Stud Girdle
03-27-2016, 11:15 AM
#25
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that,s a good question and no doubt will get a lot of different answers.imo anytime you do anything to improve the stability of the valve train you also extent the life of the components.if it is in the budget i see no reason not to use them on any engine with a roller cam,even stock merc engines but then you also need to go with valve covers to clear the girdles.
03-27-2016, 11:16 AM
#26
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03-27-2016, 11:37 AM
#27
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A couple months ago, just for chits and grins, I put a dial indicator on the rocker stud. When rolling the engine over by hand, I was getting like .004 of deflection on the ARP stud. I did the same thing, by pushing against the stud with my thumb.
.004 isn't really alot, but I can see that stud deflecting over and over and over and over millions of times on a running engine, I would think after a while that could fatigue the steel. Plus, how much is it deflecting when the valve is trying to open against cylinder pressure on the exhaust side? Then theres the spring pressures. David Vizard says in his book, just about any BBC with over 400lbs open, should consider a stud girdle.
Comp cams has a trunnion/stud upgrade kit for their Ultra Pro Mag XD rockers. It utilizes a 7/16 base stud, with a 1/2" upper portion of the stud. It is for classes that don't allow stud girdles. Just like when going from a 3/8 to 7/16 pushrod increases its stiffness tremendously, I believe the same goes for the rocker stud.
I have not had issues NOT running girdles, but like everything, we are trying to avoid failures. I've seen rockers break, poly locks break, and studs snap. Its easy to blow a head gasket when that happens , or worse, launch some valvetrain parts right into the engine. Like banarama said, if the girdle doesn't fit properly, it can do more harm than good.
I remember a time, when if you had a flat tappet cam with 575 lift in a bbc , with 120/320 springs, it was a hot cam setup. Today, guys are running around with 680 plus lift hyd cams, 500 or more lbs of open spring pressures, cams that open and close the valves super fast, turning more and more rpm, still want hundreds and hundreds of hours of service from their valvetrains in a pleasure boat, and think the rules from 1980 still apply. The game has changed a bit since then. Stuff that we all once thought was strictly for all out race engines, is now becoming standard issue, in a basic marine high performance engine.
.004 isn't really alot, but I can see that stud deflecting over and over and over and over millions of times on a running engine, I would think after a while that could fatigue the steel. Plus, how much is it deflecting when the valve is trying to open against cylinder pressure on the exhaust side? Then theres the spring pressures. David Vizard says in his book, just about any BBC with over 400lbs open, should consider a stud girdle.
Comp cams has a trunnion/stud upgrade kit for their Ultra Pro Mag XD rockers. It utilizes a 7/16 base stud, with a 1/2" upper portion of the stud. It is for classes that don't allow stud girdles. Just like when going from a 3/8 to 7/16 pushrod increases its stiffness tremendously, I believe the same goes for the rocker stud.
I have not had issues NOT running girdles, but like everything, we are trying to avoid failures. I've seen rockers break, poly locks break, and studs snap. Its easy to blow a head gasket when that happens , or worse, launch some valvetrain parts right into the engine. Like banarama said, if the girdle doesn't fit properly, it can do more harm than good.
I remember a time, when if you had a flat tappet cam with 575 lift in a bbc , with 120/320 springs, it was a hot cam setup. Today, guys are running around with 680 plus lift hyd cams, 500 or more lbs of open spring pressures, cams that open and close the valves super fast, turning more and more rpm, still want hundreds and hundreds of hours of service from their valvetrains in a pleasure boat, and think the rules from 1980 still apply. The game has changed a bit since then. Stuff that we all once thought was strictly for all out race engines, is now becoming standard issue, in a basic marine high performance engine.
03-27-2016, 07:09 PM
#29
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I liked the Boobies better ^^^^
