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The Chevrolet Rocker thread. 
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Post The Chevrolet Rocker thread.
FAQ material:

Q: I've heard alot about using chevy inline six rocker arms for a cheap performance gain, what is this? How hard is it to do?

A: To do this with no additional parts, you need pedestal mount rockers and 3/8" studs (which engines can these be found in? '85 for the pedestal mount rockers, what 'bout the studs?) (what is needed to do this for an EFI head is below) Basically, using rockers from any 192/250/292 cubic inch chevy inline six (go to the store and ask for rockers for a '75 Chevy C-10 with a 250 I6),

broncr wrote:
IF you have pedastal mount rockers AND 3/8" studs, this is a good, CHEAP shortcut. Unless you have a very high lift cam (in which case you MIGHT encounter problems), you can increase your rocker ratio from 1.6 to 1.7, for about $30 -$40. REMEMBER, Mr1ford said he did this swap with a .487/.462 lift cam - in his opening post.

ALL it involves is replacing the stock, pedastal style rocker with the chebby one, and using a lock nut to properly adjust the valve clearance. I ended up double-nutting ALL of the studs, as one lock nut had lost it's bite.

I think most any cam would provide more lift/duration, but it would take another $70 to $100+(for the cam) AND significantly more time. I did the rocker swap & readjusted the valve train in a bit over an hour.

IIRC, the lift for the stock cam is .400. By switching to the chebby 1.7, it should now be .425. Not a BIG deal but, as mentioned earlier, cheap, quick and effective. :D

Thanks again, Mr1ford :!:


80broncoman wrote:
A pedestal mount 300 head can use stud mount rockers if you use a pushrod guidplate conversion kit. I have intsalled it on my 90 cyl head and it all works just fine. Crane part number 36655-16 will give you 3/8 studs and guideplate for 5/16 pushrods. If you go this route hardened pushrods are not required becuse the kit has nylon inserts in the guidplates. I had to mix a couple of kits on mine cause I needed 7/16 studs for BBC rockers I already had. It is best for long life of the nylon inserts if you polish the pushrods to make sure there are no burrs on them. This is easy to do in a drill.
This conversion kit will also make your valvtrain adjustable.

broncr wrote:
broncr wrote:
...the link to the post on the Isky guideplates for our 300's?...


It took a while...(& courtesy of Tetraruby300 - :) )

www.iskycams.com/category_template.php? ... ory_id=167

Note the fine print on the larger pic's -" picture may not exactly match actual product" - they all show a SET of adjustable guideplates.

originating thread can be found here

more relevant info can be found over here
brocr wrote:
Q: what screw in stud sizes should I consider, and why?

SuperMag wrote:
Specifically, Big Block Chevrolet 7/16" studs. The shaft is 7/16", but the part that screws into the head is 3/8", thus enabling you to use the existing 3/8" hole. Helps in keeping the price down...


Q: Which heads have provisions that allow a direct bolt on of Chebby rockers?
A:
82F100SWB wrote:
This I think might be 84 and older with stud mount rockers, if there is any that allows it to be a direct bolt on, I seem to recall that there isn't.

Q: which rockers can i use for my BB6?
A:
StrangeRanger wrote:
SBF rockers will not fit a 300.
GMC I6 rockers will fit
BBC rockers can be made to fit
385 series rockers (429/460) can allegedly be made to fit, there has been some dispute.

Q: what was the year of the head change over to pedastal mount rockers
A: 1985 was the first year for pedistal mount rockers
Courtesy of a PM by Other Evan

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Fri Jan 11, 2008 9:56 pm
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Hi SuperMag,

Can you link this thread back over to the roller rocker thread--I've posted more info and photos regarding the I6 chevy rocker and the BBC roller rocker (on the early 240 head).

Thanks,

John


Sun Jan 13, 2008 2:02 am
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Here is a link to some stamped-steel Chebbie rockers by Manley that are 1.6 ratio. No real advantage other than they are lighter weight than the stock cast Ford units. If someone were doing a rebuild and planned to replace worn-out rockers but wanted to retain the stock ratio they may be worth a look-see.
Joe

EDIT: I deleted the link because I realized that those are for the SBC V8 and may be different from the Chebbie Six rockers. Joe

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Sun Jan 13, 2008 12:04 pm
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66 E100 Pickup wrote:
Hi SuperMag,

Can you link this thread back over to the roller rocker thread--I've posted more info and photos regarding the I6 chevy rocker and the BBC roller rocker (on the early 240 head).

Thanks,

John


Done. :wink:


Sun Jan 13, 2008 3:10 pm
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Hi guys. I had an interesting conversation with a Comp Cams help guy today and just wanted to see what you thought. Didn't realize a simple cam swap would be such a pain but the machinist where I brought my head told me I needed the springs that were recommended by the cam sheet. Didn't even look at them but luckily the performance shop nearby got them in the next day... I have Comp Cams # 66-237-4 which is the 260H cam and the springs I bought are the #903-12 springs. After talking to the machinist he told me that with the factory valve spring retainers he only had around 1.68" of height even with the +50 locks. I immediately asked about machining the spring seats and he said that he didn't like to "compromise" the head like that because the seats are too close to the water jacket. The springs call for 1.7" so I thought it would be best to call Comp. After holding for quite a while, I told the guy on the other end the parts I had and the problem I had. After calculating with the stock ratio @ .447 lift he hummed and hawed and said that technically I could go as low as 1.64" but he said, "I wouldn't". He said 1.68" should be fine. When I mentioned about going to a 1.7 ratio rocker he immediately stopped me in my tracks saying that now the lift would be up around .470 something and that's not good. Unfortunately I already bought the 3/8" rocker stud conversion AND the 1.7 ratio Chevy rockers. I guess I just wasted a bunch of money except for having adjustable rockers, and I now gotta get stock pre '85 rockers because the Chevy's will just sit here... ??

Any opinions? comments?

Darren

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Future mods: TBI EFI conversion w/ Offy intake, GM TBI unit and Megasquirt computer, COMP 260H cam, ported/polished head, upgraded fuel pump and injectors, full dual exhaust.
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Wed Aug 13, 2008 4:15 pm
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The Chebby rocker swap is usually the $40 upgrade on a bone stock cam and usually not recommended on an upgraded cam. I had a set of new stock rockers and a set of new Chebby rockers when I had my engine built. The builder suggested stay with the stock rockers...so that's what I did.

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Wed Aug 13, 2008 4:51 pm
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Post Re: The Chevrolet Rocker thread.
SuperMag wrote:
FAQ material:

StrangeRanger wrote:
SBF rockers will not fit a 300.
GMC I6 rockers will fit
BBC rockers can be made to fit
385 series rockers (429/460) can allegedly be made to fit, there has been some dispute.

Q: what was the year of the head change over to pedastal mount rockers
A: 1985 was the first year for pedistal mount rockers
Courtesy of a PM by Other Evan



385 series engines include (IIRC) the 351M/400. I know their rockers are interchangeable with the 460 rockers.


Thu Aug 14, 2008 5:31 pm
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Modifyre wrote:
Hi guys. I had an interesting conversation with a Comp Cams help guy today and just wanted to see what you thought. Didn't realize a simple cam swap would be such a pain but the machinist where I brought my head told me I needed the springs that were recommended by the cam sheet. Didn't even look at them but luckily the performance shop nearby got them in the next day... I have Comp Cams # 66-237-4 which is the 260H cam and the springs I bought are the #903-12 springs. After talking to the machinist he told me that with the factory valve spring retainers he only had around 1.68" of height even with the +50 locks. I immediately asked about machining the spring seats and he said that he didn't like to "compromise" the head like that because the seats are too close to the water jacket. The springs call for 1.7" so I thought it would be best to call Comp. After holding for quite a while, I told the guy on the other end the parts I had and the problem I had. After calculating with the stock ratio @ .447 lift he hummed and hawed and said that technically I could go as low as 1.64" but he said, "I wouldn't". He said 1.68" should be fine. When I mentioned about going to a 1.7 ratio rocker he immediately stopped me in my tracks saying that now the lift would be up around .470 something and that's not good. Unfortunately I already bought the 3/8" rocker stud conversion AND the 1.7 ratio Chevy rockers. I guess I just wasted a bunch of money except for having adjustable rockers, and I now gotta get stock pre '85 rockers because the Chevy's will just sit here... ??

Any opinions? comments?

Darren


Surely Comp has a spring that can work with that cam and .470 lift.
Just going to 1.65 instaead of the 1.7 recommend for thier spring is going to greatly increase the seat pressure.
If they really have nothing I know crane has more than a few spring that will work although some springs will require different retainers.

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Fri Aug 15, 2008 3:05 pm
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As it turns out my machinist took some hardened steel Comp retainers and turned them down the amount he needed to get the 1.7" spring height. Now I'm curious if I could use those Che-y rockers but I think I'll just stick to stock right now and see how the new cam is.

Darren

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Future mods: TBI EFI conversion w/ Offy intake, GM TBI unit and Megasquirt computer, COMP 260H cam, ported/polished head, upgraded fuel pump and injectors, full dual exhaust.
"Far Away" mods *CHANGED*: Turbocharging.


Fri Aug 15, 2008 5:40 pm
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Ok .. has anyone accomplished a Rocker Arm swap with stud mount rockers??

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Fri Oct 03, 2008 9:44 pm
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I used Scorpion 1.73:1 aluminum roller rockers for 351C/460 motor.

I had to remove .110" from the pedastals of the rockers and also some material from the u-channel factory pieces.

These was for a 1995 EFI head with BOLT DOWN rockers.

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Sat Oct 04, 2008 2:26 pm
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Craigwell wrote:
Ok .. has anyone accomplished a Rocker Arm swap with stud mount rockers??


Yup. They bolted right onto my 78 300 head.

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Sat Oct 04, 2008 3:00 pm
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Ok Thanks. After a closer look, I did see the appropriate link above in the initial post.

I'll be giving this a shot with my 1981 Stud mount head. I just need to check if they are 3/8 studs or 5/16.

Thanks to everyone for great information.

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Sat Oct 04, 2008 9:44 pm
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Craigwell wrote:
Ok .. has anyone accomplished a Rocker Arm swap with stud mount rockers??


Me too. Worked fine for me. I just torqued them down to spec for the '79. I used the stock lock nuts with the new rockers and pivots.

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Tue Oct 07, 2008 1:42 pm
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Post Re: The Chevrolet Rocker thread.
I just wanted to add that Crane Cams makes BBC rockers for 3/8" studs. They are for a 409, pn 15750-16.


Wed Apr 21, 2010 2:49 am
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Post Re: The Chevrolet Rocker thread.
I will go for the stock ratio Harland Sharp ones. I don t know which screw in arp rocker studs to buy, can someone help me ?? http://arp-bolts.com/pages/viewcatalog.shtml page 54 I have all the options. I have pushed in studs but will be tapping the thread holes for some screw in rocker studs.


Mon Apr 15, 2013 12:41 pm
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Post Re: The Chevrolet Rocker thread.
julianc wrote:
I will go for the stock ratio Harland Sharp ones. I don t know which screw in arp rocker studs to buy, can someone help me ?? http://arp-bolts.com/pages/viewcatalog.shtml page 54 I have all the options. I have pushed in studs but will be tapping the thread holes for some screw in rocker studs.


Here is the way I would do it.
1st Don't pull out alll of stock studs tilll you take some measurements.
2nd I'd measure down the length of the stock stud to the casting.
then look at the height of the hex on new studs. That is the amount that you would mill off the head stud bosses.
Also remember if you head has round holes for the pushrods and not milled slots you will guideplates and heattreated pushrods.

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When it come to engines If its .001 loose nobody knows, But if its .001 too tight EVERYBODY KNOWS!!
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Sat May 04, 2013 11:54 pm
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