devilfish

Today I adjusted my roller rockers. And I noticed that the rockers on intake vavle 3 and 4 isent centered properly over the valve tips.

Like the rocker to the right on this pics: ( pix is from a BB ut you get the ide ).

http://www.corvette-restoration.com/...earance/17.JPG

You can also se this if you look at the rockers from abow. The 2 rockers is not straight compared the the others.
Whats the trick here? Is there anyway I can adjust the guide plates?
All help is appreciated.

Thanks

AlkyIROC

That picture shows a BBC head. It's a common problem. The easiest fix is to cut the guide plates, adjust it to center the rocker over the valve and reweld the guide plate. I don't know if the holes through a SBC head will allow enough adjustment to move the rocker over.

I have 2 guide plates in my engine cut and welded to center the rockers.

For a BBC, there are adjustable guide plates available.

devilfish

Thanks for the answer

If I cut the guide plate, do I also need to make the "hole" in the guide plate ,for the rocker stud, bigger/oval, in order to adjust the guide plate postion? If you understand what i mean. ( sorry for the bad English ).


I whas thinking to swap my rockers to "self align" style rockers. And get rid of the guide plates. Will that solve the issue aswell?

Thanks

AlkyIROC

The guide plates are cut in half. They still pivot under the rocker stud and when the guide part moves the pushrod enough that the rocker is directly over the valve, the two halves of the guide plate are welded back together.

What heads are you using? Do you have guide plates or do the heads have small holes that the pushrods go through? Self aligning rockers are designed for heads that don't have the built in guides.

Stekman

Isky makes adjustable SBC guideplates.

devilfish

Ah,so I cut the guideplate, then rotate the guideplate untill the rocker align on the valve tip, then weld it? So its ok if the pushrod lies/rest against the guideplate?

Im using JEGS canfield 197cc heads. 3/8'' Studs and 5/16'' guideplates.I use the guide plates that came with the heads. The heads has "large" holes for the push-rods. If I dont use the guideplate on those 2 rockers, I can get them to align without the pushrod touch anything.

Thanks for helping.

AlkyIROC

It's normal for the pushrod to ride against the guideplate. The purpose of the guideplate is to keep the rocker aligned. If it doesn't, the rocker can move side to side on it's own.

How much gap is between the pushrod and the guideplate?
Are you using stock length pushrods? If so, they're probably the wrong length. With guideplates, you shouldn't even be using factory pushrods. You need hardened pushrods.

devilfish

I have to get back to you regarding the gap between then pushrod and the guideplate ( if any ).

I measured the pushrod during the assembly of the engine, I used a modifed hyd lifter ( that couldent be compressed ) and looked for a good "wear" pattern on the vavle tips. I used a old article from "popular hotrod" as a guide, as im pretty new to this
The length I came up with whas so close to stock lenght that I ended up using a set of hardened 7.200 rods.

Thanks

AlkyIROC

As long as you've confirmed the proper length, then they should be fine. Typically, any aftermarket head will probably require different length pushrods for whatever reason. Valve length, valve angle, valve seat position in the head etc. Most people just put stock length pushrods back in and feel it's fine not knowing how bad the valvetrain geometry can be.

I got lucky. This winter I changed heads. When I checked the pushrod length, they were both 0.400" longer which made my pushrods a talldeck block standard length in my shortdeck block. Anything else and they would have been a special order. I was able to get them from the regional warehouse overnight.

Of course now I have 2 spare sets of pushrods all in different lengths for different heads I've used. Intake and exhaust are different lengths on a BBC.

The pushrod should be a close to snug fit in the guide. That's why hardened pushrods are required. Normal factory pushrods will wear out from rubbing on the guides.

It sounds like you've covered all the bases but just need to modify the guide plates to center the rockers over the valves. I know it's usually an issue with BBC heads with the canted valves but didn't think it would be a problem with and SBC heads.

devilfish

Thanks so much for the help on this issue.

Regarding the pushrod length. I used a marker on the valetip, then installed the modifed lifter/rocker/pushrod, turned the engine and looked for a wearpattern. If I remember right, think I used this picture/article as reference:
http://www.carcraft.com/techarticles.../photo_07.html

And when I look at the vavletips now ( except on intake vavle 3 and 4 ), after 2 summers with the new engine, the wearpattern looks the same as when I measured it during the assembly.
BUT, as im in no way a experienced engine builder I cant guarantee I dident do any errors, unfortunately

The wearpattern on the vavletips on intake 3 and 4 ( the miss-align rockers ) looks something like this, and the reason is, of course, that the rocker is "twisted", compared to the 6 others.
( sorry for the crappy picture )



Cheers

AlkyIROC

Since you have a wear pattern, you can see where the valve tips are currently running. They're not through the center of the valve tip so the pushrods are not the correct length although they're close. That is providing your picture is an accurate representation of your wear pattern.

When I checked mine, I had to use some checking springs because my triple springs will collapse an adjustable pushrod. I used some bluing dye for setting up ring gears on the valve tips. I adjusted the rockers to the correct lash. With the lifter on the base circle, I wiggled the rocker across the tip. I then rotated the engine so the valve was at full lift and wiggled the rocker again. I then removed the rocker to see where the 2 wear marks were on the valve tip and kept adjusting the pushrods until I got as close to a perfect pattern across the center of the tip as I could. I then measured the pushrods and after looking through the CompCams catalog, that's when I found out they adjusted to a common size. It was a pure fluke.

Although not 100%, I think you need longer pushrods to move the wear pattern closer to the center of the valve. Maybe .050-.100 longer but it's hard to just guess.

devilfish

Hi.

The picture pretty much reflects the wearpattern. And as you said, I think I need to re-visit the pushrod lenght this fall, to get it 100%. But I think I will use the car this summer "as it its".
BUT the rocker issue on intake vavle 3 and 4 must be fixed now. The alignment of those rockers, and the indicated wearpattern on those 2 vavles is so much out of spec, that I fear my valve guides will wear out to fast
Next step is to loosen up the guideplate, cut it in half, and se if I can tweak it into spec.
If its ok, I will post some picture here, and perhaps you or anyone with more experience then myslef can give me som feedback on the results?

Thanks

Anders.