[steve25]

Be sure to check for a busted inner spring .

[Baba O'Riley]

Thanks to all of you for your expert help on this last month. To recap, the same rocker on my '71 400 with #96 heads -- the rear rocker for cylinder #6 -- came loose before I got motor long-block rebuilt and now it's thrown it again. Both times, it gave out when I 'stepped on it' to hit the freeway. This time it banana'd the pushrod for that rocker and bent the guide plate in that spot. Primary suspect, as you guys told me, is a bad stock stud that wasn't changed in the rebuild as it should've been, that'd explain it happening twice in the same spot.

I'm following your advice to switch to ARP studs and their Perma-Loc rocker nuts, then get the valve lash checked / corrected. I need a set of these fasteners that let me use my stock valve covers, rockers, and ball hardware with no clearance issues. (I'm okay with losing the oil drippers if they don't fit with this new ARP hardware.)

The original studs are about 2-1/2" long, with the bottom thread that goes into the head about 3/4" long, a 7/16" bolt with a 14 thread. The top of the stud holding the nut is 3/8" / 24 thread that ends 3/4" down from the top of the stud. So the stock stud has an "effective length" (height once installed) of 1-3/4" from the head surface. I want the replacement ARP studs to be about the same height because I absolutely want to keep the original valve covers -- none of those tacky aftermarket VCs.

Existing studs reach 1-1/2" above where the valve cover seats onto the head; there’s 2-3/8" clearance from this valve cover base to its center top. That 2-3/8" minus 1-1/2" means there’s about an extra 7/8" to play with.

So I'm thinking of using these ARP 100-7101 studs. Same screw-in length as the originals (3/4"), .150" taller installed. For the 7/16" nuts, ARP's 300-8242 -- these are made specifically for stamped steel rockers. At 1.2" tall they'll add a bit to the overall height but should fit under the valve cover.

Am I missing something, or should this do it? Thanks again to all of you for your expertise.

[Green Elephant]

You’ll have a little bit of the poly lock nut sticking above the top of the stud, whatever the length of the locking screw is. But I doubt that will be more than 3/8” to 1/2”.
If your measurements are correct you should be good to go. But if did have some contact you could always run a thin valve cover spacer and two gaskets. One on the top and one on the bottom of the spacer.

[b-man]

https://forums.maxperformanceinc.com...39&postcount=4

https://forums.maxperformanceinc.com...21&postcount=2

A couple of posts saying to use the shorter 134-7103 for stock valvetrain.

I used the 100-7101 on my 421 with Crower roller rockers. Perhaps they’ll also work for you as well, I’m using stock valve covers with a thicker 5/16” gasket for polylock clearance.

[Baba O'Riley]

Originally Posted by b-man

A couple of posts saying to use the shorter 134-7103 for stock valvetrain.

Okay, I'll go with those. Virtually identical length as the stock studs at 2.45", slightly less screw-in depth (.70, not .75) but put in with moly or Loctite they should sit firm enough. Rocker nuts will be the 300-8242's.

What is the specific moly product ARP recommends for rocker studs? I'm not seeing anything on their site.

[steve25]

All that's needed is a light coat of oil ( no drips ) and 55 ft lbs .

[chuckies76ta]

So I'm thinking of using these ARP 100-7101 studs. Same screw-in length as the originals (3/4"), .150" taller installed. For the 7/16" nuts, ARP's 300-8242 -- these are made specifically for stamped steel rockers. At 1.2" tall they'll add a bit to the overall height but should fit under the valve cover.

Am I missing something, or should this do it? Thanks again to all of you for your expertise.

While your at it why don't you get yourself a nice set of Harland Sharpe roller rockers to compliment your adjustable valve train. Making sure you check your pushrod length and pattern on valve stem. Also as mentioned have you checked the cam and lifters for any wear? Steve mentioned checking the inner springs for any breakage. None of my business, but you seem more concerned with valve cover fit than making sure your valve train is correct.
What is the specific moly product ARP recommends for rocker studs? I'm not seeing anything on their site
Arp assembly lube. https://www.summitracing.com/parts/a...09?seid=srese1

[steve25]

Yes they will work with the stock rockers , but the added height and or the added height with the poly locks might not allow you to run the stock rocker arm baffle if you where still doing such so look at that carefully.

If need be you might get away with adding a washer under the stands of the baffle.

Also the way you adjust these polylocks
Is to make your adjustment with the outside nut .

Then back it off a bit less then 1/4 turn.

Then tighten down the center Allen set.

Then tighten the outer nut back up that little bit you spun it back from.

[400 Lemans]

https://www.ebay.com/itm/27671167420...QAAOSwll1WxeKc Good stock length from Spotts.

[Baba O'Riley]

While your at it why don't you get yourself a nice set of Harland Sharpe roller rockers to compliment your adjustable valve train. Making sure you check your pushrod length and pattern on valve stem. Also as mentioned have you checked the cam and lifters for any wear? Steve mentioned checking the inner springs for any breakage.

The cam / lifters / springs are under 1K miles old, so I'm going to start with the studs and rockers and take it from there. That ancient stud that holds that #6 rocker, when I pull it (praying as I do that it doesn't break in the head) I'll check it for cracks etc.

For roller rockers on #96 heads and a '71 YS block, what's the ratio you guys would go with -- 1.52, or 1.65?

[b-man]

Stay with 1.5:1 rockers. The 1.65:1 rockers in most instances require grinding clearance for the pushrods.

The only 1.52:1 rockers are those crappy roller tip rockers from Comp Cams and you should steer clear of those.

Nothing wrong with stock stamped rockers that last almost forever.

You never mentioned what cam you have in your engine so that’s something to consider when choosing rockers. If it’s truly just a stock rebuild it probably has the 066 cam in it or possibly the 068.

[Baba O'Riley]

Stay with 1.5:1 rockers. The 1.65:1 rockers in most instances require grinding clearance for the pushrods.

The only 1.52:1 rockers are those crappy roller tip rockers from Comp Cams and you should steer clear of those.

Okay, thanks. PRW sells 1.52's as well for their stainless and aluminum RR's, that's why I asked.

[b-man]

PRW sells junk.

Good aftermarket aluminum and stainless rockers are in the $350 to $600+ price range.

Stock cam and stock rockers will be fine.

[Baba O'Riley]

Stock cam and stock rockers will be fine.

All right, if I stay with those, one question. The 7/16" ARP studs are slightly bigger than the 3/8" stock ones -- will the original rocker balls work okay?

[b-man]

The bottleneck factory studs are 7/16” where the rocker balls reside.

The top of the studs are 3/8” as well as the nuts but that doesn’t affect where the rockers fit.

No issues, direct interchange.

[Baba O'Riley]

Oh, of course, they fit on the shank of the bolt. Got it.

Thank you to everyone for your help on this, and have a great wrench-y weekend.

[steve25]

In terms of factory motors once 1971 came around only the 455s could be had with the 068 came.

It was never used again in a 400..
This tells you a good amount about 400 motors in vehicles with less then 3:23 rear gears which was the norm by then, and especially if you had AC.

The use of the 067 cam in 400s stopped in 76.

[Formulas]

Soooo EXACTLY what is the defect of the original stud again?

[HWYSTR455]

Yeah, threaded means they aren't pressed-in studs, so there must be something else going on. (maybe I didn't read the whole thread correctly?)

As I recall, the 'standard' BBC studs are a hair too long and the stud flange doesn't meet the surface entirely, or that's what I recall. There is a specific stud you must use, or is that only for conversions?

Not sure if a pushrod will bend when a rocker is too loose, that sounds like something else is going on, like coil bind, rocker/retainer/pushrod hole clearance, guide plate interference, incorrect adjustment, etc.

EDIT: You are using poly locks correct?

.

[78w72]

Originally Posted by Baba O'Riley

Stay with 1.5:1 rockers. The 1.65:1 rockers in most instances require grinding clearance for the pushrods.

The only 1.52:1 rockers are those crappy roller tip rockers from Comp Cams and you should steer clear of those.

Okay, thanks. PRW sells 1.52's as well for their stainless and aluminum RR's, that's why I asked.

Just an FYI based on my experience with the 1.52 Comp roller tip rockers as well as a few friends I know that use them on other engines... they are definitely not "crappy", I have been using a set for 30+ years on 2 different engines with cams that are bigger lift & heavier springs than stock, there are no signs of any of the problems that have been mentioned... no blue color from heat, no problems with the grooved balls or roller tips, nothing at all in 30+ years of very hard use & countless 5500-6000 rpms runs, more abuse than most average street engines will see.

Ive read a few posts about some guys not liking them, but just like anything there are a small percentage of problems with almost any aftermarket part, even heard of H/S rockers having issues & needing to be rebuilt, no way to know how those rockers were treated to have problems, but for mine & others I know of they are quality parts that have worked great under abuse for over 3 decades.

I have another set I bought used on a stock cam pontiac engine for 15+ years, those also had/have no signs of any problems at all, these are all set up with adjustable lock nuts, proper lash & good geometry. If you want to use them dont let a handful of bad comments steer you away when theres probably 100k or more of them in use for decades working perfectly fine.