at what point do i need to machine my heads for new valve springs. will all 1.250" diameter valve springs go right into the head w/o any machine work? basically what i want to know is when people talk about having their heads machined to fit a certain valve spring in there it is because they are running a larger then stock diameter valve spring?
thanks,
brady

 

It is all relevant to the head / cam /valve size combo.

 

LO3 with a ZZ4 cam and stock heads. looking at some springs from http://competitionproducts.com

 

I agree with the roc. If you need bigger springs be cautious. In older stock heads when you cut the valve spring seat to a larger size, you may hit a water jacket in the head and then you are screwed. I had the same problem with some camel backs 186's, and that is why I switched to Sportsmans.

 

i dont want to machine the heads. i want i spring that will fit in the head w/o any machining and provide for the .510 exhaust lift.
thanks
brady

 

There are many drop on stock diameter replacement springs
that are good for .550/.600" lift with no machining.
You should check and varify retainer to guide/seal clearance at full lift thou.
Some of the springs of this type are
Crane 99846
Kmotion K700 or k-750
comp cams 981
Isky 235D
Another good route is to use the factory ZZ4 spring for that cam
The part # is in the GM performance catalog and online.
They may need the installed height adjusted
to 1.7 to 1.75" (depending on the spring) with shims to get the proper pressure
and travel you're looking for but will work well for that cam.
On some heads and with some springs the inner damper may interfer with the guide boss diameter and require machinig any way. You'll have to check.
Don't sweat it. these machining operations to correct spring
pockets and guides are routine
daily stuff for a reputable machine shop and don't cost an arm and a leg. Some, can even be done on the motor (electric drill and machining tool), with a little creative housekeeping.

 

I'll vouch for that. Enlarging seats and cutting valve guides can be done with the heads installed on the engine, as well as installing screwed studs (another MUST for your installation list).

 

just curious why must it been done? why cant the cam go in and some 1.250" diameter valve springs that are good to .570 lift go in and be done with it???

 

ttt

 

If you can find some valve springs that are rated for lifts that you need and are 1¼" in diameter or smaller, go for it. You'll need to make sure that the installed height of the spring is at their specification, and will still need screwed rocker studs.

 

to make sure the installed height is at the springs specification you use shims correct? as for screw in rocker studs, do i already have them stock? jegs sells some crane cams screw in rocker studs for $40, would i need to buy these and if i did would maching be required to install them and if so what kind of maching? i know where i can get some stock diameter springs that can handle the lift, so i am not going to have to go with a larger then stock diameter spring. as you can tell i am really confused, i appreciate all the help i am getting, keep it coming

 

ttt

 

Give Competition Products a call. They don't have a toll-free number, but it's worth it. I got my heads and springs from them, used the ZZ3/LT1 version w/upgraded retainers (I intended to use a ZZ3 cam when I started all this, a cracked roller block lead me to the path in the sig). They now offer them as a spring/retainer/keeper kit as well.

Yes, the installed height is adjusted by using shims - if the height is too tall without them, that is. If it's too short, you need to get off-set keepers or different retainers.

Screw-in studs typically have a shoulder on them that requires a machined boss to mate to. You currently have press-in studs with no machined boss. I haven't seen/used them, but there are reports of a retrofit stud that doesn't have the shoulder so you can use them in a plain tapped hole.

What I'm surprised nobody has mentioned is the wisdom of using that cam with stock LO3 heads. Those swirl-ports will probably choke off any flow above .42 or so lift.

 

Mr. Gasket (P/N 1075 IIRC), Elgin (don't know P/N), and others offer a screwed rocker stud with a minimal collar. These will thread into tapped stud bosses at the stock height with no need to machine the boss flat and square - tapping only. The Mr. Gasket set is about $16.00, or a buck apiece.



I've got a set on one of the LT1s and have had no problems. Installation was easy, and they leave more space for rocker adjustment/clearance.

 

ok i am going to call competition products to order their spring/retainer/keeper combo. thanks vader for that part number i am probably going to order those, but i think i might bother you or somebody that can help one more time. do i need the studs w/ the shoulder or straight and do i need 7/16" studs or 3/8". straight only comes in 3/8" studs.
thanks everybody
brady

 

ttt

 

ttt

 

If your engine is an '87 or later and are planning to use self-aligning rocker arms (stock style) you do not need hardened push rods and push rod guide plates. In that case, you do not need to machine the heads to accept the guide plates, so you can use the "collarless" studs. The lower thread on all studs is 7/16-14, since the existing hole in the head is already 3/8". Without enlarging the existing hole, the 7/16-14 thread is tapped into the existing hole to accept the stud.

The stock SBC studs use a 3/8-24 upper thread. You can use either the stock size or change to 7/16-20 upper thread, which would require rockers designed for them. 3/8 is generally adequate for street engines that don't exceed 8,000 RPM. 7/16" rockers are a little more rare on SBC engines, and can be a little more difficult to find in all varieties.

If you are ready to change the studs, here is the instruction file:

Rocker Stud Replacement.pdf

You'll need Adobe Acrobat Reader to access the file (see link below).

 

thanks vader, do you know where i can purchase the rocker are puller?
thanks

 

oops

 

ttt

 

If you mean the stud puller/tapping guide, they are offered by Crane, Comp, Proform, and several specialty engine tool manufacturers. The studs can be pulled with any suitable shim, or stack of shims, like a deep well socket, washers, etc. The tapping does not require a guide if you are careful to start the tap straight and check the alignment as you go, but the guide can make it almost foolproof. I've seen them offered in some of the older Jegs catalogs and PAW, along with a few web sites. Jegs has one for $16.99:

 

thanks Vader, you think the car will need screw in studs immediately after the cam swap?

 

No. Before. I wouldn't even run it on the factory "pull-out" studs and a decent cam (anything over .450" lifts or with valve acceleration rates above 0.0035in/°). The amount of force generated by high lift rates and spring pressures at higher RPM can pop a stud before you know it. It just isn't worth the risk.

 

since i am having a guy in a small shop preform the cam swap and i feel like i can do this at home, is it feasible to drive the car home never getting above 2500 or so rpms, basically take it real easy on the car, then preform the swap to screwed in studs?

 

It isn't likely that they would pull out right away, as long as you resist the temptation to do some ¼-mile runs in your travels. The problem is that they slowly work their way loose and let go with little or no warning. The pressed studs just won't take serious hard use for very long, so changing them at your convenience would be a good idea - just good general practice.

 

check out the competitor's "2300" springs, it's what I'm using
http://www.competitionproducts.com/page24.html

with .492 lift, I'm at 350# of pressure at full open, which is max recommended for roller hydraulic cams. no machining necessary. i'm using aluminum l98 heads that came stock with screwed studs

 

This should be a sticky.

Vader, or FBIRD

Are the GM ZZ4 springs basically drop in on L98 iron heads? If the retainer doesn't make clearance, what to do? If I knew the sizes I can do the math. Stock seat size? Stock spring size? OD, ID?

Could you pick out a good combo from a sponsor for:

Substitute springs, retainers, locks, for 0.510" lift on unmachined l98 head (assuming screwing studs), from a sponsor, of course!?

The tools for machining spring seats are cheap enough. I just am not sure where diameter stated in spring specs is ID or OD. Gets confusing.

Any machining required for ZZ4 springs on L98 heads?

I have a ZZ4 cam installed already. I need to ensure I get better springs on ASAP. Hopefully with heads on. Thanks so much.

Seriously there should be a ZZ4 cam L98 guide or sticky. Doesn't seem as though machine shop is needed if heads are reconditioned stock. Just need a shopping list and an afternoon. . So I think, lol. I saw a thread Vader used different seals, common to Daytonas. I can't find it again. .

 

This thread is 11 years old.

Some of what was posted is still valid (replacing press-in studs with screw-in). But springs have come a long way in 11 years. A well chosen set of "beehive" springs gets you around many of these issues like retainer-to-guide clearance and adequate valvetrain control in a small diameter spring.