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Old 05-08-2020, 01:07 PM
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Default Poly locks on a non-race engine 326 HO

I have a 66 LeMans 326 HO with a 4 Speed that I like to go to cruise ins and small trips. I have been having trouble adjusting the valves correctly and having the rocker nuts loosen up I decided replace the cam, 2 worn lobes due to incorrect adjustments. I also purchased some poly locks I realize that the splash shields can't be used and valve cover gaskets will need building up.

I have the 7/16" rocker stud that's turned down to 3/8" . The poly locks that I bought are threaded all the way to the end What I need are poly locks that not threaded the last 3/16" so that they will fit OVER the 7/16" stud. Is there a manufacturer that makes these or do I need to turn them down myself?

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Old 05-08-2020, 02:27 PM
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https://www.summitracing.com/parts/m...oaAngBEALw_wcB The Mr Gasket ones are open at the bottom and will clear the 7/6 part of the stud or you can use 3/8 sbc chevy stock crimp nuts.

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Old 05-08-2020, 03:26 PM
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FWIW, The old Speedpro kits used to come with narrow 7/16 inch washers to put between the rocker nut, (Polyloks in your case) and the pivot ball to make the Pontiac valve train adjustable. The washer spaced the adjusting nut higher on the stud so you could still adjust the assembly without interference from the step on the factory bottle neck rocker studs using either the chevy crimp nuts, or a Polylok.

Before Speedpro offered the narrowed washers, I would put 8 at a time standard flat washers on a 7/16 inch bolt and grind the outside OD down on a bench grinder so it fit within the stamped rocker arms. I did that for years before the narrow washers became available. At that time almost all the older Pontiac heads used pressed in studs, so it was before 1967 and later, when the switch was made to screw in studs on many of the 4bbl/performance heads.

I wasn't particularly fond of using the chevy crimp nuts because they just didn't hold the adjustment well, and was happy with the invention of the Polyloks, that never varied after they were set initially.

Some of the Polyloks had a step machined on the inside so they could be used on Pontiac bottle neck studs, and some didn't. You needed to look for that feature when purchasing them, but you could use washers if you couldn't get the correct style nut. Sometimes the local speedshop only had the type without the step cut into the ID necessitating the washers.

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Old 05-08-2020, 03:59 PM
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Quote:
Originally Posted by arbys View Post
I have a 66 LeMans 326 HO with a 4 Speed that I like to go to cruise ins and small trips. I have been having trouble adjusting the valves correctly and having the rocker nuts loosen up I decided replace the cam, 2 worn lobes due to incorrect adjustments. I also purchased some poly locks I realize that the splash shields can't be used and valve cover gaskets will need building up.

I have the 7/16" rocker stud that's turned down to 3/8" . The poly locks that I bought are threaded all the way to the end What I need are poly locks that not threaded the last 3/16" so that they will fit OVER the 7/16" stud. Is there a manufacturer that makes these or do I need to turn them down myself?
Are they pressed in? I would replace them to the 7/16th ARP studs and get the Crower poly locks as they will fit under a stock valve cover. Ive had one break. Not fun...

Studs:
https://www.summitracing.com/parts/a...1/make/pontiac

Locks:
https://www.summitracing.com/parts/cro-86050-16
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Old 05-08-2020, 05:41 PM
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Quote:
Originally Posted by 1967Tempest View Post
Are they pressed in? I would replace them to the 7/16th ARP studs and get the Crower poly locks as they will fit under a stock valve cover. Ive had one break. Not fun...

Studs:
https://www.summitracing.com/parts/a...1/make/pontiac

Locks:
https://www.summitracing.com/parts/cro-86050-16
If I was rebuilding the engine and pulling the heads that would be an option. Not now.

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Old 05-08-2020, 06:49 PM
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I've had good success with the Comp Magnum Rocker kit on my 350P. Just be advised, the jam nuts are only good for a couple of adjustments. Provided you didn't get too aggressive with your replacement cam, it should work fine in a mild 326.

https://www.summitracing.com/parts/c...6/make/pontiac

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Old 05-08-2020, 07:45 PM
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A factory Pontiac performance cam will not require an adjustable valvetrain.

Simply torque down the factory rocker nuts to 20 ft lb and you’re good, no valve adjustment necessary.

If you’ve been trying to adjust your valves using the stock rocker nuts stop doing that, they were never intended to be used that way. Torque them down and you’re good.

Putting a non-factory cam in your 326 HO is like opening a can of worms. The press-in studs are problematic when used with cams other than stock. The factory rocker nuts add support at the weakest part of the bottleneck stud.

Seriously consider a factory grind like the 066 or perhaps the 068, it will make for a simpler and less expensive installation and save you some headaches.

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Old 05-08-2020, 09:29 PM
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Quote:
Originally Posted by b-man View Post
A factory Pontiac performance cam will not require an adjustable valvetrain.

Simply torque down the factory rocker nuts to 20 ft lb and you’re good, no valve adjustment necessary.

If you’ve been trying to adjust your valves using the stock rocker nuts stop doing that, they were never intended to be used that way. Torque them down and you’re good.

Putting a non-factory cam in your 326 HO is like opening a can of worms. The press-in studs are problematic when used with cams other than stock. The factory rocker nuts add support at the weakest part of the bottleneck stud.

Seriously consider a factory grind like the 066 or perhaps the 068, it will make for a simpler and less expensive installation and save you some headaches.
Fair points. IIRC, the 066 is what the 326HO came with from the factory. No need to mess with anything else provided it's still stock.

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Old 05-08-2020, 09:55 PM
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The 066 would be a step up from what the 326 HO originally came with. The 066 was the auto trans 1968 350 HO cam, 067 for manual trans. The 066 is a nice upgrade for any 326 I’d say.

All 326 engines came with the 254 cam, 326 HO engines didn’t receive an upgraded cam. High compression heads, a 4-barrel carb and dual exhaust added the extra 35hp over the base 2-barrel 250hp in 1966.

An aftermarket cam is best accompanied by upgraded or at least new valve springs, screw-in 7/16” studs and polylocks. All of this comes with added labor and parts costs in order to end up with a reliable engine.

If you’re keeping the valve springs you have now and the press-in studs I’d leave the stock valvetrain alone and run the 066 cam. The 068 is also a good option but it really will be asking for new valve springs, the 066 would like them too but if you’re not changing springs I’d opt for the 066.

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Old 05-08-2020, 10:52 PM
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Not a 326 but a 1975 350. I had a 'ticker' and tried to cure it by tightening the nut. After that, it lost it's locking function and kept backing off. I replaced all of them with 3/8 polylocks with no subsequent problems.

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Old 05-09-2020, 07:46 AM
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I'm with B-man, go with a 066, not sure if it'll work with the stock Pontiac nuts but I have put chevy style jam nuts in a vice and squeezed them and they regained they're crimp action, also heard of guys just wacking them with a hammer.

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Old 05-09-2020, 01:37 PM
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Quote:
Originally Posted by arbys View Post
If I was rebuilding the engine and pulling the heads that would be an option. Not now.
Crower also makes those jam nuts in 3/8ths and it does have the non-threaded shoulder that you are looking for.

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