# Please Recommend 1966 Rocker Nut Type



## peahrens (Jun 7, 2010)

Hi, I'm going to replace the valve cover gaskets and want to replace the old rocker arm nuts while I'm at it. I have 1966 "093" heads, 1.5 ratio Crane steel rockers. Can you advise what size studs I've got, what type nut I should buy. Do the fancier nuts (polylock, etc) pose clearance issues with the standard (repro) valve covers. Valve lift is 0.497". Thanks.


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## Mr. P-Body (Jan 20, 2011)

Is there a "problem" with the old ones? Are the Crane rockers "replacement" or those roller-tipped ones? Or "real" rollers?

The studs are 7/16" dia. below the "bottleneck". The bottleneck threads are 3/8-24. 

"Short" poly-locks will fit under stock covers. "Tall" ones may or may not, can't say for sure. 

You HAVE replaced the springs to the correct ones, right? The stock springs won't support lift beyond .470". 

Jim


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## peahrens (Jun 7, 2010)

Thanks for the tips (again). The rockers are Crane stamped steel, similar to OEM. A buddy (who used to run a machine shop) suggested that the rocker nuts might or might not hold their setting since they are used (and the studs of course likewise). Since I'm going to change the neoprene valve cover gaskets because of a small leak (got the 3/16" FelPro cork/rubber) we discussed adding new nuts as a minimum, so I asked about the positive locking type vs OEM type. I talked to Crane and they gave me the height of the "KoolNuts" (1-11/64") for the 3/8"-24 (including bottleneck) studs. I removed the leaky valve cover and made some measurements and it looks like these should give at least 3/8" clearance from top of the nut (atop the rocker ball) to the inside of the cover. There are some Mr Gasket locking nuts available, but (a) I was unable to determine for sure which might be for the 1966 heads (maybe #920G), and (b) I could not find a height dimension. So, I ordered the Crane locking nuts ($66) as I don't want to contend with the potential of changing valve geometry (noise, etc).

I did confirm that the springs we put on the "093" heads are not stock. They were likely new when the bare heads I acquired were set up in 1993. I just don't have a record on which specific spring was installed. I seem to remember discussing everything (cam choice, etc) with the Odessa TX machine shop guy and I know I had to order the (stamped steel Crane) replacement rockers, but I think the shop had available the right springs and nuts. Not 100% on that, but it's likely. I borrowed a Moroso seat pressure gauge from my current mechanic and the seat pressure is 95-100 lbs (best I can read it). I asked Crane today what springs they would supply for the cam I have, and the spec he quoted is 93 lbs seat pressure. 

It will be a few weeks before the various chores occur...currently waiting on various parts.


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## Mr. P-Body (Jan 20, 2011)

RED FLAG!!!

Crane has been notorious for supplying "single" springs for the Pontiac. They are known to fail. The "flat" coil inside is not a "spring", it's a "damper". If there are no additional coils inside the damper, replace the springs. 

Less than 110 lbs. at the seat is not enough for a Pontiac, either. 

If the rockers are "stock replacment" (regardless of brand), and you still have the bottle-neck studs and original nuts, torque them to 20 lbs. If using the "crimp" nuts ala Chevy small block, yes, replace them with poly-locks.

Jim


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## peahrens (Jun 7, 2010)

Jim, I don't know what brand springs I have. I have a cover off, so I'll describe what I see. The top holder for the springs is pretty flat (unlike the cup I see in the shop manual). The outer spring looks pretty typical. Inside I see some kind of gizmo that has a brass looking cup or two, maybe with something in the middle, including a small green disc or two that might be sliders or seals. It's tough to see what's what with the outer spring in the way! I can take a photo and attach if someone can advise how to do so. I'd like to determine if these are the Crane springs...if so I take it you would go to the trouble of changing them on the car (what do you think the failure rate is...1 in "x, to help with the decision? And who would you suggest I look to for spring suggestion for a specific Crane ca...Summit, my machine shop, etc.

Meanwhile, I'll search how to upload a photo (not sure I can get a pic that shows the iiinerds.

Thanks.


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## peahrens (Jun 7, 2010)

I hope to add 3 spring photos here (fingers crossed):


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## BearGFR (Aug 25, 2008)

peahrens said:


> I hope to add 3 spring photos here...


All I'm seeing is an outer spring and an inner damper (the one with the "flat" material) if there's not another coil in side that "flat" stuff, then you've got single springs like what Jim warned about.

Bear


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## 66tempestGT (Nov 28, 2009)

:agree


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## peahrens (Jun 7, 2010)

For clarity, is the issue limited to Crane single springs or any brand single spring? If helpful, I wonder if the machine shop guy can identify the brand on the car, if that matters. Is spring failure potential influenced by racing or not, or would moderate use still have considerable risk? 

And if I should change to double springs, who do you suggest I consult on the right spring set for the specifics of my Crane cam, Sealed Power (hyd) lifters and Crane steel 1.5 rockers? Options include the machine shop guy, Summit, etc.


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## pontiac (Mar 6, 2011)

poly locks will not stay tight on stock bottleneck studs unless the top of the stud is machined flat so the lock screw has a good flat contact area to hold against.


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## peahrens (Jun 7, 2010)

Thanks for the pointer on the polylocks...indeed, there's a little bump at the center of the top of each stud that could be a lousy spot for the allen screw to tighten.

I think I may visit with the machine shop guy tomorrow and get some much needed education. I found the specs on the Crane springs (that MAY be what I have) recommended for the new Crane #283801 cam installed (the specs say 110# but that may not be true on my heads) and we can measure the seat pressure together to confirm where we are re: the 100# seat pressure he recommended (based on 0.494" valve lift) and 110# by Jim. I think we'll conclude we're below that requiirement. I want to talk to him about replacement springs and whether that can be done on the car (using the tools recommended before) by substituting new parts or whether machining is required. I've got a prior Comp Cams recommendation for a cam (similar ballpark as the Crane installed) and the appropriate Comp Cams dual springs (#995-16), steel retainers (#740-16), locks (#611-16). The footnotes are not clear to me;. e.g., potential machining of the heads for the spring (vs. stock). That may have been done in 1992 for the current springs. The Comp Cam springs are 1.437" OD and the recommended Crane (if that's what's there) are 1.46" OD. I would hope I can use those Comp Cam parts with the installed Crane cam and steel 1.5 ratio rockers. I can get supervision on handling the parts replacement, but the potential weak area I see is getting appropriate parts and ensuring that they are compatible with how the heads are currently machined.

BTW, what about open spring pressure? I presume the open pressure is nominally the seated pressure, plus the lift times spring rate. That calculates to 110 plus (402 x 0.494") = 309#, Is that ok? I presume too high is bad for flat tappet hydraulic cam/lifters. And any potential issue about the Comp Cam retainers and locks (e.g., 10-degrees vs 7-degrees)? Will they be compatible with my valve tips, etc? This is beyond my expertise so your advise can be crucial.

Bottom line, if I can change the springs w/o removing the heads and be sure I have appropriate (i.e., not bad choices) parts specified, I think I know what decision to make. 

Hope this is not all covered by old threads that I haven't found...I don't want to be a bother. Thanks


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## Mr. P-Body (Jan 20, 2011)

Agreed about the studs. Have the tips "parallel ground". Any automotive machine shop can do it on their valve grinder ("butt" side). 

Those ARE the Crane springs I warn about. No. Nobody besides Crane makes "single" springs "for the Pontiac". Pontiac used dual springs from "Day 1". Comp, Howard's, Norris, PAC, all make very good valve springs. You must measure the "installed height" and use what spring matches the cam type and IH. If you get me the IH dimension, I can point you to the rght ones.


Jim


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## peahrens (Jun 7, 2010)

Hi again. Went by the machine shop today and we measured seat pressure with the Moroso and a movement gage...only 88lbs! The shop owner also measured the installed height at 1.600", which I clarified to be the spring only (not including the top retainer nor a 0.060" shim underneath). 

He said the preferred Comp springs 995-16 would need machining 0.100" from the heads (which I would love NOT to remove). A Comp spring 988-16 that could be installed w/o machining would be ok on seat pressure (117#) but only 235# open pressure, so he did not recommend that. 

He also said to be sure any dual spring has an ID that is ok for the valve seal arrangement. Jim, can you point me to any springs that I could install in this case w/o removing heads for machining? And, what open pressure range should I be shooting for (just curious)?


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## Mr. P-Body (Jan 20, 2011)

Competition Products 98341. 105 @ 1.625", coil bind at .915". At 1.600", this will yield right at 115 "seat pressure". Nowhere near "bind".

Jim


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