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As I was re-assembling my -186 heads, after they came back from the shop, I noticed that the pushrod guide plates has one side labeled "down." Why? they appear to be symmetrical. Any ideas?
Geezers Cars
Geezers Cars
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Re: Push Rod Guides
Hey old geezer:
The guide plates were stamped from steel, then hardened. Look with your old geezer reading glasses or magnifing glass, (like the one I hafta use) and you'll see that one side has a tooling flash from the stamping. At least thats what I THINK I see!
Hope I'm right,
Varooom -
Re: Push Rod Guides
Thats right, in addition, when metal is sheared as in punching the slots for the pushrods to ride in, about half the thickness of the netal is actually "cut", the rest is sheared leaving a rough surface. In addition, the side the punch strikes will have a slight depression or roll at the edge. if the pushrod contacts the rolled edge, it will be less likely to be damaged.Comment
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Re: Push Rod Guides
Ol Geezer------
I agree with Dale and Bill; the difference in the upper and lower edge configuration as a result of the way that the plates are stamped is the reason that the guide plates have an "up" side and a "down" side. But, I'll also offer this:
Several years ago GM replaced the old-style small block rocker arms, last available as GM #3974290, with a new guided type rocker arm, GM #10089648. For the last several years, if you purchased a small block rocker arm from GM, you could only get the guided-type rocker. This rocker arm is different than the earlier style in that there are ridges on the tip of the rocker which guide the rocker tip on the tip of the valve. If you happen to use the "new" guided rockers, you should NOT USE and should eliminate the guide plates. The use of both the guide plates as well as the guided rockers can cause the push rods to be put into a "bind".
Incidentally, the new style rocker arms CANNOT be used with mechanical lifter engines since there is no way to insert a feeler gauge to adjust the valves.
ALL Chevrolet small blocks since at least 1991 have used only the guided type rockers. That even includes the 1996 LT-4 Corvette engines which used aluminum roller rocker arms; these special rockers were of the guided design, too. In case you're wondering why I say not to use guide plates with guided rockers while late model Corvettes with the guided rockers also have guide plates, be advised that the plates used on late model Corvettes with guided rockers, although appearing like guide plates, are NOT actual guide plates. They are installed for assembly purposes only, have a larger slot than true guide plates and are NOT hardened.
As to which is better---conventional rockers with guide plates or guided rockers without guide plates-----my opinion is that the guided rocker arms are better. If I used the stamped steel type rockers, I would ALWAYS go with the guided variety. And, if I used the roller rocker type, I would always go with the guided type, too. However, this only applies to small blocks; guided rockers are not currently available for big blocks.In Appreciation of John HinckleyComment
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Re: Push Rod Guides
Thanx all. But, Joe, You leave me in a quandry. You state, in re: rocker arms: «If I used the stamped steel type rockers, I would ALWAYS go with the guided variety.» But you also commented: «Incidentally, the new style rocker arms CANNOT be used with mechanical lifter engines since there is no way to insert a feeler gauge to adjust the valves. »
I assume, therefore, that I cannot use the new rocker arms on my LT-1 and must be very careful if I have to replace any. Or am I confused? GEEZER
Geezers CarsComment
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Re: Push Rod Guides
Ol' Geezer-----
That's correct; you won't be able to use the GM-sourced rocker arms on a solid lifter LT-1. If you need to replace any, you'll have to go with aftermarket-sourced rockers, which are still available in the non-guided type.
When GM replaced the old style rockers with the new guided type, they probably were not too concerned with the imapact which this would have on folks with solid lifter-type engines. They never made very many of those, anyway, and the last one they did make was in 1972. So, the needs of those applications got "lost in the shuffle". In fact, if you were to go to your Chevrolet dealer today and tell him that you want a rocker arm for your engine, he'll sell you the guided rocker arm. That's because his parts information shows it as the current replacement for all 55+ small block Chevrolet engines. But, it won't work on solid lifter engines unless, of course, you have some way to adjust the valves without using a feeler gauge.
I may have read something somewhere about someone coming up with a very narrow-blade feeler gauge that might allow the guided rockers to be used with solid lifter engines. It would seem very cumbersome and imprecise to use such a methodology, though.In Appreciation of John HinckleyComment
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