How to do the boss 289 rocker arm conversion - Vintage Mustang Forums
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post #1 of 24 (permalink) Old 04-13-2018, 11:48 AM Thread Starter
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How to do the boss 289 rocker arm conversion

I have a set of C5AE heads that I wanted to do the late model rocker arm swap that has been discussed recently. I had the heads cleaned and checked first, tried my hand at porting them, and after reading some posts on folks having troubles with the original rocker arm usage, I thought this looked like something pretty cool to do! Several of the original push in studs had cuts in the side of them from the rocker arms biting into them-same on my hipo studs when I had those heads rebuilt... I have the rockers and bolt down fulcrums off some E7FE heads-they have the bolt thru style fulcrum which apparently will work if you can't find the old boss 302 style fulcrum...I also have a set of new 3/8 style screw in studs to use as well vs the 7/16 boss 302 larger ones...So my questions are how much of the square pedestal needs cut off the bottom of these fulcrums, and can I just drill out the fulcrum using a 3/8 drill bit? I was going to have the machine shop tap the heads for the screw in studs, and I am sure they could modify the fulcrums as well, but if I can do them I will. I also was going with hardened exhaust seats and 351W valves and new guides and vitron style seals-Any preference for iron over bronze style valve guides? I know alum heads are better, easier, cheaper etc...but I am enjoying the work on these old original heads for the 65 I have all apart.
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post #2 of 24 (permalink) Old 04-13-2018, 11:54 AM
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Sounds like a good plan, I used that procedure on my 289HP and it was much happier than with the original rockers.

I prefer the iron guides, it replicates the original iron head guide, and they are reputed to outlast bronze guides. Mine are still perfect, after 100,000 miles or so, for what that's worth.
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post #3 of 24 (permalink) Old 04-13-2018, 06:21 PM Thread Starter
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ok, iron guides it is! Now, since I have to use the fulcrums with the protruding pedestal, how much of that should I cut off with a wiz wheel? more or less flush as possible? leave a little on as it won't hurt anything? Do you think I will be able to just drill out the hole with a drill press and a 3/8 drill bit? The holes are oblong shaped and seem to be 3/8 for the longer side but 5/16 for side to side..so I think they would drill out pretty true if i"m careful and steady doing it....Also, do the heads boss's get milled down a little when they thread them for the screw in studs or just tap them and taper the hole a bit?
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post #4 of 24 (permalink) Old 04-13-2018, 06:59 PM Thread Starter
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I just happen to have the valve cover off the 66 hipo and took a look at the stud boss base...it is a least a 1/4 ' lower than the stud boss on the push in heads....so, they should be machined down when tapped for screw in studs I assume? I have not really talked to the machine shop yet to see what they say or know.....I'm betting 22GT will know! or others who have had screw in studs installed? LSG?
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post #5 of 24 (permalink) Old 04-14-2018, 08:06 AM Thread Starter
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any helpful input from folks that have done these things is appreciated!
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post #6 of 24 (permalink) Old 04-14-2018, 09:52 AM
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Tongue rocker studs

Geico58, working from my fuzzy memory, yeah, you have to cut the lumps down abit. Methinks . 200 or .230. I'll have to look at my notes when I am @ work. LSG
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post #7 of 24 (permalink) Old 04-14-2018, 01:35 PM
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Before I went with the AFR heads I did the rocker arm conversion on my '68 289 using this book as a guide. https://www.amazon.com/Ford-Performa.../dp/0931472059

Here is an extract from the text.



Hope it helps. Gaz

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post #8 of 24 (permalink) Old 04-14-2018, 03:05 PM Thread Starter
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danke schoen No guide plates needed with these slotted pushrod hole heads...hopefully the machine shop would have known some of this info, but it is always a good idea to throw questions like this out there for some thoughts on what to ask for as well! Any body have any experience cutting down the square fulcrum base (flush, 1/2?) and I am going to try and run a 3/8 drill bit thru them to enlarge the hole for the 289 hipo screw in stud...maybe Sunday, time permittIng...
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post #9 of 24 (permalink) Old 04-14-2018, 06:49 PM
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I would take one of the balls from the original rockers and see how a 3/8" drill fits.
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post #10 of 24 (permalink) Old 04-14-2018, 07:13 PM
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You need to be sure you are not mixing apples and oranges here.

The 351C rocker fulcrums with the large rectangular base were used on heads that have pedestals with a matching slot for that rectangular base fulcrum to sit down into. That is what aligns the rocker to the center of the valve stem. There are no close tolerance holes in the head nor are there pushrod guide plates. Your 289 heads are not capable of accommodating that fulcrum.

The Boss 302 used screw in studs and pushrod guide plates so the fulcrum did not have the large rectangular base. I have never worked on 5.0 rockers so I don't know what they use. From the Boss 289 article it appears that they use a 1.6 stamped steel 5.0 rocker. Does the fulcrum have a large rectangular base that fits into a slot machined into the pedestal? Or does it use close tolerance holes in the head or guide plates?

I used Australian 302C heads on my engine and they originally had the pedestals with the slot for the large rectangular base fulcrums. The conversion called for removing .300" from the top of each pedestal which left a flat surface. Then I drilled and tapped the holes for 7/16" screw in studs and installed guide plates before screwing the studs in. I used aluminum roller rockers and the fulcrums are integral with the rocker.

So what are you trying to use? The 5.0 stamped steel rockers? Or roller rockers? You state that you want to keep the close tolerance holes for alignment.
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post #11 of 24 (permalink) Old 04-14-2018, 08:40 PM
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Quote:
Originally Posted by geicoman58 View Post
danke schoen No guide plates needed with these slotted pushrod hole heads...hopefully the machine shop would have known some of this info.....".
sometimes you can get away with using guide plates with the slotted push rod heads, like my HiPo heads have had. And sometimes you CAN"T.

Twice I used guide plates on HiPo heads with zero binding issues, FWIW, both were on 66's. Admittedly, it was probably overkill to have this much pushrod alignment control. I can't say that it gained me anything. On the other hand I never had any valve train issues.

The 3rd time was no charm, and on the this last set of HiPo heads (1965 heads) there was significant pushrod binding with the guide plates installed under the studs.

Not wanting to drill out the slots on a good set of HiPo heads I ditched the guide plates.

BTW, with all of these heads I did not have to machine down the stud bosses to compensate for the guide plate height. No interference issues with the rocker arm . YMMV.


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post #12 of 24 (permalink) Old 04-14-2018, 09:49 PM
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If the guide slots in the heads are grooved, you'll need guide plates. It's likely, because off-center alignment of the rocker tip and grooved guide slots are cause and effect.

You'll want to remove as much of the pedestal as possible. And check them to be sure they do not bind when the valve is fully open, on performance cams. Many manufacturers make these, better safe than sorry. And of course the oval 5/16" hole will need to be drilled to 3/8", or if you use BOSS 302 studs, 7/16". This, awhtx, is what makes them compatible to the 289/302 heads.
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post #13 of 24 (permalink) Old 04-15-2018, 12:30 AM Thread Starter
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Hey guys, good discussion, when I read awhtx's comments it gave me pause..Why are these 5.0 rocker arms any better than the stock 289 ones? Even with the barrel shaped 5.0 fulcrum it would seem that the rocker arm could still walk around as on the 289 with the half a ball style fulcrum, Maybe they just spread the load out better and stay aligned better..These are not hipo heads, just regular 65 slotted hole heads with no damages to the push rod holes. I reread the article and I think if i just cut the bottom off these 5.0 fulcrums and drill them out with a 3/8 drill bit they will work just fine. I will get the stud boss's milled down .230 and tapped for the 3/8 style hipo studs and no guide plates....hopefully I will never experience the rocker arm rolling off the valve tip and gouging into the stud and getting worse as time goes on. Just trying to build a better mouse trap! Here is the article that I am using to do the upgrade. It doesn't seem like a lot of people have done this.
https://www.mustangbarn.com/image.as...BOSS%20289.pdf
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post #14 of 24 (permalink) Old 04-15-2018, 10:28 AM
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What kind of lift could you run with this setup?

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post #15 of 24 (permalink) Old 04-15-2018, 01:52 PM
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Originally Posted by Nailbender View Post
What kind of lift could you run with this setup?
That will depend upon which studs you use. If you retain the factory press-in studs you are restricted to something less than .500 lift. If you convert to 7/16" screw-in studs the sky is the limit.
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