My rockers finally came in today and I have been using the pushrod checker to determine the new length (mods include XFI268 cam, AFR195, LS7 lifers). I've posted some pictures below - seems like 7.250 was the closet to center with the smallest sweep. I added 0.0250 for lifer pre-load and set the pushrod checker to 7.275 (and gave a 1/2 turn after zero lash) and looks to be in the ball park. Check spring installed - I have only tried the intake so far - will do exhaust tomorrow. This is the first time I have done this so wouldn't mind some feedback. Thanks.



7.250 - zero lash

7.275 (with 1/2 turn past zero lash)

7.15 - zero lash

7.2 - zero lash

7.225 - zero lash

 

Don't worry about "close to center". Doesn't matter unless it's WWWWWAAAAAAYYYYY off to one side. Anywhere within the center half is fine, which all of those are.

What matters is narrowest sweep. This equates to the rocker tip "scrubbing" as little as possible across the valve stem.

What you're trying to do is, roughly center the sweep so that the rocker is pushing as near as possible to straight up and down at all times. It swings in an arc so you can't possibly get it "perfect"; but you want as little of that action as you can get. This accomplishes several useful and valuable things, among which are, the maximum lobe lift being transferred to pushing the valve down instead of making the rocker tip move sideways; and, minimum side loading on the guides.

Do this thought experiment: lay a pencil on your desk. Push on the pencil eraser exactly in line with the length of the pencil while holding the other end down gently with your finger so that it stays flat on the desk. Push on it at the very center and note how the pencil moves. Push on it somewhere else and see how it moves. Push on it out at the very edge for comparison. Didn't make much difference, did it??? Now push on the pencil at an angle, say 15 or 20°, away from straight in line with it. Which way does the pencil move?

So, what matters to your rocker geometry? Centering, or getting the arc right (which corresponds to minimum sweep)?

I prefer to find minimum sweep, then choose a slightly shorter push rod than that. Like, round down to the next .050" increment below. That way, the when the spring tension is highest, the rocker is moving the straightest; and when the sweep is less perfect, there's less force on everything. Biases the whole thing in the direction of least stress.

Of all your patterns, the 2nd seems best to me.

To avoid the uncertainty of the lifter plunger depressing, you can "solidify" a lifter with a little syringe like you'd use for administering worm medicine to a pet, and some melted Trans-Gel or Vaseline. Inject it into the oil hole until the lifter is full. Put in the fridge for a little while to cool. That material will flush right out and disappear when the engine gets hot the first time.

 

Thanks for the info - I went out again and started over, looking for the narrowest sweep. I tried some with 1/2 turn lash and some with out, pictures below are the best outcomes. Is it incorrect to check pushrod length with valve lash? What pre-load amount do I need to add for LS7 lifers? Once again appreciate input.


7.225 - zero lash

7.225 with lash

7.250 - zero lash

7.250 with lash

7.275 with lash

7.280 with lash

 

I do not know if I missed reading it... But which Rocker-Arms are you using?
More importantly, are you using Poly-Locks/ an "Adjustable" Rocker-Arm/ Valve-Train system?

If you are using Adjustable Rocker-Arms/ Poly-Locks...
I would install a set of OEM length Push-Rods, tighten the Poly-Locks to "Zero Lash"...
Turn 1/2 to 1 additional Turn, and secure the Poly-Lock (for each Rocker-Arm, with the Lifter on the Base-Circle).

We can get into more complex measurements/ configurations from there.

I feel as if many of the DIY Engine Builders here, have been spoiled by Stud-Mounted Rocker-Arms (Gen-I SBC)...
An Adjustable Valve-Train starts off very inexpensively, compared to Engines that use (the Superior) Shaft-Mounted Rocker-Arms.

Even Gen-III/ Gen-IV SBC Heads that use Rocker-Arm Pairs on a shared Mini-Shaft are reasonably affordable, compared to "proper" Shaft-Mounted systems.

 

One more note...

Always make certain that the Valve-Guides do not have excessive wear, before performing the procedures discussed above.
Actually that should also include the Valve-Seats... the must be centered/ concentric.

One of the few benefits of a Roller-Tip Rocker-Arm, is decreased side-loading of the Valve-Guides (extends the life of Guides and Seats) with wilder Camshaft Lobes.

 

@Vorteciroc, my rockers are Comp Cams Ultra Pro Magnums (1605-16) - so yes with Poly-locks. The valve guides are brand new (came with the new set of AFR heads) and valve seats all look good to me.

So you want me to use the original pushrods (when I measured them with a digital and manual Vernier they came just under 7.19 - measured a few times more with the same result as I thought factory rollers were 7.200) and install each rocker, lash at base circle - what about the check springs? should I remove them and re-install the ones that came with the heads or will the check springs still be needed for measurements? I will try to tackle this tonight when I get back home from work - what measurements did you want me to take then?

I am assuming that none of the pictures from my second attempt at the sweep method are ideal?

Thanks.

 

The way I select them is, "solidify" a lifter, as described, to eliminate any preload; install checking springs; put marking compound - Prussian Blue, white lithium grease, or sometimes just a Sharpie mark, on the valve stems; put in my adjustable push rod; adjust to exactly zero lash; run the engine through acoupla cycles; observe witness mark width. Adjust push rod 1 turn (.050"... the increment you can buy them in... although these days in some ranges you can get them in .025" increments) one way or the other; repeat. Did it get better/worse? Better: adjust the PR .050" more in the same direction; repeat. Worse: adjust it back to where it was, and .050" further; repeat. Repeat until no further improvement can be made. You can use smaller increments if you're not in a hurry, and find the "exact" length that results in minimum sweep.

LS7 lifters, if "genuine GM" or equivalent, have about .125" of travel or maybe a bit more. They are well known to want about .075" - .080" of preload. Therefore whenever you find the "ideal" length of your adjustable by the above method, you'd add that much to it to get the length you need to buy, since you will want the plunger to be pushed down into the lifter body that far in normal operation.

You can't "measure" push rods with a micrometer, and use that number to "buy" them. That isn't how they're spec'ed. "Catalog" length assumes that the end is a complete sphere; but there's a hole in them, that removes part of the circumference by making a sort of crater, which shortens them. You can approximate how much length is removed by the hole, by measuring its diameter and doing the simple geometry; but if the hole is chamfered or radiused, that introduces further inaccuracy and uncertainty. "Rule of thumb" is about .010" lost at each end, but it's very imprecise. Best way to do it is with an adjustable push rod. https://www.summitracing.com/parts/cca-7702-1 It has a known length, and since its threads are ¼"-20, each turn is exactly .050" (1/20 of an inch). It's 6.800" fully screwed together, and each turn you unscrew it adds .050" to its length; so you "measure" it by counting the turns, NOT with a micrometer.

In normal operation, the plunger gets pushed up against the push rod by oil pressure in the little chamber inside it, until the PR, rocker, etc. are all tight together and free from any play (the condition called "zero lash"); then the sudden impetus of the cam hammering on the bottom of it closes the little check valve within acoupla thousandths of motion of the lifter, capturing the oil inside it that holds it at that exact height, through its operating cycle; then when the valve is closed and all the extra pressure on that oil goes away, the check valve opens again, and the whole thing re-finds its level, prepping for the next valve lift. The whole "point" is to make preload (adjustment) irrelevant. Unfortunately it's not perfect at that; a hyd lifter with LOTS of preload acts differently from one with very little; but still, it gets pretty close. But, to make the lifter's guts happy, a typical stock one will want to be preloaded to about half of its total internal travel or slightly more. Other lifters made for other purposes can act differently. One of the things that goes wrong with this system is "pump up" at high RPMs, which is actually a consequences of valve float (the valve bouncing off the seat as it closes); the effect of it is that the plunger gets pushed up too far, and the valve gets held open slightly by this, obviously a major malfunction. These lifters are designed to have almost no preload at all, thereby leaving no opportunity for this to even happen. But LS7 lifters are basic stock design and want a good bit of preload. Cheeeeeeeeep chinesium garbage ones off ebay or from Skip White or something, are completely unpredictable; with actual LS7 lifters almost impossible to obtain these days, the market is flooded with CRAP substitutes, and results vary WILDLY. All bets are off as to what the "ideal" preload for any such trash might be; or for that matter, whether it even matters at all, because the product might be such crap that it won't ever really be "right" at ANY preload due to inherent crappiness.

 

I prefer the mid-lift method.
No rotation required.
You don't even need to snug down the rocker. It can just rest on the stud.
Measure. Adjust your adjustable push rod. Measure again.
Confirm with a sweep.

This method ensures that the rocker arm is 90 degrees to the valve stem at mid-lift and that will guarantee the narrowest possible sweep.
Centering if needed, is another matter and may require backset trunnions on the rocker.

 

@sofakingdon - thanks again for your input, I do have the comps adjustable pushrod checker, instead of counting turns I was using the caliper to check length which I know now is wrong so will redo the sweep method again tonight. I bought the lifters directly from GM Parts so I hope they are OE and not a knockoff. I just need to find a syringe to fit the oil hole in the lifter to solidify - they were presoaked in motor oil for about an hour before I dropped them in.

@SkinnyZ - I read up on the mid lift method this morning and will also try that and compare between the two and will try to post results tonight.

Thanks!

 

The most difficult thing about that method is rigging up the necessary means to get your measurements. A flat topped spring retainer is best however in my case, the retainer top has a complex shape so there's no place to measure.
I made a jig out of an old school vernier caliper and the hex bar stock of known dimension as a measuring aid. Hex keys work well.
It's a little crude looking but the measurements are spot on.
For the record, the sweep across the valve tip here was probably around. .030". That's about as narrow as I could hope. Unfortunately, to get there, I had to use backset trunnions as the sweep pattern was advancing far too close to the valve top edge.


The caliper supplies a flat plane of reference.



Suitable bar stock used from the reference plane to the centre of the trunnion.



With the lifter on the base circle and a known valve lift and rocker ratio a second measurement is taken from the reference plane to the centre of the roller tip.
A little math latter and you have your results.

Kindly excuse the cat hair in the picture....

 

The reason the rocker tip ends up too far across the stem is usually because the valves are too long or sunk too deep into the head.

The valve, push rod, and stud are NOT parallel. If you consider the stud as the reference, both the valve and the PR "lean" toward it. If you draw an imaginary line through all 3, each of the other 2 intersects the stud (reaches the point of zero distance from it) at some point somewhere above the head. Obviously as the valve gets longer, its tip, following the line, gets closer to the stud's line; and if the rocker is the correct length for when the valve is down lower, then it gets to be too long as the valve tip gets higher.

The pattern on the stem is narrowest at approximately the place found by the mid lift method. Personally I find that method too fiddly, and still subject to some of the errors and uncertainties that plague the whole system. I prefer to go directly to the thing I want to measure (ideal rocker-to-valve contact with minimal wiping) rather than "inferring" it by some other method if I don't have to. Just basic metrology. But, to each his own. Worst of all though is the stoooopid little plastic tool thing: that thing makes the assumption that ALL rockers have the same relationships between pivot center, push rod seat, and tip; and that the plastic thing EXACTLY duplicates this for EVERY rocker. Clearly, ... fantasy land.

Equally obviously, heads with geometry other than stock, affect all this differently. Which most aftermarket heads are; one of the ways they improve their performance over stock, is to move the parts around slightly.

Another thing to consider is, the rocker is not supposed to push straight down on the valve, anyway. It's supposed to kind of wipe across it in a way that tends to rotate the valve. This is why the studs are closer together than the valves. I've seen people think they were going to outsmart this and use adjustable guide plates to make the rockers move perfectly straight up and down, and then wonder why the valve seats don't last. This is yet another confounding factor introduced by aftermarket heads: the intake stud and valve are sometimes moved over slightly, to make more room for a larger intake port. Obviously this severely distorts the geometry issues even further, especially when guide plates are used.

We deliberately use longer valves sometimes to be able to fit in more spring and/or to allow for more lift. Too many valve jobs, or a destroyed seat that was just ground but nor replaced, allow the valve to move up higher as well.

The more lift a cam has, the more likely the geometry is to be different from stock. First thing to always remember is, the tip of the lobe is almost always as large as it can be, and still fit through the journals; the way a cam is made "bigger" is NOT by making it "taller", rather, since "lobe lift" is THE DIFFERENCE BETWEEN the tip and the heel of the lobe, a cam is made "bigger" by grinding the heel SMALLER. Which is why people can take a wiped-out cam and send it to the shop and they can grind it back to where it was or even larger. This would tend, generally, to make the correct push rod longer than stock, as lift goes up. OTOH, since the center of the rocker's sweep is then farther downwards, keeping the same geometry at zero lift will result in the rocker tip's arc swinging too far inwards at max lift, which would tend to make the PR need to be shorter. Virtually always the rocker has to "lay back" farther with a bigger cam, than with a stock or similar one. Small-base-circle cams such as are sometimes needed with very long stroke are a further complication. It's hard to know, in a given engine, which way it's going to go. Obviously longer valves will tend to require longer PRs, but then you get into the problem of needing shorter (or offset trunnion) rockers.

Every engine is different, even if the BOM is the same. The more we strive for perfection, the more those differences matter. For example, the difference between the Edelbrock "435 HP" Performer RPM kit as advertised (probably reasonably truthfully), and the 285 HP version most people seem to come up with when building it, is the result of just such a lack of attention to detail. Perfection, or lack of it, is what makes 2 supposedly "identical" engines run different.

[/stream of consciousness rambling mode]

 

The only problem with any of this is the use of checking springs. It's well documented that they introduce a margin of error that in some cases, most notably with heavier springs, can exceed any preload that you might have at the lifter.
Then there's the issue of the hydraulic lifter itself.
Chilled Trans Gel? That's pretty good actually.
But ideally you'd like an identical lifter in a solid version. Then the actual running springs can be used and that otherwise imposed error is gone.
Now with the mid-lift method and a suitably flat retainer top (which something like a small beehive version lacks in my case anyway) the real spring can be used as there's no pressure applied to the lifter itself. Factor in how much preload is required after the measurements and there you go.
I'm only sensitive to this because I messed up at least two sets of guides on my current heads going about it the wrong way. Which by the way, was none of the above.
(The first time was from focusing on a centred pattern...fail)
I've taken out guides in as little as 5-7 thousand miles.
My latest go round is presently in pieces due to other problems but I'll soon know if the last 15000 miles or so have been kind to the guides this time.
If yes, I'll credit Jim Miller.

 

I was trying REAL HARD not to say the name when talking about the laughable little plastic "tool". But, there it is, anyway.

He's obviously a smart guy and has been around the block a few times, and makes some VERY VALID observations, but he reduces the whole issue too far toward the simple. As someone INFINTELY smarter than me (since I'm not smart, anyone who is, could fit this description) said, "everything should be made as simple as possible, but no simpler". Sometimes the problems with oversimplification stem directly from that: knowing when you've simplified TOO far. Which in ... that individual's case, CLEARLY happened. A Good Idea, no matter how Good, must survive translation into reality, to be not only Good, but Useful; and that one, ... fails that test.

There is NO SUCH THING as a "identical lifter in a solid version", except by raw accident. Rare at best, unrepeatable and unpredictable in the RW. Yet another potential source of error. Which is why the True Path To Error-Free Nirvana is one of YOUR ACTUAL HYDRAULIC LIFTERS, "solidified" as described.

Not sure how checking springs are some kind of a source of error. None of the parts bend or deflect or compress enough to make this significant. The "error" introduced is less than the noise in the signal of the measurement. Kinda like, if a cat hair got stuck somewhere, and threw some one of these measurements off, by that much... in the same range of significance. Which is to say, NONE.

Again, not to say someone else is doing it "wrong", necessarily; only to point out to n00bz looking to develop skillz, that the EASIEST way to get the MOST ACCURATE results, is to go DIRECTLY to the thing you want measured, and measure THAT, rather than measuring something else and attempting to "infer" what that might entail for the thing you REALLY want to know.

 

Miller invented that plastic tool?
I would have thought, given all his input and effort into his mid-lift method, that that tool would be about as far removed from him as it from me.
Things that make you go hmm.

 

Ok...spent a few hours under the hood and now my back aches!

I think I have made some progress based on your suggestions. I started off with trying to figure out how to the mid lift method, issue as Skinny z mentioned is having something flat across the retainer as the measuring reference point. I ended up using a utility knife blade wrapped with some tape so I wouldn't cut myself and used a magnet to hold it in place.

The lift on my cam is 0.570, reading some of the mid-lift method articles, they mention to add .040 on top of the lift to account for the light weight check springs. So I end up with trying to achieve a delta between the measurements around 0.305 (0.570 + 0.040 = 0.610/2 = 0.305).

The closet I could achieve was 0.298 - this was exactly at 9 turns on the adjustable pushrod.


I ended up with a measurement of 0.3650 at the center.

For the trunnion measurement I had to use a fine tip marker to scribe a line then take the rocker off to measure:



From the angle the picture was taken it kind of looks like the caliper is off from center but it wasn't.

So .3650 - .0670 gives me 0.298, about 0.007 of target. Did I do this correctly? Below are pictures of the sweep and how the rocker sits.




I'll tackle the exhaust valve tomorrow. If I have done this correctly, 9 turns ends up being 7.250, can I use 0.050 for preload which would be one full turn after zero lash and I end up with 7.300 rods (at least for the intake) or use 0.075 which would be 1.5 turns after zero lash ending up with 7.325 rods?

Thanks!

 

Also forgot to mention that I've ordered some syringes off Amazon, should be here tomorrow and will fill up a lifter to solidify as suggested and check the sweep again.

 

As long as that reference knife is guaranteed parallel to the retainer it looks good.
I haven't checked the math however you're at the point where I'd mentioned do a sweep to verify.
So doing that, I'd added a tenth up and down on the adjustable pushrod and observed sweeps for each.


7.3"


7.4"


7.5"

The effect of the longer or shorter pushrod is obvious. With my choice of rocker I'd managed to get the narrowest sweep and the most centered with a 7.4". I hope it pays dividends when I pull heads apart for an inspection.

By the way that's not an indicator that your 7.3" is off the mark. As you know all engines are a makeup of the parts and machining. When I went from COMP's pedestrian lifters to their short travel versions, there was a change in pushrod length. Same with rocker brands of the same ratio. It all stacks up one way or the other.

 

Thanks Skinnyz...I am going to recheck everything tomorrow again, I am pretty sure that I was flat on top of the retainer.

Your pictures of the sweep patterns, were they at zero lash or with some preload? I am having to put my fingers under the retainer of the check spring to apply some tension to get marks on the stem. If I don't, it's all over the place or doesn't mark at all.

 

That would have been checking springs and as you'd adjust your lifters before preload. No slack in the pushrod.
I've tried all kinds of crap trying to get a good print. Those images are third time around with the same length wiping off the Prussian Blue as I went. It took some effort.

 

So I played around bit more today, 7.275 seems to be the narrowest sweep I can get at least for the intake side. I still am waiting for the sirenges to arrive so I can solidify a lifter and recheck again.

I am noticing that the check spring/retainer turns a bit when the valve goes up an down which is probably causing a wider sweep pattern. To counter, I am applying some tension from under the retainer with my fingers as I cycle the engine to prevent it as much as possible.


Intake 7.275

Exhaust 7.275

 

I can't speak for your method but it seems a little wide when compared to what I've managed (my picture above at 7.4") . It's about .030"-.040" across. Part of that I know is from whatever is used as a marking medium but then again it's really about getting to the narrowest sweep however wide it might be.
Somewhere, I think in Jim Millers tech paper on the subject, he suggests that a .550" lift will resolve to around 30 thou if the most efficient geometry is realized.

Speaking of Miller's paper, are you familiar with it?

 

Hi Skinnyz,

I thinkI figured out why I was getting wide sweeps - I was cycling through the engine a bit too fast, this time I slowed right down especially while the valve was going up and down. I ended up with a sweep around 0.345, that is with 7.300 for the exhaust and 7.275 for the intake:



If I add the recommended preload for LS7 lifters (0.075), I end up with 7.350 for the intake and 7.375 for the exhaust. Should I but 2 different lengths or just get 7.350 for both? Any recommendations for pushrods?

Thanks,

 

That's looking better.
To answer your question, here's a quote from Miller's paper.

If using a HYDRAULIC TAPPET, be sure that it is fully extended during this check. You can prime the motor to do this. After getting your pushrod length, ADD .020” to allow for hydraulic tappet compression during actual engine operation. Order EXACTLY what you need for pushrod length, rounding off to the nearest ten-hundredth of an inch (two decimals).

Now, he's referencing an .020" pre-load.
Yours is .075"? With a 7/16ths rocker stud (7/16-20), that's a turn and half? (.050" per thread).
I had no idea. My COMP short travel lifters have .020" pre-load (being the nature of short travel). Their conventional lifters are .040".
But poking around the web does suggest a .075" ballpark for LS7 lifters so yeah, your thinking is on the mark.

As for pushrods, I've COMP's 5/16ths one piece Hi-Tech versions.
https://www.summitracing.com/parts/cca-7955-16

 

Thanks Skinnyz - I read the the miller paper a few days ago, quite interesting.

As for the difference between the intake and exhaust, should I buy two difference lengths or will I be ok sticking with 7.350 for both the intake and exhaust? Took a look online for sets of 8 - nearly impossible to find in my sizes and when I do find them they are back ordered for months (mainly checking Jegs and Summit) - will search some more. Also sent a message to Briantooley Racing to see when their pushrods will be available again.

Thanks,

Pnorth

 

The correct answer is to get as close as you can for each. How much that matters is the tough call.
7.35" will fit the intake spot on and the exhaust a little short. As I see it 7.40" is wrong for both from your measurements (going with .050" increments). That makes 7.35" the logical choice I guess.
But, you have to consider this:
"Checking springs ADD about .040” (or more) NET valve lift to your engine. Or, another way to say it is you will LOSE .040” or more NET valve lift when you put the heads together with the running springs, compared to whatever you measured using the checking springs."
You can prove this by doing your measurements with your running springs (forget the sweep obviously) and see what the difference is. Then incorporate that into the pushrod length.
One thing kind of stands out is that pushrod lengths are divided into those .050" increments so perhaps that can be inferred that .025" one way or another isn't a game changer.
One thing I did read (sources unknown) is that if you have to choose, a little longer pushrod with a hydraulic lifter is preferred to shorter. I'm thinking the reasoning is that the lifter tends to bleed down some at RPM.

 

SkinnyZ, based on your feedback above I did a midlift method measurement on another intake valve with the running spring in place. With my max lift, I need a difference between the two measurements to be around 0.285. With the adjustable pushrod at 7.275 I get 0.292, and with the pushrod at 7.300 I get 0.287.

So....I am now thinking should get 7.375 for both the intake and exhaust now?.!

Aahhhhh...life can be so confusing!

Thanks,
Pnorth

 

I'm not trying to add any confusion to this, but I err on the SHORTER side. This has to do with side loading of the valve guide.
Let's use easy, round numbers for the valve spring pressures - seat (100#) and valve open (300#).
At rest (seat) the rocker begins to push down on the valve stem and only has to fight against 100#.
But at full valve lift it has to overcome 300#.
If your geometry is not perfect, then it is better to be on the shorter side where the pressures are smaller.
This is supposed to translate into less valve guide wear.

The .040" difference between checking springs and the actual running valve springs seems a bit much to me.
I use a valve spring height micrometer when setting up my heads


and I tighten it as much as I can by hand to minimize that number.
When using checking springs, I pull up on the retainer as much as I can to seat the locks, just like the real valve spring would do.

 

Thanks for all of your help, just placed an order for the Comp Hi Tech 7.350 rods.

 

Thing is, you can't pull up with 300 lbs. like the real spring exerts when the engine is running. Or 365 over the nose in my case. That stuff gets compacted pretty tight and .040" is an observed result by guys that publish this stuff. So the slack is still there.
There's certainly a case to be made for the checking spring argument.
Not so sure I'm digging the err on the short side. The pressure is the same isn't it? It's the angularity you have to address. A short pushrod puts more sweep before midlift and is pushing in front the valve centerline. The opposite is true for a longer pushrod. The balance of the sweep is after midlift and your effort is past the centreline. My experiences say neither is good. Remember too that the lifter is going settle down at RPM. Air entrained in the oil is one thing that'll have an effect there.
Here's the deal though, except for the witness mark, which is only a follow up to make you feel better, checking springs aren't necessary. Use the running springs, check and double check both your measurements and you methodology and call it a day. The centered position on the valve tip can be observed. It doesn't need to be painted.
Ideally, we'd like to do this with an identical solid lifter but that's not often possible. Then it's measure and witness mark all in one.

 

Are your decimals in the right place? .285" in the difference? Two tenths?
Your pushrod lengths make sense though.

EDIT. Re-read your post. Your referring to the difference being the half lift amount right? I was thinking you meant a difference in length.
So, yeah, 7.375".
Is that an available length?

 

0.285 is half of my max lift (.570), the number I was aiming for using the midlift method on the intake valve with the running spring.

 

That's what I figured when I re-read your results.

 

Yes sir. One of the engine assembling tools in my toolbox.
What I need is an economy orientated spring checker. I've got a box or two of springs from past and current builds that need an examination.

 

Yup, they are available in 7.375.

https://www.summitracing.com/parts/cca-7795-16

 

https://www.texas-speed.com/p-8292-t...set-of-16.aspx

 

Thanks - will call Texas Speed on Monday to check availability on the 7.375's.

 

Remember that all pushrod manufacturers don't measure their pushrods the same way.
You may want to call TSP and ask if theirs compares to COMP's as you're using the COMP adjustable pushrod.
I'd suspect they're the same as it's ball ended on both with oiling holes.

 

It does. They (like virtually all aftermarket mfrs) spec the length as if the ends were a perfect sphere, Comp included. I would say "all" but all it would take to make me a liar, is ONE that does it some other way. I don't actually know of any one though, other than "stock replacement", that does it any other way, than the spherical end method.

 

Kinda...

 

Even though I feel that this process was made to be over-complicated for the OP...
I am happy to see that everything worked-out well; there is no harm in going about this process with a more finite technique.


Fortunately in this situation, the Camshaft is very conservative, and "Stock Geometry" Valve-Train can be used.

I would like to make a simple recommendation (not really needed for this Build, but good to do none the less)...
Always use the Thickest Diameter and Wall Push-Rod that will fit.

I never use 5/16" Push-Rods anymore... not even with a 0.110" - 0.120" Wall.
11/32" or 3/8" Push-Rods should ideally be used.
Also if using 11/32" or 3/8" Push-Rods... ideally always use 210* Degree Tips (more important for Non-Stock Geometry).

 

I'll have to disagree with you on that one.
Once there's the introduction of aftermarket heads (AFR 195), cam (COMP XFI) and lifters that didn't come as part of the engine package (LS7), then "stock geometry" goes out the window.
It's imperative that the geometry is investigated and corrected. It may well be that a stock length pushrod for the OEM roller application fits the bill but it's not a guarantee.
Heads with different decks, lifters with a seat height that changes from one brand to the next or even changes within a brand (as COMPs standard lifter compared to their short travel version), cams with smaller base circles, decking the block, different head gaskets, all combine to change what will be an optimum length.
I've kept track of my results in terms of valve guide longevity and I can say with certainty that 1/10th in the difference will have a noticeable effect.
How that affects performance is another matter and open to debate.

​​​​​​Here's hoping the OP has nailed it.

 

I did not specify clearly enough, so I apologize for that.

First, I agree with you that Cylinder-Block Deck-Height, Cylinder-Head Deck thickness, Cylinder-Head Valve length, and Spring Height, Model of Lifters (total height and Piston height for Hydraulic Lifters), different Camshafts (Base Circle Diameter), different Rocker Arms, and Ratios...
All contribute to variances in Push-Rod Length... as well as the "actual measured length" from different Brands and Models.
I agree with you on all of this.

Most of my (Stock Geometry) Gen-I SBC Builds all use the same Compression-Height, are Zero-Decked, use 1 of 3 different AFR Heads, a Billet Steel Comp Camshaft, the same Manton 3/8" Push-Rods, and the same Rocker Arms...
So I don't do much fussing with different combinations anymore... Unless getting into Non-Stock Geometry.

When I say Non-Stock Geometry... I am not referring to different Rocker Ratios, or aftermarket Parts.
So, again I agree with you.
What I meant by Non-Stock Geometry, is when the Valves are not in the stock locations (spread apart or moved over), when Lifters are used that offset the Push-Rod position over to one side (for Intake Ports that are wider than Stock castings can fit)...
Situations like this where offset Rocker Arms are used or Shaft-Rockers are required due to their location being moved.

The only thing that I did not agree with you on was the extent that 0.050" either way will affect the running of the engine when Adjustable Valve-Train is used.
Also with Roller-Top Rocker-Arms, the side-loading of the Valve-Guides is minimized... even with an un-ideal length Push-Rod.
Also long as a Poly-Lock is used, the Rocker Position will usually apply proper localized pressure on the Valve-Tip.
I do agree that a better length measurement will produce a better "Wipe-Pattern".

When the length of the Push-Rod is varied enough in this situation...
it will actually alter the effective ratio of the Rocker-Arm.

 

When I get the opportunity, I'll reconcile my build notes and give a representation on how the wrong pushrod can have an effect.
Keep in mind, I'm not talking about power output as I don't have the tools or the data to put that together. What I do have however is valve guide life based on the geometry being incorrect.
Of the top of my head, I'm going to say .100" off the mark killed the guides in well under 7000 miles.

Something to note is that there are very few racers (drag racers in particular) who even consider 7000 miles as a milestone. How about 700 miles or 2500+ passes! I'll say never for a drag racing engine.
For a street guy and wannabe racer, 7000 miles is about a tenth of what I'd hope to get before taking my heads back to the machine shop.
That's where the value lies for me.
Also noteworthy is that the cast iron Vortec guides were extremely durable when compared to a bronze alloy. I'm pretty sure my geometry was way out of whack when I first assembled that Vortec headed engine but the issues never showed. Change up to aftermarket and the softer material revealed itself for what it was. Softer.

 

To me, Valve Guides being worn out in only 7,000 Miles, is unacceptable.
I am very interested in what your configuration was.
Please Post all the details.
Were the Guides Knurled by any chance? ...were the Valve Seats checked? ...Nonroller-Tip Rockers?

The Valve Guides of stock Iron Heads, or newer stock Aluminum Heads with Powdered-Metal Guides...
definitely outlast the more gentile Valve Guide materials.

 

RHS ProTorker Vortecs.
Factory and race shop valve jobs. Bronze guides. New and replaced twice. Presently setup with new intake valves. Ported too not that it matters.
COMP beehives set up for 1.8" installed height.
Guide plates.
COMP short travel lifters replacing their pedestrian lifter versions.
COMP Pro Magnum 1.6 rockers.
Then Crower Enduro full roller rockers with a .050" backset trunnion to compensate for the .100" taller valve. Something overlooked first time through. And the second time too.

This latest setup I hope is a winner as I addressed every conceivable possible issue that might arise.
I've kept track of all the various stack ups with respect to components being replaced. Lifter seat height. Basic architecture between the two rocker arms. Heads milled. Two different blocks with different decks.
Careful measurements and verification resulted in about a .030" sweep right in the center of the valve tip. About as good as it gets I would say. Previous attempts didn't have the knowledge base behind the hands doing the work.
These were in service up until recently and haven't been disassembled for inspection. They've about 10+k miles so this teardown should be a good indicator of how good the geometry is. They're on my bench now but car crafting is on a temporary hold.

Thanks to PNorth for the loan of his thread. Maybe there's some tech goodness in it for all of us.
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Good information IS good information. Period.