Piston Clearence?

[Saveit 0]

Hi there,

 

As some of you know, i am in the process of doing the XU10 on XU9 conversion using a 306 XSI 8v head. But suddenly it just crossed my mind if there is clearence enough for the skim that i am planning on. I am going to use a quite aggressive cam and my worries is if there is gonna be clearence enough between valves and pistons for a 2mm skim on the XU10 head. Details:

 

Head: XU10

Estimated skim: 2mm (going for about 11.5:1 CR)

Cam: Kent PT27

 

Product: PT27

Application; Supersports

Power Band; 2500-7000

Cam Lift(mm); I 12.49 E 12.24

Valve Lift(mm); I 12.24 E 11.93

Duration ; I 304 Deg E 296 Deg

Timing; 46/78 74/42

Full Lift; 106 deg.

VC (mm); I 0.25 E 0.30.

LTDC; I 4.31m.

 

As you see the cam has a quite high lift. I dont want to destroy the engine on the first startup

 

Thank you

Edited January 3, 2009 by Saveit

[Saveit 0]

No one knows?

[jonand 0]

Cant answer your specific question, but if you have any doubts it is best to dummy assemble the engine before machining and attach some plasticine or similar to the piston or valve heads. Then you manually turn the engine over and strip it back down to measure the thickness of the plasticine as it has been squashed. Bit of a performance but at least you then know for sure. I have also heard that you can acheive the same by using flux cored solder through the ports (saves dummy build) but never tried it.

Hope this helps - incidentally you may consider decking the block instead of the head to increase CR - usually a better option.

 

Regards

Jon

[petert 588]

As it's an 8V, with the valves perpendicular to the head, you won't have any problems with valve-piston clearance.

[welshpug 1,661]

How close can you go/what's the max Lift @ TDC possible?

[Saveit 0]

How close can you go/what's the max Lift @ TDC possible?

 

Yeah i would also like to know that?

[tony perks 1]

Lift at tdc for the pt27 from memory is 4.31mm on the inlet. so check the depth of the combustion chamber it its more than this you'll be ok, plus of course you have the thickness of the head gasket to add as well.