G'day all
I've had a stumbling block with my new motor, I've done approx 250km so far but yesterday traveling to work I've broken the rocker stud on the no. 1 exhaust valve.
Now the question I have, the rockers in it use the 3/8" stud as apposed to the 7/16" stud. Have I exceeded the limits of the smaller stud or would it simply be that the studs were old and of unknown condition be more likely to have caused the issue.
The specs of the motor are:
Red 202 with black crank and rods
Crane 1.6:1 roller rockers
Solid Camshaft
Lift on exhaust valve : 0.528"
Duration at .050: 244
Total Duration: 282
Compression 10.4:1
Total valve spring pressure over the nose: 285lbs
Installed valve spring pressure: 135lbs
Please let me know if I need to provide more info
Thanks Peter
Roller Rocker stud size
Started by
Peter UC
, Jul 18 2012 08:08 PM
18 replies to this topic
#1
Peter UC
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Posted 18 July 2012 - 08:08 PM
#2
_Brad1979UC_
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Posted 18 July 2012 - 11:44 PM
Hey Peter looks like a decent combo your running now!
hey were they arp studs you screwed into it? Where did it snap? Afaik the 7/16 studs are the same at the top as the 3/8 stud, the bottom part that screws into the head is obviously larger. So I would say a break on top would be stud and a break below/stripped thread would be the thread limitation.
I've always used 7/16 studs with the 202 twice (in the torrie and then again on the boat) and the 333 in the torrie without a hassle, mainly because they needed to be milled and tapped anyway. If you want some insurance a set of /16 studs and head re-tap shouldn't cost much for a 202.
Though I am interested in what the limitation of a 3/8 stud actually is.
Cheers
hey were they arp studs you screwed into it? Where did it snap? Afaik the 7/16 studs are the same at the top as the 3/8 stud, the bottom part that screws into the head is obviously larger. So I would say a break on top would be stud and a break below/stripped thread would be the thread limitation.
I've always used 7/16 studs with the 202 twice (in the torrie and then again on the boat) and the 333 in the torrie without a hassle, mainly because they needed to be milled and tapped anyway. If you want some insurance a set of /16 studs and head re-tap shouldn't cost much for a 202.
Though I am interested in what the limitation of a 3/8 stud actually is.
Cheers
#3
warrenm
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Posted 19 July 2012 - 08:37 AM
A pic of the stud & the rocker might explain a bit more. You may have something running out of travel eg: coil bind, retainer hitting the guide, rocker touching the flared section of the stud etc.
3/8" studs are usually 3/8" on the rocker end & 7/16" on the end that screws into the head.
3/8" studs are usually 3/8" on the rocker end & 7/16" on the end that screws into the head.
#4
Peter UC
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Posted 19 July 2012 - 06:45 PM
I'll get a pic when I get a chance, the stud broke right at the end of the thread on the 3/8" stud, I doubt it would have been coil bind or something like that as it was all set up by the reconditioner but anything's possible, although if that were the case I would have expected the pushrod to bend first but it appears straight.
And warren is correct, the stud has a 7/16" UNC into the head and a 3/8" UNF to the rocker.
And warren is correct, the stud has a 7/16" UNC into the head and a 3/8" UNF to the rocker.
#5
_Mint_
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Posted 19 July 2012 - 07:38 PM
this happened to my 253 once 3/8" studs broke half way to Adelaide (250 kays) turned out to be poor rocker arm alinement to valve stem tip
the rocker(not roller rockers) Ford Windsor v8 ones flopped over on the side and aventually broke the stud
so check alinement of the roller action over the tip of the valve
the rocker(not roller rockers) Ford Windsor v8 ones flopped over on the side and aventually broke the stud
so check alinement of the roller action over the tip of the valve
#6
Peter UC
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Posted 19 July 2012 - 09:48 PM
I have checked the alignment of the rockers when the inner springs went in and they were in the middle of the valve, as expected.
Pictures attached
Pictures attached
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Stud No1.jpg 121.85K
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Stud No2.jpg 92.66K
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#7
LXCHEV
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Posted 19 July 2012 - 10:35 PM
Just curious to know, as Brad said - are they ARP studs?
#8
_qiksix_
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Posted 19 July 2012 - 11:14 PM
Hi Peter those widebody rockers aren't hitting the corners of the rockers covers, studs don't look like arp's they look 2 peice ones. There's clearance between retainer and underside of rocker ? We still run the std pinned posts with no probs.
#9
Peter UC
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Posted 19 July 2012 - 11:26 PM
Not sure, they were on the head when I bought it for the old 173 about 7 years ago. I suppose what I need to know is if I buy a new set of 3/8 studs, double check to make sure the geometry is fine and not fouling on anything, am I likely to have the same problem again or are the 3/8" studs strong enough.
Edited by Peter UC, 19 July 2012 - 11:28 PM.
#10
_ljxu1torana_
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Posted 19 July 2012 - 11:39 PM
my 186 turbo done the same thing broke a arp rocker stud. as the bottom of the rocker was bottoming out.i took of the guide plates and this solved the problem.I have checked the alignment of the rockers when the inner springs went in and they were in the middle of the valve, as expected.
Pictures attached
#11
warrenm
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Posted 20 July 2012 - 07:43 AM
They don't appear to be ARP studs, unless the "bell" section on the stud has been machined off, should have ARP on the end of the stud. 3/8" studs should be good enough, unless your running the motor at 6000+ revs for the short distance that you have driven. If you step up to 7/16" studs, you'll also need to fit 7/16" rockers.
At full lift you need to have clearance of about .060" between the retainer & valve guide.
At full lift you need to have clearance of about .060" between the retainer & valve guide.
#12
_qiksix_
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Posted 20 July 2012 - 06:32 PM
agree warrenm 3/8 should be enough, we still run the 3/8 posts
when checking rocker geometry the roller wont be centre, at zero lift the rocker should start on sparkplug side then cross centre to the in/ex side at full lift, if not you need different lenght pushrods but most 6 bangers are close anyways. check the yella terra site i think diagram's on there.
i just realised you have 1.6 rockers make sure you double check all clearances; retainer to rocker at all lifts, rocker to stud at all lifts, retainer to guide(rotate to full lift and see if you can get anymore by levering the rocker or have a good visual)
one other thing to check i've never come across on a 6 banger is pushrod ball to rocker cup, sbc pushrods have a 120* ball end for high lifts.
when checking rocker geometry the roller wont be centre, at zero lift the rocker should start on sparkplug side then cross centre to the in/ex side at full lift, if not you need different lenght pushrods but most 6 bangers are close anyways. check the yella terra site i think diagram's on there.
i just realised you have 1.6 rockers make sure you double check all clearances; retainer to rocker at all lifts, rocker to stud at all lifts, retainer to guide(rotate to full lift and see if you can get anymore by levering the rocker or have a good visual)
one other thing to check i've never come across on a 6 banger is pushrod ball to rocker cup, sbc pushrods have a 120* ball end for high lifts.
#13
greens nice
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Posted 20 July 2012 - 06:38 PM
looks like it's been overtightened.
Edited by greens nice, 20 July 2012 - 06:38 PM.
#14
greens nice
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Posted 20 July 2012 - 06:41 PM
i took of the guide plates and this solved the problem.
sorry jason but you really need to stop saying this over the net without explaining yourself, some bloke without a clue might go and rip the guideplates off and wala, rocker is now pushing down on the retainer, bang and engine drops a valve.
im assuming this head had the broached pushrod holes?
#15
Peter UC
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Posted 20 July 2012 - 07:29 PM
I have remembered a piece of information that I reckon is important, back when I first installed that head 7 years ago on the old motor, I didn't realise the the nuts had the grub screw in the middle and to adjust them I just kept tightening the nut. I did actually sheared one of the studs doing this, I replaced it, realised my mistake and adjusted the rockers properly and it has been fine since. Until I put a lot more revs and spring pressure on the studs. I think the stud was damaged when I broke the other stud and hence caused the failure, therefore I will buy a new set of studs, check everything and not worry about the stud size.
Thanks for your help fellas
Thanks for your help fellas
#16
_ljxu1torana_
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Posted 22 July 2012 - 01:22 AM
well kevin, i am saying is that removing my guide plates worked for me.this is only a suggestion.sorry jason but you really need to stop saying this over the net without explaining yourself, some bloke without a clue might go and rip the guideplates off and wala, rocker is now pushing down on the retainer, bang and engine drops a valve.
im assuming this head had the broached pushrod holes?
#17
_oldjohnno_
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Posted 22 July 2012 - 06:56 AM
Jason, if you're going to suggest to anyone that they remove their guideplates you must make it very clear that you first have to make sure that the head has the narrow slotted pushrod openings, not the round holes that the later heads have.
As Kevin said, a 202 novice could easily trash his engine if he wasn't aware that some head/rocker combinations must have guideplates fitted. What worked for you could be disastrous for someone else.
As Kevin said, a 202 novice could easily trash his engine if he wasn't aware that some head/rocker combinations must have guideplates fitted. What worked for you could be disastrous for someone else.
#18
_ljxu1torana_
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Posted 22 July 2012 - 06:01 PM
exactley right.Jason, if you're going to suggest to anyone that they remove their guideplates you must make it very clear that you first have to make sure that the head has the narrow slotted pushrod openings, not the round holes that the later heads have.
As Kevin said, a 202 novice could easily trash his engine if he wasn't aware that some head/rocker combinations must have guideplates fitted. What worked for you could be disastrous for someone else.
#19
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Posted 05 September 2012 - 09:35 AM
I'm using 1.6 rollers too, 3/8 ARP studs, with slotted (YT) head holes. Summit Racing Chev rockers. I have found (and remedied) the pushrods foul on the back of the rocker, where you can't see it till you take one off. Maybe the rocker is being pushed over, putting strain on the stud? My cam isn't quite as big as yours though - Wade 373.
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