My Cam Research for the Experts Eye


Well-Known Member
I had initially said. 001 but that was embarrassingly waaay off.

Here's one link but I didn't download from this site:

Engine Professional magazine archives:

Here's the actual magazine, you can view as pdf and print out his article, p20 in contents or p22 in the pdf:


Staff member
I read the complete article, that was very interesting to say the least !

I will then go through the Straub mid-lift method (also outlined by Jim Miller) and see where that puts me on the geometry.
If I remember correctly now (it's been a few day now) there could be some difference between the two processes for setting pushrod length. I wonder how much thou?


Well-Known Member
When I used the plastic pushrod tool after I had adjusted pushrod length with the mid-lift method , there was easily 1/8" gap to the valve stem as the tool rested on the pushrod.
But with that said, as you've seen, I've made mistakes along the way. So that's why I went back to understand this. I'll also contact Straub for info.


Well-Known Member
I will revisit this in depth but I'm delayed waiting on delivery of a new 12in dial caliper.
I intend to resolve and understand all of these measurement methods.

surely one of the most frequently used tools in my tool chest
Last edited by a moderator:


Well-Known Member
That's interesting - he also tends to look at stem pattern. When I get back to my pushrod fiasco I'm very curious to see the stem witness mark vs with rocker set to Miller's criteria. I don't have the pic handy but the witness marks with rocker set per Straub video are too close to the exhaust side of the stem.

I thought I could get the timing cover (removed to get to dropped washer) back on without issue but it was about impossible getting the pan gasket to stay in place below it. One piece fel pro. I got tired of monkeying with it and pulled the pan to redo everything right. So I'm going backwards at the moment - sometimes I hate this hobby


Well-Known Member
Well, I'm back where I was a week ago :confused: Timing cover and oil pan are back into place. New pan gasket, timing cover repainted and I also installed a new balancer seal. I used socket/hammer to install it last time and it had a dent in it - not large but it bugged me, so this time I used my press for an easy smooth install. Actually, this cover/pan install was like a textbook version - everything fit perfectly, all bolts lined up/torqued smoothly and the small bead of rtv in the corners squeezed out just right.

20220618_154501_HDR_resized.jpg 20220618_154443_HDR_resized.jpg

So, next week I will resolve all the pushrod drama, I need to move forward and finish this engine.
What I want to do is compare what I see as 3 methods of setting pushrod length, with 2 of them so far giving entirely different results. The lack of consistency is what has been bugging me. I'll return back to this post and edit accordingly. I will use the Melling solid roller lifter for all 3 methods, so I can use the installed valve springs - if I can establish proper length using the Melling, then I can repeat the same process for the Morels.
Also noted are two perspectives - that proper length/geometry should create a centered witness mark or proper geometry is set on rocker trunion/roller relation to lift and therefore final witness mark is secondary. But it still cannot be closer to 020" to the stem edge.

So here's what I'm looking at - to be edited.....

Method 1 - Proform tool / setting base lobe rocker at top 1/3 line of valve stem
This method is a simple check that uses a plastic tool to set length of adjustable pushrod. One side of tool rests on valve stem and the pushrod is adjusted to touch the other side. The one I bought "should" be a 1.7 ratio for BBC, but my question is what rocker is it modeled for? Stock steel or aftermarket roller, and if roller, then which one?
The other part of this is simply visually setting the rocker up to get the witness mark about 1/3 down on the stem, with the idea to get the overall movement close to center stem.

Method 2 - Straub video - setting base lobe rocker arm at 1/2 lift (90d perpendicular half lift)
This method takes gross lift divided by 2 and adjusting rocker nut turns accordingly. 1 turn of nut on 7/16 stud = .050"
In my case, GL = .578", divided by 2 = .289".
.289" divided by .050 = 5.78 turns without preload, 6.78 turns with recommended 1 turn Morel lifter preload. But using the solid Melling roller, it would be 5.78 turns.

The rocker arm axis is very close but not exactly perpendicular to the stem at half lift. My further checks will use a laser line on top of retainer to try to get an accurate parallel measurement.

And the witness mark on a full roll is close.

Method 3 - Miller method of setting base lobe rocker arm at 1/2 net lift below top of spring retainer
The complete article is linked in previous post.
This method takes the net lift (which I take to be lobe lift on hydraulic - solid would subtract valve lash I think), divided by 2. This dimension is where the trunion centerline is set using adjustable pushrod.
That number is the "trunion reference" dimension in the figure below.
So my case again, .578"/2 = .289" which is what my trunion reference point would be set to.
Back thinking on net lift, I will re-check lift at valve stem to use this number as well to see where that puts the trunion reference point. I believe that the net lift at valve is usually less than actual lobe lift due to parts flex, discrepancy in rocker ratio, etc. So that will be an interesting comparison. I will also look at the witness pattern, but according to Miller, this is not the governing factor of proper geometry. However, I think it should be fairly close - if it's way off almost off the edge, then something is not right.

His directions for measurement below.
One difference is that the Morel preload is recommended to be .050" (1 full turn) vs the .020" in the text.

A couple of quotes from J. Miller:


Well-Known Member
Here's what I did today. I just focused on the exhaust. I used the Melling solid roller so that I could rotate the engine.
I used an adjustable pushrod to set the length, then duplicated that length with a cut-down pushrod, which was verified to match the adjustable pushrod length. All lengths were measured with a 12" digital caliper.

If I can get this process squared away then it can be duplicated on the intake side. I will say that looking at the witness mark does play into my "analysis", such as it is. I had already looked at the Straub method on a prior post so I didn't repeat that. If you recall that witness mark was at the exhaust edge of the valve stem.

First setup was the "Miller method".

I didn't like the results, pushrod seemed too short at 8.367"
Here's the witness mark for this method, which isn't too bad. Note the actual valve lift is short of the gross lift.

This is using the Proform tool. Same comment on the valve lift.

Next I decided to look at pushrod length vs lift at valve vs witness mark

This one is with 8.513" length.

This one seems to be in the ballpark, with 8.664" length. Note the lift at valve has gotten closer to the gross lift, although I don't expect it to match exactly. The pattern is also slightly narrower and slightly on the exhaust side. I think a longer pushrod will be too much of an outboard shift.

What is interesting here is that Straub told me that for my application, they typically see 8.65" exhaust pushrod.

If I take the info from the 8.664" length pushrod using Melling solid lifter, I would subtract .065" (for the sake of the math I will call it .064"), giving me 8.60" pushrod length for the taller hydraulic Morel. Taller lifter means shorter pushrod.
I would then add in .050" for the recommended 1 turn Morel hydraulic lifter preload.
This gives me a pushrod length of 8.65", which matches up with info from Straub.

So I think after all this I probably took the long way around to get back to the beginning :bhow:
But it's ok, it's all about learning for me.

Your thoughts?


  • 20220620_113457_HDR_resized.jpg
    254 KB · Views: 4


Well-Known Member
Was this measurement done using the Straub method ?
No, the last two were looking at witness mark and lift at the valve.
I'll do the Straub method once again though just to be sure of the result. The new dial caliper works well for a very moderate priced tool.
I did check lift at lobe again and verified it at .338. Considering I had a small extension on my dial indicator centered into the Melling lifter cup, this was close enough to .340 lift spec.

Rockers are USA made Harland Sharp 1.7 ratio. If I used .338 lift x 1.7 ratio that should give me .575 lift at valve or at least something close. I'm not entirely satisfied with the last reading of .552 lift - seems that .023 is a lot of difference/flex unless you've seen that in your experience.

I'll bet you're getting tired of pushrod posts ! o_O I know it's wearing me down lol.


Staff member
I'm not entirely satisfied with the last reading of .552 lift - seems that .023 is a lot of difference/flex unless you've seen that in your experience.
I never measured the valve lift vs the lifter, wish I did thou ! So I can't say if .023 is alot, just my gut feeling is it's OK.

I'll bet you're getting tired of pushrod posts !
No not really, it's not just pushrods. It's much more involved than just their length, the story goes much deeper !


Well-Known Member
I believe that I'm ready to move on with my life. I've spent a ton of time trying to correlate several measurement methods and as you've seen it's been a struggle. So I took the best average of all measurements and came up with this conclusion at the end. Note that I reverted to ensuring the witness marks were generally centered. I wasn't concerned about dead center but I just could not see how a valve guide could survive with the rocker pushing the valve close to either the intake or exhaust side of the stem.

I also looked at what the lift at the valve was. This was my setup on a plate attached to the valve cover rail - so I'm confident in those measurements. Pushrod lengths were measured with a 12" digital dial caliper.


Pushrod length 7.475" using solid Melling roller

Pushrod length 7.505" using solid Melling roller

Pushrod length 7.609" using solid Melling roller


Pushrod length 8.600" using solid Melling roller

Pushrod length 8.615" using solid Melling roller

Test with Morel Hydraulic rollers

At this point I used the "best" pushrod length in terms of valve stem markings and lift at valve.
To convert the length, I subtracted .065" from the Melling pushrod to get to the Morel pushrod (without preload).
I did some additional research as well and the recommended Morel preload varies from 1/2 to 1 turn so I used 1/2 turn which is an additional .025" on the 7/16-20 rocker stud. If it winds up needing a full turn that will mean that the roller position shifts very slightly to the intake side of the stem.

I also only looked at start point (base lobe) witness marks only. Full rotation would not be accurate since the lifter would slightly collapse with spring pressure.


Pushrod length 7.453" with 1/2 turn preload on Morel.
Witness mark for base lobe only, no engine rotation.
Looks like a reasonable start point.


Pushrod length 8.525" with 1/2 turn preload on Morel.
Witness mark for base lobe only, no engine rotation.
Looks ok, but slightly to the center.

So for my pushrod length range it looks like I can use intake length of 7.50" and exhaust length of 8.50". Looking at online info, people set Morel preload anywhere from about 1/2 turn to 1 turn, and I won't really know what they like until I run the engine. I think these lengths give me some latitude. I know that I will need at least 1/2 turn and quite possibly more.

My other conclusion is that after trying to correlate mid-rise geometry/length and looking at the trunion reference point, the trunion reference got me close to a reasonable stem pattern. But I say that with a caveat that I could well have made mistakes in measurements. However, it seems that thousands of engines survive fine using the witness mark methodology - of course I want an engine that works well, but there's a limit to my capability and tools to get to the fine detail that a race motor would require. Maybe I'm wrong, but this is where I landed after untold hours of working through all this.

A side comment - in my opinion trying to measure pushrod length with a tape measure or ruler may give you a ballpark figure but for accuracy a dial caliper is needed. I did some comparisons and the difference was enough to shift the roller position on the valve stem.

I really really hope I'm done with all this lol.


Well-Known Member
I have no doubt that you will be fine !

Time to get it running and enjoy !
Well I put my order in so next step is getting the heads bolted on. All bolts (ARP) go into water jackets , so they get Permatex #2 on the threads and ARP lube at the bolt heads/washers. P#2 is great stuff, last time lasted the life of this engine, zero leaks.


Well-Known Member
With cast iron heads and balancer this is going to get heavy really quick. Even with Gr8 hardware I don't like it hanging in space so I made a front support. There should not be a need to flip it over again.


Well-Known Member
A few pages back I had posted info on Fel Pro head gaskets and my final selection per some research verified with their tech line.

I had mentioned that the engine always had an issue with a slow heat-up. One aspect of this was the selection of the original head gasket that (from advice) possibly allowing too much coolant to pass through the primary chambers of the head but less to to the exhaust side of the head.

The original 1017 gasket is shown compared to the new 1037 gasket. The 1037 is stamped "Marine Performance" which is fine, as from what I understand it's a common replacement on mercruisers (GM). Anyway, as you can see the original end double coolant passages are now one single passage. Everything else looks pretty much the same.

(note - old gasket is shown backwards :rolleyes: )


Another change is chamber size and compressed thickness.
Original was 4.520"/.045", new is 4.370"/.039" which should help on the quench side of things.

It also fits much better on the 4.28" bore and around the chamber, plus there's more gasket width between the cylinders.

'bye pistons, I hope I don't see you again for a long time. The paint marks are verification of first torque to spec (I did 4 steps to get to ARP instruction of 70#), and the slight loosen/retorque after an hour. As noted on the other post, bolt heads/washers got ARP lube, threads got Permatex #2. I will recheck torque after first run cool-down.


Staff member
Are you getting excited yet ???

When you are getting close to starting the engine for the first time take a look at the following link. Feel free to make the list your own. Try to avoid the calamity shown in the video linked in post #3.

Page down to post #7 and download the PDF if you like to work with a paper copy. It has lots of blank lines where you can add to the list. Or there is also a Excel file if you would rather edit first and then print.

Good luck !!!


Well-Known Member
Rick, sorry did I miss the link you mentioned?
I don't think its your Dart build link.
Thanks if you can point me in the right direction.

Not that yet excited yet but glad to see it starting to look like an engine. I've still got stuff on the car to finish to support that first start.