It wasn't a good sunday afternoon cruise. Im driving through town at 20mph about 3miles from my house and BANG. A rotational clunk as if the driveshaft is hitting the floor board but its not coming from the back its in the engine. I pull into the side street and shut it down. we open the hood and fire it up and the clunking sounds like its under the valve cover and quickly shut it off. After the flat bed took us home we pulled the valve covers and found the #8 exhaust rocker sitting in the head next to the #7 and the polylock also sitting there with maybe 3/8ths of the top of the rockerstud sitting inside it sheared off clean. It sheared off at the last thread of the poly lock. The pushrod must have been banging the inside top of the allum cover. I cant believe how loud it was. The titanium retainer has a small scratch on it, other wise everything looks ok. What could cause this its such a clean break? The pushrod looks straight and rolls nice on a flat table. Could that spring have coil bound causing this. The valve train is all new with titanium retainers and keepers and isky redzones and crane energizer roller rockers. Im thinking maybe I should replace all the studs with ARPs. Its the only part in the valvetrain I did not replace from the original bill mitchell build. Any thoughts on why and what to check or how to proceed.

Thanks Rich

Hi Rich,
Well,, that sucks :(
Kinda ruins the afternoon but glad it wasn't serious.
You have Dart heads correct?
Definitely check for coil bind, retainer to seal & also that the rocker has room for the nut at full lift.
What kind of lift & spring pressure? I would suggest running a stud girdle to help distribute the load also if you aren't.
How much of the rocker is on the unthreaded part or shank of the stud? I like at least 2/3rd's & preferably having the rocker almost completely supported by the unthreaded portion of the stud.
There are different ARP studs with differing amounts of shank below the thread & I try to use one that will get the rocker down on the shank even if it means removing a few threads inside the adjusting nut.
If you don't find any problems with bind or interference could be it was just a bum stud, it happens.
I would replace them all & if you are running much pressure I would also opt for something besides the energizer rockers with a roller. This is not what Crane had in mind for those "economy" rollers ;)

Also, if the "scratch" in the retainer is enough to feel, I would replace it or polish the scratch out. Titanium is very "notch sensitive"

Hey Mike,

Thanks for the quick reply, it certainly wasn't what I expected for a last cruise before tucking her away for the winter. It appears that a fair amount of the rocker mount is wrapped around the threaded portion of the stud. We are working with Mitchells Merlin alluminum heads, I believe they are the grumpy jenkins design. The rockers clear the retainers and theres more than a tenth of an inch of clearance in the coils. Im using the cast alluminum chevy valve covers the ones that say chevrolet across them, do you know if a stud girdle will fit in them? Im using the isky 9375plus springs with a 685 lift and the retainers are titanium iskys as well. Is there such thing as a lower profile girdle and what rocker and stud would you recommend? Thanks again Rich

Originally posted by 67ragtp:
Hey Mike,

Thanks for the quick reply, it certainly wasn't what I expected for a last cruise before tucking her away for the winter. It appears that a fair amount of the rocker mount is wrapped around the threaded portion of the stud. We are working with Mitchells Merlin alluminum heads, I believe they are the grumpy jenkins design. The rockers clear the retainers and theres more than a tenth of an inch of clearance in the coils. Im using the cast alluminum chevy valve covers the ones that say chevrolet across them, do you know if a stud girdle will fit in them? Im using the isky 9375plus springs with a 685 lift and the retainers are titanium iskys as well. Is there such thing as a lower profile girdle and what rocker and stud would you recommend? Thanks again Rich =
Hi Rich,
Probably those crappy Isky parts caused it :D
,,,,, I'd get ahold of the guy you got them from & see if they got a lifetime warrantee :D

Did you check the back side of the nut in the rocker slot at full lift?

Not sure about the covers but I would think a girdle would fit, how tall are they?
Aren't they like the Dart & brodix tall covers?

I like the Comp Pro Magnums or the Comp or Crower Stainless for rockers & ARP studs but I can't remember the number of the long ones. They might have the specs on their site. If not email me & I will look them up for you.
Measure the studs you have now from the guide plate to the tip & the thread length.

I second the use of a stud girdle. I broke #5 intake rocker stud and didn't know it till I went to check my valve adjustments a couple of months ago. The way the stud looked it was broken for awhile but the stud girdle held it in place. My cam is 690 lift 195/533 spring pressures and I also changed to the Comp Cams magnum roller rockers also. I purchased the Crane's like you have but didn't feel comfortable using them with this cam.

ARP does have there info online, I had to order the ones I needed after determining my correct pushrod length. I had to make sure the rocker stayed on the none threded part of the stud. Then get as much of the threded pat of the stud in the nut.
John

I would likely not use those Energizers with the pressures of a SR cam either. But has anyone ever had an Energizer failure?

Nevertheless, the full Crane Golds can be had for $230 at competitionproducts.

Busted off #7 ex rocker boss from the head. Although I bought a spare Energizer rocker, the one on #7 ex looked and felt fine.

Also had to use the 1.5" thread ARP long studs on the exhausts. No damage anywhere else.

Didn't have the pushrod whacking the cover since it was running a gentle-ramped Crane solid and not a 'slingshot' SR shooting the pushrod out the hole via accelerated ramps! That's kinda funny actually.

Hopefully it was just an abberation. TRIPLE check everything including your pushrod lengths.

Thanks for all the advice. The clearances all look good and the pushrod lengths as well, with the exception of the stud not being long enough.The lock nut was only grabing 3 threads. But the interesting thing is the threads were not pulled the thing was broken off clean and the set screw was still tight in the broken peice. I ordered new pro magnum rockers, pushrods,ARP pro series longer studs, and a girdle. Hopefully I will get some reliability out of the valve train. I will be double checking every thing again as I assemble it. I really do hope it was an abberation because there really isn't any clearance issues that I can find. Im praying this girdle fits in my covers because they were mighty expensive covers, Ive also come to the realization that I could build aanother BB with all the spare go fast goodies that are'nt heavy duty enough. Thanks for all the help you guys are great!

Rich

If you need some extra clearance for the valve covers and the girdle, Felpro has 5/16" thick valve cover gaskets. You could also glue a thinner gasket to the Felpro for extra clearance.

not having a stud girdle isnt the reason why that stud broke, if it snapped at the base of the stud, one might draw the conclusion that flexing caused it, but shearing the top of the stud is, in my opinion caused by not engaging enough threads.

Rich, what are your plans for the rest of the season?

My stud broke flush with the bottom of the adjuster nut. When I drilled out the stud to use an easyout there was about 1/2" of stud threaded inside the nut. I figured the last time I adjusted the valve I might have gave the wrench alittle extra tug to get the clearance closer rather than back out the allen screw, and put a strain on the stud.

Brian,

Ive been up to my eye balls building the G-maro, bought another 67 but its a coupe this time, my son and I just finished installing new floors. Its amazing how much rust is in these old cars when you start unpealing them. The subframe is complete, we were getting ready to tackle the mini tub kit from DSE but the funds were just spent on the valve train parts. Ive got to get the 540 running again before I put it away.

Rich

Brian,

Ive been up to my eye balls building the G-maro, bought another 67 but its a coupe this time, my son and I just finished installing new floors. Its amazing how much rust is in these old cars when you start unpealing them. The subframe is complete, we were getting ready to tackle the mini tub kit from DSE but the funds were just spent on the valve train parts. Ive got to get the 540 running again before I put it away.

Rich

had this happen with a sbc, only thing we found was a bad roller rocker. they were the cheapest crains with 50000 miles on them.

Originally posted by 67ragtp:
Brian,

Ive been up to my eye balls building the G-maro, bought another 67 but its a coupe this time, my son and I just finished installing new floors. Its amazing how much rust is in these old cars when you start unpealing them. The subframe is complete, we were getting ready to tackle the mini tub kit from DSE but the funds were just spent on the valve train parts. Ive got to get the 540 running again before I put it away.

Rich let me know if you need any help with the ethier car!

You did the right thing and ordered the long studs. That was your problem. I seen this same thing on a friends boat motor. I finely talked him into getting longer studs and that fixed the problem. That is just not enough threads to hold the pressure. I think you will be happy with the longer studs and rev kit. (girdle) It will make your valve train more accurate. Best of luck.

Rich ... valve cover clearance with GMPP BB cast valve covers and stud girdle .... if you have the covers like the ones that come on the 572 crate motors any stud girdle I know about wont clear ....just went thru that also dbl gasket no go, with Harland Sharp rockers and Howards stud girdle ( similar to Crane) I ended up getting the valve cover spacers from Stef's/B&B ... $94.00. Maybe with some grinding on the girdle etc it might work but I decided not worth the risk and my bolt in breather too close to the girdle ... the B&B spacers were better quality than expected
see my engine pic
Bill FWIW

I think you will be happy with the longer studs and rev kit. (girdle) It will make your valve train more accurate. Best of luck.

He had said he had ordered stud girdle. A rev kit, fits between the heads and the liftes. It will keep the lifter in the bore incase of rocker or pushrod failure with spring pressure. That way oil pressure will not be lost if lifter or lifters are pushed out of the hole.
John

Brian,

Thanks for the offer, I'll let you know if I have a problem.

Bill, Thanks for the info, I didnt think they were going to fit, BTW thats a great looking engine did you paint the covers or did you buy them orange. Mine are the same only alluminum in color. Where did you buy the b&b extenders?

Thanks Rich

Rich .... I had the valve covers and block powder coated orange and then powder coated clear .....but I now see you can buy them from GM powder coated orange ....... anyway the spacers I checked all over and best place to buy is call B&B, B&B was bot by Steff but you can call direct and I think they will ask if you want Steff's or B&B when you call I was expecting to pay 99.00 which I think was on their website others sell these same spacers under their own name for 129.00 ..... Bob said " racers net 94.00 plus shipping" , I had them same week smile.gif
If you using studs ( highly reccomend ).... call ARP direct they have all kinds of lengths they don't list ....I was not smart enough to ask to buy direct they gave me pn and told me to order thru my preferred dealer ( comp products for me)

But your right these covers not cheap I thought they would clear a girdle , so after Powder coating, spacers and studs haver a friggin fortune in valve covers , HTH Bill

Originally posted by ricks_67:
I figured the last time I adjusted the valve I might have gave the wrench alittle extra tug to get the clearance closer rather than back out the allen screw, and put a strain on the stud. :eek:

Man, I do it that way everytime, deliberately!

Last night I installed the new studs, the comp promagnums sit lower on the stud a good majority is on the shank instead of the threads. The locknuts engauge more than double the threads I had previously. The girdle sits high, I used one made by Doug Herbert performance, Which I might add gave me a great price on all the parts. Super nice people to deal with. One question I have is how much torque do I tighten the clamping bolts on the girdle? And the valve covers, Forget about it, I think I need 10foot tall covers! Really the B&B extenders will do the job- Thanks Bill.

Rich