No, I put the heads back on the motor a couple days ago so I can't measure the valves.
This engine has never been run. I think these pushrods were from an entirely different engine, so I think the cause of their bending will remain a mystery.

Yep, I know that the piston has been compressed, but I figured even with it compressed it would be useful to see what it looks like with the lifter on the lobe of the cam.

Measuring with a digital caliper, the plunger depresses approximately 1/8" at max lift. The cam's gross valve lift with 1.5 ratio rockers is .510", which translates to .510/1.5 = .34" cam lift, so that puts the actual pushrod lift at .34" (cam lift) - .125" (plunger movement in the opposite direction) = .215", or about two thirds of what it should be. Even with it at .215" lift, the line from the midpoint of the trunnion and the midpoint of the roller tip is nearly perpendicular to the valve stem tip, meaning that more lift will move the roller slightly further across the valve stem, but then back towards the pushrod side.

Long story short, the second picture shows the roller tip nearly as far across the valve stem tip as it will travel.

Unfortunately, this being only my second engine and the first still being in the car, I don't have any spare lifters lying around. On top of the adjustable pushrod, a lifter would cost $30 from Summit--nearly the cost of a whole set of pushrods.
I also would prefer not to find a valve spring compressor and remove a valve spring. Every time I do something like that I invariably end up with some sort of problem that takes time and money to correct.

I measured and the roller tip contacts the valve stem approximately .073" from the inside edge when the cam is on the base circle. The stem is .325" wide, which places the tip just under 1/4 (actually 2/9) of the way from the edge.

It sounds like any less than 1/3 of the way from the edge is too close? Would it work, or would I have serious problems? From what I can tell, the major detriment of an incorrect pushrod length is faster valve stem retainer wear?

On a positive note, I inspected the clearances on the rockers and everything checked out fine.

I'll keep researching this and give an update if I decide on something.
Thanks for helping me work this out guys. Can't wait to get the new engine in!

Edit: Found this very knowledgeable article which gives a method to determine pushrod length that I could do without any tools I don't already have. I estimated I'll need a pushrod about 1/8" longer to achieve proper installed geometry as explained by the article, which coincidentally happens to be about the amount I estimated the pushrod would have to be longer in order for the contact patch to be in the center of the valve stem.

 

I really think your the expert now C4. U keep eating this up like an engineering student before finals.

Hope u hang around long enough to help others here. Too much bad info on net and we can read u are resolving common issues as u go. Believe me more than alot of owners have learned the hard way with broken parts and engines what u are learning on your first try.


Getting closer and almost there Smokey Junior.

 

Believe it or not, I plan to go into engineering.

I calculated the vertical distance between the trunnion's centerpoint and the roller tip's centerpoint, using the valve guide as the horizontal axis, as described in the Crankshaft Coalition article, and got a measurement .181" less than suggested. So I need a pushrod .181" plus my preload distance (this method is measured with the poly lock off of the stud, meaning there is no preload when you measure) longer than I already have. With a threadcount of 24 threads/inch, one-half turn comes out to 1/12", or .083", for a total of .264". My current pushrods are 7.192", so I need pushrods 7.456" long.

I'm a little concerned the roller tip will be close to the inboard edge of the valve stem tip at max lift, so I may end up getting an adjustable pushrod to check that out if I can't find another way.

Edit: The only pushrods I can find on Summit that are close to 7.456" are chromoly and run about $100 for a set. As much as I'd like chromoly, I'm on a budget. Does anyone happen to know budget pushrods that length or a bit shorter? When I first looked for pushrods, I saw some sets from reputable brands for around $40.
Also, will any 5/16" pushrod work? I see Comp sorts their pushrods based on vehicle make, but I'm not sure if that's because each has a unique design or just because certain lengths are stock for certain engines.

Edit 2: Found these Summit G6400-LS pushrods for $30. These look like they should work? Also, do you think it will matter much that these are 55 thousandths shorter than the optimum length I calculated?

 

7.456" is huge. Dude, i think u need to re-evaluate this. Try melling p-rods for best prices. I found MPR-324 = 7.500", 5/16", MPR-363 = 7.260", 5/16" and stock size #373H = 7.195", 5/16".
U can look at the melling chart yourself as it made me cross eyed: http://www.melling.com/Portals/5/pdf...tion-chart.pdf

U still need to find a vendor but Melling should be in your price range - i know nothing cheaper. U can find them online for $35.

Kinda funny but Pioneer uses the same part numbers (w/o the M in front) for the same size p-rod. So u can price those out too - PR-324, PR-363, PR-373. And heres theyre catalog for more fun: http://www.pioneerautoinc.com/wp-con...06/EP-2011.pdf

Good luck and let us know what u find.

 

Hmm, thanks. Is there anything intrinsically wrong with using long pushrods, or does that just seem too long? Miller's mid-lift geometry seems to be fairly highly-recommended, plus the geometry it would have with a 7.45" pushrod looks to be pretty good. A 7.45" (actually 7.40" since that's how long the rods I found were) rod would roughly center the roller's path on the stem tip and wouldn't get too close to either edge. It would also open the valves a bit faster, since the rocker arm is approximately perpendicular to the valve stem with the valves closed. Due to the physics of it, the vertical component of motion is greatest and the horizontal least when the rocker and valve stem are perpendicular, whether that occurs at the beginning of the stroke or at the end.

Aside from the method I used, I'm not sure how I'd figure out optimum pushrod length. To me it seems I have three options. I could buy an adjustable pushrod and a lifter to find the right length by trial and error, I could just guess at a length a little longer than the pushrods I have, or I could go with the number I calculated with Miller's method. Unless longer pushrods come with inherent drawbacks, or I find another problem with longer rods that I had overlooked, I'm leaning toward the third.

However, I realize I'm still learning and you're the one with experience doing this, so what do you think?

 

Your figures are impressive however the "KISS" axiom applies.

Hydraulic lifters: engine running, Rockers are backed off until there is noise from the rocker to valve stem = lifter piston cup is all of the way up inside the lifter. valves are adjusted 1 full turn down (1/4 turn at a time waiting for the lifter to bleed) after rocker to valve stem noise is eliminated.

3/8x24 thread pitch on the rocker stud = the lifter piston cup is .0416 down inside the lifter.

7/16x20 thread pitch stud = .050 in the lifter.

You need soft valve springs + an adjustable push rod to actually check required p/rod length.

Since the heads are on suggest a stock 7.2 length pushrod, cam on base circle, adjust free play out but do not compress the lifter cup.
After the above post a pic of rocker tip/valve stem you may be good to go with stock length push rods.

 

I have many oem roller lifters and several length pushrods (in usable condition.) I you want, you can PM me with your mailing address and I will send you some of each. Up to 16 each.

 

go to a U-Pull It Yard, you'll find one for next to nothing...or any auto repair / machine shop...most places will just give you one...they're not rare and used lifter's don't hold their value well either!

p.s. they don't have to out of a corvette, any GM roller lifter from any v8 or v6 engine should work

 

Perhaps I am overcomplicating this, but I'm doing this to learn so I'd like to figure out what's best.

Can't you simply find zero lash and then add an extra 1/2 - 1 1/2 turns without needing to have the engine running?

Here's that picture. I posted one earlier with half a turn of preload. This pushrod is actually 7.192".



You see, even without lifter preload factored in the roller tip contacts the valve stem less than a third of the way from its inner edge. If this wasn't the case I probably wouldn't have given 7.2" rods a second thought. However, if I'm going to change something I like to research it and find the best way to do it.

That's good to know, thanks. I found a machine shop that may be able to lend me a solid lifter and adjustable pushrod (waiting for him to call back after talking to the machinist) and I'll call around to other shops and some Pick-N-Pulls in case that doesn't work out.

Wow, thanks for the generous offer! I'll try to get a lifter locally to avoid shipping, but if you happen to have a set of pushrods the length I decide to get I might take you up on that (assuming I'm not misreading your offer).





Miller's mid-lift valve geometry dictates that the rocker should be at its point of inflection at half-lift. That is, when the cam is at half-lift the roller tip should stop moving outward on the valve stem tip and begin moving inward. If it is set like this, the maximum amount of the cam's lift will translate to vertical valve movement and the minimum amount will translate to movement of the roller tip across the valve. This is how I was planning to set my pushrod length.

On either side of this ideal setting, you could have the rocker's stroke either beginning or ending at the point of inflection, at which the travel of the roller tip would change direction on the valve stem. Both of these settings will have an equal amount of vertical valve travel as they are equidistant from the "ideal" setting.

My cam will result in approximately .545" of valve lift if the pushrods are the length that result in Miller's ideal mid-lift geometry. Doing the trig, I was able to calculate the amount of valve lift that would result with either of my two hypothetical scenarios, which involved the rocker's stroke beginning or ending at the point of inflection. I calculated these would result in .535" of valve lift--about a 2% difference.

While this 2% is essentially free valve lift that would result from optimum geometry, it really won't help me much at all. Looking at the flow specs for my heads, I can estimate a .01" lift difference would give me about .4 CFM more flow at most.

This being the case, I think my best option is to choose a pushrod length that gives me good roller tip position on the valve stem to minimize wear and promote reliability. Because valve acceleration is greatest when the rocker is near the point of inflection, I think it would be best to have the rocker near the point of inflection at the beginning of the stroke--valve lift has diminishing marginal returns.

I estimate 7.3" - 7.35" will be best, but I will have to check it out with an adjustable pushrod to find out for sure.

For anyone interested, here's the (admittedly messy) math:



F is the center of the trunnion (pivot point) of the rocker, and B is the point of inflection. With ideal geometry, the rocker would sweep from A to C, and with a longer pushrod it would sweep from B to D.

I'm doing this project to learn, so if anyone sees somewhere I'm wrong I really appreciate you pointing it out.
Thanks guys!

 

You are not overcomplicating anything, contiue as you are.
The pushrods will fit in a flate box, so shiping is nothing.
I have been building street performance SBC engines since 1966. The method of adjusting hydraulic lifters varies and the method puplished in manuals always caused backfire and flames, not good.
What I do: run oil pump until oil comes out most all pushrods, rotate pushrod between thumb and finger and slowly tighten stud nut. When I determine drag on rotation, tighten nut 90*, or quarter turn more. I rotate crank and do the cylinders in firing order. Having the lifter piston near the top of its travel range is good. I mount starter and do a compresson check with the engine on the stand. There are many short cuts, but building an engine is no place for shortcuts.
I adusted the lifters on my 66 L-79 with clearence, like solid lifters running, and would peg a 8000 rpm tach.

Looks like you need longer pushrods to locate the rocker arm farther from the spring retainer as well as alignment correction.

 

Great, thanks! I'll let you know when I decide what length I need.

What is the purpose for priming the lifters with oil like that? Does that extend the plunger in the lifter further than the spring holds it? (This is a learning project, so I like to know the reasons for doing things)

Also, I've read different values recommended for preload, ranging from 1/4 turn to 1 1/2 turns. From what I can tell, more preload increases reliability but hurts performance. Could you explain this to me?

 

I already answered this. All u need is 1 of those p-rod length checkers i linked and a straight original p-rod. U only need to get the roller lifter on base circle - no pre-load adjustment.

Like i mentioned to u close is good enough for a street cam. If u want to make rocket science out of it good luck finding $35 p-rods in 0.001" increments.

BTW i use 1 full turn for pre-load but i never rev into vlv float with my short cams. If u gonna rev high and maybe hit vlv float then <1/2 turn is the better (more like 1/4 turn).

 

I know that checker would have worked (and thanks for suggesting it), but I was interested in figuring out how rocker geometry works.

After some more math and some more calculations, I've decided a 7.290" rod will be my best bet.
http://www.summitracing.com/parts/lu...2-16/overview/
Even if they won't give me perfect geometry, they're the closest I can get without spending a lot and I know they will work. I'll probably order them tomorrow.

Once I get the pushrods I can put the rockers on, and then I just have to install the intake base to get the new motor back together. Although I may hold off on reinstalling the base so I can gasket match it.

 

Good choice and good price. Lunati uses the term "heat treated" rather than "hardened". But Lunati says ok with guide plates so it looks like a good value and what your shopping for.

U should take one of your lifters and p-rods and try and push down that lifter cup. That will give u an idea of what spring press inside the lifter resisting the p-rod is like. So when u go to set preload u will know for yourself what to expect and not someones elses BS about pumped up or bleed down. And a report on what u find would be nice for the rest of us. All i ever could do was put a dent in the block of wood i used to push the p-rod with. And ive taken lifters apart before then tried to compress the spring to install the cup and its retaining clip - dont go there if u plan to ever use the lifter again (it must take special tools).

BTW im sure u know u can port the intake any day of the week and u may want to research it more first - i would never port or gasket match the intake on a street motor.

I hope i dont annoy u with all these words of wisdom. When u get ready to start it i will likely blaberate some more. I have to control my caffeine intake also.

 

I tried that when I was trying to figure out how far the plunger would compress. Nope, that sucker is strong. The fact that I can tighten the poly lock by hand to compress it gives a good indication of the multiplication of force you get with a screw.

Yeah, I'm undecided right now. I've been researching it a bit but am seeing lots of conflicting information.

Absolutely not! I couldn't have gotten this far without the words of wisdom from everyone on the forum and I appreciate all the advice that I can get.

 

Hey i never noticed the poly lock could adj preload by hand force only (multiplied in the thread/screw) - then i rarely use polylocks, mostly stock type lock nuts. But i have to mention if your setting preload u shouldnt be watching the polylock. U need to observe the p-rod as that has what to key on. Once the u turn the polylock enought to stop the p-rod movement up and down u are close. But u need turn the polylock until the p-rod just begins to drag as u turn it around with your fingers (either way). Watching the polylock will not give u good indication. Once u get to zero lash then u set the preload with however much turn u choose to use.

What u need to watch in ploylocks is getting them to "lock" w/o slipping later. They seem to need an extra snug/bump on the nut (after preload is set) to lock up.

 

Got it, thanks.

My pushrods just arrived (gotta love Summit's 2-day shipping) so I'm looking at installing the pushrods either tonight or tomorrow night.

I'll follow Comp Cams' installation instructions except I'll use STP instead of assembly lube (I've read STP works just as well and I already have STP).

Should I loctite the poly locks?

Edit:
I put the rockers on (no loctite, as that seemed to be the consensus online unless someone had problems with the poly locks coming loose) but as usual encountered a problem. I noticed that the roller tips were not centered on the valve stem. I loosened the rocker studs and shifted the guide plate as far as I could (not very far), but some of them are still off. Just due to the clearance between the pushrods and guide plates, I found that the rocker can wiggle back and forth a bit. I'm not sure if it will eventually settle in some place between the two once the motor is running, so here are pictures of the most misaligned rocker shifted to each end of the extreme.





Notice the roller tip doesn't contact the full width of the valve stem tip in the second picture. Is this a problem, and if so, what are my options?

After some further research, it appears I have old style AFR guide plates. The new ones are 2 pieces to allow for adjustment. Although they'd allow for better alignment, I'd rather not have to spend money where I don't have to.

 

Yea, i can see from the pix the polylock nut is too high: http://www.dragracermag.com/wp-conte...3960797317.jpg

I think you have the trunnions inside the rocker arm upside down. Giv'm a flip and see how that works.

Sorry if i sound sarcastic but dont be surprised if your still not centered on the vlv tip. Calculations just cant replace direct measurements so take it easy and learn to laugh when building an engine.

 

Dunno, it's set to zero lash (which is pretty simple - I couldn't be off by more than 10 degrees in a worst-case scenario) plus half a turn of preload.

I had the trunnion on upside down when I was first doing measurements to calculate pushrod length, but I caught it and definitely have them the right way now. There's a flat spot on the top of the trunnion for the poly lock to push against.

What are your thoughts on the left-right alignment of the roller tip and the valve stem tip?

 

Well that much side loading aint good either. That first pic showed a #1 intake vlv with the rocker nearly off the end of the vlv tip. Yea u dont want to run it like that. If u cant correct the guide plates with bendology and filing u may need the adj plates - sorry. But dont run it until u get the roller centered on the vlv tip - it looks like u still have a problem with p-rod length or at least vlv train geometry.

Geeze, those poly nuts stick out so high they look funny but i googled pix of others like that so only u know if correct.