Pushrods & preload - school me

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rapom65

rapom65

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I purchased a pushrod length checker due to recent head & rocker changes. Done a bunch of reading through old threads but I'm not finding consensus answers to my questions. Engine: 360, Eddie RPM package (heads/manifold/hyd cam) and Crane Gold adjustable rockers.

So, riddle me this Batman (you know your old if you understood that!!):
1. Adjuster threads. Recommendations ranged anywhere from 1 to 4 threads showing after preload is set. I have not been able to find on-line what Crane actually specifies, if they do. I stared at my valve train for quite a while yesterday trying to figure out what difference it makes. Why does there need to be any threads showing? My guess is geometry but I thought up many reasons; optimized oiling of the ball & cup, adjuster strength, pushrod cup to rocker/spring retainer to rocker interference, manufacturer's design spec, ect..... My old pushrods, from my iron heads. result in the threads just begining to emerge, or 0 to maybe 1/2 thread showing on all rockers. I could find no binding issues anywhere and plenty of clearance everywhere. Can some of you more knowledgeable gents enlighten me on what the significance of # of threads showing results in, and why, so I can justify to myself the expense of new pushrods?

2. Preload. My old pushrods, with 0-1/2 thread showing, is with 1/2 turn on the adjuster which supposedly = .030 preload. Again a wide range of recommendations, most between .020 to .060, with a few outside of that but no rational behind why. Some vague talk about rpm ranges, varying thermal expansion of the involved parts and valve train noise, but again, no details. Rpm range on my cam is 1500-6500 and I intend to use every bit of it on a fairly regular basis for autocross, road courses & street duty. I lean towards the performance end of the spectrum if that helps anyone in answering.

3. Is there a torque for the adjuster jamb nuts? Use of thread locker on adjuster/jamb nut?

4. What is the correct way to determine length for ordering a ball/cup pushrod? End of ball to top of cup or subtract 1/2 of adjuster ball diameter to get end of ball to bottom of cup? Or let the supplier figure it out?

5. Pros/cons of 5/16" pushrod vs bigger diameter for 6500 rpm range?

Thanks in advance guys and let's keep the "discussions" civil please.
 
Ok got some, not all, answers from Hughes Engines web site, thanks again MH. Short answer to adjuster threads showing is geometry.

From Hughes:
"The proper rocker arm geometry and pushrod length is critical to obtain the maximum performance out of your engine. The ratio of the rocker arm can be altered (reduced) if the geometry is incorrect. This will reduce the area under the curve and available breathing time thereby lowering the power output. The ratio of the rocker arm is affected by the position of the adjusting screw ball (or cup). The small block is the most sensitive to this adjustment, due to the angle of the pushrod."

Hughes recommends .320" adjusting screw protrusion as a starting point and using a dial indicator to adjust for max valve lift from there. So thread protrusion will get you in the ball park but to wring the most performance out of your combination you need to obtain max valve lift/optimal geometry.

Preload seems to boil down to onset of valve float at higher RPMs and how much valve train noise your willing to live with. From Hughes application chart:

RV/Cruiser/4 x 4 Turns 2 to 3 Preload .085”/.148” Quiet
Street use Turns 2 to 3 Preload .085”/.148” Quiet
Bracket racers/Oval track Turns 1/2 to 1 Preload .022”/.042” Some will click
Record attempts Turns 0 to loose Preload .000”/+.003” Tick all the time
(One turn = .042”)

So the info I got for 1/2 turn on the adjuster screw = .030 preload is off somewhat. Emphasis: don't believe every thing you read on in the www. The majority of preload recommendations were in the .030 to .040 area which puts you in the middle of the performance settings. Good to know.

Bottom line: Anyone have an opinion on how much performance is left on the table by just adjusting to X amount of threads showing on the adjuster, adding your desired preload to pushrod length and just buying a set of off the shelf pushrods as close as possible to the determined length????

That still leaves questions 3, 4 & 5.
 
All of the Hughes info is correct, however, if you adjust preload at zero to .002" lash, you must have lifters with the heavy duty flat style snap ring retainer, NOT the stupid little wire retainer made from round wire. If you run the round wire retainer type lifter, get ready for your lifters to bang the retainer out and come apart.

Lastly, FWIW, I like to run preload a bit light, probably in the .020" range. I am sure I'll get some arguement here, I always do, but you CAN taylor hydraulic lifter adjustment similar to a solid to have an effect on engine opreation. A lighter preload will allow a few more RPM and make the cam seem a touch "smaller" while a tighter preload has the opposite effect. That's about all I can offer.
 
q3. I imagine there is a torque spec. but I`ve never found any, besides I`ve never seen a Tq. wrench that has a hole in the center so you can hold the adjuster? I`d go by feel and get em tight, I used penetraiting locktight on mine, cause mine came loose twice.
Q4. You could use a ball bearing the same size and subtract or- I just used an adjuster and subtract the whole thing and let them know how you measured.
Q5. con. haveing to grind/mill the holes if interferance.
 
Thanks for the responses. After a career of maintaining helicopters and turbine engines I find these push-pull Rube Goldberg devices a bit confusing sometimes. The info available on the web is so divergent at times that I find most of it unusable. The manufactures don't seem to care, they just want Billy Bob to whip out the Visa and buy whatever the catalog says fits their application whether it's appropriate or not.
 
I understand your concern, but honestly on some of this I believe you're overthinkin it a little. I wouldn't worry about the torque on the adjuster nuts, for example. Just make sure they are tight.
 
My intent is to try the understand the why behind the differences in opinions so that I can make an informed decision on how I will set up the "set up" for my intended useage of the car. You get a lot of short and snappy responses to questions posted on boards like this but rarely will someone offer an explanation to their thinking. Perfect example: Rusty Rat's quote "I like to run preload a bit light, probably in the .020" range. I am sure I'll get some arguement here, I always do." Why do you like .020 vs .040 or even .060. What are you setting the engine up for, high rpm, low end power, street, race?

Just hate wasting time, effort and dollars to have to redo something that with some education I could have gotten right the first time.

Guess this all boils down to my previously asked question... given the 6500 rpm limit of my cam and intended use of the car (autocross, road course & street) anyone have an opinion on how much performance is left on the table by just adjusting to X amount of threads showing on the adjuster, adding your desired preload to pushrod length and just buying a set of off the shelf pushrods as close as possible to the determined length???? Or will it be insignificant?
 
I did answer it. Read the rest of the text you left out of the quote. I like running light preload because it will add a few more RPM. It's all there in my post.
 
LOL I thought you might come back on that. Probably should have made up something. My point was most guys stop right there.... set it at .020 with 2 threads showing. The next guy says BULL, set it at .040 with 4 threads showing. Unless a pissin contest starts the explaination of why you like those settings ends. Period. Just trying to suck some collective knowledge out of the brains of guys who have been building motors --- succsessfully--- over the years.

Where you at in Georgia? My wife is from down that way and I spent a lot of time at Ft. Rucker (SE corner Ala-BAM-a)
 
I have always shot for 1-2 threads below the rocker arm. One reason is it puts less side load on the adjuster on engines that have severe push rod to rocker angles. Just make sure if you have cup type PR's that they don't hit the rocker at max lift. On lifter preload ?
I have always ran the adjuster 1/2 to 3/4 past zero. Done it this way for 42 years. How does it effect performance? I really don't care, this has worked for me for 42 years, I guess I'll carry on until I can't do it no more.
 
Thanks SGB, that's the type stuff I'm looking for. I've kind of settled on 1-2 threads showing with 3/4 turn preload in my head unless someone makes a compelling argument for something else. Do you think it's worth the cost of a dial indicator set, custom pushrods and the time/effort to determine max valve lift for the Nth degree of performance or would the gain over your settings be minisule?
 
If you haven't noticed when I use "you" I'm thinkin southern, like in " you all". To much time spent down south. After rereading what I wrote about RustyRat's quote I can see his confusion. Must have been thinkin "can't this guy read?"
 
rapom65 said:
Thanks SGB, that's the type stuff I'm looking for. I've kind of settled on 1-2 threads showing with 3/4 turn preload in my head unless someone makes a compelling argument for something else. Do you think it's worth the cost of a dial indicator set, custom pushrods and the time/effort to determine max valve lift for the Nth degree of performance or would the gain over your settings be minisule?
Click to expand...

The time it takes to get the right length push rod with 1-2 threads showing @ 1/2-3/4 preload I think is a great idea. Other than that I wouldn't worry about what is to be gained at more or less of a preload.
 
SGBARRACUDA said:
The time it takes to get the right length push rod with 1-2 threads showing @ 1/2-3/4 preload if think is a great idea. Other than that I wouldn't worry about what is to be gained at more or less of a preload.
Click to expand...

X2 1-2 threads showing is a time tested rule of thumb for proper geometry. (and for strength) The 1/2-3/4 turn preload (up to a full turn) is a proper amount of lifter preload. Whoever made your lifters should have recommendations for proper preload. The lifter is like a hydraulic cylinder but too loose and it comes apart. Too tight and all sorts of ugly things can happen from holding valves open to flattening cam lobes. tmm
 
I understand your concern, but honestly on some of this I believe you're overthinkin it a little...
Click to expand...

Now being in aircraft maintenance for 17 years, I know exactly what he means...you're molded from day 1 to follow technical data and perform steps in the prescribed order with a basis in theory of operation and why the system works the way it does so you can troubleshoot any malady that may manifest down the road-regardless of what you thought you knew before. I still do some cowboy mx type ****, or I did when I was still actively crewing aircraft...now it's my job to direct the mx, and set priorities. In any case, after basically half my life, sometimes it's a little tough to simply accept a suggestion or recommendation without some type of black and white technical specification with some background information as to "why" it works the way it does and what pitfalls to avoid.
 
So, riddle me this Batman (you know your old if you understood that!!): No problem - Edward...lol.
You work on aircraft - there are HUGE (and critical) reaasons why you're trained to think as you do. Auto engines do not share the criticality of operation. So a lot is left up to individuals in terms of interpreting and worrying about the technical details - and for the most part the specs are wider and the enthusiasts you inteact with less concerned with detail. I have a couple aircraft techs I deal with and they are drastically more intense and detailed than most car people. Also - in case you haven't yet - you have to realize the web is not the home of most pros. Their shops are. IMO there is only one site where well known experts answer questions regularly. That's speedtalk.com. No offense to any here but that's my opinion and I include myself in the kiddie-pool of respondants here...lol. So all this is "in my opinion" and you can take it or leave it.
1. Adjuster threads.
My opinion - less is best. But you need to have some room for expansion and wiggle room. I measure for custom pushrods as the last part of any build and that lets me put the preload and adjuster exactly where I want it.
2. Preload.
There is no "one fits all" deal. That's because manufacturers are dealing with unknowns. Preload is designed to work with oil pressure and a certain amount of oil pressure bleeding off. If the lifter bores are worn, and/or if the lifter is at the "wider" side of it's manufacturers acceptable limits, or if the oil pressure delivery is on the lower side of the lifter's designed in expectation - you may have issues with noise. In terms of rpm potential - the more oil you have in the lifter, the less likely it is to compress before the ifter moves the valve.Which is what was noted - less preload is noisey but can be better for power production. One thing you'll note is the majority of posts here are for noise...
3. Is there a torque for the adjuster jamb nuts? Use of thread locker on adjuster/jamb nut?
No thread locker. I've always made sure they were tight. I've never used a spec but the manufacturer of the arms (or adjusters if they are different0 will have one.
4. What is the correct way to determine length for ordering a ball/cup pushrod? End of ball to top of cup or subtract 1/2 of adjuster ball diameter to get end of ball to bottom of cup? Or let the supplier figure it out?
Pushrod companies will either assume you're supplying the total length or assume you're not. The best thing to do is read up on the brand you're looking for and then supply the right length. It's up to the customer to get it right...

5. Pros/cons of 5/16" pushrod vs bigger diameter for 6500 rpm range?
I much prefer a smaller diameter pushrod - for weight and fit primarilly and I'd rather pay a little more for the top-of-the-line 5/16 than run cheaper 3/8. Either will work fine for yours.
 
TXSTANG84 nailed it on the head: "it's a little tough to simply accept a suggestion or recommendation without some type of black and white technical specification with some background information as to "why" it works the way it does and what pitfalls to avoid".

and

moper: "Auto engines do not share the criticality of operation. So a lot is left up to individuals in terms of interpreting and worrying about the technical details - and for the most part the specs are wider and the enthusiasts you inteact with less concerned with detail".

Bingo...


So we harken back to the thread title "pushrods and preload - (emphisis )SCHOOL ME. Yeah I realize most guys are well intentioned but there is too much hot air floating around the web. I was hoping some of the engine guys who's opinions I respect would chip in with some suggestions along with an explaination of why those settings work for them. Kind of searching for a concensus opinion on best set up for my application. Even though I have an extensive background in mechanics I was a bit fuzzy in this area. Lots of folks offered up suggestions and I appreciate the hell out of it. I now have the info I need and know what I'm going to do, thanks everyone.
 
The biggest inconsistency with asking for others input is that all their engines are likely all different deck height dimensions, different pushrod lengths, perhaps their heads have been shaved, and there's a halfway decent chance the owners of said engines don't all know the specs of their own powerplants.

They're using a formula that "should" work for the lion's share of LA engines with adjustable rockers within a rather wide variance of those aforementioned specs. Of course, the best way to do it when you can't get all the info requested the first time is to mock it up with a dial indicator, and blueprint it out yourself for your combination of parts...try different methods, see what you think will work best for you and your setup, and press on. Then, post up your findings with better, or more concise detail so that others may learn from your toil. :)
 
rapom65 said:
3. Is there a torque for the adjuster jamb nuts? Use of thread locker on adjuster/jamb nut?
Click to expand...

2 threads showing here at zero lash then with another 1/2 a turn and tighten down. I have used thread locker on the jam nuts before and would NOT recommend it. It caused major problems loosening them back up. Loosening the jam nut is not the problem its breaking the allen wrench adjuster from the jam nut. Nearly impossible with only a allen wrench for leverage. It took me a great amount of effort and stress to get them apart without rounding the allen wrench wholes in each adjuster. Stay away from the thread locker. Plus most are aluminum bodied rockers and I dont think thread locker is good to use on aluminum.
 
Good point on the thread locker 71swing, thanks. Reason for the Loctite question was one of my friends had a real problem with his 383 valve train years back. His lock nuts and adjusters kept coming loose and backing out. Bent multiple pushrods and we really struggled to resolve it. I think the manufacturer sent us several batches of adjusters and a couple new rockers to try and we finally found a set that stayed put. Just wondered if anyone had tried it and their results.
 
TXSTANG84 - That was why I asked if the performance gained from purchasing a dial indicator and setting everything off max valve lift was worth the effort and cost opposed to the standard 2 threads + preferred preload method. Probably only a professional mopar engine specialist would know for sure after they had tested for it on a dyno. I haven't messed with the internals of small blocks much so limited on first hand knowledge.
 
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