What exactly need to be done to convert to a roller valve train? What parts do I need? What tips or special setup needs to be done? Thanks.

 

The easiest way to convert stock heads to roller rockers is to get rockers that have the self aligning tip. If you're running a cam with less than 0.480", then you can skip the screw-in studs and guide plates. Use only 1.5 ratio rockers, 1.6's cause interference with the factory guide holes.

 

I'm talking about he whole sabang! Roller cam and roller lifters too. Would i need different push rods, rockers, screw in studs, springs, valves, distributer gear? Comp Cams XR270HR looks like a nice one! @.050 int .495 lift exh .502 lift int 218 duration exh 224 duration 110 lobe center. Thats about as big as I can go while almost staying under the .500 mark. What is the max lift you can throw a pressed in studs on a 882 casting? Also what about piston to valve clearance?

 

The initial question would be, do you have a factory roller block? There are differences in roller lifter selection depending on your answer ... Large selection of roller rockers out there so it will depend on what you want to pay... Pushrod length will change.

I would not run any performance cam with the stock springs. Always change the stock springs out. Valve float is not fun after all that work. Pressed in rocker studs are also a no-no with perf cam and springs. False economy is the result, because when you least expect it you could pull a stud and things will break as the result.

Do it right in the first place and there won't be any war stories afterwards.

 

Block is set up for flat tappet lifters. How much lift have with pressed in studs? So I guess I would need the special lifters that stay alinged.

 

You need a roller cam & lifters (duh), a thrust button, and shorter push rods. Stock push rods for a roller setup (GM or aftermarket) are about 7.300".

Any roller cam worth using will be too much for stock valve springs. I would strongly recommend screw-in studs, but you might be able to get away without them, if you don't mind the risk of the pull-out ones pulling out.

There's nothing particularly difficult about doing this. I don't understand why the factory invented some college freshman engineering project of garbage when they finally wised up to rollers, when the system all the rest of us had been using for decades has been working fine. Better in fact than the factory's does, and the original design is actually compatible with existing blocks, unlike the factory's bizarre Rube Goldberg.

There is no lift limit as such on pull-out studs. What matters is the open spring pressure. As long as it doesn't exceed 350 lbs or so, it's probably OK. That will effectively eliminate the possibility of using that 270 cam, because any 1.25" diameter springs will have too much open pressure.

Get rid of the stock stamped sheet-metal rockers. They flex an unbelievable amount, and are never even close to the theoretical 1.5 ratio anyway. They will cost you power and reliability.

 

RB83L69 thanks! lots of good info there. I did get aftermarket springs when I was building the engine. I bought all my parts out of the machine shop that did my machine work. He said the springs would be good to around .500 lift. I dont have the exact part # so I can't be absolutely certin. At .500 lift do I have to be concerned with coil bind and valve to piston clearance? If I do it I will probably convert to screw in studs, definently sounds like the way to go.

 

Coil bind will be an issue. Any 1.25" (stock diameter) springs on the planet will be at their limit of reliability at .500" of lift. I would recommend getting your spring pockets cut for 1.45" springs if you're going to get head machine work done; the springs don't cost much different.

The parts I would recommend using that Comp cam would be their 1302 1.6 rockers, their guide plates, ARP or Comp studs, Comp 986 springs and the retainers for them, and the better push rods at probably 7.400" long.

Piston-to-valve clearance will not be an issue.

 

Not true, the stock Z28 302 springs are pretty stout, and I belive that the solid lifter cam that came in the 302's were around the 0.5" lift mark, and used push-in studs.

Roller cams do require more spring pressure. Best to consult cam manufactor. Looking at Crower cams, they require their roller cam (with about 0.5" lift) springs that have 105 lbs seat pressure and 275 lbs full lift pressure.

I believe that the Z28's will fit the bill. No reason to do and pay for unnecessary work, IMHO.

 

I had that cam (spec .485"/485" lift actually), and those springs, and those heads, and lost some pull-out studs. I also broke a spring after a while, maybe 15,000 miles or so. And that was with sheet-metal rubber rockers. It probably would have been alot worse if .030" or more of lift hadn't been getting thrown away in the 1.35-1.42 ratio bendable rockers.

The GM springs are no better than anybody else's (no special iron atoms available to them, no variances granted from the laws of physics) that allow them to be any better than anyone else's. I would not recommend using a cam with ramps as steep as that 270 on springs already at their absolute lift limit, with pull-out studs besides; that's just a sure recipe for requiring future motor work (not far in the future I might add).

Your specs from Crower are similar to Comp, Crane, Lunati, etc. I could be wrong but I don't believe Crower or the others will spec a 1.25" spring for any lift over .500"under any circumstances; I know for sure Comp won't.

 

I guess I should stop being sooo cheap and open up the pruse string for some quality parts! I guess I feel a little guilty spending the money with a kid on the way. Not to mention feeling the pinch once the wife stops working.
I was looking at the Sportsman II heads and they support a .540 in lift with a 1.25 in valve spring. I also priced out a roller cam, roller lifters, pushrod, roller rockers, ect. I guestimate around $1640 to add everything I want.
I have been itchin to get one of those roots style blower and they are around $1600 but after running both combos through the dyno software the heads and roller valve train will end up giving me a little more power. Well thats a no brainer, heads a valve train up grade all the way! Then I wont have to worry so much about melting holes in my pistons.

 

It's interesting about those valve springs on the heads...

Several of the head mfrs supply 1.25" springs that they claim are good to lifts in excess of .500". However, none of them warranty your valve train parts at all! On the other hand, among the [/i]cam mfrs[/i], not one of them that warranties valve train parts will honor their warranty when a cam with over .500" of predicted theoretical lift is used with 1.25" springs. Alot of them will only honor the warranty when you use their cam with their own springs, just so they can be sure the combo was properly applied.

So whose ratings are we to believe? Somebody to whom it doesn't matter when your push rods bend and your cam lobes wipe out, or the people who replace that stuff for free whan that happens?

I used to live in Memphis, and knew alot of people on the staff of several of the major cam mfrs personally (Comp, Lunati, and Ultradyne are all located in the Memphis area), and even did some engineering work for Comp, and 2 of my brothers worked there at various times. It really made a believer out of me when I saw the mangled remains come back in to their support depts where people had cheeped out on valve springs... after you see a few hundred cams with that particular destruction pattern, it gets real easy to recognize.

So, you might get away with the 270 cam, pull-out studs, and 1.25" springs; but then again, you probably won't. And the consequences are a whole lot more expensive than setting it up right in the first place. IMHO, it's not a risk worth taking.

 

I trust you opinion but does that still apply to the World Products Sportsman II heads? Then do have screw in studs so that should not be a problem but the 1.25 springs may be a problem huh? The advertise .540 lift which is waaay more that the .500 I would like to run. But I have learned not to turn my back on experience so if it needs a bigger spring it needs a bigger spring
So should I consider a different head? Just trying to keep my budget reasonible.
Just looked at a set of Dart Iron Eagles with the 1.437 springs. Looks like that would bump up the price another $200-$300 bucks. Cheaper than picking broken chuncks of metal out of my motor and haveing to start over I suppose.

 

Call Comp, see what they say. Let us know the results.

Just for comparison, I have a 400 with their XR282HR and 1102 stainless 1.6 roller rockers; they say it's close to the limit of the 986 (1.45") springs they spec for that combo. Next time I buy springs, I'll go up a step.