|01-27-2013 03:50 PM|
|helrazr3||i read through those tips, the funny thing is that all of these things involve cam shaft break in but in my motor the top end was fine there was a small amount of wear on 2 lifters and both of those had sludge stuck in the pushrod. all my problems came from the bottom end my main bearings were wiped out most of the material that wasnt sucked into the oil pump was stuck to the crank.|
|01-27-2013 02:13 PM|
thanks mr p-body to begin with i was falsely under the impression that you didnt have to adjust roller rockers and that you just installed them bolted them down and you were good to go. i figured that would be one variable i could eliminate. i now i know thats not true so all things being equal i think at this point im going to go with the suggested cam and keep it all stock with the exception of the suggested valve springs retainers and locks.
cost is a big factor for me but that being said im not going to skimp on something vital if it is a must have. its a nice thing to be able to upgrade everything just to be on the safe side. but as long as the stock parts are within there specs i will leave them be. thats if im reading all of this right lol
oops tech inspector snuck in there and posted this before i read it i will read it thank you.
|01-27-2013 02:11 PM|
Roller cams are expensive compared to flat tappet combinations, but currently everything in the real world is geared toward rollers. Before you make a final decision to use a flat tappet camshaft, please read through this tutorial several times.....
|01-27-2013 12:59 PM|
We've been using the Comp Magnum rockers forever. No issues. I HAVE studied failures from other builders. The "bluing" of the rocker body may or may not be an indication of a problem. When the rocker ball shows some galling (material migration), it's a problem. The correction is the proper length pushrod. It's not the rocker's "fault". If the pushrod cup isn't in the right position, the oil hole is "too open", squirting the oil instead of weeping it. The result is indequate oil to the balls. The use of oil deflectors has also proven effective.
The two major benefits of using a roller-tipped rocker are the accuracy of each rocker, one to the next (already mentioned) and the significant reduction is "side-loading" of the valve stem against the guide. The wheel allows the force to "move" along with the tip.
Harland Sharpe colaborated with Smokey Yunik to develope the first truly successful "full roller" rocker for the 1960 Pontiac NASCAR program (Ed Cole traded with Mac McKellar for some goodies from the small block for the ball-fulcrum rockers in '54 when the engines were being developed. He improved them by oiling through the pushrod, which Pontiac didn't adopt until '61). For many years, Harland Sharpe were the "old standby" and more affordable than the "better" roller rockers. In recent years, Scorpion has actually suplanted HS as the "good, affordable" rocker. The Scorpion offers much less "deflection" during operation. A typical HS rocker will measure a higher ratio than advertised when "light" springs are used. At running speeds, they "deflect" enough to reduce the ratio to the advertised level. Either are an excellent choice for a street engine, although it is said the alloy used by HS will be more apt to "work harden". They can become brittle over time, but I have never seen any "hard evidence" of this.
It must be noted, though, the Comp and Crower steel roller rockers are far superior for street use. Far more expensive, too...
The XE268H is the grind listed. It's not radical enough to really warrant true rollers. Magnums would provde the desired results. Be CERTAIN you use the springs called for by Comp and follow THEIR break-in procedure. You'll like the cam...
|01-27-2013 11:48 AM|
thanks i was just looking on summit to try and figure out some prices if im correct that cam is not a roller. it looks to me like the roller cam and lifter sets are about 700+ if that's right i'm going to have to re think this whole thing i definitely wasn't prepared for a jump like that in price. i will go with that profile but i may scrap the whole roller thing.
at times i don't know how i can hate something i love doing so much.
|01-27-2013 11:12 AM|
That cam profile is in the 260 - 300 lb. valve spring range. A set of Comp Cams 981-16 single valve springs will be the ones to use. They will drop in without any machine work and set up at 105 lb. seat pressure at 1.700" and 283 lb. open pressure at .480" valve lift. Use Comp Cams 742-16 retainers and Comp Cams 601-16 locks.
With those valve springs, full roller rocker arms are not necessary.
|01-27-2013 09:32 AM|
this is what the comp tech guy recommends for me
12-242-2. Duration @ .050 224/230 Lift is .477/.480 with a 110 LSA.. This will give you some sound at idle as well..
so this should mean im in the 301 to 350 area so if this means the stock springs top out at 300 i should replace them.......i think this is getting more expensive than i wanted it too but oh well what can you do
|01-26-2013 04:20 PM|
SB Chevrolet hydraulic Roller Camshaft valve spring pressure
VALVE SPRING OPEN PRESSURE
Min. - Max. - Valve lift -
260 lb. - 300 lb. - .450" - .480" Daily driver - stock rocker arms
301 lb. - 350 lb. - .481" - .500" HP daily driver - full roller rocker arms
351 lb. - 400 lb. - .501" - .550" Racing - full roller rocker arms - 7/16" rocker studs
400 lb. - Up - .551" - up Racing - solid roller, steel billet camshaft, T&D shaft rocker system
and frequent parts inspection and replacement.
|01-25-2013 08:29 PM|
|helrazr3||i guess that's why i come here and ask lots of questions lol|
|01-25-2013 08:09 PM|
Push rod length and its effect on where the roller (or sliding shoe for that matter) establishes two things:
- The off center forces introduced into the valve stem that cause it want to bind in the guide, this is a wear issue for guide and stem and an oil seal issue for the stem seal. You see the result of this in the guide wear being an egged shape in the direction of the rocker rather than uniform wear around the guide bore.
- The other is dynamic rocker ratio; the stated rocker ratio is a static dimension from the center of rotation to the push rod cup on one side and the tip contact point on the other. Production parts tend to be a bit sloppy here. However, in addition to that problem is the fact that the push rod end and the valve stem end actually make different motions of rotation so the dynamic ratio of the rocker is always changing a little from the static dimension calculation. So using a push rod length that keeps the movement of the tip across the stem to a minimum, also keeps the ratio more constant to the advertised. God, I'm beginning to sound like Jim Miller!
|01-25-2013 06:59 PM|
|helrazr3||ok so do i need to change the valve springs too? its not a big race engine with crazy stuff i started this idea because i know roller is an upgrade from stock and i can eliminate the stock rocker arm adjustment from the equation|
|01-25-2013 05:00 PM|
Mousefink, I agree 100%
Mertz, I dont think you can do a proper geometry check with the stock rockers, besides their ratio is all over the chart. Check those rocker for blueing from heat. I had very low hours on these rockers. Watch here:
|01-25-2013 08:00 AM|
Aftermarket performance flat tappet and roller camshafts usually have higher valve lift and require a higher than stock spring rate in order to control valve action. Stock rocker arms with ball fulcrums are not designed to be used with more than 300 lb. valve spring pressure. Grooved rocker balls will give you an additional 30 lb. open load but open valve spring pressure more than 330 lb. should always be used with full roller rocker arms. When using high lift camshafts, full roller rocker arms will reduce oil temperature, diminish side load on the valve stems which reduces wear on the valve guides. Tight valve guide clearances and the use of self lubricating phosphor-bronze valve guide liners will allow more accurate valve seating.
This is why full roller rocker arms should be used with high performance flat tappet or roller camshafts. GM came to the same conclusion in 2000 when they introduced pedestal mounted, roller fulcrum rocker arms and the factory ball fulcrum rocker arms went the way of the Do-Do bird.
|01-24-2013 11:14 PM|
|01-24-2013 10:17 AM|
|Mertz||I used them on my 350 and will be installing them on my 283 bacause I was told they are more accurate in ratio. I tried setting up the geometry on my 283 with the stock stamped rockers and I could not get them to leave a mark so I could not tell if they are centered on the valve. When I put them on the 350 it was clear where the rocker was riding on the valve. I know roller fulcrum rockers would have been better but I am on a budget and still wanted the geometry to be correct. The balls do have grooves for better oiling and less surface area so there is some reduced friction.|
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