cplonner

I have pressed in rocker studs in my vortec heads, I was curious to how much of a lift this limits me to. I already know the whole deal about having to get special springs or machine the valve guides for bigger springs. Im just wondering what my draw back is as far as pressed in rocker studs. If anyone has any idea let me know!
Im thinking about getting 1.7 or 1.6 roller rockers. my cam right now has a .474 lift.

CFI-EFI

I am not familiar with Vortec heads and their studs, but bring "press in" doesn't automatically limit the lift they will support to and particular number. Everything else being equal, an equivalent screw in stud would have the same limits of lift as your press in studs.

RACE ON!!!

cplonner

So who is reliable to call for the exact information? I called summit and asked them but that guy problably is just guessing, he gave me a real general answer, "well they problably only can stand the same amount of lift that the springs they come with do". that could be true, but it also could not be.

Mkos1980

Your going to want to stay under .490 I've seen even stock cams pop the stud out. I would have the heads drilled and tapped for studs or pin the studs with a 3/32 dowel pin.

Morley

Summit sells a tool for removing the pressed in studs and is also a guide for drilling and tapping for screw in studs.

rick lambert

I used the tool-pretty easy, I did this because a couple of the pressed ins actually backed out-but the heads were tired-I don't think cam lift has alot to do with it as much as what you're doing with the car-drag etc.-for a DD, and occassional run or so I think your fine.

rklessdriver

I'd like to point out its not really a matter of how much total lift the camshaft has that causes pressed in studes to come out of the head. Its a matter of valve spring pressure and the opening/closing rates on the cam.
As a general rule on our limited class oval track engines, if an engine has over 120lbs (seat) and 350lbs of spring pressure (open) we at least use the Mr Gasket "stock apearing" screw in studs. If the rules allow we use conventional screw in studs and guide plates but that cost more money as you have to machine down the rocker stud pad and many tracks forbid it in a attempt to cut the cost of engines in the class and limit HP potentional.
This does not mean every set of heads in the world with pressed in rocker studs will start popping them out once you reach/exceed 120/350lbs of valve spring pressure. Some will go much more before failure and some will never make it that far. I do not pin stock rocker studs, nor would I recommend anyone doing it anymore. Its far to easy and inexpensive to pull the press in studs out and tap the holes and install the Mr Gasket stock apearing screw in studs. Yes it helps to have a mill or Seat and Guide machine so that you tap them all perfectly strait but if your really cheap and don't want to pay a machinest (or just like doing things yourself)... take your time, pay a little attention to detail and you can accomplish it tapping by hand.
Just my .02
Will

cplonner

Do you think its too much of a risk tapping them while they are still on the block? Cover everything up and clean up really well after wards? If not it will be a while before I can pull these heads. if I pull them Ill just have them ported and polished, but id really just rather keep em on.

rklessdriver

I know you would rather not take them off but its not a good idea to tap them on the engine IMO. The exhaust stud holes go through to the water jacket and the intake stud holes go all the way to through the intake port itself on some cyl heads. I'd look for you but the only set of Vortecs I have in the shop currently are on an engine I just finished so I can't really pull the intake manifold off it. Not to mention I won't be back in the shop until this weekend. Even if they didn't go through on the intake side (and I'm almost positive they do) the potential damage to the water pump should be a good deterant for nixing that plan. Not to mention the amount of metal chips from tapping all 16 rocker studs is a lot more than you would think. No matter how careful you were in sealing things off you would never be able to get it all out of the engine. I did 1 at the race track on a cutomers motor that broke a stock stud in the heat race once and even then I felt like we were taking a big chance.
Hey look at it this way, You've been looking for a reason to get the heads ported anyway right??
Will

Mkos1980

You can do this with the head on.


This can also happen while trying to remove the studs.

CFI-EFI

As I tried to explain above, it isn't the method of stud installation that limits the valve lift. Usually it is spring, coil bind, or valve spring retainer to valve guide, or valve seal, interference that prevents greater valve opening. Whether the stud installs with a, push, or a twist, if it is configured the same from the head casting. up, the amount of allowable lift won't change. There are other, good reasons for screw in studs, but clearance for lift isn't one of them.

RACE ON!!!

rklessdriver

[QUOTE=CFI-EFI]As I tried to explain above, it isn't the method of stud installation that limits the valve lift. Usually it is spring, coil bind, or valve spring retainer to valve guide, or valve seal, interference that prevents greater valve opening. Whether the stud installs with a, push, or a twist, if it is configured the same from the head casting. up, the amount of allowable lift won't change. There are other, good reasons for screw in studs, but clearance for lift isn't one of them. QUOTE]

This is absolutely correct. Your press in studs don't have anything to do with physcially limiting how much valve lift you can have. You could have .700 lift at the valve as long as the springs didn't coil bind, the retainers didn't hit the valve guide, ect or you reach the point where you have so much open valve spring pressure that the stud pulls out of the head, that is what limits press in stud useage. You need to know what your open spring pressue is going to be at the new lift you will have with the 1.6/1.7 rockerarms. If its around 350lbs you could have a problem with the studs pulling out and it would be a good idea to upgrade. If its less than 350lbs most likely you will be ok with the press in studs.
Will

rocco16

I'm with ol' Will on this one.

Larry
code5coupe

CFI-EFI

EXACTLY! The type of stud doesn't limit the amount of valve opening, but the spring pressure (and RPMs) limit the ability of the stud to STAY pressed in.

RACE ON!!!

cplonner

Then ill have to see what kind of spring pressure im looking at. Thanks for the info guys, this was really helpfull. Now to find that pressure! You say 350 lbs is the limit? How do you figure that out? Is that standard for pressed studs?

rklessdriver

Look at the manafactures spec for the spring, it should tell you how much seat pressure and how much open pressure it has as well as the recomended set up height and coil bind height. They might give you springs the "rate per inch".
As an example here are the specs for the popular Comp 918 spring.
Seat Load: 130@ 1.800
Open Load: 333@ 1.150
Coil Bind: 1.140
Rate(lbs./in.): 313

Yes, IMO 350lbs open pressure is about the max for pressed in studs. Now if your asking how I arrived at that, its through experience with limited class oval track racing engines. We are forced to run the stock pressed stud in many classes to cut cost and limit Hp and RPM. Some tracks make us run on a .425 lift rule so the camshafts we run are custom grinds and very very hard on valve train parts. Also because its the widely accepted max valve spring pressure for hyd camshafts. Yes there are special hyd lifters that let you get away with running alot more pressure but for normal hyd lifters (or hyd roller lifters) anything much more than 350lbs is going to collapse the lifters plunger.
I won't say there is a definate standard for how much spring pressure a pressed in stud will stand up to, b/c there is always that one guy you know... someone may have used them and they stood up to a Mech roller, its doubtful, but hell wierder things have happen in the world.
Many other things play into it than just the pressure althou spring pressure is the biggest factor IMO. Really aggressive lobe rates jerk up on the stud harder everytime the lobe comes around. Also potential for high RPM, higher RPM means it happens over and over faster and faster placing alot of stress on the stud. All that stuff adds up and over time it could work a pressed in stud loose from the head, espc if you happen to be close to the max on you spring pressure.
Add up your spring pressure take into account how radical your camshafts lobe rate is and how many RPM you plan to be turning. Decide if your willing to risk it. If your still really unsure take all your info and ask a few different engine builders. Before I stop I want to give you some info to educate your self... Look up when GM used screw in studs on the SBC with iron heads from the factory. You will find out it was only in the high performance solid lifter cam engines (LT-1, DZ302 ect) Why? b/c they were capable of high RPM and in the case of the solid lifter LT-1 had 130lbs of seat pressure and 350lbs of pressure open.
Will

cplonner

hey thanks for all that really good info will!

rick lambert

I did mine while the heads were on-I was just meticulous about cleaning
all the way through-and then changed my oil and filter-then again after 500 miles-if I ever had any problem from it-I'll never know.

cplonner

Yeah I would figure it wouldnt be too bad just as long as you covered everything up, and those stud holes dont enter any other passages.