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Whoated
Samba Member
Joined: July 05, 2018
Posts: 18
Location: Holland, MI
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 Posted: Sun Sep 16, 2018 5:38 pm Post subject: Cam Gear Offset Issue |
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Hello all, the camshaft on our '73 1.7 manual engine needs replacement, which I'm researching as far as a low-end-torque, low CH temp cam. Just a bit of a bump up from stock, researching the forums and Interwebs I'm finding that a Raby 9550 or comparable grind or maybe Webcam 73 or Scat C25 may give me the results I'm looking for. Unfortunately the Raby is out of my range as far as how much I want to spend on this bus for what it is, but comparing grind profiles etc I'm getting a good understanding of what to look for and am slowly narrowing it down. Still plenty of research to do on this end, any input appreciated but it's been pretty well covered elsewhere on the forums. Meanwhile I have a real cam problem that I haven't been able to solve:
As most know, the cam gear has an offset to deal with the various crank/cam bore spacing that the cases had when new. Surprising to find that most claim that the range is -4 to +4, when I've found that it's actually something like -7/+7. The original crank/cam gears on our engine are in excellent condition, the problem I have is that ours is a -5, and on top of that it's a "B" gear (magnesium). I can easily handle grinding out the rivets/machining/converting to screws, the problem is it's a mag gear and if you listen to most here the mag gears weaken over time (which I understand) and catastrophe lurks at the next milepost. I'd rather "upgrade" to an aluminum gear if possible. It's difficult enough locating an aluminum gear with a -1 or -2 offset...-5 has been impossible, most don't even know that they existed. So what's the fix aside from line-boring the case (ain't gonna happen) or something similiar? Any suggestions much appreciated, thanks in advance!
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Take care,
Ted
‘73 Westy Stock 1.7 |
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SGKent 
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Sun Sep 16, 2018 7:45 pm Post subject: Re: Cam Gear Offset Issue |
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I use the webcam 142 and highly recommend it in a bus. A bus is not a normal car and it can't be compared to a 411, or 914 like a lot of people here do who understand about cams only what they read in the ads.
As for the B gear - yes they get brittle with age. I would not use it myself. To find the cam gear number you want, you may need to shop a while for a used 2L cam with an aluminum gear that is the right number.. I might have a couple used -4 aluminum gears but all my gears have been visually inspected, milled already for an aftermarket cam, and I have about $125 in each spare gear with the cost of the used cam it came out of, paying shipping both ways, and the machine work at the old RIMCO. I'd have to get what I have in it back out plus shipping. A -4 might work because it is worn a little but there is no guarantee it will fit. Maybe someone else here has a good used aluminum -5 and you can pay to have it machined locally. Keep in mind that no one, including myself can guarantee what a gear will do in the years ahead. A used gear is a used gear. AND, it could turn out you need a worn -3. That is why I bought every used cam I could 10 years ago, ground the gears off and had them milled. That way one can pick and choose gears to find the right fit. I tried a new Brazilian gear and got burned - had to split the case again to replace it. The new gears aren't always round and they can walk the crank and cam back and forth - hammering at the thrust surfaces.
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Abscate
Samba Member
Joined: October 05, 2014
Posts: 22670
Location: NYC/Upstate/ROW
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| Posted: Mon Sep 17, 2018 5:34 am Post subject: Re: Cam Gear Offset Issue |
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I know its buried here on the Samba somewhere but can someone remind me exactly what the designations -7,-6..... ,6,7 physically refer to?
Is is some tolerance of angle on the helical cut, depth of gear cut, how many times you should filter your transmission fluid?
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12728
Location: on a bike ride somewhere
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| Posted: Mon Sep 17, 2018 5:45 am Post subject: Re: Cam Gear Offset Issue |
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| Abscate wrote: |
I know its buried here on the Samba somewhere but can someone remind me exactly what the designations -7,-6..... ,6,7 physically refer to?
Is is some tolerance of angle on the helical cut, depth of gear cut, how many times you should filter your transmission fluid? |
Pitch of gear teeth, though not unit based.
Throughout VWs servicing of air-cooled engines, they realized that tolerance stackup issues between case bore, bearing size, crank runout, crank gear tolerance, and cam gear tolerance all had slight production differences. To obtain proper gear mesh so that your engine doesn’t rattle at hot idle or grind the bearings to death during break-in, there were six or seven original pitches of gears. As the potential for line-bore cuts were needed over the years, VW introduced more sizes. I’m not sure of the Type 4 sizes, but I have held, in my hands, Type 1 engine cams from +6 to -6, flat and dished, for a total of 26 stock cam gear possibilities.
Because of wear like SGKent mentioned, used gears might also vary from one another. You will also find that simply replacing your main bearings or can bearings or crank gear will allow you to find perfect gear mesh with different cam gears.
I took a lot of shit from vendors for asking them to dig through their old boxes for +4 and -3 gears over the last three years, but there’s a reason my Type 1 engine sounds brand new at hot idle after 70,000 miles... I really think every Engine Builder should make their best-faith effort to locate the most appropriate gear for their situation. Otherwise you’re just an Engine Assembler.
Are you using single or double thrust cam bearings?
Do you know how to check for cam gear backlash?
Robbie
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Mon Sep 17, 2018 7:18 am Post subject: Re: Cam Gear Offset Issue |
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The gear pitch +/- number is a narrowing or expansion of the gear diameter based from the centerline to the outer circle of the teeth....divided by the number of teeth.
The complexity of the gear.....comes from the fact that since we cant change the number of teeth...or the centerline spacing of each tooth.....in order to change the diameter from smaller to larger without changing gear teeth or helical mesh angle .....the triangular cross section of each gear tooth changes very slightly across the cord of the gear.
All of Web cams gears are -4.
The information about cams and Raby cams is a bit dated. Out of the three cams mentioned so far in this thread.....the Raby 9550 has been superceded a few year back by the 9590. I'm pretty sure its no longer available except maybe by special order.
They are both very slightly split pattern versions of the same cam. And both are verions of the web #73. The difference in the two RAT cams is that the 9590 has slightly more duration on the exhaust (among other small nuances) to run a little cooler with ethanol fuel.
The 9555 is a Web #73 with 5° more exhaust duration for better port scavenge for cooler running. Otherwise its identical....same valve lift.....426° on both E and I and same lobe center and valve event timing.
The web #73 runs excellent.....yes....IN A BUS.....been there....done that........but ONLY.....with a 1.7L with its small valves and short stroke.......and ONLY with carbs.....and only with a manual trans. I am just assuming you are keeping it 1.7L and wont be grafting on L-jet injection.
The 9550 or 9590 are both slightly cooler running versions of the Web #73.
The Web #142.....as suggested.....is what you would want if you were building a 2.0 with L-jet. It has LESS valve lift AND duration ...which is better for the larger diameter valves and keeps the intake velocity up. It is also a split pattern cam with 5° more duration on INTAKE instead of exhausr.......to have better/longer overlap. This makes a positive diffference with the longer stroke of the 2.0L engine. It has the same lobe center (108°).....as the other three cams mentioned here.
If you are staying with a carbed 1.7L.....WITH NO OTHER MODS (like head porting or larger valves)......I would go with a basic Web #73 which I know for a fact runs very well in a carbed 1.7L....IN A BUS.....or even better...a 9590...which will run a little cooler. Ray |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Mon Sep 17, 2018 7:30 am Post subject: Re: Cam Gear Offset Issue |
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| Abscate wrote: |
I know its buried here on the Samba somewhere but can someone remind me exactly what the designations -7,-6..... ,6,7 physically refer to?
Is is some tolerance of angle on the helical cut, depth of gear cut, how many times you should filter your transmission fluid? |
As Robbie indicated, it is variance in the pitch of the gear teeth so VW could control the mesh between the crank gear and the cam gear. If the two gears are too tight one goes minus on the numbers. If the gear fit is too loose one goes plus on the numbers. Hence - one might have .003" lash with say a -4 so they try a -3 and have .002" lash +/-, maybe then they try a -2 and have a .001" lash - or maybe the -2 is .000" lash which is Ok too as long as the lash is not to tight that the gears try to lift one another. I usually shoot for about .001" lash. The way it used to work because the gears are riveted on is VW sold the camshafts new with different number gears on them. Or you walked in, handed the parts house a worn -3 cam and they handed you back a -3 reground cam.
For some reason type 1 motors do Ok with reground cams but type 4 seem to wear out quickly with reground cams. Also reground cams can't bring back wear to the thrust surface so often the thrust surfaces are already at the limits if a type 4 cam needs to be reground. Adding double thrust cam bearing just accelerates that process of wearing the cam thrust surfaces.
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Mon Sep 17, 2018 10:35 am Post subject: Re: Cam Gear Offset Issue |
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| SGKent wrote: |
| Abscate wrote: |
I know its buried here on the Samba somewhere but can someone remind me exactly what the designations -7,-6..... ,6,7 physically refer to?
Is is some tolerance of angle on the helical cut, depth of gear cut, how many times you should filter your transmission fluid? |
As Robbie indicated, it is variance in the pitch of the gear teeth so VW could control the mesh between the crank gear and the cam gear. If the two gears are too tight one goes minus on the numbers. If the gear fit is too loose one goes plus on the numbers. Hence - one might have .003" lash with say a -4 so they try a -3 and have .002" lash +/-, maybe then they try a -2 and have a .001" lash - or maybe the -2 is .000" lash which is Ok too as long as the lash is not to tight that the gears try to lift one another. I usually shoot for about .001" lash. The way it used to work because the gears are riveted on is VW sold the camshafts new with different number gears on them. Or you walked in, handed the parts house a worn -3 cam and they handed you back a -3 reground cam.
For some reason type 1 motors do Ok with reground cams but type 4 seem to wear out quickly with reground cams. Also reground cams can't bring back wear to the thrust surface so often the thrust surfaces are already at the limits if a type 4 cam needs to be reground. Adding double thrust cam bearing just accelerates that process of wearing the cam thrust surfaces. |
Yes!
On the reground cam hardness issue....I have no idea if its because type 1 cams had a thicker hardening layer on the lobes (I doubt it...they are all just case hardened from the factory)....but I suspect its mainly because type 4 cams have sharper lobes and ramps...and that offset wear path applies more nose pressure.....but reground type 4 cams I have never had good luck with combined lifter and cam lobe wear.
Unless something special was done.....its just not hard enough after regrind.....all the more reason to ALWAYS get a NEW cam at high miles when rebuilding. The web cam products are pretty nice as they are nitrided.
When I spoke to Web cam a few months back....I had always "heard" their cam gears were all -3. They noted they are actually all -4.
Also.....to be clear....the gear does not necessarily get bigger in total diameter...say from a -3 to a +3. It might....but that is not really what they are aiming for as that would put deeper tooth penetration into the valley. What "grows" is the triangular cross section through the cord of the gear tooth and/or gear valley angle. There are several tooth profile/geometry changes that can be done to make a gear fit tighter or looser with its counterpart.
Its hard to say exactly what someone like web cam is varying to change their pitch.
I also agree with Robbie that there are enough subtle dimensional changes in building an engine that...just changes to cam bearing shells and the cam blank itself....can make a new cam gear with a number several steps away from what you had stock.....fit just fine.
I was actually quite surprised a few months back on the 1.* build I am working on ...that a brand new -4 cam gear from Web...actually fit so tight. Ray |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Mon Sep 17, 2018 11:05 am Post subject: Re: Cam Gear Offset Issue |
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| Quote: |
| When I spoke to Web cam a few months back....I had always "heard" their cam gears were all -3. They noted they are actually all -4. |
I have heard from usually reliable sources that those gears are both 0 and -3. To be frank, I don't think anyone knows for 100%. It is all together possible that VW stamped the originals after putting them on a cam and running them in some kind of machine that tested them. - Thus those gears could be all over the place with most of them falling in the low negative numbers. The one I had ran from zero clearance to .0015" in runout, with two high spots. If one just says that was .0075" clearance then it was tighter on that engine than all the -2 and -3 gears I had. A -2 gave me about .001" all the way around, and -3's about .0025". Based on that, the aluminum gear I had (which cam from WebCam) was closer to a -0- or -1. It is a moot issue because it made such a racket I split the case again and went to a factory gear which is quiet.
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Whoated
Samba Member
Joined: July 05, 2018
Posts: 18
Location: Holland, MI
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| Posted: Mon Sep 17, 2018 5:06 pm Post subject: Re: Cam Gear Offset Issue |
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| raygreenwood wrote: |
All of Web cams gears are -4.
If you are staying with a carbed 1.7L.....WITH NO OTHER MODS (like head porting or larger valves)......I would go with a basic Web #73 which I know for a fact runs very well in a carbed 1.7L....IN A BUS.....or even better...a 9590...which will run a little cooler. Ray |
Thanks Ray, much appreciated. My steep learning curve re: VW cams is beginning to level out (slightly), I think I'm on the right path with the Web 73. If the Raby 9550 didn't cost more than we paid for the bus I'd be all over that kit, I appreciate the value of the lower CHT and think it's worth the extra cash. But we're just going to putt around the next few years, nothing stressful to the bus, very little highway. Stock 1.7, keeping the carbs, everything stock. Just want a slight bump up from stock.
Re: the -4 Web gear, Hmmm...I'll have to call to see if one could be returned if it didn't play nice with the crank. Hand-turned in the "half shell", not driven of course. 
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Take care,
Ted
‘73 Westy Stock 1.7 |
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Whoated
Samba Member
Joined: July 05, 2018
Posts: 18
Location: Holland, MI
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| Posted: Mon Sep 17, 2018 5:37 pm Post subject: Re: Cam Gear Offset Issue |
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| asiab3 wrote: |
I took a lot of shit from vendors for asking them to dig through their old boxes for +4 and -3 gears over the last three years, but there’s a reason my Type 1 engine sounds brand new at hot idle after 70,000 miles... I really think every Engine Builder should make their best-faith effort to locate the most appropriate gear for their situation. Otherwise you’re just an Engine Assembler.
Robbie |
^^^This. I am an assembler at this point with VW and large aircooled engines. But I like to think I'm smart enough to absorb everything I can from this site as well as others before I get into trouble. Thirty-eight years ago I got into Italian iron and have or have had a variety of Alfa Romeo sedans, Fiats, Lancias, and assorted oddball stuff. I knew very little about them in 1980 when I bought the first one (and think: NO INTERNET SUPPORT), but now I can perform a quality drivetrain overhaul on most, know the specs, know the tricks, I know what matters and take my time to do it right. Today with the bus I feel like I did 38 years ago with my first Fiat: combined apprehension/intimidation/utter ignorance. And it feels great.
I've read Wilson's bible right thru at least twice, and use the Bentley. They're both always close at hand and along with many folks here are what make me a quality VW engine assembler. And I'm not giving up on making sure that the cam gear is a correct fit, there's no choice but to do it right.
Thanks Robbie...another good Sambista.[/i]
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Take care,
Ted
‘73 Westy Stock 1.7 |
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Whoated
Samba Member
Joined: July 05, 2018
Posts: 18
Location: Holland, MI
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| Posted: Mon Sep 17, 2018 5:45 pm Post subject: Re: Cam Gear Offset Issue |
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| SGKent wrote: |
| I use the webcam 142 and highly recommend it in a bus.............The new gears aren't always round and they can walk the crank and cam back and forth - hammering at the thrust surfaces. |
Thanks for the offer and the input, if I run out of options I may have to try one of yours. A $125 cam gear would be a tough pill to swallow but I completely understand.
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Take care,
Ted
‘73 Westy Stock 1.7 |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Mon Sep 17, 2018 6:52 pm Post subject: Re: Cam Gear Offset Issue |
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Just as an FYI defending the 142 - - the Webcam "stock" 142 is the "stock" 100 HP GA 912E and 914-4 European 2L cam. The stock North American bus cam is 70 HP and peaks about 400 RPM lower. I already see a slight drop in manifold vacuum with the 142. You'll see an even bigger one with the 73 and better think about your spark advance system before you give up that vacuum.
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Whoated
Samba Member
Joined: July 05, 2018
Posts: 18
Location: Holland, MI
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| Posted: Tue Sep 18, 2018 6:24 pm Post subject: Re: Cam Gear Offset Issue |
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| SGKent wrote: |
| Just as an FYI defending the 142 - - the Webcam "stock" 142 is the "stock" 100 HP GA 912E and 914-4 European 2L cam. The stock North American bus cam is 70 HP and peaks about 400 RPM lower. I already see a slight drop in manifold vacuum with the 142. You'll see an even bigger one with the 73 and better think about your spark advance system before you give up that vacuum. |
I was aware of that, fortunately it has a centrifugal only distributor. Thanks for the heads up though! Looking at my notes now I noticed that I have the 142 preferred over the 73 since I’m not monkeying with the heads (new Brothers “stock” 1.7’s, I had a sunken valve seat in one of the originals) or anything else besides maybe increase the carb jets from 140s to 160s to feed the little bit of extra breathing. At least that’s what I think it says, I can barely read my own scribbling and I tend to drink a lot of wine while doing research.
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Take care,
Ted
‘73 Westy Stock 1.7 |
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Abscate
Samba Member
Joined: October 05, 2014
Posts: 22670
Location: NYC/Upstate/ROW
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| Posted: Sun Sep 23, 2018 3:58 pm Post subject: Re: Cam Gear Offset Issue |
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| Abscate wrote: |
I know its buried here on the Samba somewhere but can someone remind me exactly what the designations -7,-6..... ,6,7 physically refer to?
Is is some tolerance of angle on the helical cut, depth of gear cut, how many times you should filter your transmission fluid? |
I’m rebuilding a 36 HP for the second time in its life and just found my notes on the cam sizes.
I wrote ....Size’s -3 to 3 designate the off set in 0.01mm from standard cam tooth pitch radius , which is a zero cam
I sure didn’t figure this out on my own but I was around very knowledgeable VW guys in the 60s and 70s who I got this from.
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tommu
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Joined: November 15, 2011
Posts: 618
Location: L.A.
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| Posted: Sun Sep 23, 2018 5:27 pm Post subject: Re: Cam Gear Offset Issue |
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I too have a -5 gear. I posted a wanted add for another -5 gear and got a couple of offers. One from German Supply who may still have one in stock. They have a bad reputation for shipping but they do come through - sometimes with a little some polite reminding..
The replacement -5 gear I bought was actually too tight and caused the cam to lift out it's bore. I went back to my original one but would have gone to a -4 if I didn't have that option. Let me know if you really get stuck and we can work out something for my spare -5.
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