I'm about to bolt up my heads on the 327 I've been rebuilding. The block has been decked so I am sure I will need non stock length push rods. I have a solid lifter cam installed and was wondering if I should check the pushrods length with the lash setting specified by the cam mfgr or zero lash? Maybe a dumb question but figured I'd ask. Thank you. Posted using the Full Custom H.A.M.B. App!
Zero lash? Or at 0.016" lash as specified for this cam? Thanks Posted using the Full Custom H.A.M.B. App!
Are you sure you need to? All the motors I've built, or had built, never needed non stock pushrods. There's more than enough adjustment on Chevy rockers to make up for a little head/block shaving.
I'm not sure if I need to but I need to buy pushrods either way and would like to check before I make the purchase. Posted from the TJJ App for iPhone & iPad
if you have a stock push rod laying around put it in with a dab of Prussian blue on the valve tip turn the engine over one full revolution and the rub mark on the valve should be centered on the tip
Well you want proper geometry thru the valve motion. You need a good contact patch on the valve stem, not too far forward or back. This is something you'll have to watch go thru its motions to see. Somebody makes a little doohickey that you place over the stud to measure for pushrod length. Supposed to be set at optimal rocker angle. Ill see if I can find it for you.
http://www.lunatipower.com/Tech/Valvetrain/HowToVerifyValvetrainGeometry.aspx http://m.summitracing.com/search/part-type/pushrod-length-checkers/mockup-rocker-arm-included/yes
Just wondering,I build vintage British bike engines.Besides trying to get the rocker contact near the middle of the valve stem there's also getting rocker at a certain angle at mid lift for best valve guide life. Is the rocker angle a factor on OHV car engines?
Yes, if its off by gross amounts the guides wear faster. Sometimes the height or length of the valve stem is manipulated to obtain the desired rocker angles. It's not much of a change and end results are just a few degrees but they make a difference on valve guide longevity of a max effort engine. In theory they help on a street engine also but the required effort is more $$$ than a valve job at 50-150k miles.
Set your valve lash, that way you will be sure that the length pushrod you use will allow you some adjustment. Remember to take into account that once things heat up all your measurements will change. Did your cam grinder give you cold or hot valve lash? If that carved enough off the decks for you to need different pushrods you are likely going to need to get the intake milled as well.
I have both cold and hot lash settings. Check with the hot lash measurement? Thanks Posted from the TJJ App for iPhone & iPad
Not if your engine isn't hot. If you are checking cold you use a cold setting. The difference between the two allows for thermal expansion. You got a good cam grinder many cams these days only come with a hot setting.
You are getting good advice so far. In my experience, with original heads/studs/rocker arms, it is unlikely that a clean-up decking by itself will require a change in pushrod length, but certainly no harm in checking. The use of any or all of: aftermarket cylinder heads, longer-than-stock valves (to allow more spring/more lift), full roller rocker arms (which may use longer studs) are the kinds of changes that are very likely to require a different length pushrod.
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