All,

Assembling the new motor and determined the stock pushrods were too long for the new setup, so I bought an adjustable pushrod and set about checking for the correct length using knowledge from the forum. Made my own solid lifter by disassembling an old one and shimming it internally (forum suggestion)

After a few tries and adjustments, we got the below contact patches. We think they look OK, but I wanted to get some opinions from people who have done it before to make sure we're right.

Do these look correct? I'm using Comp 1.52 roller tip rockers in the motor. The new length is quite a bit shorter than the old ones, like .25". Is that common?

Thanks

Contact Patches


Exhaust Fully Open

Exhaust Fully Closed

 

Looks good to me. What lifters will you be using? I would suggest rechecking with the actual lifters you are going to be using.
Redecking of the block and head, gasket thickness and rocker arm geometry could all affect pushrod length.

I had to get a pushrod 1/4" longer than stock for my set-up, I was told that was not very common, but the witness mark on the valve stem is what you have to go by.
good luck

 

I'm using the comp lifters that cam in the cam kit, which are hydraulics, so we won't get an accurate patch due to the lifter compressing during the actual lift. We verified that the lifter we shimmed (old GM lifter) was identical to the comp one (without compressing) before using it.

Thanks

 

You want the valve closed contact to be just inward of the center of the stem head. When the push rod pushes up, and opens the valve, the rocker will slide outward just a bit, and end up a bit past center. You don't want your closed valve contact patch exactly centered because it'll move outward and get very close to the outer edge.

Your patch does look good though, just something to keep in mind.

 

That will probably work OK....but it sure looks to have an awful big sweep across the valve. The actual placement of where the rocker hits the valve is primarily determined by the stud placement and the actual rocker arm design. Are those 1.5 or 1.6 rockers?

You also want to play with pushrod length to try and cut the sweep down to the minimum as it goes through the arc. Narrow is good. Like .030-.045 type of narrow.

Any chance the pushrod "ball* or tip end is not the same radius as the rocker arm seat?

Again, that will work, but I'd double check to see where the patch is at rest and make sure it's back to intake side and try to keep that large sweep pushed back to intake side a little more.

On a side note...is that red silicone on the studs? Are they going into water? Either way....I'd get all the excess off before you button it up. All that stuff will end up in the oil pan and in other bad places.

Looks like someone did some nice port cleanup there!

Good luck!


JIM

 

We used a diagram from Comps site that showed just that. You can't see it well in the pics of the opn and closed valve, but when you look closely at the geometry, we are starting on the intake side, rolling through centerline and at max lift (106 degrees ICA), we are on the exhaust side of the valve centerline. We tried to get the patch centered on the valve centerline. Thanks

 

They are comp 1.52 ratio roller tips. I checked the push rods (brought them to work with me), the checking pushrod and the old stock rod are the same diameter and the tip of the checking push rod shows wearing of the black oxide finish across the whole tip. I would suspect that if the diameter were too large, I would only see wear on the outer rim of the rod. I don't think too small is an option since they are 5/16" rods (I thought that was the stock and smallest diameter available, but correct me if I am wrong please).

You mention a small sweep path, since everything is fixed, can you really affect the contact patch area by just changing the length of the rod? My pea sized brain is having a hard time with that, can you explain further?

Not sure if the studs are going all the way into the water jacket, but I definitely trust my machine shop and they probably put it on there for a reason. I will definitely clean up the red sealant prior to final assembly. We have too much time into this motor to let it get fouled up by that kind of oversight.

Thanks.
Fred

 

Fred,
The patch looks good to me. I would not mess with it.

The polish job on the ports looks pretty too.

-Mark.

 

looks good to me too. as long as your bearing blue mark gives you an even line from centre on the stud you are sweet. i used thread sealer on my studs as well as some of those holes are blind but others go through to the intake port. the brand i used doesnt actually go hard,just pasty so i wiped away the extra but yours looks more like a silicon style so if there was any daggy bits i would cut off the excess as well. i like your step up (Z) style guides. unfortunatly i couldnt use them, they contacted the bottom of my rockers.

 

It's really difficult to make a good call from photos, but that pattern doesn't really appear to show the correct pushrod length. It' has a very wide "sweep" for the "correct" parts.

Also, the rocker seems to be sitting close to the stud and the pushrod area of the rocker seems somewhat close to the guide plate.

You may want to check the pattern with a slightly longer pushrod.

Again, all this is judging from the photo's only.

Thanks, Gary in N.Y.

P.S. It does appear to have an additional issue with the spring seat dimension and the diameter of the springs themselves! Does not appear to have anything there to locate/steady the lower section of the springs!! There may be a "locator" or something else down there that I'm missing! The springs MUST be stabilized at the bottom, they should have a "snug" fit much like the OEM's used the guide O.D. as a type of cast-in "locator".

 

Are those factory screw in studs or did machine shop add them?

As I mentioned.....the static placement of studs and valves determines most of it. If studs are off..it's a tough battle. Just ask anyone with a set of AFR aluminum heads on a big block. It's a pretty tough job to get rockers working as they should. Usually involves cutting guide plates in two, using back set rocker and or offest lifters to get them right. Supposedly they have finally recently started drilling the holes for intake studs in the right place.

Cams usually increase lift by reducing base circle somewhat, so that changes the relationship.. Valvejobs are often done and valves get sunk into seats and no one corrects valve length/height and that messes things up some more. True roller rockers will act different than a stock type like you have with a rocker ball.

You can't move much, but I'd play with the adjustable pushrod in .100" variations to see what you get. A longer one will lift rocker higher and can position tip in a better position on valve to start. You might be able to pull it back out of the *sweep/sliding* area somewhat. You can vary the sweep based on where it starts in relation to all the other height variables. In your case you might even try a shorter one too and see what happens. All you can do at this point is work to get as small of a sweep as possible and position it where it doesn't go too far overcenter.


JIM

 

Gary and Jim - I think the geometry light is starting to get brighter.

The center of rotation of the rocker arm and the tip of the valve stem should be almost equal in height. If the rocker is too far down on the stud, that puts the contact point on the valve higher and since the rocker will move in a circle around it's center of rotation (mounting height on stud), the leteral movement of that sweep will be larger.

If the rocker rotation point and valve stem tip are very close to even, the lateral movement during the rocker rotation will be minimized. Ideally, you should strive for the valve tip to be a tad higher than the rocker point of rotation. In that scenario, the rocker tip will move laterally outwards during part of the rotation, and then inwards on the lower part of the stroke, which will minimize the contact patch.

You're right, I need to go back and re-check the length to see if I actually need a rod that is longer than stock, which will allow the rocker arm to sit higher on the stud.

Regarding the locators on the springs, you're correct in your observation. The heads were opened up (previous owner, the guy who did the porting everyone is commenting on) to allow for larger diameter springs to be used. The machinist and I spoke about this and he wasn't overly concerned since the motor won't be revving too high. The cam and manifold die off after 5500. But, that being said, I've had the springs off before to get them coated, so if you can suggest a part number, I'm capable of getting the seats and putting them in myself.

Jim - The studs and plates were installed by previous owner so I don't know if these came from the factory with studs. They are 041 castings. The machinist that did the work for me did make sure we replaced the valves with valves whose length would ensure we had the correct spring height at rest.

You guys are awesome. I'll let you know what I find out when I measure again on Wednesday.
-Fred