Thread: SBC 350. Rebuild in stock.

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Originally Posted by wbud

I'm going to re-cut valve seats, and pair valve-stem guides. Now I need new valves - in my machine shop they told me that I need more than 8.65mm diameter of valve stem - it's .341 in. if I calculate correctly.
I found that my old valves were about 4.911 in. - it's correspond the information from books about SBC.
But I'm not understand, how valve overall lenth wiil correspond with my camshaft kit.

HMmmm.. consider that the rocker changes the direction of the pushrod, if you lengthen the valve stem you'll need a shorter pushrod, if you have a shorter valve stem, you'll need a longer pushrod. There is a certain length "range" that you need to stay within so you can effectively adjust the lash of the valve train.

The machine shop (I would think) can give you the original measurement and since it's a chevy, I'm certain the tech guys at Summit or Jegs know it by heart / committed to memory!

Hope this helps!

I measured my old valves:
- exhaust 1.5/4.928
- intake 1.94/4.88
I think, last time my engine was assembled using parts from junk, and they use parts that was in the workshop at the moment.
Also I measured valve stem diameter - it's varied from .339 to .340
I still cant understand, what valve lingth should be in stock and what should be valve stem diameter in stock(.341??)

Try this page.. Valves - SummitRacing.com they have a good tech help group also!

stock chevy valves are over all about 4.911 for ex and intake you valve should be around 11/32 .. abit under that around 341 but some gm truck and boat used a 3/8 stem or the ex valve only . most of the time ream the guide or hone for clearance for the valve stem real size .so oil can get in there and valve can work. makeup of guide iron . bronze valve guides for clearance for use of engine as well street ..race.. what fuel. when useing a old valve over check for tapper of valve stem and if hard chrome is coming off . most all the time i buy new valves. stock length valves will set up in them head with your cam .so there is no need for longer valves . the cam kit should of came part numbers for a spring kit for that cam . springs retainers valve locks they should setup ok . at the machine shop they must know were to set the seat to chamber so the valve sets right in the head when putting seats in and cutting the seats if to low the valve will be sunk and valve will not work to good to hi in the chamber the valve may hit piston and you may not get the valve spring set up height you need the keep the valve spring s for working right .if springs do not set up were they need to offset keeper /valve locks can more setup height for spring or a retainers . the locks come +050 std and -050. GM over the years made many valve retainers i would go with moly steel one the copy of the older GM retainer should be fine . keep away from the stock gm rotator retainers