Page:
Home > Technical Chat > Valve to block/piston clearance

wil_h

User Avatar

9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

19th Nov, 2010 at 10:07:43am

What clearance would people generally allow between open valves and block/pistons?

I am using a 998 block that I had decked to clean up some damage, so the cut-outs for the exhaust valves (using 940 head) are not as deep as they once were.

It cleared before, but I've always just done them to a fixed depth as I know they clear. Just want to know what people would run so I can check.

cheers

Fastest 998 mini in the world? 13.05 1/4 mile 106mph



On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


minimole23

4309 Posts
Member #: 1321
Post Whore

Wiltshire

19th Nov, 2010 at 10:17:46am

You could always sit the head on with no gasket, turn the engine by hand to check it clears.

Not scientific, but no doubt a good way to ensure there is a safety margin there.

On 7th Oct, 2010 5haneJ said:
yeah I gave it all a good prodding

BENROSS

User Avatar

9812 Posts
Member #: 332
Resident Cylinder Head Modifier

Mitsi Evo 7, 911, Cossie. & all the chavs ...... won no problem

19th Nov, 2010 at 12:14:14pm

1.6mm is the limit for a HIGH reving engine wil............your safe at that, but i have built some at 0.6 and no problems todate

wil_h

User Avatar

9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

19th Nov, 2010 at 03:11:00pm

lovely job. My feeling is that it will be around 1mm, so should be ok.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph



On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


gr4h4m

User Avatar

4890 Posts
Member #: 1775
Post Whore

Chester

19th Nov, 2010 at 08:23:27pm

I went off the clearances as described in my cams instructions kent 266. 1.5mm but I could only manage a bit under that 1.44 I think.

info here
http://www.minimania.com/ArticleV.cfm?DisplayID=1766

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Home > Technical Chat > Valve to block/piston clearance
Users viewing this thread: none. (+ 1 Guests)  
To post messages you must be logged in!
Username: Password:
Page: