Valve Train Geometry - HELP, Added 96mm P&C's to 1.8l Options

[vesnyder]

I am reassembling my rebuilt motor and have just installed teh heads and am installing the valve train with push rods, etc. For some reason the geometry seems to be off? After studying the rocker arms, it seems the push rods are too long - is that possible? After backing off the valve adjustment screws the rocker still seems to depress the valvle too far - not that I know what too far is? It seems the valve and pistons are hiting each other (just a feeling I have).

Just to complete the picture I've changed out the cam and lifters, and teh lifters seemed the same height as the ones I replaced. Any chance the new pistons are not as high? I am afraid to keep going in fear that the valves will bang the pistons.

[blitZ]

There is an excellent article on Jake's site on setting rocker geometry.

Jakes Rocker Geometry

It's not difficult, just measure 3 times cut once. You'll probably need some new pushrods, which you will cut to your new length. The chromemoly PR from the Type IV store work great, no valve lash.

[Cap'n Krusty]

STOP! Did you calculate the compression ratio and adjust the deck height accordingly? What cam? If the lift is higher, the pushrods will behave as if they're longer. Are they seated in the lifters? If the heads have been surfaced, if you've deleted the head gaskets, there's shimming to be done. These issues need to be addressed BEFORE you do any cutting. The Cap'n

[Joe Ricard]

Damn it

He beat me to it again.

You changed EVERY variable possible and now you are wondering why it don't work?

If you are concerned about valve to piston clearance put some play-doh in the combustion chamber and see what's going on.

I have had it recommended to me to shhot for .100 clearance face/edge of valve and .050 side of valve if you need to machine valve pockets.

you got domes or flat top pistons.

If the valve is contacting the piston it will STOP the motor near dead in it's tracks if you are turning over by hand.

[Dave_Darling]

If the rocker arm is pushing the valve open even with the adjuster backed off all the way, chances are pretty decent that the inboard end of the pushrod is hung up on the edge of the lifter, not seating down into the cup in the outer end of it.

--DD

[Twystd1]

Lets start here.......

Everything The Crusty one said.

And one more question. Is this a STOCK cam...??????

Clayton

[Joe Ricard]

You can look down the push rod tube with a flash light and see if the tip is seated in the lifter.
If it is and you still have this problem you are really screwed.

[Jake Raby]

Following my article while doing the process should eliminate guesswork...

DO NOT CUT CORNERS WITH THE PROCESSES!! DO THEM EXACTLY AS I HAVE WRITTEN THEM!!

The main problems that guys experience come from skipping portions of the procedure- there is a good reason for the way I have presented the procedures, if followed step by step its easy as pie.