D6B Head Depth / Inlet Valve -Piston Contact

[jimmi 0 1 Cars]

What is maximum that can be skimmed of a D6B head before it is rendered scrap ?.... I'm running standard 1.9 pistons, standard cam pulley /PTS 4078 Grp. A cam and a 1.5mm headgasket. Head chambers are 24.2cc . I've measured the head after it came back from machine shop - depth is now only 87mm .. I've problem - Inlet valves are lightly touching all piston rims on the intake stroke......

[DamirGTI 342]

No idea how much is maxi acceptable skim value , anyways , OE chamber depth is 35cc . Mine was 27cc after the skim last time i've rebuilt the engine (also an D6B) and i haven't had any valve-piston clearance issues .

 

With that amount of skim/low chamber depth you'll need (not a must but ...) to adjust the camshaft especially if it's an aftermarket item as the cam will be in the retarded position in relation to the crankshaft thus you'll loose some compression ratio (static) it'll be a little down on power/torque .. ignition timing will be affected also if it's OE (mechanical dizzy) ..

Also , when timed up via adjustable cam pulley perhaps you'll sort out that valve-piston clearance ?!

 

 

D

[petert 589]

2.0mm

[jimmi 0 1 Cars]

Have ordered a vernier cam pulley... cam ( PTS4078 ) has full lift at 106 degrees,,,, thinking ... will I have to retard or advance the cam timing to stop the valve /piston contact ?

[petert 589]

It HAS to be timed at 106 deg. to work properly. If the piston is closer than 0.080" to the valve at any point in the cycle, you'll have to fix the problem, not the cam timing.

[Telf 224 2 Cars]

Guys can I ask how/where do you measure the chamber depth from?

[DamirGTI 342]

You'll need an piece of Plexiglas with the hole in the center , an syringe , colored fluid (diesel , or died water) and some grease (to seal the Plexiglas)..

 

Flip the head up side down and place in level , clean up the head around the chamber , fit the spark plug in the cylinder/chamber to be measured , smear some lithium based grease around the corners of the chamber (head base) , press an piece of Plexiglas over the chamber with the hole in the center and fill up with the fluid with syringe via hole on the Plexiglas till you fill the chamber completely - count how much you're filling ! and that'll be the chamber volume/depth .

 

 

D

 

 

Edited September 6, 2015 by DamirGTI