I have done a lot of Chevy motors...and for the life of me (and my buddy), I dont remember seeing these plates below the rocker arm studs that guide the push rods....I could have forgotten I guess.

Now; I put them on the new heads I have...but obviously the machining isnt *exactly* the same, causing 5 push rods to bind. I can move them over about .004 by loosening the rocker arm studs, but by that time, it binds the other.
So move it back and it guides the push rod *out* of center of the lifter and puts that one in a bind.

So; are these actually necessary on 2.02 heads?

or

Do I need to grind more tolerances in them for side-to-side push rod clearances?


Jim

 

May be a dumb question,but are your heads machined for guide plates?
The stud bosses need to be milled down and the pushrod holes have to be opened up.

 

In all honesty; I didnt *exactly* check neither of those two...but I will...I definalty will.

Just by noticing:
The heads were machined lower and flat where the rocker studs bolt in.
The holes in the heads looked the same (and have plenty of natural clearance, and I used the OEM guide plates.
I used new rocker arm studs.

The binding comes from the push rods not centing in the lifter and/or rubbing the side of the guide plates.

I backed off the studs...the push rods loosen...I hold the plates in a position where the push rods are *free* (ie. spin)...by the time I re-torque the studs, then add the rocker arms, and attempt to tighten the rocker arms, one will get in a bind.


I am ready to remove them and leave them out...I would have to imagine hey are there for higher RPM's

Thanks,

Jim



Jim

 

You need em, unless you have self aligning rockers. You should be able to move them just enough to give ample clearance.

 

It sounds like the pushrod holes in the heads havn't been opened up.

 

They are never binding against the head..

They either dont line up in the push rod center...or rub against the guide and bind.

I have moved them over a slight here and there to free them up.


Maybe they will work themselves loose after I fire this puppy up


... just make them work, or make them break.




Jim

 

heads without guide plates guide the pushrods by the hole in the casting if, the heads weren't factory equipped, you need to drill out the cylinder head casting for more pushrod clearance. Guide plates are to keep the valvetrain more stable at high RPMs if your not winding to 6500RPM or better they are not needed.

 

Thats exactly what I thought they were for...high RPM stability.

Anybody else agree with whats written above?



If I eliminate them..then I dont think the studs can be torqued correctly because of the lack of spacing...ok, maybe a flat washer in thier place.

But


butt...

I am thinking more along the lines of slightly opening each guide with my dremel and gain the tiny bit of clearance I need on those 5.




Jim

 

Without a picture, I'm guessing you have TWO pushrod guides: the factory slots in the cast head and the guide plates that I'm assuming you installed along with screw-in studs. The machine shop that did the stud work should have opened up the heads when they machined and tapped the studs.

If the heads are on the car, your only choice is to remove the guide plates. No point in machining the plates; it would basically wreck 'em. If you pull the heads off again, then you can have a shop (hopefully a different one!) machine out the pushrod slots to allow the use of the guide plates.

As was mentioned earlier, the plates are needed in higher RPM and flat tappet applications with a SB engine.

Hans

 

But if the pushrod holes have been enlarged, you need guide plates regardles of how high you're going to wind it.

I really don't understand how they can be binding unless you're using some kind of self aligning rocker arms, in which case you wouldn't need the guide plates.

Can you post any pictures?

 

OK, after seeing this, what type of rocker are you using? Also, is it possible that the machine work for the studs is slightly canted and the plates warp as they are torqued down? That would explain why the pushrods free up if you loosen them slightly... Weird problem, and I wouldn't let it "break in", as it would surely cause something else to just "break".

Hans

 

Ok...The heads are new from Summit.
they are machined for guide plates...they do have ample spacing thru the heads for the push rods all the way down to the lifter.

In the pics (this is one of the binding push rods) you will see that when I have one push rod free, the other binds ---just barely---maybe I am a little to critical...and this is mock-up before final start...so I am working out all the bugs now.



push rod binding at left of guide




guide plate tolerances for both push rods





Keep in mind...I did swap cylinder to cylinder...in other words; I just did NOT disassemble and put parts on randomly....so; this guide plate and those push rods did come from that cylinder.

This is a 1979 L-82 with 50k original miles.




Jim

 

Ahh, the value of a picture! Your probably worrying needlessly, but it wouldn't hurt to take a .001 off guide plate with a flat file to clearance them a little. Your running what appear to be stock rockers, and I'm guessing you won't be buzzing this thing too high, so super tight tolerances are not a big deal here.

Hans

 

Right..everything is stock parts...except the heads.

I like I stated before..I may be being too **** about this...I just dont like doing things twice.
As a matter of fact; I am not going to be too fond of seperating them again...but I want to do it now, and clean up so I can fire up.

I actually want to do it with open headers; but then I couldnt hear the lifter ticking (if they would tick)....



Jim

 

Ooooo, open headers (insert Homer donut drooling here)
Neighbors been irritating you a bit, have they? That should fix 'em!

Hans

 

Nope...only neighbor that irritated me is the guy across the street that gave me new Bow-tie valve covers...he came over Fri. night to "help" work on the broken exhaust bolt....bent my dip-stick tube out of the way...but did it the wrong way.
You know...like now it will never seal again because it kinked at the crimp

I forgave him because he is a want to be mechanic and dont mind lending a hand...not to mention the freebies.
I just cant turn my back on him though; as he started disassembling the stock heads and I caught him before he scattered parts, and they couldnt be mated back to the cylinders or intake and exhaust matched.

I have it in mind to send him on an errand in a few minutes (when I get back outside he'll see me)...gonna send him for a lower radiator hose (which I really do need), a *special* left handed pipe-wrench for tightening Corvette side-pipes (he loves telling people he is working on a Vette).
then; I'll send him the the local speed shop for high-speed tire *air additive* (w/special dye to leak check).

when I get ready for the hose, I'll call his cell and get him back...if he pesters me; I'll have him rotate the air in the tires and forget the additive!

Thanks for the help and the laugh!


Jim

 

New heads, don't forget to check push rod length. improper length will add to your geometry problems. I agree from the pictures that the guide plate slots need to be opened up for that size push rod. One thing, I dought this is the problem, but I have AFR 195's and their guide plates are not simetrical, you can't flip them over, one side for exhaust- one side for intake. The valve centerline was moved but the stud location is stock, so the guide plates are necessary from a geometry stand point. Also check your rocker arms for valve spring clearance. With stock rockers this is a long shot, but if your push rod length is wrong it could be a factor. Last DON'T start it untill you work out the binding issue, you could dammage anything in the valve train including the cam.

 

I didin't see it mentioned yet but,, if using the guide plates, make sure you use HARDENED pushrods.

 

I was just going to post this, but you beat me to it! hardened pushrods must be used.

 

All done...and all is good.
No prob after I grinded 3 plates about .001.


Only fly in the ointment is....

*drum roll*...


A ferkin weld is broken in the collector to one of the tubes...and I am not sure exactly where yet as it was dark....hopefully it will be in a place I can braze or TIG.



Jim