bigvic

I was thinking about going the vortec head route sometime in the future, but I don't want to pay the associated cost involved with preparing them for high-performance use. I want to know if it is possible to install screw in studs and machine the valve guide bosses down myself. I found a stud puller for cheap down at the local Harbor Freight, so that part is taken care of. I just want to know if an off the shelf tap would do the job or do I need some sort of super-tap? Also is there some way I can machine down the bosses myself to accomodate larger valve springs. Can I just grind it down or does it need to be a precision machining job? As far as installing larger valves, I don't mind paying for that machining unless you guys know of a cheaper way to do it yourself.

Vic

RB83L69

All you need for pulling the studs is a nut and a stack of old rocker *****. That's the easy part.

The tap is a standard 7/16"-14. Again, nothing exotic there.

In order to set them up for push rod guide plates, which is the truly correct thing to do, you need to at least get the 2 stud bosses for each cylinder to exactly the same height, even if all 8 per head aren't identical. I don't know of any real good way to do that with hand tools. If you have a drill press with an adjustble work piece clamp or mount, you could do it with that. IIRC both Comp and Crane sell a cutter that will work.

A machine shop will either put the heads in an end mill or use their deck plane to do it. A deck planer can do them in literally seconds per head once the table is set up.

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"So many Mustangs, so little time..."
ICON Motorsports

MikeS

Similar question and similar answer in april HOT ROD mag. if anybody cares. It only deals with taking out the press in studs, tapping the holes, and replacing them with screw in ones though.

bigvic

Thanks for the replies guys. The studs and guideplates will definitly be handled by myself, but how much do I need to machine down the valve guide bosses in order to run approx. .500 inches of lift. If I understand correctly the most lift one can run with this head stock is .480. Isn't it because the valve guide bosses stick up too far causing interference with the seals and the retainers or locks?

I haven't seen these heads in person and I don't know a lot about heads, but from what I've been reading, if these bosses are machined down X amount of inches then you can install better springs and run more lift. Please correct me if Im wrong, but that's the jist of what I pick up from reading articles and threads about these heads. Now if that is the correct procedure then please enlighten me as to how much needs to be removed, and if I can do this myself. I do have access to a Bridgeport and Im somewhat good at machining, so that is not the problem, but I am unclear on this mod, and I don't want to waste a good set of heads. Thanks againg,

Vic

RB83L69

That's essentially true, you mill the guides .001 for every .001 of lift above .480 that you wish to run, plus a safety margin, plus the thickness of the top of the seals if you use positive seals. You can buy a "check" valve spring for checking clearances from Comp, I suppose you could get one at the hardware store that would work too. Then just dummy up a valve, the retainer you are going to use, and the keepers, and use a dial indicator to find the interference point.

Another thing worth considering is machining out the spring pockets to accept 1.45" springs. There are basically no 1.25" springs that are safe at more than .500" lift, so if you want to exceed that, you need to step up the pocket size. Again, I believe both Comp and Crane sell a cutter for doing that. It's easy to hit water in some heads by machining right there, so what some people do is machine .030" too little, and use a 1.25" .030" thick shim.

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"So many Mustangs, so little time..."
ICON Motorsports

SCRA rules!

With vortecs, you are not only taking material off the top of the guide, but reducing the O.D. of the boss also, as they are very large and don't leave room to put a single spring and damper over it-the damper will sit of the chamfered edge of the boss and possibly bind at high lift.

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'93 2wd truck
408 sb, vortecs, 454 TBI, Comp Cam, dual exhaust

Vader

Two words - longer valves.

Longer valves will require the use of taller valve covers (available almost anywhere), longer push rods (which you'll probably need with a decent cam anyway), and possibly enlarged push rod openings in the heads, but precludes the need for any deep machining of the valve guides or spring seats. In essence, you can do this with almost no machining if you use a drill bushing or file to elongate the push rod holes. If you don't plan to use guide plates, there is no machining required other than the valve seat work and porting. Just pull the studs, trim the tops of the stud bosses to a uniform depth, and tap the holes. Install the studs without too much concern over slight variations in height.

If you decide to use guide plates some machining will be necessary. If you calculate well, you should be able to mill only a few thousandths from the stud bosses to provide a flat surface for the plates. If you decide to use larger diameter valve springs (and you may not have to), additional machining will be required, but can be minimal. Simply slightly enlarge the spring seats without going any deeper than stock. This prevents thin spring seats and cracking through the water passages from heavy valve action and stress. Another advantage of this is that you can raise the ceilings of the intake port runners quite a bit without concern over interference from the lower ends of the rocker studs.

Since you should be looking at new springs anyway, select a spring that provides adequate seat pressure at the installed height. You can use stock diameter inner/outer spring set that provides at least 120 pounds of seat pressure at an installed height of 2.200". The longer valves allow the use of longer springs for more consistent pressure, spring rate, and better control without fatigue. Just find a spring that provides adequate seat pressure at the installed height and forget about coil bind forever. You might even want to increase spring pressure slightly and prevent wear on the heads by installing some spring shims. Everything else is standard, stock parts and supplies.

Unless you are planning to run some crazy-fast RPMs (like over 9,000 or so) the extra mass of the valves should not be a problem with the correct springs. If the valve mass is a concern, you can use undercut valves that are lighter than most "performance" stainless valves, and run at whatever RPM the cam will allow.

It's amazing how well some of the Ford 351C and older 11/32" BBC valves fit into SB Chevy heads in this configuration, They are all over 0.250" longer, so the guide plates fit with minimal depth machining. The springs can be well over 2.200" installed height, so even a 1.250" spring can handle a valve to over 0.650" lifts without even breaking a sweat or getting close to binding. Since the studs install over the guide plates, the standard length stud works fine. (Ever wonder how the top fuel guys got such long springs in there so they can run the 0.800"+ lifts?)

And if you're concerned about geometry, the slight angle change at the valve end of the rocker arm is insignificant with roller tipped rockers, but I'm glad you were thinking about that one anyway. The tip of the longer valve only moves inward about 0.006", hardly worth losing sleep over.

The bad part is that it's hard to find the BBC valves that are much over 2.300", so if you want a real monster valves, you're out of luck. Then again, if you've ever tried to squeeze even a a 2.10" valve in a SBC head, you won't be too concerned about only being able to go 0.200" bigger.

Just a little trick us "old farts" used to pick up by hanging around the "older farts". When racing on a budget, big valves for little cash can make a big difference.
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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
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[This message has been edited by Vader (edited March 14, 2001).]