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  #31 (permalink)  
Old 01-29-2012, 04:12 AM
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Quote:
Originally Posted by lash540
I will tell you a situation we had just a little while ago, we kept lengthening a pushrod on a big block chev until we got maximum lift, about .013 thou over the pushrod with the "right" geometry. I had been reading a lot of talk on this forum and we were going on the dyno with it so I decided to take a set of long pushrods in with us. They were pretty long but nothing was binding up. To make a long story short the longer pushrods made a few more horsepower, not a lot but it was there. We then put 1.8 rockers on the exhaust with the same pushrods and gained 10 horsepower. If it matters the engine was a 760 horse 454. Now do I tell the customer we have to put the shorter pushrods in and make less power to make the geometry "right". I know this engine won't have problems because I have seen it done for many years. All theories need to be tested ,not just drawn on paper or swipe patterns but on the dyno or race track and they need to be tested back to back. All Jim Millers website has is theories, sarcasm and negativity to other companies. This gets too complex for the majority of people whether you like it or not, and these are a big portion of the customer base. I have viewed both sides of the story and believe this whole thing has been blown out of proportion for a stud mounted rocker and that's probably why it hasn't really caught on and why he doesn't make them anymore. Grant 4060, did you test his rockers against the comp rockers on the dyno? and if not how can you know for sure that they worked for you? All I am saying is too much classroom and not enough real testing.
LASH540, read my previous reply for "theories," and as for your allegation of sarcasm and negativity to other companies, there's only one or two where that is implied, and again "read previous reply" on this matter.

I tell it like it is. If you spend any time really checking what is going on with your rocker geometry, then you won't be chasing your tail with measuring horsepower by juggling pushrod lengths. Your logic about what you tell the customer if you lose power for shorter pushrods is typical with most engine builders who fail to understand the difference between "symptoms" and "causes."

If you use a shorter PUSH-ROD to remove wasted motion in the valve train, then LOSE horsepower, then guess what? You've got the wrong cam! The symptom is lost horsepower, but the CAUSE is not enough cam for the efficiency you've just gained. Anyone can increase valve acceleration by OVER-ARCING the rocker arm. That's a no-brainer. But the consequences for doing it to the pushrods, the harmonics, the drag coefficient, the spring life, and on and on, is a pretty high price to add a second camshaft to your engine.

What? "Seocond camshaft?" Yeah. Second camshaft. When you use your rocker arm for forcing a bias into the acceleration ramps (at the valve) by shifting the arc from low lift to high, or high lift to low, then you're adding a second CAM dynamic to the valve. That is what you're seeing the results of.

So tell the customer the truth. Tell him he's got the wrong cam, and use the data you have with WRONG geometry to figure out where the acceleration needs to be, then regrind a cam to provide that with MID-LIFT geometry, and make an extra 20 horse (or more) from the 20 horse you lost to drag coefficients.

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  #32 (permalink)  
Old 01-29-2012, 04:28 AM
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Quote:
Originally Posted by Grant4060
Jim, much appreciate this information! However, I'm working with an NHRA stock eliminator engine with the 502 BB stamped steel rocker arms and a Comp Cam custom ground with likely a non stock base circle diameter. The valves also may not be exactly at stock stem length. I'd like to optimize the valve train geometry, but unlike your explanations have no axle shaft centers to measure. Could you explain how I could proceed with readily available tools such as dial indicator, checking pushrod, etc to check and correct my geometry? Can I use the rocker arm stud as a reference point and a protractor to either the pushrod tip and/or the valve tip? Perhaps at the mid-lift point? I have already tested two pushrods .100 different in length and noticed the longer one produced more lift at the valve but also a wider swipe pattern that moved inboard a bit compared to the shorter pushrod. The reason I initially tried the longer pushrod was to get closer to my allowed lift of .398". With a .240" lobe lift and theoretically 1.7 rocker arm ratio the calculated lift would be .408", but using race springs at 210/400 lbs pressure I was only achieving .382" valve lift after deflection losses. After reading these posts, I'm thinking that I might be better off sacrificing maximum lift and trying to get the narrowest swipe pattern on the valve stem tip by testing different lengths using the adjustable pushrod? You've mentioned that could get it close, but how do I get it optimum? What do I need to do to get the best power and performance, given that I can likely only change the pushrod length, or after establishing that length possibly having another cam custom ground with more lobe lift to reach the spec. maximum. Would very much appreciate your advice, thanks!
grant4060
Grant4060: As you might tell, I don't play the Blog game very often, so sorry for the delay. In response to your question, you need to keep in mind what you probably already know, and that is the radial dynamics of a "shoe" tip rocker is much different than a "roller" tip rocker, so the 1/3 rule from which the shoe tip principles was born have a little less negative consequence than using them with roller tip rockers.

If I was you, I would make a little fixture that allowed me to set a ball fulcrum with a stud and adjuster in place (to measure from) that allows you to see the axis of rotation on the outside of the stamped steel body. The GM fulcrums (and Elgin, and Crane, and Pioneer, and Ford) all have odd-ball radius dimensions. AND, the top of the ball fulcrum is NOT the axis of its center. I make this point, because the PVS "OE" series I designed a million years ago DID have a uniform radius (.500") and DID have the top of the ball fulcrum as the AXIS point. SO making fixtures to measure from was easy. But as anyone who's had those rockers knows, I made the top of the rocker arm a specific angle that already had the engine's DESIGN geometry calculated, so all you had to do was to make the top of the rocker arm rails (flats) 90 degrees with the STUD at perfect MID-LIFT (half lift).

You do not have those options with the OEM rocker (or any other brand). But you can get very close to what would be correct if you simulate the OEM rocker's arc in a fixture (vice with a junk stud clamped in it, and a dial indicator), and if you have sharp eyes you will see within .010" where the center of motion on the side of the rocker arm that is NOT moving is, and that's your axis.

Now use that for the INSTALLED geometry in the CLOSED position, by setting it HALF of your net valve lift below the valve tip. THIS IS DIFFERENT than the 1/3 rule. Your rocker will be lower this way, than with the 1/3 setup. But you will have the least amount of back and forth motion. Check the Pushrod in-and-out motion after you do this. The factory rocker won't give you only .015" pushrod motion, so be prepared for twice that. But this is the lesser of evils, in my humble opinion. :-) It's the way I would set up a factory stock rocker. And the best thing about this, is that you have a method to always return to when comparing one cam grind over the other.

Don't do like some readers here, and expect that juggling your rocker height around based on what horsepower you get is the best way to set geometry. It's not. Use valve lash to determine cam phasing, and duration requirements, which there is a separate procedure for in doing this. Also, understand that CAMs are SOLD (especially by some brands) without ANY rocker geometry data to validate what works good from one customer to another. They are truly throwing darts. So don't be surprised if you end up needing something entirely different than what the cam company told you. In spite of what some readers may think.
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  #33 (permalink)  
Old 01-30-2012, 07:13 PM
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Quote:
Originally Posted by millerrockers
Grant4060: As you might tell, I don't play the Blog game very often, so sorry for the delay. In response to your question, you need to keep in mind what you probably already know, and that is the radial dynamics of a "shoe" tip rocker is much different than a "roller" tip rocker, so the 1/3 rule from which the shoe tip principles was born have a little less negative consequence than using them with roller tip rockers.

If I was you, I would make a little fixture that allowed me to set a ball fulcrum with a stud and adjuster in place (to measure from) that allows you to see the axis of rotation on the outside of the stamped steel body. The GM fulcrums (and Elgin, and Crane, and Pioneer, and Ford) all have odd-ball radius dimensions. AND, the top of the ball fulcrum is NOT the axis of its center. I make this point, because the PVS "OE" series I designed a million years ago DID have a uniform radius (.500") and DID have the top of the ball fulcrum as the AXIS point. SO making fixtures to measure from was easy. But as anyone who's had those rockers knows, I made the top of the rocker arm a specific angle that already had the engine's DESIGN geometry calculated, so all you had to do was to make the top of the rocker arm rails (flats) 90 degrees with the STUD at perfect MID-LIFT (half lift).

You do not have those options with the OEM rocker (or any other brand). But you can get very close to what would be correct if you simulate the OEM rocker's arc in a fixture (vice with a junk stud clamped in it, and a dial indicator), and if you have sharp eyes you will see within .010" where the center of motion on the side of the rocker arm that is NOT moving is, and that's your axis.

Now use that for the INSTALLED geometry in the CLOSED position, by setting it HALF of your net valve lift below the valve tip. THIS IS DIFFERENT than the 1/3 rule. Your rocker will be lower this way, than with the 1/3 setup. But you will have the least amount of back and forth motion. Check the Pushrod in-and-out motion after you do this. The factory rocker won't give you only .015" pushrod motion, so be prepared for twice that. But this is the lesser of evils, in my humble opinion. :-) It's the way I would set up a factory stock rocker. And the best thing about this, is that you have a method to always return to when comparing one cam grind over the other.

Don't do like some readers here, and expect that juggling your rocker height around based on what horsepower you get is the best way to set geometry. It's not. Use valve lash to determine cam phasing, and duration requirements, which there is a separate procedure for in doing this. Also, understand that CAMs are SOLD (especially by some brands) without ANY rocker geometry data to validate what works good from one customer to another. They are truly throwing darts. So don't be surprised if you end up needing something entirely different than what the cam company told you. In spite of what some readers may think.
So Mr. Miller what is the future? It looks like you've retired from the rocker business? You taking up beach combing with Jimmy Buffet or are Miller rockers out there in the future?

Bogie
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  #34 (permalink)  
Old 01-30-2012, 08:07 PM
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Jim Miller Rocker Arms

Quote:
Originally Posted by oldbogie
So Mr. Miller what is the future? It looks like you've retired from the rocker business? You taking up beach combing with Jimmy Buffet or are Miller rockers out there in the future?

Bogie
Bogie...

Candidly, a number of things several years ago took the fun out of it, and I chose to downsize considerably from what had been built. I am constantly teased with resurrecting several product groups, again (which means keep inventory on the shelf that I really don't want to do), and I've always been dogged for putting the BB Chevy shaft systems on the market; not to mention all the LS series stuff.

I have always been involved in two other totally different worlds outside of automotive, although neither is joining Buffet down in the Keys (although I used to get down there quite a bit). Lately, I have been reconsidering the headaches of "production" and if I could decide on the optimum product group to develop a new production around, I might resurrect this on short order. Whether that would be BB Chevy, LS, something in the Ford lineup, or Chrysler, or whatever.

Having had a long background in Cylinder Head develop, long ago, I still see many of the same fallacies being sold on how to choose a good set of cylinders, which take NONE of the critical Valve Train parts into consideration when they're developed, so engine builders are left to fend for themselves and this is where they get into trouble picking and choosing parts. Too many cylinder heads, from top companies, make changes in their designs over the years -- as part of marketing more than anything -- and give no consideration to the other consequences that often effect the valve train.

This is a story unto itself, but the point is, I have considered selecting several of the top name brand cylinder head manufacturers, for the top sales number applications (has to be a profitable decision), and building a "kit" around them which includes my own cam profile and of course the rocker system. The only thing the engine builder would have to provide is the short-block; then buy the pushrods (hopefully from us) after he bolts the top end to his short block and determined exact Push-rod length.

I've been kicking this around for several years, wondering if anyone else would do it, and it hasn't got done; so don't hold your breath. There are any number of good heads out there, whether it is AFR, Brodix, Dart, Edelbrock, or a half dozen others (but no Chinese junk!); so it is just a pragmatic decision I would have to make based on choosing a package in one of the more popular classes where demand would justify the investment.

For all the arguments that MID-LIFT can generate, and all the benefits of setting most rocker systems up this way, the bottom line is that to really optimize it, you have to have a dedicated cam designed around it, because in most full race applications, going to MID-LIFT over one of the other two or three brand of rocker systems, means you now have to REDUCE your cam stats, since more is going through the rocker, unless you were way under-cammed in the first place.

All the cam data used to sell existing choices when you call a cam company up, is tainted by inaccurate testing and records from inaccurate rocker geometry where NO STANDARD was used between one test and another.

99% of everything out there is generated, applied, tested and sold with any number of variables in the rocker geometry, from incorrect DESIGN geometry, to incorrect INSTALLED geometry. So whether the cam was good or not is meaningless if you can't validate the test to have been constrained solely to the cam profile (not influenced by a compound rocker dynamic), AND... quantified how much that influence was at ALL THREE CAM dynamics: Velocity, Duration, and Lift. Meaning, you have to have a specific understanding of what EACH of these achieved or lost, graph it, compare to the cylinder head flow efficiency, and use that data for comparison to the next test. To make all this dead on, you HAVE TO STANDARDIZE the rocker geometry to PERFECTION.

The "1%" difference from the 99% I mentioned above, is NASCAR. They've been doing what I just mentioned for the last 10 years. There's also a short list of good PRO STOCK guys who've been dialing in on this for a long time too. But very, very few people talk about it -- once they know.
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  #35 (permalink)  
Old 02-02-2012, 02:51 AM
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Originally Posted by millerrockers
LASH540, read my previous reply for "theories," and as for your allegation of sarcasm and negativity to other companies, there's only one or two where that is implied, and again "read previous reply" on this matter.

I tell it like it is. If you spend any time really checking what is going on with your rocker geometry, then you won't be chasing your tail with measuring horsepower by juggling pushrod lengths. Your logic about what you tell the customer if you lose power for shorter pushrods is typical with most engine builders who fail to understand the difference between "symptoms" and "causes."

If you use a shorter PUSH-ROD to remove wasted motion in the valve train, then LOSE horsepower, then guess what? You've got the wrong cam! The symptom is lost horsepower, but the CAUSE is not enough cam for the efficiency you've just gained. Anyone can increase valve acceleration by OVER-ARCING the rocker arm. That's a no-brainer. But the consequences for doing it to the pushrods, the harmonics, the drag coefficient, the spring life, and on and on, is a pretty high price to add a second camshaft to your engine.

What? "Seocond camshaft?" Yeah. Second camshaft. When you use your rocker arm for forcing a bias into the acceleration ramps (at the valve) by shifting the arc from low lift to high, or high lift to low, then you're adding a second CAM dynamic to the valve. That is what you're seeing the results of.

So tell the customer the truth. Tell him he's got the wrong cam, and use the data you have with WRONG geometry to figure out where the acceleration needs to be, then regrind a cam to provide that with MID-LIFT geometry, and make an extra 20 horse (or more) from the 20 horse you lost to drag coefficients.
Wow, I didn't think I would be able to draw you into this, but I guess your arogance got the better of you. clearly my "logic" was to simple for you to understand. I was simply voicing my opinion, which I am told I am aloud to have, about how the "majority" of people do things and don't have catastrophic failures or even the slightest problems. I never said your theories don't work,I just questioned the importace to the average joe. Believe it or not most people have bracket cars and street cars, not nascar or prostock cars. They will most likely never notice the horsepower loss or wear prevention. .165 thou of pushrod movement? isn't that a bit extreme? You seem to think everything is black and white and in the real world it's not that simple. "Just tell the customer the truth?" your such a hero. You've got what's wrong with engine builders all figured out, give me a break. I feel sorry for people that have to listen to your "retoric" day in and out.
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Old 02-02-2012, 03:11 AM
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Originally Posted by lash540
Wow, I didn't think I would be able to draw you into this, but I guess your arogance got the better of you. clearly my "logic" was to simple for you to understand. I was simply voicing my opinion, which I am told I am aloud to have, about how the "majority" of people do things and don't have catastrophic failures or even the slightest problems. I never said your theories don't work,I just questioned the importace to the average joe. Believe it or not most people have bracket cars and street cars, not nascar or prostock cars. They will most likely never notice the horsepower loss or wear prevention. .165 thou of pushrod movement? isn't that a bit extreme? You seem to think everything is black and white and in the real world it's not that simple. "Just tell the customer the truth?" your such a hero. You've got what's wrong with engine builders all figured out, give me a break. I feel sorry for people that have to listen to your "retoric" day in and out.
Yeah, that must be it. Arrogance. I've always wondered my problem was. I appreciate you pointing this out for me. I will try real hard to fix this, maybe forget that a wrong length set of pushrods costs the same as the right length. Maybe forget that I'll never know about a cam I spent 30 minutes on the phone listening to some cam company guru explain how great it was, when I just lost 4 degrees at the valve because I was too lazy to measure (or know how to measure) for the right length pushrods.

We aren't talking about "the real world." We're talking about precision geometry. Precision measurements, for which is the reason God created micrometers for. No one is forcing you to do anything. You just keep throwing whatever you like together any ol' way you want, get your magic marker out and die your valve stem tip, until it "eyeballs" the way you like, and remember how sharp you are because you'll never see the 14 degrees of your camshaft you left somewhere in the overarcing pushrods. Nobody cares. I certainly don't.

By the way, retoric is spelled "rhetoric." At least get that right, you've missed everything else. (But nobody cares.)
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  #37 (permalink)  
Old 02-02-2012, 10:14 AM
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Originally Posted by millerrockers
Yeah, that must be it. Arrogance. I've always wondered my problem was. I appreciate you pointing this out for me. I will try real hard to fix this, maybe forget that a wrong length set of pushrods costs the same as the right length. Maybe forget that I'll never know about a cam I spent 30 minutes on the phone listening to some cam company guru explain how great it was, when I just lost 4 degrees at the valve because I was too lazy to measure (or know how to measure) for the right length pushrods.

We aren't talking about "the real world." We're talking about precision geometry. Precision measurements, for which is the reason God created micrometers for. No one is forcing you to do anything. You just keep throwing whatever you like together any ol' way you want, get your magic marker out and die your valve stem tip, until it "eyeballs" the way you like, and remember how sharp you are because you'll never see the 14 degrees of your camshaft you left somewhere in the overarcing pushrods. Nobody cares. I certainly don't.

By the way, retoric is spelled "rhetoric." At least get that right, you've missed everything else. (But nobody cares.)
First of all,one person apparantly cares, second of all if that's the only spelling mistake I made I am doing pretty good and third you keep failing to address my main point. Don't confuse me with someone who doesn't know how to measure or use a micrometer, and by the way god didn't make it, but that is another story. I am talking about the people who can't and aren't going to, you know, the MAIN Customer base? Your attitude about those people is written in every post you make wether you see it or not. Your exagerations keep geting worse, it's gone from 10 to 14 degrees lost in camshaft. And yes "ARROGANCE" It spews out of everything you say. You can sit here and talk about "precision geometry" all day to the five guys here who are listening but it doesn't change what I am saying. I unfortunately do agree with your methods but I am challenging how important they are to most people.
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  #38 (permalink)  
Old 02-02-2012, 11:10 AM
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Whether to use the rockers or not is obviously up to the individual and a lot depends on the goals.

Anyone building competition engines- especially those that are limited by lift or any other cam-related specification- would be foolish to not look very closely at this IMO.

If it not for the cost I would be using them in a NY minute even in an engine that would be mainly street driven. But for those building street engines on a tight budget, the cost-to-benefit is harder to justify.
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  #39 (permalink)  
Old 02-02-2012, 12:53 PM
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Quote:
Originally Posted by lash540
I will tell you a situation we had just a little while ago, we kept lengthening a pushrod on a big block chev until we got maximum lift, about .013 thou over the pushrod with the "right" geometry. I had been reading a lot of talk on this forum and we were going on the dyno with it so I decided to take a set of long pushrods in with us. They were pretty long but nothing was binding up. To make a long story short the longer pushrods made a few more horsepower, not a lot but it was there. We then put 1.8 rockers on the exhaust with the same pushrods and gained 10 horsepower. If it matters the engine was a 760 horse 454. Now do I tell the customer we have to put the shorter pushrods in and make less power to make the geometry "right". I know this engine won't have problems because I have seen it done for many years. All theories need to be tested ,not just drawn on paper or swipe patterns but on the dyno or race track and they need to be tested back to back. All Jim Millers website has is theories, sarcasm and negativity to other companies. This gets too complex for the majority of people whether you like it or not, and these are a big portion of the customer base. I have viewed both sides of the story and believe this whole thing has been blown out of proportion for a stud mounted rocker and that's probably why it hasn't really caught on and why he doesn't make them anymore. Grant 4060, did you test his rockers against the comp rockers on the dyno? and if not how can you know for sure that they worked for you? All I am saying is too much classroom and not enough real testing.
According to Miller's concept, if you put the "wrong" pushrods in your engine, you are effectively losing as much as 10 duration of your cam specs. So, buy putting the "wrong" pushrods in your engine, if you saw a gain in HP over using the "right" pushrods with the same camshaft, it probably should tell you the camshaft is too big to start with, because you effectively put a smaller cam in it by using the "wrong" pushrods. Because with the "right" pushrods you are getting the full use of the cams duration and makes less HP. Just like loosening or tightening the valve lash increases or decreases the cams duration causing the same effect, just not 10 worth of change, but enough to make a noticeable power difference. Saying all that to say this, the "wrong" pushrods make the cam smaller than what you intended when you selected it for your engine.

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Old 02-02-2012, 01:01 PM
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And the possibility also exists that by using the 'wrong' geometry the rate of lift might be changed in ways that could show a change in output- plus or minus- that could be pointing to a cam profile that's not optimum.
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Old 02-02-2012, 01:54 PM
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Wow

How did I miss all this? I appreciate Mr Millers time and efforts to hold some hands through this discussion. I'd also like to say as a sort of 'boutique' manufacturing firm, we're left dispelling well-intentioned, yet wrong wives tales about products from 50yrs ago, young boys dreams and 2 lane blacktop.

I wonder if the large market cam companies KNOW their information is off-base to a degree, however it is 'common practice' and an easier methodology for the largest percentage of the buying public to replicate at home.

I've been a fan of the MID-LIFT for years. I applaud Mr Miller for his efforts, and sympathize about having to fight off rumors and erroneous material published in magazines.

Mr Miller; please hang around, share in the discussions and wave off those who won't or can't understand (or at least share in the discourse).
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Old 02-02-2012, 02:23 PM
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I would like to say I have purchase probably 50 sets of Mr. Millers rockers thru the years, some direct from him and some from mail order discount folks and they have been the best of the best.

In a stud type rocker I see valvetrain reliability and wear in the same range as Jesel and T&D Bar style rockers. This is using his rockers, Jomar Girdle nuts and Stud Girdles with 3/8 " ARP Rocker Studs, without girdles I use 7/16 studs.

In a time where companies sell the "sizzle" and not the steak, Mr. Millers stuff is the SHIZZ!!! His company got killed by folks selling the stuff at a discount an not supporting the product, and also by some early prototypes having some manufacturing problems.

I hate to say it but this is why we are stuck with "chinese junk" is our only option other than high dollar shaft systems. Here is a guy that put his life saving on the line only to be bashed down by the big guys who don't know "proper rocker geometry" from a hole in the ground.

Keep up the great work Jim, I will eventually get on some of your shaft stuff...

P.S.
I know for a fact that one of the Winningest CUP Teams ever in Plate Racing used his stuff for a long time until the driver was unfortunatly killed. Dale was a person who applauded American Built and American Innovators and a lot of stuff change when he left us.
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Old 02-02-2012, 02:45 PM
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There is junk made EVERYWHERE. The Chinese produce our mainshafts that are in 600hp road race and endurance racing applications. However, we control the prints, we inspect the product 100% when it hits the floor, and if its not right we send it ALL back. After the first or second time, they learned we want what we pay for. If the person at Acme Rocker Corp insisted on a quality Chinese product and held their feet to the fire over it...he would get the same. Ethnicity has nothing to do with it. Example: what if the person programming the CNC machine at (insert american valvetrain company) was chinese or indian etc etc.

Its really really hard to come across as contrary to magazine spin...You're immediately branded as an idiot, or having an axe to grind because you fly in the face of advertising dollars and media personas
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Old 02-02-2012, 03:11 PM
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AG,
You are exactly right but I don't know of too many companies that will properly inspect items of less than $500. Cranks, rods, pistons and rockers are running amuck in the performance market. The market being better than the stock chevy stuff and I am not real sure of that as I have had stock steel cranks and rods last quite a while in performance applications below 600HP.

What type of mainshaft you referring to??? Transmissions? You have probably spec'd materials, heat treat and machining tolerances and checking them when you get them here. I know it probably works for your applications but I am really partial to the VAR Shafts Jerry Hemmingson produces at Jerico in North Carolina. I know they ain't cheap but I have owned 50+ of his trannies and have never had a failure.

I have often told him that his race transmissions are the only product I have ever used straight out of the box with no alterations or mods to get it ready for 4-5 hours of 9500rpm, 850HP thrashing in ARCA, BGN, & CTS.
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Old 02-03-2012, 09:13 AM
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I'll PM you to keep this thread for rocker arm discourse
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