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With the 302's there was a specification based on zero lash and how much farther you had to turn the bolt to reach the torque spec.
Based on the thread pitch, it was calculating the preload that way. You could at least try that.
But unless I'm missing something, you need new rockers anyway!
Did you fellas discuss that already and I missed it? Or am I seeing that pushrod pocket pic wrong and that's not as severely worn as it looks?
And if that little bit of stuff at the top of your second pic isn't a chunk of worn metal, it sure looks like it from here!
On some engines that's correct, you use lock nuts or poly locks and adjust each one like you would with adjustable rockers. but not on this one.
You're right on the picture, but I assume it's an optical illusion . I also don't know why the bottom looks unused and around the pocket looks used. almost like a cup was used rather than a ball end . I'm sure that's not the case but it's odd, half the time pictures are deceiving.
I tooled around on it last night to check out the push rods and rockers. I pulled off the rockers and colored the valve tips with a Sharpie. On base circle (valves closed) reinstalled each pair manually turned the cranked 1-2 times. Pulled off the rockers and inspected the witness marks. Worked pretty well (I don’t have machinist blue). Each valve had marks dead center. I think that means the geometry checks out.
I had a set of new Melling rockers and push rods on the shelf so I installed them after performing the same geometry test on two cylinders. I also ran the starter on them a bit to ensure each rocker oils properly. Looked good so it buttoned it up.
The sound is still there once pressure drops to 25 or so. The sound, as Tbear describes it, is a sewing machine ——- just louder than it should be with a little tick.
I may experiment with some 20w50 to see if that has any impact.
I may also just accept it as a nuance of my first build.
I’ll update a bit later this weekend.
Last edited by LandAndStone; May 29, 2026 at 06:54 PM.
Just remember, where the rocker arm contacts the valve stem makes NO difference when it comes to geometry. It is the motion of the tip on the end of the valve that matters. As long as it stays on the end of the valve it is ok.
I ran the mark-on-the-valve-tip test to check the length of the push rods. I thought that a mark on the exhaust side indicates too short — and mark on intake side means too long. Between Dave’s note and 440s response, I think I may be off target. Let me try to course correct:
- If witness marks are on the valve tip, geometry is fine.
- Good geometry doesn’t mean preload is correct.
- Preload needs to be checked using 440s method above for each valve.
- Prelioad can only be adjusted with push rods of length determined by adjustable rod length using same method
- Geometry should be rechecked and preload rechecked with new rods
Correct me where needed. This wasn’t part of my Tom Monroe reading (but I might need to go double check)….
Yeh, Tom speaks to it.
Last edited by LandAndStone; May 29, 2026 at 08:50 PM.
Looking through the section, he (Tom) is assembling an engine and is using thread count to get a feel for how far a lifter has room to pump up to adjust for valve wear at the seat or tip or pushrod end wear, looking for 3/4 to 1-3/4 turns from bolt just closing the excess to bolt fully seated before torquing to 18-22 ft/lbs. With a 351M/400 he is aiming for 0.100-0.200". The whole section from the book isn't seen.
Elsewhere (pg 34 chart) he says PR length is 9.51", and that they were then available + or - 0.060" lengths. Your's are mighty close.
I'm sorry if obtuse sounding I am, I just never grew comfortable with the term "preload", I like the word "adjustment". You are looking to make sure the adjustment created by hard parts when assembled results in the needed tolerances that the lifter where the lifter has the needed range to final adjust with the use of oil pressure.
Last edited by tbear853; May 30, 2026 at 07:01 AM.
You don't need to check preload on every pushrod, just doing a few should tell you if this is your problem or not. if it is you can dive deeper to get the right length. if you do need to change them I'd get a set made exactly the length you need. I've never waited more than a week for them. just getting something generic that might be good enough doesn't make sense to me.
Don't get too hung up on geometry, we're talking a minimal difference in pushrod length that is unlikely to make enough difference to matter. when and if you change the pushrods you can check it but it's very doubtful it will matter.
Your preload might be just fine. but it's something you always check, and since your symptoms sound like it might be a problem it should definitely be checked. it should be added that while it's not great to have things rattling around it's not like you're destroying your engine. if it's something you want to deal with later you can.
With this type of valve train the pushrod length will only determine the amount of lifter preload it will not change the geometry of the rocker arm. This is simply because with a bolt down rocker arm the height of the pivot is fixed vs a stud mount rocker arm where its position can change up and down.
Also, I can't remember what camshaft profile you ended up using but in some cases the noise is in the design of the lobe itself and changing the amount of preload won't have any real effect on the amount of noise. Comp XE designs and some others are bad about this sort of thing.
Last edited by DaveMcLain; May 30, 2026 at 06:51 AM.
I will check the preload using both methods this weekend. As I reread Tom’s book, I definitely remember the bolt turn procedure when assembling the engine. I just didn’t realize I was checking preload. In fact, as I torque each of the bolts afterwards, I remember asking myself what did I just accomplish?
With this type of valve train in normal use the amount of lifter preload makes no difference as long as you have some. The lifters have a lot of travel so it is very forgiving. I've never seen a noise problem with an Erson profile but it seems like if that was the problem the valve train would just be generally noisy and not noisy on just one side of the engine. A few lobes ground with a bunch of base circle runout could possibly be noise makers. That is possible but not likely.
... etc ... it should be added that while it's not great to have things rattling around it's not like you're destroying your engine. if it's something you want to deal with later you can.
Yeah, worst that happens is a hair less valve opening and a solid lifter sound.
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