guide plates rubbing

[TMat]

Here's my problem I have a BB chevy with GM aluminum oval port heads comp cams guide plates and harland sharp roller rockers. The problem is the guide plate is rubbing on the back of all the rockers except 2. In the description for the guide plates it says "raised". Does this mean the slot portion is raised from its normal height from the head. If this is so a normal height guide plate would solve my problem, but I can not seem to locate any standard height guide plates on Jegs or Summit.



Any help would be greatly appreciated, I would rather replace guideplates instead of rockers.

[bbcc]

That is a bit odd. Do you know the part number of the guide plates? Should be stamped into the top. Also, just out of curiosity, are you sure that your pushrods are long enough? If they are to short this will cause the pushrod end to drop down close enough to the guide plates to cause this rubbing.


cheers bbcc

[orange69]

i would use +.100 long pushrods.that should fix the problem.

[bbcc]

Check and see if that is the problem. Remove one of the rockers, with a felt marker colour the top of the valve, and reinstall the rocker. Then rotate the engine through two complete cycles. Remove the rocker again and see where the marker was worn off, it sould be roughly in the middle of the valve. If not you will need longer/shorter pushrods depending on where the wear is located. There are a few how too's on sites like car craft and phr. I would recomend picking up an adjustable pushrod gauge, this way you can tell for sure what length you will need to correct your geometry.

hope this helps

cheers bbcc

[TMat]

I was wondering about the pushrod length too, but we checked the pushrod length when the engine was built. When I was working at Shafiroff I built the engine with the help of one of the guys who worked there. People do make mistakes, but I had no issues with this interference until recently.

I'm stumped, when the engine was built we also put oil restrictors in the lifter galleys on the back of the block ( solid roller cam) Could this have caused a problem on a street engine? Not enough oil to the lifters? cam? not enough oil too much heat? I have since removed the restrictors.

[TMat]

That is a bit odd. Do you know the part number of the guide plates? Should be stamped into the top. Also, just out of curiosity, are you sure that your pushrods are long enough? If they are to short this will cause the pushrod end to drop down close enough to the guide plates to cause this rubbing.


cheers bbcc

The part # on the guide plates is 4806, let me know if this means anything.

Thanks

[bbcc]

Those are standard run of the mill 3/8 guideplates, the "raised" designation just refers to how all big chev guideplates are oriented. The oil restricters should not have caused a problem. If you just started to see this issue, then something must have failed. Check your oil for shavings. Look to see if your cam lobes have been wiped off (unlikely with a solid roller, but another failure could have caused the lobes to be worn down). Also check for bent pushrods on the rockers that are experiencing the interference. The last thing I can think off is maybe the valve seats got pounded out causing the valve to protude further from the head on the spring side. The one thing I have to ask though is did you notice if the engine was running poorly when you decided to take the valve cover off? If any of the issues i've stated above are the case, then the engine will run horribly and make drasticly less power than normal. Also, how many miles have you put on the engine?

cheers bbcc

[TMat]

Well, I found this rocker interference problem after I discovered 13 inner broken valvesprings. SO, I think what you are saying about the valve seats might be the problem. I mentioned the oil restrictors causing a problem because this car sees a lot of low rpm idling and cruising and at those rpms the restrictors have an effect. Restricted oil, hot valve springs, broken springs at least that is how I see it.

I ordered longer pushrods but I have a feeling that is not the cure?

[bbcc]

Wow, 13 Broken dampner springs. Did you over-rev on a miss shift? Not entirely sure the restrictors would do anything to the dampner springs. I would definitly yard one of the heads off and take a look at how the valves are sitting. I believe, from what you have described, that this problem is a little more in depth than incorrect pushrods.

Oh, and what are your cam specs, I just had a realization. You need to check if any of your pushrods are bent. If your springs were not capable of handling the lift your cam has, it would have caused the springs to stack, and the dampner is usualy the first to stack. Such a situation would cause the weakest link in your valve train to break, hence the broken springs, and possibly some broken pushrods.

So to reiterate, an over-rev or just a cam that is to big for your springs could have caused this. I'm leaning towards over-rev because there is a possible problem with the valve seats in combination with the broken dampner springs.

This is just an idea though, you really should rip a head off and check the valve's/seats for any damage.

cheers bbcc

[TMat]

BBCC,
It looks like I am going to be taking off one or both heads, to see what is going on.

Thanks for all your help