Psston TDC to Eht. Valve clearance?

In a 'worse case' set up Ie: tall pistons with an aggressive duration overlapping cam, how close might the piston get to the exhaust valve at TDC?

Since the piston chases the exhaust valve closed you should have .040. I have run them as tight as .020 with a less aggressive cam and good valve springs but it is not very safe. Jim

Thanks Jim, that clearance is more than enough for me to ignore. Piston follows valve closing - wonderful mental image to help me think on it.

Back in the days of the Arc , they used to worry about Valves Tangleing . Valve Float , weak springs or harmonics ,
The Opening Valve could catch the Closeing Valve . From there on things got expensive .

If ' a dude ' had a knackered Barrel they could cut the side out of , they could observe all sorts of issues at set up .

New Valve seats could get them close to tangleing if set proud .Wasnt unknown to cut seats in for more clearance ,
Valve to Valve , though this theoretically reduces output .

Id aim for 35 thou minimum , piston to valve . Shimming off coil bound its usual to add ten to that clearance at the
valve to piston, MINIMUM .To allow for S t r e c h . . .

Spinning over , Judiciously , minus 40 thou head gasket , with the rockers set 40 thou tight , to check . If it goes through
without catching like that , youre smileing .

Hey Matt I'll be watching out like you describe and have got valves to foul didling with a vernier cam sprocket, hand turning slow and easy.

"minus 40 thou head gasket , with the rockers set 40 thou tight , to check "

I don't get it - why isn't that 40 thou plus 40 thou, or 80 thou total, for 40 too tight?

If you loose the Std 40 thou head gasket , and alls clear , theres ' clearance ' .
If also , as a check , put the adjusters in a turn from touching, it pisses in . :wink: ( i.e. - 040 Tappet (non) clearance .

( presumably at .010 , 1/4 turn . Minus the gasket , its correct for a street engine ( piston to valve ) for the odd missed
shift or suchlike . However , Valves ' Knitting " was major concern , overreving ( see missed shift ) . :| )

Presumably combined would be ludicrist on a closely fitted raceing engine , BUT , if it does clear set thus , should be plenty .

Freeking , the Int. opening to early , and at a rate faster than the piston travel at that part of the stroke , in the Long Rod
engine , would be nasty . Probably entirely hypothetical condition . HOWEVER , observeing the components in question
operate ( static ) and KNOWING the clearances reasures and removes any guesswork . Or saves a lot of measureing & sums .