Longer push rods ?

Greg Reimer 7376 · 09-01-2011, 10:05 PM

Got splainin' to do, so with my limited technical expertise and comprehension skills, I'll delve into my experience and try and help.
I built a 327 Stocker motor some time back, and it took 040" off the deck of the block to get it right, and around .078' from the heads, and all this with an .017" head gasket. This, of course, brought the head down a lot, and with each chamber volumn good by a half a CC,things are just about optimal.This, however, has the effect of shortening the push rods approximately .125".When I checked valve lift, (spec calls for .390" intake,.410" exhaust) I used a stock length OEM pushrod and a test lifter shimmed to the same height as the Smith lifters the engine was to get.Lift checked out to be -.005"- +.014", clearly over on around ten valves. A set of .150" short push rods brought the max lift down around .020" consistently with all 16 valves. i used Elgin 7/16" rockers and ARP 7/16' BBC studs. A set of pushrods .100" short would bring the lifts very close to optimal.One essential item never to forget is to make sure the slot in the rocker arm has room at max lift so as not to bind up the valve train and break studs, rocker arms,and push rods. If you have an engine(like we did) that exhibited numerous valve train failures, start checking there. Try a shorter push rod and see if it loosens things up.
I have seen and used different length push rods between intake and exhaust valves in order to adjust lift specs accordingly. Stocker camshafts are ground with a higher level of precision than most other performance camshafts, but that doesn't mean you can assume ANYTHING.The numerous machining processes necessary in the construction of any stocker mother, as previously mentioned, are enough to take it WAY away from the OEM configuration.Practically nothing measures out OEM anymore,it's essential to have a plan B,C,or whatever it takes when these situations surface. Your comparison of a rocker arm to a device swinging in twin arcs at once is a good way to put it. A cylinder head guy needs to be able to visualize this in order to work with it.Your descriptions of all this indicates your level of understanding of all this is quite high. A real reminder of the degree of departure from OEM will settle in when,once the long block is assembled,will be when you try to install your intake. Sometimes, now that the engine is narrower, the intake is now too wide, and nuttin' fits, its necessary to flycut .060-.090" off both gasket surfaces in order to facilitate installation. Then,when that's over, see how much too long the distributor is. At least, aftermarket spacers are available for that.
Thanks for the mentally stimulating discussion material.I like to think once in a while.

09-01-2011, 10:05 PM	#6
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,139 Likes: 172 Liked 727 Times in 221 Posts	Re: Longer push rods ? Got splainin' to do, so with my limited technical expertise and comprehension skills, I'll delve into my experience and try and help. I built a 327 Stocker motor some time back, and it took 040" off the deck of the block to get it right, and around .078' from the heads, and all this with an .017" head gasket. This, of course, brought the head down a lot, and with each chamber volumn good by a half a CC,things are just about optimal.This, however, has the effect of shortening the push rods approximately .125".When I checked valve lift, (spec calls for .390" intake,.410" exhaust) I used a stock length OEM pushrod and a test lifter shimmed to the same height as the Smith lifters the engine was to get.Lift checked out to be -.005"- +.014", clearly over on around ten valves. A set of .150" short push rods brought the max lift down around .020" consistently with all 16 valves. i used Elgin 7/16" rockers and ARP 7/16' BBC studs. A set of pushrods .100" short would bring the lifts very close to optimal.One essential item never to forget is to make sure the slot in the rocker arm has room at max lift so as not to bind up the valve train and break studs, rocker arms,and push rods. If you have an engine(like we did) that exhibited numerous valve train failures, start checking there. Try a shorter push rod and see if it loosens things up. I have seen and used different length push rods between intake and exhaust valves in order to adjust lift specs accordingly. Stocker camshafts are ground with a higher level of precision than most other performance camshafts, but that doesn't mean you can assume ANYTHING.The numerous machining processes necessary in the construction of any stocker mother, as previously mentioned, are enough to take it WAY away from the OEM configuration.Practically nothing measures out OEM anymore,it's essential to have a plan B,C,or whatever it takes when these situations surface. Your comparison of a rocker arm to a device swinging in twin arcs at once is a good way to put it. A cylinder head guy needs to be able to visualize this in order to work with it.Your descriptions of all this indicates your level of understanding of all this is quite high. A real reminder of the degree of departure from OEM will settle in when,once the long block is assembled,will be when you try to install your intake. Sometimes, now that the engine is narrower, the intake is now too wide, and nuttin' fits, its necessary to flycut .060-.090" off both gasket surfaces in order to facilitate installation. Then,when that's over, see how much too long the distributor is. At least, aftermarket spacers are available for that. Thanks for the mentally stimulating discussion material.I like to think once in a while. Last edited by Greg Reimer 7376; 09-01-2011 at 10:07 PM.