kfoley

I'm doing my own headwork and I had a few ?'s. Here's what I plan on doing to them: mill/tap for studs, cut valveguides for .530" teflon seals, cut in 1.94 valves and mill them a tad. I'm going to have the machine shop cut in the valves and mill them, but I want to do the rest of the work to save some money (and for the experience).

I plan on getting a stud boss cutter from Crane Cams (pn 99023-1) that cuts the boss down .340" to use guideplates and then tap for screw in studs. So, the first question is, has anyone used this and can they give any tips?

I will also be getting the valveguide cutter (pn 4726) from Comp Cams to cut the ID down to .530" so I can use their teflon seals (pn 503-16). Has anyone used this tool? Has anyone used the teflon seals? I plan on doing this for the better seals, and the tool cuts down the top of the valveguide to accomodate higher lift which I need to run the cam I want (I've already measured and max lift with the stock seals and guides was .410") the cam I'm using will be .486" lift.

Also, what kind of guideplates will I need, flat or raised? I plan on getting Comp Cams guideplates and ARP studs. I also have a set of 1.52 Magnum rockers I will be using.

All this work is for a set of 461 casting 305 heads (or is it 416 casting?) that I have ported/polished and will be getting a set of 1.94/1.5 stainless undercut valves.

I think that covers everything now, if I left out any details let me know. Thanks ahead of time!

Vader

Installing 1.94 or larger valves in 14014416 castings will require you to either flycut or grind the perimter of the chamber around the intake valve to prevent shrouding the edge of the valve (rendering little if no flow in that area).

Instead of "milling a tad", you can control the depth of the valve seat cut so that the valves will seat a little lower in the heads. As long as the seats are cut so the springs are installed at the correct height (or you use + length valves), you can maintain chamber volume (and correct compression) without having to mill the heads, even after unshrouding the valve perimeter in the chambers.

F-BIRD'88

There is no need to go to all the bother and expence of all this modifications for a mild, moderate street motor using 416 heads.

There is no performance benefit or advantage over the method discribed below

Y drive to cost up?



You can drill and pin the rocker stud bosses for a lot less $$$
once they are "Pinned" the stud will not move.
You can buy small roll pins and slightly smaller drill bits for a few dollars.

You can use the factory machined slot in the head to guide the pushrod. it does the same job as guide plates.
If you want to use 1.6:1 rockers just elongate the guide slot in the head.
A 5/16" rat tail file in a drill makes this a quick easy job.
Other wise the factory slot is fine.

If you go to the bother to convert to guideplates you'll need new hardened pushrods to eliminate premature wear on the guide plates.
Again no performance advantage over the factory machined slot in the head.
You will want to eliminate the factory exhaust valve rotators and use stock type retainers like on the intake side. You have to shim up the exhaust spring seat to take up the difference. a 3 stack of a .060"+.030"+.015" shims on each exhaust spring seat will do the job nicely.
Shim assortments are available through most good performance auto parts stores.

You can use Stock 1996 GM Vortec valve seals. They are a better seal and fit the stock 416's guide boss. Now all you need to do is shorten the guide boss for high lift. Comp or Crane makes a cutter for this
that does not reduce the diameter. You can do this at home with a drill.

Now that you have a good valve seal you can eliminate the factory spring oil shield if you like. It is .030" thick which will allow an
additional .030' spring installed height if your springs require it.
Or you can reuse the oil shields and get the stock installed height.
Up to you.

You only need to relieve the combustion chamber a minimum
amount to allow clearance for the new larger valves . Contrary to popular belief, this is a low flow area anyways so no need to get carried away here.
For use on a 305 motor use a 305 head gasket to mark out the cylinder wall on the head surface. Again don't get carried away.
This is not a Shrouded area or an area that needs to be "unshrouded" Nothing to gain here.
You just want to grind the chamber wall so the valve doesn't hit it, plus say .060" clearance.

Put the $$$ you save on this to better use.

jamesbob02

I don't have tremendous headwork experience, but my car, how I bought it, had pinned rocker studs. This, however, did NOT keep the studs from breaking the rolled pins and pulling out anyway. Take a little extra effort and put in threaded studs.....Vader made the tech article I used so he can help you out. Just a suggestion.

kfoley

Ok, I've been told several different things so I wanted to make sure what I was going to do, besides saving money is good...

So here's the new plan: pull old studs and tap for screw in studs, cut valvespring pocket lower on intakes if necessary for proper install height on springs, mill down the valveguide bosses for clearance and use the vortec seals.

So I need to get the guide boss cutter from comp and the 11/32" arbor for it and possibly a valvespring pocket cutter.

I'll use the magnum rockers w/o guideplates and shim up the exhaust springs (and intakes) to proper install height.

Does this sound good? Any other suggestions/tips when I do this?

Thanks!

Oh, do you have a pn on the vortec seals, or should I just ask for '96 seals at the parts store?

F-BIRD'88

There is no need to cut the intake spring pockets deeper.

What camshaft are you planning to use that needs all these mods?

kfoley

Something similar to the 280H. 230/230 dur @ .050, .486/.486 lift w/ 1.52 rockers.

I misunderstood what Vader said, so ignore the part I mentioned about cutting the spring pockets...

F-BIRD'88

Quite a serious cam for a 305.
Did you know you can buy 4.56:1 rear gears for your car?
Gona need 'em.
But thats another issue.......

Probabily won't need to machine the guide tops at all thou.

Just get the vortec seals from GM and put them on.

If there is not enough clearance between the botom of a stock retainer and the top of this seal at full lift, the top of the guide can be shortened a little by hand with a grinder.

Just have to chamfer (smooth) the sharp edge on the top of the guide after.
Any guide top shortening nessessary will be minor at best.
make sure the seal is pressed all the way onto the guide when checking clearance.
Again I don't think there will be a clearance problem.

A Comp #981 spring is a bolt on.

kfoley

Yes, it's going to be a stout lil' motor. I'm bracket racing it this spring and I'll have some 4.10 gears and a locker by then. Hoping for some 12 sec passes.

I'll get a set of seals and measure clearances. I'm glad to hear I don't have to buy $200 in tools to run a that cam.

Thanks for the help!

F-BIRD'88

If you're going to bracket race it. I'd run some 4.56 gears.
This motor With that cam will make peak horsepower way over 6000rpm and you want to use all the motor up in the quarter mile.

You want to just pass peak hp rpm at the traps.
Remember your T-5 trans will still allow a decent cruiseing rpm in 5th. (5th is od and really cuts the gear down) Get some sticky S/S tires and don't wimp out on the gear.

4.10's is not enough. with a 26" tall rear tire you'll still be cruising at under 2500rpm on the Hwy with 4.56's.

I'd use a Performer RPM and a 750cfm carb.

kfoley

I've got a Holley Street Dominator (old low rise single plane style) and I'm getting a Holley 750 DP (list 4779). I wasn't really sure about the 4.56's b/c I didn't want to overgear it, but I'll take your advice and go with them. What tires would you reccoemend? M/T, Hoosier, Goodyear? Any other suggestions? I've already put the car on a diet and I'm looking to get it down to 3400lb race weight.

F-BIRD'88

M/T Et streets work great. use 26x10.5x15 with 4.56:1 rear gears. Thats a good match for this combo.

Ditch the Holley Street Dominator single plane the first chance you get.
Its an old, outdated design that never worked well even back then.

Get a Edelbrock Performer RPM or a Professional Products TYphoon or Crosswind (air gap intake)
They will make more hp and way more torque than the old Street dominator.

If you do the heads up right and raise the compression ratio to 10:1 you should have an honest 350+hp and tons of torque for a 305. should be good for 103 or 104MPH quarters.
With the proper rear gear and S/S tire you should be able to run very low 13's or even crack into the 12's with it.

Measure the piston deck clearance and accurately calculate the compression ratio. Use thin shim style head gaskets, cc the heads and get the heads planned to achieve a true 10:1.

With this much cam in a 305 you'll want a lot of initial advance at idle. It will make the motor much more responsive.
I'd try locking out the mechanical advance and setting it at 32/36deg. You can still use the vacuum advance for efficiant street cruising.

You'll want to experiment with positioning the cam in the motor at different points of advance from the normal 106intake center line
of the COMP 280H magnum.
advance the cam 2 to 4deg at a time and let the motor tell you what it likes the best.
If the et and MPH is the best with the cam in at 99deg then run it that way. Should like somewhere between 99 and 108 intake centerline.
Again let the motor tell you what it likes.

A COMP Cams #941 is a stiffer spring than the mentioned 981's
A Crane 99846 is a good bracket racing spring too.
All are drop on install.
Might be an idea to go with the stiffer Street/ Strip valve spring as this motor will live at the upper end of the tach.
The Cam companies are the best source for advice on this.

Its all about details..... let us know how you make out.

85TransAm406

iTrader: (1)

Nice to see good advice given out, expecially about the valve seals. Every time someone wants me to put new valveseals in, they ask about teflon seals. There fine if you're running that much cylinder pressure, but almost noone is. i've got 10.5:1, zero gap rings, and a relatively small cam and i only run positive type Viton seals on the intake valves, and run the vortec style on the exhaust. i prefer to let a little oil get to the exhaust valve guides, my car is a daily driver.