Landracing Forum
Tech Information => Technical Discussion => Topic started by: rebelce on November 06, 2015, 01:58:44 PM
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I'm building up a Jimmy straight 6 and need to make some rocker arms. Pat Riley was kind enough to show me the set he built for his and of course the Ferguson's always have nice stuff. Mine need to be slightly different than stock, both angle and offset. So do any of you guys have any suggestions? I have a lathe and an old J-head Bridgeport as well as a lot of friends who do machine work but I like to keep things in house. There are a lot of Jesel rockers in the cupboards for ideas and mock-up parts if need be. Would 7075 be a good material to use? There is nothing in a modern engine that is long enough. Help is needed!
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I have seen articles the adjustable ones off of the 305-351-401-478 being used
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I've never seen a set but it's highly doubtful they would full fill my needs. Roller tip for a start.
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When we needed roller rockers for the straight 8 Buick we went to T&D Rockers and they said that they didn't build any that we could use. We went to their online catalog and looked in the catalog index and found three part numbers that were stock parts. We had to have a shaft made to fit and have it hardened but we've been happy with their arms. They weren't real expensive but the hardened shaft was pricey.
Doug :cheers: :cheers: :cheers:
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Buickguy3, that is a real possibility, I took a quick look at their site and noticed they provide lengths for the valve side but is there a way to find the overall length? That's the problem on Jimmy's. I'll call them and see what they have to say. Still want to explore the idea of building my own in the meantime. Thanks, it's book marked!
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I have built a few sets from scratch.
It is not hard, just follow good design and engineering practices.
That said, used 7075 and 6061, both work fine.
You can contact me privately and I will attempt to answer your questions.
It can be done reasonably in terms of cost. You just have to shop around.
John
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Panic, yes, the valves are being moved .090 to towards the exhaust to center them in the chamber and tipped towards the port 5 degrees as well. I'm only going to do a section of an old head first, Mike Kirby will play with it and see if it's a worthwhile endeavor. I have to think the whole thing through. No need to have it half done and no way to finish it.
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You may want to check with Blake Machine in Phoenix also. They custom build the Buick rockers and will do the shafts, too.
Doug :cheers: :cheers: :cheers:
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For smaller overall size than aluminum, I made cam followers from 4140 steel alloy. It's easy to machine in pre-heat-treat form; had them treated to 49 Rockwell-C afterward. I purchased the rolling elements (wheels, tip rollers, axles) from Ron Iskenderian because I wanted to use the original non-needle wheels. Ron shared with me the factory process of coining the wheel axles (ends aren't hardened) into their EZ-Roll lifters- I built a small jig to coin them into my followers. The Isky roller tip axles use Circlips. I'm presently doing spin-tests of the OHC assembly, with no faults so far (springs are 290# seat, 590# @.686" lift) to about 6,600 [engine] RPM.
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After following your windage thread Jack, I've decided you are a much better man than I in the shop! You do beautiful work and if any of my things come out half as nice I'll be a happy man. I will keep Isky in mind for the rollers.
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Around 1990 or before, Bob Dalton and I made roller rockers for my Hourning-Fisher head GMC. Bob set the whole thing up. He cut the rockers out of 6061 on the CNC mill he had at the time. And he had made a jig for me to drill and ream for the roller axles and drill and tap for the adjusters on a manual mill. Took us a Saturday afternoon. Bob had got the rollers and adjusters from Isky. With todays machines I am guessing a few hours.
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Rich, that's about the best news I've heard all day!
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I made my own, at least designed them and traded some electrical work in a machine shop to make them for me. He made the stands and right/left rockers. Like many above, I used Isky rollers and Titan adjusters. Used 7075 for the material and the stock rocker shaft ground down a bit to fit the Torrington bearings. Stock shaft did break after 20 or so years of running so I had a couple of replacements made. Rifle drilling was pretty easy along with the grinding and heat treating. Since every thing was straight up and down it went fairly easy.
Offsetting the push rod to the roller tip needs to wait until you know what the distance will be but I didn't concern myself with that since I was not moving the valves. I adjusted the rockers to the stands by using washers I bought from McMaster-Carr. I kept the stock springs for tension. Fergie used aluminum spacers as I remember. When I was done with them I was very pleased with the ratio and what the shop said they would have cost. This was just the machining on the rockers and stands. All assembly and the shaft work was done by me.
I now have 3 different sets, 1 for the stock head, 1 for a Skinner/Fontana, and 1 for a Howard/Arias. All 3 are different and would hard to move from head to head. I would not bother with bearings on the shaft if doing it again. Aluminum on the hardened shafts is sufficient. I would change a few other things today in the design but not much as they have proved themselves.
A friend is using an Arias 12 port set he bought from someone in the Inliners for a stock head and is making a new shaft to make everything line up. I believe he is going to hard chrome the shaft and grind it to the proper diameter. A little leg work but I think he'll have less than $200 in the new shaft. My pair were right at $200 5 years ago with no chrome plating.
I have 2 sets of new Thomas Magnisium hi-lift rockers for a GMC I never used because I wanted the rollers to keep from wearing out valve guides every year. They ride on the stock shaft with no bearings and use the stock adjuster and just shortened the pushrod side for the additional lift. The pushrod hole in the would need to be enlarged for them to work with better springs as the stock push Rod was pretty small....GoodLuck
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An aluminum part under cyclic loading that is designed for long term fatigue resistance will often be heavier than a steel item designed for the same life. Steel is a more forgiving material in this respect. In my case, where I do not have sophisticated design and test facilities, steel is a very attractive material.
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Jimmy6, How wide are your rockers? Would you mind sending me a picture of their profile? I saw the ad in the 12PN for the Aries rockers but they were gone pretty quick. I think the hardest part will be getting the overall profile cut out. I can take it from there as New England is good for indoor projects! steel or aluminum? Oh boy. 7075 or 2024 would be easier for me to work with I think. Man that's a hard one though. Panic, you're right, 10 degrees may be too much, 5 is better, the chamber is too thin and yes, the exhaust is tipped as well.
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Mine were stock width both the stands and the rockers and flat on top. The adjuster side was offset to side of the stock one; if you look at a stock ones both right and left from the top down you will see what I mean. Width was about .850" to hold the nut.
The roller tip side was .750" width 3/4's of its length just to remove some weight. And it's offset just matched the stock one too.
The lower side looks like a stock one with the thickness around the bearing at .250". If you didn't use a bearing it should be thicker in my opinion. The Arias ones are .275" and they seem to work for the guys that use them. However the shaft is much smaller in diameter at .750"
After the gentleman who made them for me finished the basic rocker (1 left and 1 right) and one stand he had me mount them on the shaft and put on a head to see where center the roller tip should be placed. The .750" width came from the width of the Isky pin and room for the clip and they are not in the center but in the center of the valve end.
That's about it. I'm no engineer I just wanted roller tips and a little more lift and the offset of the shaft stands gave me that. You need to measure that for yourself. Since I used the stock shaft all the oiling remained the same altho I didn't continue with the overflow or have squirters for the top of the push rods cause I didn't know shaft systems like the T & D had them.
As a side note the gentleman running the machine shop told this job was worth about how $2000 not including my parts which was everything but the rockers and stands. I had this done in the late 80's. Good Luck
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Panic, interesting comments. When I was designing mine I didn't think about the clearance for the spring but was lucky as nothing touched. That part of the fulcrum is pretty long (and your going to make it longer) when you consider the original measurement from the center of the valve to the center of the hole for the push rod which is what I started from. It was said the stock ratio was 1.5 to 1 but it was closer to 1.4. Today 1.70 or 1.75 seems to be what is wanted. This and the correct geometry so the roller moves correctly over the valve tip. Luckily today you have long stem valves, lash caps, stand shims, and beehive springs to make "errors" correctable. One good thing is I don't need to do it again and as long as my rocker cover is on no one knows what I did or what I'm doing under it and that's way it will stay.....JD
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“the remaining contours are entirely for weight reduction and clearance.”
Nice to know that the stress levels and structural integrity can be disregarded.
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Fixed it.
Happy now?
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Spin-test result doesn't speak well for my design skills...
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Dang, get up in the morning and the entire thread is shorter. You know JD, we've known each other for many years and what happens under my cover will remain a mystery too, despite what is said on this forum. There's so much more to building an engine than this, it's in the process of building, the details, that's the devil of it. I have a set of Jesel Sportsman rockers here and was thinking of emulating their general shape out of 7075 T6 along with their bearings and roller tips. I have a good friend who is an engineer at Boca here in CT and he's in on this. At least his mill is DRO equipped. The Jesel's are apx. .895 wide and because of the extra length involved 1" seems a better way to go. I can see why the Arias rockers would be .275 around the bearing area at the bottom. With a length of apx 4" from the pushrod to the valve contact point there's a lot of stress. I don't have a set of stock rockers. Head, block and crank was all I picked up, figuring I'd have to build or buy all the rest anyway.
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Spin-test result doesn't speak well for my design skills...
Jack, I'm sure that fertile mind will come up with a solution. You've just offered proof that it pays large dividends to test rather than completeing everything and then having a series of linked failures. Well done. Keep up the great work.
Pete
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Reb, funny these questions seem to have a mind of their own after the first few statements. When I was designing mine on a sheet of graph paper (that's all the machine shop got too) I don't remember why I arrived at the lower demension on the underside. I was using Torrington bearings an new there strength there too. The machinist may have made that .desision. The Arias set is rocker on shaft and the bottom needs to be strong. On my sons 1/2 mile Super Stock engine we are moving to T&D's as I really don't like guide plates and stud mounts; one of the many things we changed since starting 5 yrs ago.
Many years ago I considered moving the valves around but $$'s got in the way plus (a big one) I felt I had not met the full potential of the head as manufactured and maybe I still haven't. I've continued to improve speeds as the records show at Bonneville and I am going to concentrate on El Mirage until I'm too old to drive. We will see this weekend if I've still got it. :? We've not run there much and I'm looking forward to getting into the seat with the car actually set up for there.
When I ran 171 at Bonneville I had reached the goal I wanted with a stock head on gas and now I would like to reach the number in my mind at El Mirage. I'm smart enough to know it will not be easy as nothing ever is and there is always disappointments thrown in. And....there is the reason I own 2 different 12 ports after all these years of stock heads......Good Luck on your project.
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That might be a good application for titanium.
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If you go with Titanium, I'd suggest G5 which is 90-6-4 alloy. Has around 120,000 tensile as opposed to 65,000 for commercially pure.
The fatigue strength of G5 - Ti 6-4 is Plenty for rockers, just get rid of sharp corners. Shot peenning or tumbling will make them look better, I'm not sure just how much it really helps longevity, but can't hurt, and dues soften sharp edges.
Rouse
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There is a long thread on Speedtalk about what alloy might be best as well as other thoughts on making your own rockers here:
http://speedtalk.com/forum/viewtopic.php?f=15&t=40559&hilit=rocker+arm+material
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I think we need to go the original question about making rocker arms for an obsolete engine that hasn't been made since 1959 to actuate valves with a push rod that makes a SBC look like a tooth pick. There always will be an expense that some thru friendship can get made reasonable. They will never be a viable sale item so you do what you can do. I for one will not spend my retirement making unobtainium rockers for 5 horsepower on an engine with shared intake and combo exhaust. I made roller tip rockers to quit wearing out valve guides which is what you get when you go from .300" lift to over .500 with a cam. I feel the same about having 7 main bearings instead of the stock 4. I'm not looking to spin my engine some pie in the sky RPM, I look to get out of it what I can with the restrictions of the engine and under the SCTA rules.
I am not against innovation and using new thoughts and ideas and probably have used many of them to get my engine where is today of which I am very proud. Many things I have done came from other forms of racing and also worked in LSR. I applaud my competitors and others using other obsolete engines for their achievements. Good Luck.
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Jimmy, obsolete is not a bad thing. As an example, this four valve Triumph engine I am working on as compared to an old style two valve one. The old engine has cams with gear drives that can be indexed to set the cam timing exactly where needed and also to make track side adjustments. The new engine has cams with the sprockets press fit on and no way to adjust them. What I use for cam timing is what they have when I unwrap them after the UPS guy brings them.
The valves and ports in the old two valve heads could be opened up without much of an issue with shrouding and removing metal from the combustion chamber to keep good flow. The four valve head has the seats at the corners of the chamber and putting in bigger valves requires lots of metal removal.
The bridge between the intake valves on the new 4 valve motor is sorta like an intake charge heater. Exactly what I do not need. There is a lot of surface area in the split ports with accompanying heat transfer and friction.
The dual cam towers reduce cooling air flow to the top of the combustion chamber compared to the old pushrod one. The new motor weighs over 200 pounds and that's 1.5 times as much as the old one.
I could rattle on, like the parasitic oil drag in the new wet sump design compared to the old dry sump, lubing the tranny with engine oil rather than proper gearbox oil, etc.
Old can be a good thing.
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jacksoni, that was one heck of a read! Very informative, thank you, it gives much to consider. I know the Jesel rockers are 2024 and for general availability and machinability the T351 temper might be the way to go. Jimmy6, I love racing the old iron, there's something about taking that engine out of an old car or truck, designing and building your own parts or digging through a ton of parts manuals to find something that might work, that is satisfying to me. Yes, cost does come into play but doing as much as I can helps on that end. Ray wants to do this and I'm all for giving him my best shot.
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Does anyone know where I can find a program to help with the strength calculations for rockers? I'd rather go into this with some idea of what's happening rather than guess by what looks good and no, I can't use a slide rule.
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Yesterday I was mocking up the T&D sport comp rockers on my sons engine. To do this it necessitates removing the 2 rockers from the shaft, mounting the shaft to the head, and using the supplied tool to determine the correct height on the head to calculate the correct push rod length.
What did I find in the rockers? The exact same system I designed over 30 years ago including bearings and oiling. Sometimes being lucky is better than engineering. What this taught me is using needle bearings IS a good thing and I'm glad I did it. This engine sees a lot higher RPM than my GMC. J.D.
PS. A slide rule is a ruler with something in the way when your trying to draw a straight line.
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solidworks is pretty good for modeling your parts.
This is a rocker built recently, Alum with roller tip and bronze bushing.
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Wow! pretty impressive but maybe a bit more than I need. Maybe the by luck might be the way for me!