/chamber in this areas, leaving about 0.35mm left in chamber floor over the recesses, this thickness is for the final polishing.

This shows a finished chamber with the pocket area totally removed, the seats are flush with the head, as flush as poss anyway without deshaping the exits, there is NO restriction to flow even at 0.25mm valve lift. You can see the area in the bottom of the (chamber)image also now follows the contour of the valve, where before is was a straight line.

Where before you needed about 1mm to get anything happening...You can easily get over 1/3rd (funny thats the shrouded area) extra flow at these small lifts now, that makes for stronger torque, economy, efficiency, higher gas speed potential as gas gets flower stronger, earlier in the lift phase and doesn't get jammed up in the inlet.

The area between the valves also has been contoured to follow the valves seat area/angle...So mirroring the valve shape to control turbulance or so is the ideal.

I could have ground this area flat as seen on some other K heads, but I don't want to skim too much off the head to get the compression back, atm, 0.010" should do it, that leaves me with another 0.020" for future skims + can use a 0.010" shim to save the head, so hopefully many years of use! The exhaust valves don't fall apart or so I read...They bend in the case of piston contact.


Doesn't get much better than this surely? I am very happy with this work, I am sure a "pro" wouldn't be able to do any better. Most people wouldn't even come near to this. You are probably only going to get work like this at old guys in greasey sheds, certainly not off the shelf, or sold by farmers who never lift a finger.
Exhausts have been fully decked and blended into the chamber where ever possible, not totally possible to deck everywhere without cutting the chamber out more to get the right angle on the pocket areas... The remaining recesses are under 0.3mm..

The inlets have a more contoured meeting with the chamber, hense there is still some tiny rings of black round the inserts, these are only about 0.3mm deep and to remove them, would in my eyes, make the area where the valve seat cut meets the chamber not optimal and too angular. You can see this below.

All nicely contoured and blended.
Exhaust valve, these inserts are decked flush. I will be rounding off the sharp edges on the exhaust valve heads too to a nice round radius, as atm that angle is a bit tubulance maker!

Hope you have enjoyed a look at my chambers...

So just the other chambers to do, may polish them with soap to stop carbon build up...Then lap in the inlets, knife edge the seats, cut back exhaust valves and radius edges, cut back inlet valves...Thats it! Thank god.

This kind of thing is what I'd expect from any stage 2-3-4 head...Except no less.

Maybe I should start porting Triumph heads, proper heads, no "stage 2-3-4" junk, whatever a "stage" means, just an excuse to sell rubbish in a scale from "really crap/moderately crap/average", a good head is a good head right? no need for staging, its all out or nothing right?

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