Hotrodder

I have changed to collarless screw in studs on my Vortec heads.
Used the Comp Cams 5306 tap guide, but It didn't turn out perfect.

When I lay a straight edge in the threads close to the top of all the studs, some of them lean app 1/25":



Have I ruined the heads, or will the studs stand the bending forces this create?

sofakingdom

iTrader: (1)

That's more or less inevitable, given the tolerances of the casting.

It doesn't really cause anything to "bend", as such. Rather, it just leaves the original uncertainty and variability that the factory didn't care about, in the valve train geometry.

Should be OK. If you ever have trouble with it, you still can have the heads drilled & tapped for studs with 7/16" on the side that goes into the heads, in a more precise machine shop environment.

skinny z

How's the alignment along the other axis? That is, stud to the valve? If that's off a considerable amount, then the rocker tip won't sit flat on the valve. That could cause some problems.

Vader

What type of tap was used - Plug tap or bottoming, cut or roll-form?

novaderrik

the studs are already tapped to 7/16", just like every other small block Chevy that has ever had screw in studs.. you aint going to be pulling a 3/8" pressed in stud out and tapping it to 3/8". the holes were drilled crooked at the factory, which means that they got tapped crooked by the OP. nothing can be done about it short of having a machine shop drill the holes straight and install 7/16" heli-coils, and honestly i wouldn't worry about it.

redneckjoe

i wonder if a stud girdle would help straighten things out? maybe something like this howards one or the like?
http://www.summitracing.com/parts/hr...make/chevrolet

Hotrodder

Thanks for all your answers and info. Very valuable, as always.

The heads are already tapped 7/16".

I used a tap like this:
http://www.ebay.com/itm/DORMER-SKF-T...sAAOxy14VRRaMA

My guess is that the misaligment is about the same on the other axis as well. Not more, not less.

Wouldn't a stud girdle put even more stress to the bolts. as they are not 100% aligned?

skinny z

Once you have the heads assembled with rocker arms, you'll have the opportunity to check on how the rocker sits on the valve tip. The leaning "in" with respect to the valve wouldn't make much of a difference as was pointed out. That would change the point at which the "sweep" appears on the valve tip when you doing your geometry check. As for the other way, if the difference is slight, the clearances that exist between the stud and trunnion (or rocker ball) and other moving/rotating parts may be sufficient to keep the tip square. Whether that's OK or not is open to argument.

ploegi

It may tweak 'em a bit, but, it also distributes the forces the studs have to deal with over a much greater area...... All in all, I think it would be a good compromise. However, it isn't really necessary. So long as rocker to valve geometry is good, you're golden. (unless you want to rev to the moon, then, they are just about a requirement.)

Vader

It looks like a cut-thread bottoming tap. Despite the tap guide, if the lead picks up at a slight angle the entire hole will be tapped that way. Been there. Even using a tapping table would not eliminate that 100%. If you ever do it again, start with a plug tap to insure a square thread, then change to a bottoming tap if you need full thread depth.