In putting my engine back together, I noticed that the rocker arms are slightly "crooked" in relation to the valve stem -- that is, the tip of the rocker isn't completely centered on the tip of the valve stem. The deviation seems no more than 1/16".

This is the first time that I've used guide plates, and it appears as if the distance between the pushrod notches is causing the slight lateral angle. Even if I could adjust the guide plates, the angles generated would be the same. I turned over the motor a few times by hand and they don't straighten out at any amount of lift.

Is this something that I should worry about? The factory rockers never seemed this crooked, but I could just be imagining things.

 

Delete, I misunderstood the question

 

You wouldn't happen to be using Vortec or AFR heads, would you? If so, you can't use standard guideplates- the spacing is wrong.

The tip of the rocker should be lined up over the center of the valve stem. You probably won't have a problem like that since it's not too far off, but definitely not ideal.

Isky makes adjustable guideplates which is what I used when I set up a pair of Vortec heads I converted over to use guideplates. They were a godsend in getting everyting to line up correctly.

 

as long as the roller is still on the valvestem, dont worry too much about it.


LOTS of engines are like that... id go as far as saying most SBCs are like that.


ideal? no, but it wont hurt it.

if you're building a all out race motor, do as someone suggested and get adjustible guide plates, then weld them so it lines up perfectly.

 

These heads are just your typical '601 casting for 305 SBCs. They've been worked over a bit for use on my 350, but from a valvetrain standpoint, they're just like every other stock GM casting.

Nope, no race motor here. This is just a regular street-driven car; I don't even put more than 5000 miles on it annually.

 

I dont know, that looks a lot more angled than mine did when I put it together. Looks like the same roller tip rockers though.

 

Yes, the rockers are suppost to be a bit angled. Again, make sure that the roller is centered to the valve tip.

 

A bit angled is one thing, the roller tip should still sit even over the valve tip, at least all of the ones I put together do.

 

I may be wrong but it sure dosen't look like them valve spring retainers are for them valve springs???

Auggie

 

Auggie, the retainers are ZZ4/LT4-style for use with ZZ4-style springs. I too thought that they looked a little weird, but it's the right kind of retainer. Just to be sure, I compared a few pictures of the ZZ4 valvetrain and it's the same way.

I know that the rockers do look "too" angled, but I'm not really going to worry about it. They're all that way and it's due to the size of the guide plates. The plates are Comp Cams brand, so I know they're of at least decent quality and design.

Just as a side note, the pushrods are evenly spaced within the drilled pushrod holes in the head. That tells me that the pushrods are lined up correctly, to some extent.

 

Like I said, it looks that way, but that doesnt mean that it isnt correct. Give it a shot, and see what happens. It'll probably be fine.

 

Blue86iroc, do the valve sp. retainers fit snug inside the valve spring and are you useing hardend push tubes???

Auggie

 

Auggie,

Yes to both. Here's a picture of what the retainer looks like on its underside (from the GM Performance Parts website):



One of the footnotes for this retainer is that it should be used with the ZZ4-style valve spring (what I have).

My pushrods are a hardened version of Comp Cam's SBC roller block pushrod... "High Energy," maybe?

 

Looks like you done your home work. I would say good luck but it looks like you won't need it.

Auggie

 

Problem is....GM was never too accurate in its pushrod hole placement. It is quite common to find misalignment like this. Some cylinders are worse than others. If memory serves me correct #3 and #6 are the worst. Core shift during casting can also cause variation.

Many aftermarket vendors take the " Blueprint" dimensions direct from Chevy. IE: Valve centerlines, Sparkplug Centerlines and pushrod hole centerlines. Unfortuately they never correct GM's inaccurate pushrod hole placement. Edelbrock heads are like this as probably some others.

I spend about an hour setting up my pushrod guide plate alignment with Isky adjustable guide plates. Having the roller tip that far off center can cause side loadings on the valve stem. This can shorten valve guide life....although by how much is debateable.

Note that when you correctly align the rocker tips, the pushrods will NOT be centered in the pushrod holes. Nothing you can really do about that. Watch out for side clearance to the pushrod and head. You want to leave at least .010" clearance. You may have to enlarge ( ovalise ) the pushrod holes if you want the rockers dead nuts centered. Every little bit helps.

 

Thanks for the advice, Chickenman. I think I'm going to spend some extra time on the next engine I do to make it all line up perfectly. Those adjustable guide plates definitely sound like the way to go.

I think it's kinda interesting that even aftermarket companies don't bother to correct these things. You'd think that at least one designer would use the product on his car and question the alignment.

 

Yeah..it certainly was annoying when I found the Edelbrock pushrod location had not been corrected. Some mfg's must have clued into this. All it would take is a minor tweaking of the CNC program...but I'm wondering if there is some other reason. I'm thinking that the casting thickness between the pushrod hole and the outer wall of the Intake runners plays some part in this.

I think it goes back right to the Fifties when the SBC was first designed. Some engineer did not pay close enough attention to this detail. Not important with stock engines, but it is a concern with Race engines. However I can see the problem......

Shift the pushrod centerlines to correct the rocker alignment...whoops...now you've just broken into the Intake runner wall, or made the wall too thin. ( Have to allow for core shift variations remember ). You really have to re-design the whole engine, with a taller and narrower Intake design. That's exactly what GM did with the LS1

Other option is to use offset rockers or valve lifters with offset cups. Isky carries these. Course that all costs more money....so round and round it goes.

PS: Thinking more on this I'm sure that this particular problem is an evolutionary process that has developed over time. Originally, back in the early days, the intake runners were narrower and the valve sizes smaller. Ther was probably no misalignment problem.

As cylinder heads developed, valve diameters were increased....this pushed the valve centerlines apart. Intake runner sizes were also increased leaving less room for machining of pushrod holes.

The block designers were still stuck with a particular lifter diameter and camshaft orientation to match that design. Build a taller and narrower Intake runner and now you have obsoleted decades of intake manifold design ( both factory and aftermarket ). It is extremely expensive to retool a factory for a small dimentional change that does not affect a stock engine to any degree.

It's finally come to a point where the origianl design simply can't be " massaged " any more. When you start changing component centerlines, one thing affects another. Pretty soon you have to design a whole new engine. Thus the SB2 and the LS1.

 

For the people that have used the adjustable guide plates, did you weld them? or is tourqing the rocker arms stud enough?

thanks

 

Torquing the Rocker studs is enough. I've run mine that way for years. No problemo.

 

I had a similiar problem when I was installed roller rockers on my L98 eng. I was able to swap guide plates around and get most of them to look better. On one cyl I had the pushrod guide slots too close to each other.
My original plan was to cut the guide plate in half. Bolt everything up so it looked good, then weld the 2 halfs back together while on the eng. This seemed like a lot of trouble since my welder is buried under a bunch of stuff.

Then I had a better idea.

I was able to place the guide on an anvil and hammer on it. This made the guide slightly thinner and longer. The slots shrunk a little in the process and had to be opened up again. Just used the slot dimensions from an un-modified guide plate and file'ed the slots back to their original size, then smoothed the openings with crocus cloth. I only have abt 400 miles on the eng now, but so far, so good.

 

Torqueing the studs down is enough to keep the Isky adjustables from moving around. If you're the nervous type, shoot a dot of weld to tack them together while still installed on the head, but my experience says you shouldn't have any problems if you don't.