Making vintage speed rocker arms?? CNC? or cast? metal?

[vintage fiberglass]

Does anyone have machine / metal knowledge to know what the process was to make the 36hp rocker arms?? were they cast and then machined? and out of what grade steel? or were they a solid metal block machined?

How did these companies in the 1960's like Racer Brown or Empi and others make rocker arms? and what metal did they use??

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I think if your trying to make rocker arms i would go with forged or billet 4340 rocker arms there stronger than cast rocker arms ..

[vintage fiberglass]

So 4340 is a type of steel? It can be CNC machined into a rocker arm and will be strong enough? Just making sure I understand? So if I want to do this, I make a 3D drawing of the rocker arm and a machine shop can use that to machine them?? Obviously holding a real one helps as well.

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[vintage fiberglass]

Wow! Good information and exactly what I needed. A big thank you my friend!
I am going to investigae to make Denzel rocker arms and shafts to make complete assemblies. Thank you!

Anyone have any spare Denzel rocker arms??

[TomSimon]

You probably already know this, but Denzel 36hp heads have angled valves, similar to a type 1 (but I don't think the same 9deg). They require their own proprietary rockers and shafts. 36hp VW heads, and 36hp Okrasa (and WW replicas) have no angle, the valves and guides are straight up and down, parallel to the bore, and use oem VW 36hr rockers and shafts.

Do you have a pr of Denzel heads that have no rocker arms or shafts?

I saw a pr once, in a VW's guy's glass case, where he had (I think Dick Nuss at EMS) adapt/modified a set of aftermarket Type 1 rockers and shafts to his pr of Denzel heads.
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2-time NASA Pro Racing Champion, Bonneville 130 Club and 150 Club Memeber, BRS Pro Gas racer

[vintage fiberglass]

Tom,
'Yes I knew that. I also have owned a Denzel engine in the past and now at 59 years old want one more. I know of bits and pieces but most heads I know about are missing the rocker assemblies. Not sure why. I had Denzel aluminum rods, they are no good. Most guys use Porsche internals but they did have their own full circle crank at a weird stroke and a wired bore as welll.

I will chase the heads without rockers that I know of and then make a few sets of rockers. I just didn't know what metal was best and method to make them?? Tim

[vintage fiberglass]

Tom,
'If you know of any heads or rocker assemblies let me know. Tim

[Ebel]

Depending on the design you could even use aluminum. But they would need to be physically larger. I would think steel would fit better. And look more original. I would also check if the original rockers were drilled for oil passages. That’s something that might change the design. If it has oil passages the machining will end up with an open hole that needs to be plugged on at least one end. You could weld it like vw did. Or plug if with a plug or screw. It also kind of looks like there’s some sort of swivel foot valve screw. That would either need to be copied or adjusted to use an available part. Much easier and cheaper to design around an available part. Also you need to consider possible heat treatment. I think the socket the push rod contacts would be hardened. It may not though. It could be possible to only harden that area of the rocker. But generally heat treatments will distort parts and are generally made oversize to allow machining of the finish surface. It won’t be as easy as just machining them and be done. At least I don’t think so. You will most likely need to grind the socket somehow after heat treating. I’ve been machining for 25 years and have never seen how you would do that quickly. I have steel parts hardened and the only way to get a consistent accurate size is grinding. I have an extremely expensive Cnc grinder and I don’t know if it could do a spherical ball the size on a rocker. I wouldn’t be inclined to figure it out unless you were paying a whole lot of money. But it might be possible to do it in a much easier process. If I were making them for myself I would just have a cnc mill plunge a grinding ball into the socket. But the grinding tip would need to be dressed often to maintain the correct size. But. If you go into a shop with drawings sawing you need a 6mm ball socket it would just be milled. I’d suggest getting an original arm to measure everything. It’s possible that the rocker shaft hole may need to be hardened and ground as well. While it’s completely possible to make them, it might just need more work then you have thought of. If you walked into a shop with a drawing and said you want it made, they could make you exactly what you specified. But if it’s not designed properly you might end up with expensive paperweights. A rocker arm machined from 4140 would be much cheaper then the same part with the proper heat treatments and finish. I could make rocker arms myself and thought about doing so. But in my case I could buy them for a 1600 based engine. Denzel’s are rare enough that making new arms might be the only way to go. But if improperly made might cause a failure. I don’t want to discourage you, but I think it’s important you understand all the possible issues with making them. If you came into my shop I would tell you this. But someone else might just make your part and not care. Or they might not know anything about rocker arms. I think you really need to figure everything out before hand.

[TomSimon]

^^^^^^^^^

great post, above, a lot of thought and experience in a few paragraphs.

I was giving this some thought as well, and would agree that 4140 steel would be a great place to start if making them from billet. But a guy would need to figure out if he wants a copy of a Denzel rocker arm, or something that will work, with the correct geometry for an angled valve Denzel head. If I wanted the later, I'd purchase cup adjuster screws, with t he 8mm spherical radius already made for me, and use a wear pad on the valve tip side, like 95% of the aftermarket T1 ratio rockers do. BTW, that design doesn't use drilled oil holes through the arm, like VW did, the shaft pivots rely on splash oiling, the adjuster screw pivot is oiled through the pushrod, then spritzes the valve spring, and everything else under the valve cover, like a lot of other engines.

Berg had T1 forgings made to their spec,machined them in Orange county back in the day, expensive retail and the gold standard for aftermarket rocker arms They will still service your old ones, but don't offer them for sale any more. They probably ran out of forged blanks.

The ratio rocker that CB, and Scat sell look to me to be forged, most likely in China. You might be able to find out what they are made from. But people who forge have several characteristics they are looking for that are specific to the forging process, and post heat reatment.

There's cast, but casting results in not very dense final product, Sig Erson, Autocraft and a couple other companies cast T1 rocker arms, that were pretty good. Autocraft were a nice casting, probably an investment casting, look to be some type of steel, but as valve spring pressures and rpms increased, lots of guys broke Autocraft rockers during high rpm race use (including me), before Autocraft started making their 'pro series' rockers, which look machined from billet, maybe forged and heat treated? (problem is they were made with the wrong geometry, but that's another story). I've even seen some real crude cast iron T1 ratio rockers, but they were bulky to make up for lack of strength. I'm not sure I'd do that for a rocker arm.

Additive manufacturing is still pretty young, but the size can be scaled within the software. It would be a whole development project (I'm on the periphery of an AM dev project right now for a very specific complex part). a guy machining from billet makes the most sense to me.
_________________
2-time NASA Pro Racing Champion, Bonneville 130 Club and 150 Club Memeber, BRS Pro Gas racer

[RWK]

Yes, billet would be the most cost effective, lay them out in cad across a piece of pre-hard 4142 bar stock its approx 30 Rc, profile machine one side and rocker arm hole then flip bar over and do other side, leave web say .03 -05 thick and knock out, done this with alum. 3D parts many times, you can flame harden tips or have them ion-nitrided, completely, leave .001-.003 in arm bore to hone to size, ion-nitride is about .005-.01 thick, very little distortion if any. If you are concerned about ball pocket size and finish and get them done, I can EDM the pockets for you, can get a 1.2 um, finish pretty quickly, then you can lap or polish them out. You can also pre drill all the holes if you lay out in cad first, other wise you will have to fixture each and do individually.
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73 Type 181
63 Type 113
63 Type 261- 428 071
62 Type 241-378 025 178 530

[RWK]

The old cast and forged anything were the most cost effective way years ago, even in small quantities, huge advances in cad /cam even in the last 20 years, makes billet machining affordable, of course nothing beats a forging in some applications for strength and economy.
_________________
73 Type 181
63 Type 113
63 Type 261- 428 071
62 Type 241-378 025 178 530

[vintage fiberglass]

What is the 36hp record right now for an unlimited engine?? meaning duel carb denzel or Okrasa or whatever? I heard it was like over 115mph??

I have a picture of a Denzel engine long block hooked up to a Pepco supercharger. Crazy?? I always wondered of it really worked.

For some weird reason Denzel heads are often missing heir rocker assemblies.

[mark tucker]

I wood do aluminum with bush.if it has a good oiling system the bush isant all that necessary.,I would also dfl coat the bush or rocker bore.. you can also look at other rocker arms to see if they can be modifyed to work. getting the geo is very important. you may be able to use some off the shelf rockers and just make stands to put them at the right angles& geo locations. you may also buy some rocker arm extrusion bars and have them machined. there are many aspects to a rocker arm that is made right and desgined correctly.not just drawn out.