Afr Cylinder Heads Ques..
- Thread starter 5.0stang_gt
- Start date
Pedestal mount heads use a pedestal that the rocker mounts down on and then a bolt goes through to hold the rocker down.
Stud mount heads have a stud on wich the rocker attaches to. Stud mounts are much stronger and adjustable whereas ped are weaker and non adjustable.
I would say get the studmount heads, but then you have to buy new rockers (not a bad idea if you still have stockers).
Stud mount heads have a stud on wich the rocker attaches to. Stud mounts are much stronger and adjustable whereas ped are weaker and non adjustable.
I would say get the studmount heads, but then you have to buy new rockers (not a bad idea if you still have stockers).
Not to muddy the waters, but their is a pedestal mount system that's adjustable and as strong or stronger than the stud mount.
Steeda sells a pedestal mount shaft roller rocker system (here) that is pretty slick. Reasonably priced too at $350 bucks. The really good pedestal roller rocker kits cost just as much. The Cobra 1.7:1 kit is not that great IMO so I won't go there.
Steeda sells a pedestal mount shaft roller rocker system (here) that is pretty slick. Reasonably priced too at $350 bucks. The really good pedestal roller rocker kits cost just as much. The Cobra 1.7:1 kit is not that great IMO so I won't go there.
tjm73 said:
are you sure about that?
here's a quote from http://www.mustang50magazine.com/techarticles/18679/
For most street applications, pedestal-mount rocker arms are perfectly adequate. However, when high horsepower and proportionately high valvespring pressures are used, pedestal-mount rockers have their shortcomings--the most important of which is strength (or lack of it). Though the basic rocker layout is the same used in higher-horsepower racing applications, pedestal-mount rockers employ a 5/16-inch cap screw, which has a tendency to deflect and even break in a high-horsepower application. We’re reluctant to state specific numbers here because we know of many racers who have used pedestal-mount rockers well into the 500hp range with a variety of cam/valvespring combos.
The other shortcoming of the pedestal-mount rocker is its lack of adjustability. Factory rockers and some aftermarket replacement roller rockers use shims for adjustment, while other models use pushrod cup adjusters. These, however, are mainly for the purpose of obtaining correct lifter preload during installation.
Suffice it to say that if you have heads designed for pedestal-mount rockers, use them. If you get the chance to run heads that use stud-mounted rockers, do it.
Stang8URMPRT
Active Member
He was talking about shaft mounted peds... Those are way stronger then your run of the mill peds or studs.
Stock pedestal to a stud mount, the stud mount is stronger hands down.
But take a look at the Steeda rocker set. You have 2 studs tied together via a short shaft. For one to deflect or break the other would have to do the same. It's the same basic concept as axle splines.
The splines on a 28 spline axle are bigger so youwould think they are stronger. But a 31 spline axle has smaller splines and it's stronger. It's stronger becasue the work load is more evenly distributed to a larger contact area.
With this setup, two smaller bolts are better than one bigger bolt. Shaft mount rockers are the best setup you can get. This setup is a hybrid shaft type set up.
I can't point to any hard data, but I know from research that shaft systems are the strongest, most stable systems you can run. So even if the shaft only contains 2 rockers, it's stronger and more stable than a single rocker on a single stud.
But take a look at the Steeda rocker set. You have 2 studs tied together via a short shaft. For one to deflect or break the other would have to do the same. It's the same basic concept as axle splines.
The splines on a 28 spline axle are bigger so youwould think they are stronger. But a 31 spline axle has smaller splines and it's stronger. It's stronger becasue the work load is more evenly distributed to a larger contact area.
With this setup, two smaller bolts are better than one bigger bolt. Shaft mount rockers are the best setup you can get. This setup is a hybrid shaft type set up.
I can't point to any hard data, but I know from research that shaft systems are the strongest, most stable systems you can run. So even if the shaft only contains 2 rockers, it's stronger and more stable than a single rocker on a single stud.
Modular2v said:
each spline cut adds more surface area to an axle for engagement to a center section. More surface area = more holding power, to a point at least.
Take 2 identical axles and cut one with 28 spline, the other with 31. Test for strength. The 31 spline will win.
Or take a flat blade screw and screw driver. How many screws have you messed up over the years when getting heavy resisitence to turning the screw? NOw think about the last Torx screw you fought with. You used A LOT more force getting that undone than a flat blade screw would accept.
