My Cam Research for the Experts Eye

Well I can't seem to find the recorded measurements but here's a pic of the P-V clearance of the old cam using clay. Looks like a lot of room, but I'll still check new clearances.
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Interesting ....
As mentioned, new guides and rocker studs to replace old hardware.

I bought slightly longer Dart studs which had identical spec to ARP, complete set $49 vs ARP $140. They do have a locating shank for the guides.

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I had seen comments on the studs and they turned out to be true. They are repackaged ARP studs
:like:

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I worked on pushrod lengths today, I wanted to ask if I'm on the right track.

First thing I did was to use the plastic checking tool to initially set the adjustable pushrods. I double checked to be sure I was using the correct face of the tool for intake and exhaust.

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Next I put machinist dye on the top of the valve stems.
I then installed the roller rocker, tightened polylok to remove slack from pushrod, then an additional 3/4 turn for lifter preload.

I rotated the engine twice to see where the roller sat on the valve stem. I repeated this several times to get the mark centered. With the cam on base circle (valves closed) the arm of the rocker looked perpendicular to the stem.
Here's where I wound up.

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Am I on the right track here?
 
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I've never used the plastic tool, but the witness marks look perfect !

Are you using an adjustable pushrod with those valve springs ?
 
Yes 2 different sizes (BBC has different intake/exhaust lengths). They are both almost fully threaded in, at shortest point, so for a slow roll of the engine they haven't deflected.
I'll get some additional info on what I expected on the lengths vs what was needed.
 
So I decided to go back to square one yet again to really nail down pushrod lengths. This is just what I did today, I'll have follow-up in a couple of days. Jury duty tomorrow.

I made a solid lifter out of the melling hydraulic roller I bought. That plastic ring is there just to help keep the lifter from rotating, need to keep the roller wheel aligned on the lobe. It slides against the block. Works fine.
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Since I've got 16 pushrods I won't be re-using I cut a couple of them to the lengths that Straub cams mentioned as being somewhat more popular. 7.8" intake, 8.65" exhaust. I slightly enlarged the pushrod bores and turned a threaded rod down a little for a snug push-fit inside the pushrod to avoid a wobbly fit. This way I can try different cut lengths to get to the final length.
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The reason I'm doing all this is that I want to see and verify that the final choice of lengths will work, plus I'll measure P-V clearance. I want to be dang sure before I spend money for a set. Also, because when I used the plastic tool the pushrod lengths were considerably shorter than what I expected, even though the valve witness marks looked good. I will also be able to check half lift geometry with an actual pushrod vs adjustable version to be sure there's no flex.

These marks were made with the pushrod lengths mentioned above. As you can see they are off - pushrod lengths are too long. The mid- lift geometry was also slightly off (rocker axis not perpendicular to valve) So now I'll simply try another pushrod set cut .01" shorter and see.
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I'm sure for more expert eyes this is a lot of fooling around, but its a way for me to understand and verify these bits and pieces before I move forward.

One side note - no issue with valves touching pistons as I rotated the engine but I'll still get actual clearance measurements with clay.
 
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you do of course realize they make the correct tools

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I've got them and have used them. This is my comfort level of seeing operation of actual length pushrod.
 
Here's what I came up with today, does this process look ok?

Intake
I started with the pushrod length indicated by the blue checker tool - 7.468", and I used the Harland Sharp roller rockers that will be installed. I actually modified a couple of stock pushrods to use when rotating the assembly so no flex.

I made a witness mark on lobe base, my understanding is that the start should be about 1/3 to the inside of the stem.
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I then rotated the cam a couple of time to get this.
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This is at mid-lift, note that the rocker centerline is not perpendicular to the stem
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Exhaust
Initial witness mark on lobe base
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Full rotation
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Mid-lift, similar to intake, the rocker is not perpendicular to the stem
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If I use longer pushrods, the witness mark for rotation moves outside of the center area, virtually to the outer tip of the stem.
I read where the key factor is ensuring that the rocker tip remains as centered as possible to the valve stem.

If I've done the above process correctly, if I add 1 turn preload (.050") (Morel recommends 3/4 to 1 turn) then the lengths I need would be:

Intake - 7.518"
Exhaust - 8.58"


When you order pushrods, do you go to the next longer length? I think they are made in .050" increments. So does that mean I get 7.55" intake and 8.6" exhaust?
 
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Last step today was to verify pushrod lengths using the Morel lifters when rotating the engine. I kept in mind that the lifters will compress slightly so this was to look at start point and general range of motion at the valve stem. General descriptions are in the pics, which are readable but not as sharp as I'd like. I think I had some oil or something on the phone lens.

Intake
Pushrod length 7.44" with Morel, no slack in pushrod, no preload added to lifter. This is just looking at the base lobe witness mark.
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Witness mark is generally centered, 1 turn (.050") lifter preload added, with consideration that the lifter had probably slightly compressed during the rotation.
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Exhaust
Pushrod length 8.50" with Morel, no slack in pushrod, no preload added to lifter
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Witness mark generally centered, very slight offset to outside,1 turn (.050") lifter preload added, with consideration of probable lifter slight compression. Still looks acceptable.
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Conclusion:
Previous check with modified (solid) Melling lifter was:
Intake - 7.518"
Exhaust - 8.58"

Today's check with Morel hydraulic lifter was:
Intake - 7.45"
Exhaust - 8.50"

Looking at the witness marks and taking into account an adjustment window of .050", it seems that workable lengths would be:
Intake - 7.5"
Exhaust - 8.5"

But again, this is not using the lobe mid-rise position of rocker arm to valve stem as that is not perpendicular. If I make it perpendicular as a criteria, then the witness marks move too far outboard (almost to edge of valve stem) because that necessitates longer pushrods.

As a sort of quick check I looked at the difference in stock pushrod lengths vs what I came up with. Stock intake pushrod length = 8.28", exhaust pushrod = 9.25.
If I compare my numbers, there is a .78 difference in intake pushrod length and .75 difference in exhaust pushrod length, virtually the same difference for both when you take into account my measurements may not be exact to the thousandth. So this tells me that using the taller Morel lifters yield about the same result in pushrod length reduction which makes sense to me. If there was a greater difference in the numbers then I would look at what I measured wrong. So I believe that the lengths I came up with are valid.

What I can do now is use the Melling solid roller with the same pushrods and rotate the engine to check piston to valve clearances. If clearances are ok with the Melling setup then they will be ok with the very slightly shorter final Morel setup. Hope that makes sense.

I also found that the new Comp Cams guides were shaped slightly too high at the pushrod ends and slightly rubbed on the rocker trunion. I'm returning them and re-using the Manley guides, which are shaped with a bit less rise and fit fine.
 
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I checked P-V clearance and looks like there's a lot of space. I rotated the engine with both the solid melling and the hydraulic morel. I did take into account a slight compression of the morel.

Here's the result.

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I also had a self-kicking moment - I ALWAYS cover up the valley. Except for today, so of course as I was monkeying with the cylinder head, a washer came off the head bolt and rolled right down into an opening. What an idiot. It sounded like the Plinko game on the Price is Right as it bounced off of things and finally landed on the upper section of the oil pan. So I was mad but got grateful quick thinking how that washer could have lodged into a crevice somewhere that would require the oil pan coming off plus a good search. The washer was too big to go through the pan drain hole so the next best thing was to remove the timing cover. Hated to pull it and ruin the gasket but that's not a big deal I guess. I used a flex magnet to snake past the crank timing gear and snagged that washer right away. So lucky.
 
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Upon measuring, I came up with intake 7.685 and exhaust 8.625 - using Morel hydraulic lifters. POST # 317

Looking at the witness marks and taking into account an adjustment window of .050", it seems that workable lengths would be:
Intake - 7.5"
Exhaust - 8.5"

But again, this is not using the lobe mid-rise position of rocker arm to valve stem as that is not perpendicular.
Why do you think these two measurement differ by .185 / .125 inches ? Seems like a significant amount when they should be the same, if I'm reading your posts correctly ???
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Rick, I honestly don't know. I've checked and double checked but cannot reconcile the difference.

Using mid-rise perpendicular geometry of stem to rocker centerline always brings the full rotation witness marks too far outboard on the stem.

Using shorter pushrod that shows witness line at one-third onboard on the stem yields almost perfectly centered full rotation witness mark on the stem. This length pushrod is the same as what that plastic proform checker came up with.

Rockers are Harland Sharp supplied by Straub, nothing that exotic.
I had also looked at this article:
 
There are a couple of different schools of thought concerning proper pushrod length. Looks like you have discovered them!! In your link directly above, it seems the most important to you are the last two paragraphs. Maybe Straub was talking about a racing application, although he really didn't say.

This is a simple and effective way to establish proper pushrod length. There are other procedures that some people may comment on that are an attempt to minimize rocker travel or place the rocker at 90-degrees to the valve at mid-lift. These processes will often require a different pushrod length.

We won’t get into this on-going battle except to say that these other procedures are aimed at race engine applications for ultra-high-rpm use. The process we just offered is easy, concise, and will offer great durability on any street motor.
 
I feel once again like a dummy lol - seems that this should be simple and I've spent a ton of time trying to understand and sort it out. Hopefully at the end of it I will have learned something!

I've also seen where a key critera for proper length is to look at the width of the sweep witness mark on the valve stem. This seems to be of more priority than a dead center placement.

Since I've got the melling roller lifter set up as a solid lifter, I can experiment a bit with a couple of other pushrods just slightly shorter and longer than the current version and see what that does to the width of the sweep.

But I still don't get why the method on the straub video doesn't result in the same pushrod length as using the checking tool/base circle setup where the beginning witness mark is placed at that approximate 1/3 high of the stem center.

I will go back yet again to think about the mid lift method of setting pushrod length. I think Jim Miller had an in-depth paper on this.
 
I read the Jim Miller article in Engine Professional magazine, Apr-June 2010, very enlightening and I know I will re-read it. I kept thinking about why the geometry was not coming up consistently and had a small brainstorm. I simply did not want to move forward until I could completely understand what's going on here.

I know the experienced engine builders will laugh or get tired of repeat posts on valvetrain geometry, but I hope this may help somebody at my skill level. I think my basic lifter comparison measurement was wrong and that I compounded it by using the difference incorrectly. Dumb....

I went back literally to the start and thought about the tool I used to compare lifters, so I decided to make it a more rigid setup that captured each lifter without movement. This is the "updated" version that held the lifter in place without any rocking, and the stand itself sat without movement. In this pic, it's holding the Melling lifter. Remember, both are roller lifters so they want to roll when standing up. You can/t see it, but there's a small spacer/insert at the bottom to hold the lifter base in place without movement.
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The dial gauge was slightly pre-loaded and set to "0" for the Melling lifter.
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When the Morel lifter was set into place using the same pushrod and without movement of the gauge or stand, the Morel was .065" taller than the Melling. This was with no compression of the Morel lifter. This comparison was repeated 4-5 times to ensure it duplicated every time.
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So, first of all, my initial reading of .030" difference was dead wrong. I went back and found that my previous stand version had allowed the lifter to roll ever so slightly but this made the difference, as each lifter did not sit exactly the same. I could barely touch the lifter or anything else on the stand and see a change in the reading

Next, I believe that instead of subtracting pushrod length from what I established with the Melling, I added the difference, so I made the pushrod too long for the Morel application. The pushrod needed to be shorter to allow for the taller Morel - I checked my notes and I had done the opposite. So I pretty much screwed up every step.

I can still do my final install on the heads with the new head gaskets, as there's a substantial P-V clearance margin. I will then go through the Straub mid-lift method (also outlined by Jim Miller) and see where that puts me on the geometry.
 
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Well I can't find that article by Jim Miller.

I thought there was a .001 difference, where did I get that from?

According to that article from Onallcyclinders linked above, the parallel at mid-lift process is for a racing/high rpm application and will still indicate a different length pushrod from the center witness mark process. It's going to be interesting to see what you learn next !!!
 
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