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Old 07-14-2022, 05:29 PM
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Default Poly locks too long or rocker studs too long?

Poly Locks are hitting the valve covers I need a poly lock about 3/4" long does anyone make them? Or do I need to get a new set of rocker studs that are .300" shorter?

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Old 07-14-2022, 05:46 PM
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Default poly locks

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Originally Posted by Tim Corcoran View Post
Poly Locks are hitting the valve covers I need a poly lock about 3/4" long does anyone make them? Or do I need to get a new set of rocker studs that are .300" shorter?
spotts performance he sells on ebay. he has some that are supposed to fit under stock covers. he also has thicker gaskets you might just need those.

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Old 07-14-2022, 06:01 PM
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How deep is your set screw in the body now?

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Old 07-14-2022, 06:26 PM
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They list the length on Summit. I had the same problem & bought some that were shorter than what I had. Don’t remember which brand, Sorry

Murf

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Old 07-14-2022, 06:38 PM
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First you should just use a plain nut and some washers to adjust a intake and exh valve and confirm that at max lift of each that the rocker arm heel itself does not hit the valve cover.

This way if need be you can pick up thicker gaskets along with the needed length poly locks.

The other factor between stud length and poly lock length is that you want real close to 1/2” of thread engagement between the two!

You do not want the poly lock to dangle off of only 1/4”! Worth of threads.

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Old 07-14-2022, 06:48 PM
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What ever you find get the 5/16 thick gaskets.I know Butler sells them.Tom

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Old 07-14-2022, 07:42 PM
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Is your center lock Allen set sticking up above the body of the poly lock when the proper adjustment is made?

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Old 07-14-2022, 10:42 PM
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Crower has em in stock.

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Old 07-14-2022, 11:10 PM
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When adjusted the set screw is about .310" below the top of the nut. I don't think the 5/16 gaskets will get me enough clearance. If I had a lathe I would cut down all the studs about .310" and that would do it. I found some poly locks listed as short but no dimensions. I sent Paul Spotts a message from ebay asking the length of his short nuts :-). I am pretty sure the valve cover will clear the rocker arm. If I had a set of studs that were 1-5/8 long I think that would do it. I think the short poly locks and the 5/16 gaskets would do the trick.

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Old 07-14-2022, 11:35 PM
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i broke a rocker stud once that was too short. freaking scary.

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Old 07-15-2022, 12:22 AM
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I don’t think they make poly locks as short as 3/4”?

Anyway, you have to play around with both the stud height and the poly lock height. IIRC, the magic number is a minimum of five turns in on the set screw.

ARP has a bunch of different heights of each, all listed on their website. I ended up with ARP 300-8246 locks and ARP 334-7202 studs.

And if you really want to get neurotic about it you can try to find the right stud height, lock height, and also just the right thread length so that the rocker is only riding on solid metal and not the threads at all. Probably not going to matter with the strength of ARP hardware, but apparently rocker studs do snap sometimes.

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Old 07-15-2022, 12:34 AM
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I have the Paul Spotts poly locks and studs on my 68 #16 heads. Valve cover fits fine with the. standard gasket. Oil drippers do not however

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Old 07-15-2022, 02:30 AM
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Quote:
Originally Posted by Sun Tuned View Post
Crower has em in stock.
These are what Sun Tuned referenced:https://www.summitracing.com/parts/cro-86050s-16. Less than a quarter inch shorter, but enough to make a difference.

I can get large roller cam setups under the '67 and later chrome valve covers. It takes these polylocks, 1.75" stem length studs, Crower stainless Rockers, and 5/16" valve cover gaskets. You can skip the thicker gaskets on initial assembly and go with stock thickness, but will find out on about the 2nd tightening after about six months you will start getting some rocker to valve cover interference.

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Old 07-15-2022, 05:28 AM
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It can be challenging to get everything under stock covers but it can and will work if you have the correct components.

First you need to make sure that when set correctly you have at least five FULL turns with the locknuts. Anything less will not hold the strength of the parts.

You also have to make sure that the allen set screws are fully engaged in them.

The reason we run into so many issues these day is that many of the parts are non-standard. Heads, valve lengths, lifters, cam base circles, rocker arms, etc.

Not really a big deal you just have to take the steps to make things work. Sometimes you'll need to get longer studs or shim up the ones you have as well to get enough engagement with the locknuts. They make short ones, but I have a lathe here so can cut down the typical long varieties that show up with a lot of these aftermarket roller rocker arms.

Obtain the thick valve cover gaskets as well, I have a set here and they are listed for sale in "parts" on this Forum.

So the short version of events here is to establish correct geometry at the plunger depth you are looking for (hydraulic lifters). Obtain the correct length pushrods. Tighten down the locknuts where they are going to end up at. Make sure you have at least 5 full turns on them, see if the valve covers will fit. If you need to cut down the locknuts make sure you end up with clearance for the covers AND enough engagement with the set-screws at the same time. It's really not that complicated and once you come up with the correct length for the locknuts either cut them down or buy them.

I'll add here that even if you have a lathe they are very hard parts and difficult to cut down. I short-cut that deal by cutting them off with a high speed thin grinding wheel then facing them in the lathe afterwards. This reduces that operation to minutes........

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Old 07-15-2022, 07:42 AM
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Using crower Enduro rockers I had to machine down the nuts to barely clear the rocker and still had to double up the gaskets to get the valve train to clear the stock valve covers.
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Old 07-15-2022, 09:12 AM
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There are so many things different on my street 455 engine vs my 389 original engine,
I just install the tall valve covers and forget about it.

Tom V.

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Old 07-15-2022, 09:50 AM
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On a 7/16 -20 stud, 5 threads is 1/4". More than enough in my book .

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Old 07-15-2022, 04:48 PM
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I appreciate all the replies by the number of replies it seems a lot of people have had the same problem. Yes Tom tall valve covers are an option but since this is an AC car and it has a large PB booster it's not practical for this car. The valve train geometry has been checked and proper push rods have been installed. It's a mild hyd roller with Scorpion 1.65's and lift is .600 and the valves have been adjusted with 3/4 turn preload.
Current poly locks are 1.055 tall
Current studs are 1.915
Set screws are .300 below the top of the poly lock
Poly locks are engaged 7 turns with valve adjusted (3/4 turn preload)
Top of Poly lock is .400 above top of rocker arm at the pivot point

The Crower poly locks are .875 and that reduces my interference by .180. So maybe that plus 5/16 gasket will get me the clearance I need without messing with the studs.

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Old 07-15-2022, 04:57 PM
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Scorpion rocker arms are the tallest (and fattest) of just about any rocker arm. If you keep those you might be doomed.

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Old 07-15-2022, 05:07 PM
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It’s the bending / leverage forces applied to the top of the stud with only 1/4” of thread engagement that needs to be taken into consideration also especially when open spring forces exceeded 380 psi .

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