NEED HELP WITH PUSH RODS

Here is the problem I am having. The rocker arm geometry is good on the intake valve side & on the exhaust valve side it seems like the pushrods are to long because the roller tip is riding on the outside edge of the valve tip & the exhaust valve spring is fully compressed when on top of the cam lobe. The pushrods are all the same length. The cam,lifters,pushrods,heads & rocker arms are the same that was running in the car when I purchased it. However when rebuilding heads I had to replace all the exhaust valves because the tips were worn on edges. The cam is custom ground & do not have the specs, the heads are c9ve. I have never heard of having to run different length pushrods but I guess it is possible but does not sound right.

Don't really matter where on the valve tip the pattern is as long as the geometry is correct. Is it possible that the ex rocker studs are bent? Do you run a stud girdle?

What brand rockers are they? I bought some cheap aluminum 1.73 rockers off ebay and they rode right on the edge of the valve stem on my c8 heads just like you are talking about. They also started to wear the edge of the valve. I bought some crane 1.7 rockers and they still sit out side of the center, but they don't ride right on the edge. I threw my cheap junk rockers in the trash can. When I buy my next set they will be scorpion rockers.

what brand rockers?

the exaust valves may have been replaced with shorter valve stems and the new cam profile has changed the geometry.like schmitty said it dosent matter if the push rods are longer or shorter just as long as they are correct.

mustangjeff wrote:Here is the problem I am having. The rocker arm geometry is good on the intake valve side & on the exhaust valve side it seems like the pushrods are to long because the roller tip is riding on the outside edge of the valve tip & the exhaust valve spring is fully compressed when on top of the cam lobe. The pushrods are all the same length. The cam,lifters,pushrods,heads & rocker arms are the same that was running in the car when I purchased it. However when rebuilding heads I had to replace all the exhaust valves because the tips were worn on edges. The cam is custom ground & do not have the specs, the heads are c9ve. I have never heard of having to run different length pushrods but I guess it is possible but does not sound right.

More than likely, the old exhaust valves were the long ones, and when the heads were rebuilt, the builder ordered the shorter exhaust valves. With the pushrods you had in the engine, this let the pattern move towards the outside of the exhaust valve stem. It would be nice, if you still had one of the original exhaust valves, to measure and compare it's length, to those that are in the heads now. I think you'll see that's where the problem began. Meanwhile, I'm thinking the correct fix for you is to order some shorter pushrods to run on the exhaust,,,,,, or order some lash caps and run them on the exhaust only. The first thing i'd do is the lash cap deal and see how your geometry and roller travel looks. I assume you know that in order to run lash caps, you need to have the valve locks that have a lash cap recess in them.

Hope this helps,
Charlie

The rockers are scorpion 1.7 rollers.My only other concern is the valve spring bind on the exhaust side. The valves that were replaced came out of a set of d3ve heads I had laying around so I do not know if there shorter are not but I am sure one of you guys would know.

tiger wrote:What brand rockers are they? I bought some cheap aluminum 1.73 rockers off ebay and they rode right on the edge of the valve stem on my c8 heads just like you are talking about. They also started to wear the edge of the valve. I bought some crane 1.7 rockers and they still sit out side of the center, but they don't ride right on the edge. I threw my cheap junk rockers in the trash can. When I buy my next set they will be scorpion rockers.

You may have thrown away a perfectly good set of rockers,you probably just needed to change the length of your pushrod.

Has anyone had experience with Procomp PC2333 1.73-7/16 stainless roller rocker arms? Seems like a reasonable price for stainless.
http://www.procompelectronics.com/index.php?target=products&product_id=36895

72GTSNCode wrote:Has anyone had experience with Procomp PC2333 1.73-7/16 stainless roller rocker arms? Seems like a reasonable price for stainless.
http://www.procompelectronics.com/index.php?target=products&product_id=36895

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Randy

mustangjeff wrote:The rockers are scorpion 1.7 rollers.My only other concern is the valve spring bind on the exhaust side. The valves that were replaced came out of a set of d3ve heads I had laying around so I do not know if there shorter are not but I am sure one of you guys would know.

The D3 valves are about .100" shorter than the C9VE exhaust valves and the tip is probably longer also so, the necessary installed height of those springs is greatly compromised.

That solves the mystery & thanks for the info.

Measured valve spring hieght & compared old valves to new ones & they all seem the same, so I am thinking the guy that built motor before had the wrong length push rods in it. After closely examining the intake valve geometry it is off to. Thanks for everybodys help.

Then there must be a whole lot more going-on than you know 'cause the valves ARE a different length between a C9VE and D3VE cylinder head.

If the valves I had installed were .100 longer or shorter then I would definately see a differance in spring height? There is still one original exhaust valve in head that was reused.