Tall rocker covers + Yella Terra platinum rockers for Buick?

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Tall rocker covers + Yella Terra platinum rockers for Buick?

Postby vlad01 » Sun Jun 19, 2022 5:32 pm

Have a bit of a conundrum, I am looking to use the Yella Terra platinum adjustable rockers for my next engine build as you might know the cam is the Formula Holden cam which needs mechanical roller lifters and thus needs adjustable rockers.

These are the ones but the pics are are ecotec ones but similar.

https://store.yellaterra.com.au/holden- ... io-yt6307/


The question is what to do with rocker covers? There is next to no options out there bar a few, unlike the L67 which has more options.

I found these and have been talking to the manufacture but it's apparent they made them unnecessarily tall which interferes with the booster, coil packs, power steering high pressure line, thermostat housing and worst of all blocks the entrance of the throttle body which I can't see a way around (literally).

https://www.aussiespeedshop.com/product ... er-covers/

The stock rocker covers are 60mm tall, these are 98mm which are way too tall and will cause the above issues. The throttle body will be clipped by almost half vertically and 1/3 front to back.

So does anyone know of the height of the platinum rockers? and how others get around these issues? They mentioned machining down the fins on the covers but I don't think that's enough and the amount of mods needed to them, would it be better to get custom CNC'd ones? and that can also allow them to be made with factory O ring and seals in mind over the backwards paper gaskets these use.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.

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Re: Tall rocker covers + Yella Terra platinum rockers for Bu

Postby immortality » Sun Jun 19, 2022 10:12 pm

I thought someone made spacers to suit.

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Re: Tall rocker covers + Yella Terra platinum rockers for Bu

Postby vlad01 » Sun Jun 19, 2022 10:38 pm

Yes there are spacers but I think they are only tall enough for the run of the mill yella terra rockers, not the platinum race ones which are flatter across the top and have the adjusting nut sticking out, the normal yella rockers are closer to the OEM shape (trapezoid shape). So as far as I know the stock covers with spaces don't work with the platinum rockers due to the shape and being ever taller. But Gareth made the spacers work with the Kilkenny castings covers as they are a box shape, not trapezoid like stock.

I am not keen on using the KC covers as I feel like they are a big step backwards, shitty cork gasket and 1970s style oil cap.

I have asked the Formula Holden guys on FB what rockers they use as their covers are the original ACL ones made for that series that are OEM shaped but maybe 10-15mm taller, and they clear the throttle fine.
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Re: Tall rocker covers + Yella Terra platinum rockers for Bu

Postby charlay86 » Wed Jun 22, 2022 10:13 am

Maybe something like this: https://zzperformance.com/products/polished-aluminum-valve-covers
Then apply grinder tig grinder process to the top until they fit.

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Re: Tall rocker covers + Yella Terra platinum rockers for Bu

Postby vlad01 » Wed Jun 22, 2022 11:57 am

Actually, come to think of it. Those are the ones Gareth used on his current engine with spacers with the platinum rockers but he has the ZZP alloy L67 heads, these won't fit the Buick heads as they don't have the injector bosses in the casting. I was thinking of cutting up a few stock covers and stack a section into it like you suggest just to see what height is needed and clearance etc... which i can do with the VN early alloy covers but in the end of the day I would prefer CNC'd custom covers based on the factory plastic covers and alternations to make them as low as possible and cut away for the throttle if needed.

I don't like the seals for the bolts the early VN alloy covers use, kinda crap and the plastic later covers addressed the issues and are much better. I suppose I should get the platinum rockers first so I have something to work with.

Also the Holden Formula group is pretty useless, they seem very secretive and won't answer questions which is no surprise given what FB users are like. I miss the days of dedicated forums when people were more helpful and cluey. :thumbdown:
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Re: Tall rocker covers + Yella Terra platinum rockers for Bu

Postby vlad01 » Mon Jun 27, 2022 2:49 pm

I have determined that CNC'd billet covers are the only way to properly address fitment for these rocker arms and other areas of the engine. The Aussie speed ones are about 23mm higher internally at the center compared to stock even with the internal ribs and bracing inside the stock ones taking up room. The external height is about 40mm higher which is bonkers.

I suspect that the height in the center will only marginally need to be raised, unlikely more than 10mm but the main clearance area will be the inboard slope of the covers which are far lower than the center so that inboard slope can be flattened out to raise clearance, outboard hopefully not so much and keeping the same angle with total height raised should be sufficient and also will benefit booster clearance. It should be possible to clear everything else too, PS pump line, throttle, thermostat housing (although an ABS housing will be better so that the housing does not need to be removed to get the cover off for every lash adjustment).

Seems silly no decent cover exists given the popularity of the yella rockers.
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Re: Tall rocker covers + Yella Terra platinum rockers for Bu

Postby Charlescrown » Mon Jun 27, 2022 4:36 pm

Have you contacted Yella Terra and run it by them?
I'd imagine CNC billit ones would require the sale of a Kidney.

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Re: Tall rocker covers + Yella Terra platinum rockers for Bu

Postby vlad01 » Mon Jun 27, 2022 7:13 pm

Probably 1.5-2k for a pair I'd say, but hey the conrods cost 2k for what I need, and 5k last quote I got for the heads more than 5 years ago. :lol: I have asked them before, they didn't have an answer.
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Re: Tall rocker covers + Yella Terra platinum rockers for Bu

Postby antus » Mon Jun 27, 2022 11:30 pm

For that kind of money you probably could get it 3d printed. if your technical enough to draw it up in auto cad, after maybe sketching the mount and the bolt holes on to graph paper if you need to, to get the measurements right, you could then extrude the end by the extra length required. Then you could ask a commercial 3d printer to print it in ABS and do a test fit on your engine with that and if its all good get them to print it in some kind of advanced metal material that can handle the heat. But then for less money you could also get a machine shop to cut the top off and lengthen it out and clean up the edges so it looks original... maybe. I have 3d printed and used a carby adapter before, but nothing like this. It wouldnt be the first go to, but since this thread is still unsolved maybe it is worth looking in to.
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Re: Tall rocker covers + Yella Terra platinum rockers for Bu

Postby vlad01 » Tue Jun 28, 2022 10:10 am

My 3D skills are limited to early 2000s game level deign. With something so complex as these rocker covers, 3D scanning will save a shit ton of time and money, the heads and rockers should be scanned as well to model clearance in both seated and lifted position.


I agree, 3D printing some test pieces is a must but I wouldn't use such materials for the final product as finish and durability isn't all that great and in my experience scaling with different materials is a huge problem due to each material having different expansion and contraction rates and some of the more exotic printing methods and materials needed still don't match billet and cost almost as much.

I have gone through this before, outsourcing 3D scanning and design and printing for my C pillar moulds since it was a complex part and no replacements exist so I had to do this out of necessity. It took quite a few iterations and materials to get it right and $$, but hey, I have the files now and can get them made any time I need them.

My biggest issue with the last project was the printing itself and CNC milling would have saved a lot of headaches and money.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.

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