Rocker geometry for woods tw68 (pics)
 

4.250” bore twin cam for dragracing
110 heads w/2.150 and 1.650 valves
setting it up for woods tw68 (.678@268 —260/226 tdc lift #’s)

This a preliminary check of where the rockers are hitting on the valve tips...haven’t addressed tdc lift clearance and I know will probably need to sink VJ to get there
i just wanted to see where it was at right now
the lines across the tips are there but very hard to make out in one of the pics (for anyone not getting what this shows—these are the contact points at basically zero lift or the beginning of opening and then at max lift—-showing where the rocker is sweeping across top of valve)

the intake is quite centered over the tip
the ex is more to one side but doesn’t seem too bad, maybe ?????
granted I come from 4cyl dragbikes so these are relatively new to me but building engines is somewhat universal

what do you guys think? If one needs to alter this geometry what’s the preferred method—offset rocker mounting pad, spacer under pad or conversely machining base of pad to “lower” rockers????
what is your guys methods for getting an accurate measurement of tdc lift (v to v) clearances?
im thinking make a tool like the Trock dial indicator/screw mount.
One that has screws to open the valves and hold a dial indicator that tracks movement. Haven’t seen the Trock piece up close and can’t tell if it can do both at same time but I can make one easy enough (have a small machine shop)

Here’s some pics


https://cimg9.ibsrv.net/gimg/www.hdf...0be74306b.jpeg
https://cimg6.ibsrv.net/gimg/www.hdf...a5434d935.jpeg
https://cimg5.ibsrv.net/gimg/www.hdf...f5a786192.jpeg
https://cimg1.ibsrv.net/gimg/www.hdf...514bd5172.jpeg

Pics got out of order
mainly concerned with the two of the valve tip (close up shots)
just threw the others in cause I’m sure you guys like pics of shop work, engines and stuff !!!!!

https://cimg3.ibsrv.net/gimg/www.hdf...f23a402e92.jpg

110 heads intake port 2.150” 315cfm@.600
https://cimg2.ibsrv.net/gimg/www.hdf...8c150c7a2.jpeg
Messy engine area

Baisley makes corrected geometry rockers for such situations; they are pricey but you probably know that. Trock tool is the ticket; I have one reasonably priced; PM me if intersted.
https://cimg6.ibsrv.net/gimg/www.hdf...1044a35740.jpg
https://cimg0.ibsrv.net/gimg/www.hdf...0dc6db00b8.jpg

The Trock tool is convenient for checking valve to valve and valve to piston. It's not as good as using solid lifters and bolting the motor together. I've checked the valve to valve with a piece of welding rod and a hammer to flatten until it just fits then measure. The Baisley rockers are a way to go. Ultima roller rockers have a little more arm (1.725 t o1) for better centering on the exhaust but the quality can be hit or miss.

@Maxflow. Yeah I started making a tool last night fashioned around the Trock design but mines adjustable for different valve angles and just a steel weldment rather than a purpose built aluminum casting—gonna go in today and finish it up
So have you ever used the woods tw68 grind, or something compareable ? If so, do you recall what you had to do make it all work?

So Bob Wood told me I had to use his w200 springs but didn’t really say why no other springs would work. Now I fully understand and am experienced with “MOST” aspects of setting up any cam. NOT saying am an expert by no means. So, I’ve been doing these preliminary check with kibblewhite spring setup I had laying around. They are the .655 max lift capable springs, complete kit with bases retainer and keepers. Springs are behive. If I can sneak that extra .025” lift in there without coil bind, retainer to seal contact, and maintain very close to proper installed height, then what else would determine or necessitate a different spring (bobs w200).?????
Kpmi recommend, and that’s the operative word-recommend, an installed height of 1.850”. In my heads, they drop in at 1.950. To get their recommended height that requires a couple shims under the bases (an acceptable method everyone uses). With those shims I can get the travel I need but I’d only have like .020 before the retainer smashes the seal. I want .050. So if I took some shims out and raised the installed height a little I can get that clearance. I’d loose a few pounds of pressure on the seat. What I don’t like is at max lift while still in what kibblewhite says is safe territory (.050” before coil bind), I don’t like the actual appearance of the spring’s coils being so close to touching (coil bind).

i guess I’m wondering if the woods springs are wound in such a way or have different wire od so as to give more clearance, give more overall travel to allow running the recommended installed height and still have “room” to put .650+ lift cam and not be so close to binding

i build stuff based on what works and what’s actually necessary not just what a manufacturer claims is necessary. Don’t fall for the marketing mambo jumbo. But in this case, I’m not as experienced and could be missing something I don’t encounter in 4 valve bucket follower engines.

I've not used the woods cam. The only thing close is the SnS 640 with the ultima rockers which got me into that region. The thing is that I did not use 110 heads, I used ultima and everything lined up. I've used the stock ultima springs and some AVnV Beehives. IIRC the ultima springs were above 200 and the AVnVs were right at 185. No issues but I only spin the motor to 6500 and 640s have gentler ramps.

Wouldn't a longer valve stem change the position of the rocker on the stem?
Also wouldn't a roller rocker beer the rocker of choice at that lift..?

@98hotrodfatboy longer valve would mean having custom made or machining one up from blank
I’m on the fence about roller rockers, from what I can tell don’t get you any measurable performance, don’t really save the guides, pretty much just save tips from getting beat up. Now they may help with geometry but for their price I’m just first gonna look for alternative methods first especially since I can machine my own stuff except
for valve jobs and for relatively simple parts like a rocker stand with relocated/offset mounting I could probably make myself too

get blanks & cuy to lenght & and cut keeper grooves,only proper way to do very high TDC cams,we do all the time on race heads

Not mocking you but to play you do need to pay.. I also think you should reconsider Rollers.. With that much lift there is a lot more lateral force on the stem... Building a hi performance motor does not include shortcuts.. By the way it would be more economical with longer valves than changing the height of the rocker shaft..

Kirby has a very good solution..