Is it me or is it the cam and does it really matter?

[scubaseas]

Help! I have been tossing lobe centers and cam timing around in my mind for long enough that MC Escher 's "Relativity" is starting to make sense. Or the album cover from Greatful Dead "Mars Hotel". I am trying to decide if good is good enough or if I should replace a brand new cam shaft. I guess I am just asking for a check on my "logic" and methods.

All new parts. New case, new gears, new bearings, new push rods, lifters and rockers, new cam. Cam manufacturer says measure at valve retainer at .050" lift. No problem. Type1 upright engine.

Dig out my timing degree wheel, set up dial indicator, Find True TDC, Make pointer. Set up dial indicator to measure at retainer. Make sure gauge/dial indicator(DI) is parallel to valve in 2 planes, not hitting anything and rides in the same spot on the retainer for total travel. Use both small ball tip and roller tip on gauge/DI and get consistently the same results. Small ball tip used. Take readings, compare to card in box from manufacturer. Compare card in box to manufacturer's website. My results vary from manufacturer on one lobe, and only the back side of that lobe. Stop, have beer, come back next day. Try again. same results. Three times. Come back next day, measure all four lobes and find as below. Note that I would take a reading, mark it down and completely remove the measuring gear and the set it up again. I am consistently getting the same readings =/- 1/2 degree and within .002". So 9 readings over three days removing and setting up measuring tools each time and all readings are the same. All open/close readings at .050" and after locating TDC by putting a long bolt in the spark plug hole, mark/measuring when it hits bolts, rotating engine around until it hits on the other direction and dividing those two marks by 2 for true TDC. TDC is spot on factory mark for both 1-3 journal and for 2-4 journal. Rockers are 1.1:1. Push rods all the same length. Zero lash obtained by no play rocking arm then turning adjuster just until push rod will not easily rotate with finger. Valve lift is total max lift measured at retainer. Open/Close time measured at retainer and at .050" lift.

CAM CARD SAYS:
Intake Opens 13* BTDC Exhaust Opens 49*BBDC
Intake Closes 49* ATDC Exhaust Closes 13* ATDC
Valve lift .460" Valve Lift .460"
Duration @ .050 242 Duration @ .050 242
Lobe Center 108 Lobe Center 108

MY RESULTS CYL 1-3 CYL 2-4
Intake Opens 14* BTDC Intake Opens 14* BTDC
Intake Closes 49* ATDC Intake Closes 49* ATDC
Valve Lift .462" Valve Lift ..462"

Exhaust Opens 49* BBDC Exhaust Opens 47* BBDC
Exhaust Closes 9* ATDC Exhaust Closes 7* ATDC
Valve Lift .453" Valve Lift .435" (sic)

From my results which I think may be close to accurate, it seems that the exhaust closing is advanced on #1 cylinder by 4* and on #2 cylinder by 6* Which changes the exhaust lobe centers from 108* to 110* and the duration @ .050" down to 238* on # 1 cylinder exhaust and to 236* @ .050 on #2 cylinder exhaust. Also the lift is off from the card spec by approximately .025" on #2-4 and .009" on #1-3

+/- a degree shouldn't be a big issue. Nor should the .009". The exhaust closing sooner would presumably make more low end torque but slightly less power ? I have no idea if the results I got, presuming they are accurate are "normal" for a cam grind or not. Is difference in the valve lift of .025" a concern or normal for a cam?


So question are: 1) Is it me or is the cam off and 2) Would you use this cam or get another one?

Thanks in advance for your time and consideration. Apologies for how this is typed, for some reason it drops spaces and you're not seeing nice neat blocks of readings. Beyond me to figure it out.
_________________
Al

08/1970 T2a Westphalia owned since 1980

ASE Master certification. 50 years pushing a wrench
Retired

[modok]

Don't measure at retainer, measure at lifter.
Yes I know it says at retainer, so good job following the instructions but really the SPECS are at the lifter. So if you want to compare the CAM to the spec, check at lifter.
If you want to know how it all works out, check at retainer.

If you knew the lift at the cam, then you could rule out your rockers. Rockers are a lot harder to figure than lift at the cam!

Even a very good cam, expect lift to be +/- .005", and timing +/- 2 degrees compared to card

Cheaper cams, will vary twice that, very commonly.

[scubaseas]

Thanks very much Glen,

I have now measured (albeit just once so there maybe some set up error) at the lifter and have gotten the lift numbers to be closer together but the exhaust closing points are still advanced. Although there is still a difference of about .009" between highest and lowest which I guess is fine. The difference of .025" must be in the rocker which I should be able to confirm by moving it or using another in it's place.

I am getting the same open/close times measuring at the lifter as I get measuring at the valve retainer. The 2-4 exhaust close point is measuring 4* advanced, the 1-3 exhaust close point is about 6* (maybe 5.5*) advanced.

I suppose the 4 to 5* advanced exhaust timing may not be a bad thing. In theory more low end torque.

I am surprised to see this much difference between what I see and what the card says. Cam is a Web Cam 218.
_________________
Al

08/1970 T2a Westphalia owned since 1980

ASE Master certification. 50 years pushing a wrench
Retired

[Dan Ruddock]

I second what Glen has said. It is very rare for you to get a exactly match to the card for many reasons.

Dan

[vugbug68]

I'd be most worried about the lift on the #2 and 4 Exhaust lobe. Measure the lift at the cam and see how it compares to the others
_________________
71 Super - Backroad Thrasher
66 Corvair - Weekend Cruiser
90 4 Runner - Muddin

[mark tucker]

there are a lot of parts that flex, do as morloc says, at the lifter. I doubt there are many off the self cams that are what the pre printed card says it is.

[scubaseas]

[scubaseas]

[modok]

It is a bit strange. I measured a web 218, and found duration to be within 2 degrees, all lobes.

[vugbug68]

[mark tucker]

FYI many engines have diferent "port timing" to broden the torque and power band. also to sometimes to combat issues,like heat. just like the v8 cams that have swaped firing order to cure or move a issue to another cylinder or get rid of it all togeather. ford did this on thier small blocks, some had one firing order and some had the other. basicly the same engine but diferent cam with diferent firing order. so there may be a method to some maddness that you dont see. or..the cam is just a normal production cam withen tollarances. remember these cams only have 4 lobes...just think if it had...16 lobes and quality like that . might be why they like doing the vw stuff. I wish I had a cam grinder..... that way I would still be in the same boat..I would not get what I wanted but I would get what I got...just like now. ( Im from the v8 world and have many billet cams that are what the card says they are...and the card isant what the catalog says it is...it's better.) I wouldent worry tomuch, it's only a vw.

[scubaseas]

[Clatter]

Rockers are always all over the place.

When racing classes require stock factory parts,
Guys will sift through bins and buckets of rockers,
Looking for matched sets with max lift.

I have seen differences in lift far worse than what you show here.
Yours actually look good.

Swap the rocker location around,
And see if the numbers follow..
_________________
Bus Motor Build

What’s That Noise?!?

[scubaseas]

Got a new cam. Put it in, followed same measuring procedure, inclusive of beer and multiple days.

New cam matches the card within 1* timing and lift within .004" for all four lobes when measured at lifters. Yes there is a slight difference between the rockers if measuring at retainer but the original cam appears to be not ground quite right.

Thanks to all for your input, greatly appreciated.
_________________
Al

08/1970 T2a Westphalia owned since 1980

ASE Master certification. 50 years pushing a wrench
Retired