I'm making a jig out of a 1"x1"x8" CRS steel, to pull out the rocker studs (instead of washers), as well as to guide the tap to be straight.
Is the spacing between the studs constant on SBC heads? I'm going to practice with a set of 993 heads I have lying around, then use it for real on my 416s. Any foreseeable problems?

My main question is, what is the rocker stud spacing exactly? Between two rocker studs, and between a set of two studs.... Know what I mean?
I want the block to sit over 4 of the studs on say the front side of the head, so it will be kept very still, and i'll use nuts to tighten it down to hold it in place while I pull one stud out, then tap the hole, then put in a bolt to hold the jig down while I do the others... Then go on to the other 4 studs on that head, then go on to the other head....
Then take the heads in to my work to mill down the bosses... (I know what your thinking, but I don't have the ability to power tap on the mill at work..)

Thanks
-J

 

It can vary, especially with aftermarket heads.

 

Damn, not the answer I was looking for...
Just to clarify, I need these two dimensions, A&B


I figured factory SBC non roller type heads, it would be same measurement.... Basically just for 993's and 416's, or just 416's I suppose....

 

Why not just drill and pin the rocker stud bosses?

 

Dimension A is 1.773" on most heads, some are 1.807, and I suppose there could be more options.

I've seen stud pullers that only go over 2 studs at a time. I don't know how necessary it would be to pilot the tap.

 

I could just pin it, but I figured it'd be better/more reliable to tap the holes, and with it only being a bit more expensive if I do it myself....
Pinning will be plan B.

? That's kinda an oddball dimension.....
Yea, the comp cams stud puller is just for two, but I figured once you pull one out, it'll just be floating there, and won't be constrained over the hole you just left behind...but if it's over 4, then it won't be going anywhere, and I can do a few at once.... oh, and it was $50, yet a 1x1x12" piece of mild CRS is $9.....
Anyone know my last dimension? Thanks

(was that 1.773" a 416 head by any chance?)

 

I'm going to use a caliper and give it a shot. I'll drill the 4 holes with a "U" drill bit, then tap them to 7/16-14, then slide it over the 4 studs. I should be able to stack some washers on one stud, and tighten down and pull it out, meanwhile do the same to the other 3 studs, but just tighten it enough to hold the jig down. Then after one stud comes out, i'll run the tap through my pre-tapped 7/16" hole, and tap the boss...
After it's tapped, I can mill down the boss .4"

If it works i'll post dimensions and a solidworks model or something...

How crucial is the .4" ? As long as it's level across all the bosses, it could be .35" or something right? The threads could be a little taller or shorter (just consistent), but you tighten your rocker down correctly and the boss height isn't super critical right?

 

If I was that concerned enough with making sure that the tap was straight, then I wouldn't tap it as you describe unless the tops of the bosses had been milled perpendicular to the holes first.

I'd probably stick it on the drill press table with sine plates under it, put the gears in neutral and use the chuck to keep the tap straight while I started turning it in by hand.

Rather than go through all that though, I'd be a lot more likely to just run the tap in by hand.

 

Sine plates? what are those? I'm guessing this is how I would get the head to be angled such that the top of the bosses are perpendicular to the milling bit?
Any more info on "sine plates" would be helpful...

well, i'm pretty sure I wouldn't be able to tap this by hand very straight at all, (like freehand)... I guess if it's not too crucial that these studs are absolutely perfectly straight up, then i'll just make this piece of steel into a basic guide, not too exact or anything...
Well, i'll see, I just drilled a piece of aluminum flat bar with 1.773" hole spacing, i'll take it home and check it with the heads, if it's ok, i'll drill my 1x1" block and use that...

 

Nevermind, found the sine plates on mcmaster carr...
I'll have to dig around and see if we have some of those...

 

Well for your (and my) purposes, pinned studs are just as reliable and ther is much less chance of breaking the stud boss trying to remove the old studs Avoids errors machining the tops of the stud bosses for guideplates and not to mention broken taps. Its a lot easier and less $$$ too.

retaining the cast-in pushrod slots (as opposed to guideplates) lets you run stock non hardened pushrods too. If you want to run 1.6 ratio rockers just lengthen the pushrod slots in the heads with a 5/16" rat tail file in a electric drill. Lengthen them not widen.

 

hmm, would stock pinned studs and stock pushrods and no guideplates be ok for a comp268XE ? (lift-wise?) and 1.5 roller tip rockers?
I wasn't clear on when you'd need guide plates, and when it'd be ok just to lengthen the pushrod slots...

Thanks
-J

 

Should be fine with 1.5s. You might want to see if you can get enough lift for the XE268.

 

You'll be fine... I've run stock pinned studs with stock pushrods thru stock castin pushrod slots with roller tip rockers on my 350 with a huge .560" lift solid race cam to 7000+rpm with no problems. Well up until the rings butted and took out the piston ring land and the very shaved deck on one of the cylinder heads. But we won't get into that...

 

I believe Mr. Gasket sells a stud kit that does not require machining of the bosses in case you dont need guide plates.



http://www.jegs.com/cgi-bin/ncommerc...66&prmenbr=361

This is also a good idea.

http://www.jegs.com/cgi-bin/ncommerc...11&prmenbr=361

 

yea, i'm juggling the idea of pinning the studs, or collarless threaded studs, or machining it down for hex collared studs with guideplates+hardened pushrods (apparently new pushrods are needed for that... go figure)...

My main concern was if a comp268XE would be ok with the stock pushrods slots, which, judging by f-bird, sounds ok.... (heads will be 416s I believe)...And/or if they would need to be lengthened, or if that's just a >1.6 rocker ratio thing...


I don't understand, enough lift *for* the 268? or you mean from it?

 

oh, shaggy, I never followed the links until now, so yea, that's the idea....


and, the point of this thread is that I get to make that tool from the second link.... I just have to drill out my holes big enough to clear the 7/16" tap.... oops.


Other than that:
1.773" hole spacing
2.79" spacing for dimension B
I drilled it with a 'W' bit, which slides over the studs, but not big enough to get the tap in... so, i'll try bigger and see if it guides the tap well...
I tried it by hand (on my 993 practice heads), with a bottoming tap (all I have...), and it was basically straight, but I don't know how straight it has to be to be good enough... (since rod bearings have to be within .001" for example, and that's not exactly something you can eyeball...)

 

Make sure your valve guide bosses are short enough to take .480 of lift.

Check the size of the recommended valve springs too, your spring pockets will probably need to be enlarged and/or deepend.

 

oh, yea yea, i'll check those. I think I have the tooling to shorten the valve guide bosses myself (HSS or carbide endmill, 1/2" say...), but enlarging the spring pocket... might be cheaper to get a shop to do it rather then buying a tool...
I have to get a valve spring micrometer (would a digital caliper work?), and shims, etc. etc..
-J

 

If you're going to shorten the valve guides, you might as well cut them for positive valve stem seals at the same time.

A valve spring micrometer is nice, but not absolutely necessary.

When you get shims, it's a lot cheaper to get them in bulk at the local parts store than to order the sets from the cam manufacturer. For stock sized pockets ask for a 203X shim, replacing X with A for .060", B for .030", or C for .015". If you enlarge pockets you might need a 303 instead. If your counterperson is any good they'll be able to figure it out from the I.D. and O.D.

You might even want to think about larger valves and seats, too.

I don't know what the going rates are like in Calgary, but a shop here will mill the face, cut the valves and seats, and assemble for $100 a head.

 

yea, I was thinking 1.94 intakes, and positive valve seals sounds good...
$100 a head sounds too good to be true, but I suppose it's worth a look, I just want to do as much myself as possible for the learning experience...
I'll see what machine work is possible for myself to do, and what i'd have to buy a $100 cutter to save $50 of machine work

 

The funny thing about tools like that too is that you're never going to have every tool you need to do all your machine work yourself, so you might as well just get the shop to do it when you take it in to have something else done.

Unless you're an automotive machinist yourself, of course.

 

I've been piddling with a Mill I bought a few months back, I'm far from an expert machinst, but have done so much in the past with much less.

My suggestion is to mill the bosses first, I took a set of 083's I ported, measured (via the quill) the lowest boss and took .4 off (ede's suggestion) then set the quill depth to that, and did all the rest.

I then let the mill tap all the bosses, set it up fpr 55rpms vs quill speed (have power down on mine) and just kept squirting in tapping fluid. I tapped after the mill to keep the integrity of the start thread...ran a hand bevel reamer for a bit of touch up.

That's kinda secondary though, I made a jig with 3/4 flat bar to pull the studs...was going to run them out with the impact wrench (heard many have done it this way, but was concerned I'd crack the boss from the chatter) so instead I pulled them by hand...After the first set of washers was used up, I used body washers...look like a "U", and crissed crosed them...this way I didn't have to reove the nut, just backed them off and slid in the "u" washer...made it a bit quicker, IMO.

 

hmm... what's the quill?
I guess you meant you set the depth stop to .4" down from the lowest boss?
That's a good idea with the body washers..

Well i'm still a ways off from P'n'P'ing my heads, probably this fall, along with the 350 build this winter, so right now i'm just toying with the 993s... I might just do everything *free* I can to the 993s as practice, time for me is free...

Thanks
-J

 

The quill is the downfeed mechanism...least I always thought it was called a quill...yeah, pretty sure it is.

Yes, set you depth stop to .4 from lowest boss...I used the edge of the "bit" i got from my machineshop, it cuts the guide and the seal (.50-something) at the same time, they told me it was about a 40 dollar bit, and told me to try it out.

It worked well, seals have a good tight fit...although I haven't run the heads so can't tell you if they'll stay on...but I'm pretty optimistic that they will though.