rocker geometry prod length (solved) Thanks everyone

[veltror]

I hope somebody can give me some sane advice once this is done i can fit the motor.I have read just about every post on geometry amnd making cutom length pushords. I have been doing dome work on my 1955 but I need to know if I am an idiot.

This is what i have done, torqued up the rovker shaft, out in the adjustable pushrod set ti to its shortest.
Set valve clearance to 0.06.

Put on dial gauge, find max lift
Divide that by 2
set the motor so half lift is achieved.

On number 1 and 2 all pushrods come out as 28cm similar to stock
Now this is number 4 exhaust does this geometry look right. I think I need some more shims.

Motor ia 90.5x76
webcam 163
cb ratio rockers 1.25

This is geometry at half lift on number 1

[busman78]

Did you determine calculated max lift first and try to achieve that with the adjustable push rod and shims?

(advertised cam lift) X (rocker ratio) = Calculated Cam Lift

You have to have that number and get as close to that lift, the number usually ends up being lower, from there you get the needed half lift, then you need to do the fitting and fussing, shimming, measuring and the good old eyeballing.

edit - the above the "Clifford Notes" version

[veltror]

valve lift as per cam card is 0.430,

so 0.430 x 1.25 gives 0.537

I thought the formula was

lift on cam card / 1.1 and then ,ultiply by 1.25
giving

0.430 / 1.1 x 1.25 = 0.488

I was seeing something like 0.471

This geometry of the vlave train is driving me up the wall, i must have tead dozens of threads...

I appreciate the comments

[Dan Ruddock]

Ok, you choose a very good cam but made a very poor choice on your rockers. Sell them in the classifieds to the next unsuspecting victim. Buy this type

https://www.thesamba.com/vw/classifieds/detail.php?id=2093819

Buy an adjustable pushrod tool. Assemble without any shims, adjust the screw with three threads exposed above the jam nut and adjust the pushrod tool to fit. Then copy the tools length to your new pushrods. Done

The cam you chose is what I call a tweener cam that works best with 1.25-1.3 rockers. It will have about .480" lift with the rockers I have recommended.

Dan

[MConstable]

[busman78]

Okay just making sure you got the start calc right for without it nothing really works. What Dan said is easy and real close if not dead on.

But...going from a squared up half lift you can see the relationship of the rocker to the valve stem and if gets off a decent angle then it is time for shims under the rocker stands, from that the whole process starts over again, you have to set the PR length again, get to half lift and watch the contact points. Yes it can take hours.

Possibly with the rocker assy Dan recommends with the cam you have all the planets align and you just need proper sized push rods.

[Danwvw]

The elcheapo 1.25:1 ratio rockers don't set right on any engine. I have them (Scat ones) on a Webcam 118 and they give a nice lift and sort of work. The Webcam 163 doesn't really need ratio rockers though. Yes get the quality ones or go with stock rockers. With those your need wide mouth pushrod tubes so they don't rub the pushrods like these did.

_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[Dan Ruddock]

[veltror]

This is all great knowledge, first stroker I have built, all my other builds have been stock type1 or type 4. So I went with a clear mind to have another go at this.

I placed a 2.2mm shim under the rockers, adjusted the swivel feet to .002 with a couple of threads showing. measured full lift at .486, so at half lift the adjusting foot is pretty much in line with the valve , looks like I may finally have cracked it, What do think

half lift

[UK Luke 72]

Take the pic from the exhaust port side... Makes visualising it much easier...

No lift

Half lift 0.211"

Full lift 0.422"

_________________
2276 Beetle build https://www.thesamba.com/vw/forum/viewtopic.php?t=670744&highlight=2276+beetle+daily
2276 EFI Conversion https://www.thesamba.com/vw/forum/viewtopic.php?t=689172

[veltror]

just spent some time on this and this is what I have so far

no1 ex 0.468 max lift half lift 234 prod length 281
inlet 0.474 0.237 pushrod 282

no2 inlet 0.462 half 0.231 pushrod 281
echaust 0.466 half 0.233 pushrod 281



These look pretty good as doe the angles, i will photo these later from the exhaust port as you say. But i think i may have cracked this.

[mark tucker]

hose are very good rockers....with that said I like the type dan recommended better.....I have used cb rockers with that cam..although I don't remember weather they were 1.25 or 1.1 I think they were 1.25. I don't remember too much other than those rockers are much nicer and far better than the vw or scat's. but I prefer the adjuster on the pushrod end rockers for all my personal stuff...( although I have 2 sets of the scat oe type 1.25's on my shelf.... like dan said the pivot length is just too short.I wish cb had re did that when they re did the rocker. if you do use those I set them up with a max of 1/2 turn out from seated.I used lash caps with those so I under cut the rocker for the adjuster to go farther up in there. and sloted the threads where needed to ensire full time oiling...although I wont use elefeet adjusters so that dosent matter there.I only use ball foot adjusyers with those type of rockers.and lashcaps on all engines regardless of rocker type. 1.1 rockers usualy need to go up about 1mm shim from my experience..I think the 1.25 need about 1/2mm, but it's been about 4 years since I did a set of them. so...I cant remember.. but I do not do the half lift crapola. I could give a crap what half lift is or what the geo is at half lift, I go for the best opening and wfo geo. the 1.1 rockers are bad about pushing outward before depressing the valve if they are too low. that is lost motion and guide wear. also you really need to use a soft spring for checking so you can see what the rockers are doing.they will slide with a soft spring. they will bend the valve stem& deflect when full spring pressure is used. they slide when the engine is running and everything is oiled up good,most will not slide when operated slow by hand. even roller rockers slide more than they roll when running.and roller rockers can also bend the valve stem when turning the engine over by hand or bump switch with stiff springs. as for your being a idiot....I haven't a clue. but you did ask for help&sugestions and most idiots don't...some do but don't listen. good luck.

[veltror]

Well i took everything off and started from scratch

I am getting a max lift variance of between 482 and 472 so pretty close to the 480 I expected. used a 0.86 shim under the rocker blocks and every single pushrod came to 282mm i was expecting some variance. I hace some nice heavy duty aluminum pushrods from John at aircooled.net, so i now need to find somebody with a lathe.

Below is a picture of laf lift for your delight and derision !

Unless somebody says this is noot good enough I good to go. Thnaks very much for the advice it is really appreciated.

[FreeBug]

Usually, for proper geometry, the stock-type rockers need to be ground/milled down under the elephant's feet. This would mean that your existing push rods are too short?

How is the valve stem's contact area at half lift, too high, or too low?

[Dan Ruddock]

[veltror]

It looks about right