For a faily hefty solid roller cam (260/268@.050 and .685 lift), is a stud girdle really needed? The machine shop said I should install one, but the racers I know say that its not really needed. This motor going to see a lot of street miles. :D

Originally posted by 68SS454:
For a faily hefty solid roller cam (260/268@.050 and .685 lift), is a stud girdle really needed? The machine shop said I should install one, but the racers I know say that its not really needed. This motor going to see a lot of street miles. :D =
Is it necessary, no

Should you run one, Yes it is a very good idea

Many racers dont see the need for one, but at least for many drag racers they dont run their cars alot in terms of miles or running time... vs a street engine.A dual purpose type engine with a cam of that magnatude will see different type of stress than a drag race only engine would. I have used them on much much mildier flat tappet engines and would not hesitate to use a good stud girdle like a Crane unit if I had an engine like yours.

Not to hijack this thread but what is the purpose of a stud girdle?

I would run one. My old motor had a cam like yours with 500 pounds on the nose, with ARP studs, when bumping the starter over adjusting the valves, you could see the whole stud flexing during the last portion of the lift. I didn't run the girdles until I saw that, then ordered a set that day. I couldn't believe how much flex it had, and the motor had been 7500+ rpm many times like that. I believe Comp recommends anything over 350 lbs should have a girdle.

A rocker stud is subjected to quite a deal of stress...you have the rocker are captured around the stud and you have the cam trying to open and close the valve against the valve spring pressure.... Well the stud can flex....

As an example way back in 1955 when the 265 first came out many people were trying to figure this new SBC out.... Frank McGurk was trying to figure out why his 265 would go to 5700 RPM and stop...wouldnt go to 5800 RPM...... He suspected something wasnt quite right with this new rocker stud assembly that Chevy was useing.... So he placeed dial indicators at the sides of several rocker arms and the engine was turned over by hand and he measured that the rockers were deflecting as much as .008 laterally.... He also placed dial indicators on the rocker studs and found them to wobble in any direction as much as .012 !...... All this with a .375 in lift mech lifter cam useing stock springs with 75 lbs on the seat and 150 lbs open.....this of course with the stock press in studs......This info came from an article written by Racer Brown in 1955.

Since those days nearly every componut involved has been improved drastically ... but even with really great parts big lobe cams and heavy valve springs can still cause the valve train to flex and move.... A stud girdle
" Ties " all the studs together with stiff bars bolted together and increases the stiffness of the studs and helps prevent the studs from flexing.The girdles also act as a clamp on the adjusting nut and they tend to keep the valve lash in adjustment longer.

Whenever you talk with any sportsman racers at the drags it is much like getting info on the internet - beware that most in either group are non-professional engine builders/racers.

Junkyard, a stud girdle should actually be called a rocker arm adjusting nut girdle - because the way it works is to clamp all the (extra long for the girdle) rocker arm adjusting nuts together. In theory tieing them all together stops unwanted stud deflection due to high spring pressures. With the solid roller that 68SS454 is running the spring pressures should be on the hefty side.

No matter what you may think about stud deflection under pressure, there is one reason why I strongly like a stud girdle for this street/strip application: as an extra lock for the rocker arm nut adjustment. In the past I have had street solid rollers without a stud girdle that would sporadically loosen up a rocker or two. Sometimes even the best locking rocker arm nut can work loose. With a stud girdle, the girdle itself also serves as a secondary lock for the rocker arm nuts.

Just make sure you install it correctly - I have seen big block girdles installed COMPLETELY wrong. Some big block girdles allow you to install them at different heights on the extra long rocker arm nuts. Typically, you want to install a big block girdle at the lowest height that leaves ample rocker arm clearance (say ~ .100"). I have seen a big block girdle mounted so high that it was pulling the rocker studs several degrees out of plane.

Thomas

Wow, I didnt expect this much info!
Thanks for all your help guys! graemlins/thumbsup.gif
Looks like something I shouldnt skimp on. graemlins/clonk.gif

My Son's 331 will be running girdles, he has only press in studs without pins so the girdle should eliminate any of the studs from pulling out. The cam is only .501 lift. I do remember CHP running tests on an engine awhile back, I think is was Dangermouse when it had the camelbacks on it. They put a stud girdle on and lost power for some reason which made no sense to me :confused: I sure wish they would have figured out why the girdle caused a loss in power instead of leaving it a mystery.

Here are two ways that a girdle can cause a loss of power:
1) An improperly installed girdle that pulls the studs away from their centerlines, or that allows power sapping rocker arm contact with the bottom of the girdle.
2) Harmonics: as in when spring bounce gets transmitted through to the other rocker arm nuts, studs, and ultimately to the other valve springs.

Other than using a high speed camera to catch valvetrain harmonics in action, you need to do comparable dyno pulls. Dyno pull with and without the girdle in place. Compare power, especially look out for harmonics related dips and peaks in power in the upper 5,000+ rpm range.

I believe that most girdle vs harmonics issues are related to the camshaft choice. I.E., some camshaft profiles are more prone to excessive valve bounce when closing the valve.

I will hazard a guess that whenever harmonics pulls power from a girdle application, that a better camshaft choice could be made.

Thomas

Originally posted by Bomber '67:
Here are two ways that a girdle can cause a loss of power:
1) An improperly installed girdle that pulls the studs away from their centerlines, or that allows power sapping rocker arm contact with the bottom of the girdle.
2) Harmonics: as in when spring bounce gets transmitted through to the other rocker arm nuts, studs, and ultimately to the other valve springs.

Other than using a high speed camera to catch valvetrain harmonics in action, you need to do comparable dyno pulls. Dyno pull with and without the girdle in place. Compare power, especially look out for harmonics related dips and peaks in power in the upper 5,000+ rpm range.

I believe that most girdle vs harmonics issues are related to the camshaft choice. I.E., some camshaft profiles are more prone to excessive valve bounce when closing the valve.

I will hazard a guess that whenever harmonics pulls power from a girdle application, that a better camshaft choice could be made.

Thomas =
Thomas,
I likes da way you think,,, but I will have to disagree a bit on the "harmonic" part. ;)

While I suppose it is possible to transfer some movement across the girdle, in my experience I have never seen anything done to the valvetrain that stiffened it induce more instability.
I would think it would dampen more than transfer "harmonics"

I can't account for the loss of HP unless the test was flawed or the thing had something goofy like too much cam & taking deflection out changed timing at the valve slightly??
Or they stuck a girdle on & adjusted the valves different??
Or they were trying to say stud girdles weren't necessary in this application???
Who knows with magazine tests :D

I have done a little testing & it is amazing how much the studs deflect in some cases just turning the engine over. It is quite a bit less with a girdle.

I certainly do agree about cams & harmonics or spring surge or instability in general.
If you ever watch a spintron test you will probably want to quit building engines :D
It gets ugly!!
I don't think you can get the valvetrain too stiff.
Went from a very good quality 3/8 .080 wall pushrod to 7/16 .120 double taper & picked up about 12HP with no other changes on an 18 deg deal & the curve got a bit smoother above about 8200 with a lot less of the cute little dips & spikes we were blaming on the springs.
And these were very short pushrods,
(Tall lifter, shaft rocker)

But now that you got me thinkin on this I guess I'll have to add a few with & without pulls in my "spare time" so I know that I'm not just amusing myself putting on girdles :(
Crap,,, more tests,,,,,,,,

For now though, I still feel a properly installed stud girdle is a good idea.

I'd definatly run girdles with that spring pressure,FYI aluminum head's flex at the stud boss far more than iron.

Mike, yeah more tests! Every pro builder that I know tells me that they get suprised all the time - its just so hard to fully understand the relationships between all the different parts, clearances, etc. I'm no pro, I'm just a guy knee deep in hot rod jack-assery. I have no way of proving harmonics or simple acceleration deflection - but I do know that dissimilar metals can transmit vibration that can't directly be seen.

Here's what I think may have happened on that flawed magazine test (ugh, magazine tests graemlins/sad.gif ) - the pushrods were not strong enough, and they deflected more with the girdle in place than without. Either that, or they had an undetected interference issue (I have actually had reputable shops miss minor interference issues). Minor interference contact will not keep an engine from running, but for sure it will sap some amount of horsepower.

On the next go-round of my 496's valvetrain I'm going do away with the studs and girdles and go with individual $haft mounts.

Thomas

Originally posted by Wolfplace:
Went from a very good quality 3/8 .080 wall pushrod to 7/16 .120 double taper & picked up about 12HP with no other changes on an 18 deg deal & the curve got a bit smoother above about 8200 with a lot less of the cute little dips & spikes we were blaming on the springs.
And these were very short pushrods,
(Tall lifter, shaft rocker)

So, would you say always get as thick of pushrods as you can afford, regardless of the horsepower and rpm's.....or is the amount of instability problems proportional to the agressiveness of the cams? Spill your guts if you want, I engoy studying this kinda stuff :D .

He'sa talking about some pretty extreme stuff there! 7/16" rods are ProMod material, 3/8" are plenty enough for MOST street/strip apps. One piece - not pressed ends. Pressed tend to mushroom at R's , I've found.

[/qb][/QUOTE]So, would you say always get as thick of pushrods as you can afford, regardless of the horsepower and rpm's.....or is the amount of instability problems proportional to the agressiveness of the cams? Spill your guts if you want, I engoy studying this kinda stuff :D . [/QB][/QUOTE]
=
Not exactly ;)
I doubt you will see any difference with a .500 lift 5500 rpm hyd cam but I have never tried it so who knows??
It get kinda expensive when you start putting in $25 pushrods though ;)
Then you need shaft rockers because you can't run guide plates anymore.

But, given the crappy way rats open the valves with pushrods going in all directions the stiffer the pushrod is the better it is going to be.
You go get a .700 lift cam & by the time you factor in say .025 lash, pushrod angle & deflection you are probably at about .650 net.
The big deal is pushrods act like springs & can cause some real problems at certain rpms just like springs.
I think GM was looking at this when they put 7/16 pushrods in some of their performance engines as far back as the 70's
I personally don't think it is a bad idea to at least run a 7/16 pushrod in a rat with any kind of serious spring & or RPM or better 7/16 tapers but you would need to be running shaft rockers with tapers.

I could basically care less about pushrod weight & have seen more power in the same engine with pushrods that were probably twice as heavy as the ones that came out.
It has been proven that within reason weight on the cam side of the valvetrain is not real important especially at the expense of rigidity.

All that aside, we normally use 5/16 in SB & 3/8's in rats in almost all engines & don't seem to see any problems. (that we know of :D )

But,,, I am starting to look at this more after seeing what the big pushrods did in this little 332" engine considering they were only about 6.5" long smile.gif
12 HP is a lot for such a simple part & yes we went back to the 3/8's just to verify it was the pushrod.
Of course, this deal runs over 9000 rpm & does have a bit of spring pressure :D

I have been going back and forth on this stud girdle question myself ....I think I even posted the question back a ways , anyway if I decide to go with a girdle for street strip car ......which one do I get seems to be ones as cheap as 120.00 to 250.00 or more ...for my application which way should i go
......BBC with solid roller and Brodix Ovals , assume these Brodix's will take girdle that would fit stock GM heads, Bill