Checking backlash - Camshaft backs out

[kkirwin]

Building an engine for my buddy's '70 bus, 1600 SP. I installed the camshaft and rotated the crank backward per the Wilson manual to check the backlash and it popped out of the bearings. It also seems the end opposite of the cam gear doesn't sit all the way into the bearing, I know for sure the crank bearings are seated on the dowels. I called the mechanic we got the parts from and he said that what it is doing is correct since it is a +1 cam. This contradicts the Wilson manual as he says that if the cam walks out of it's bearings during counter rotation of the crank the backlash is too tight. It doesn't clunk when you rock the cam gear back and forth against the crank gear however. Rotating it in the direction of rotation it seems fine. Who's right on this one and is it anything to worry about?
_________________
1978 Riviera FI Auto Trans
1973 Super Beetle
2003 Dodge Ram 1500 4X4 5.7 HEMI
2012 Suzuki VStrom DL1000
2006 Yamaha WR450

[Tcash]

Hi, Show the Mechanic Wilsons book. If it is too tight it will wear out the cam bearings and the cam gear. If you have the old cam see what number is on it. Next step smaller is a (0) there may be no number, which still is (0). Good Luck

[kreemoweet]

If you are building an engine, you should have the tools to actually
measure the gear backlash. That's what counts. You don't say
how much pressure you're using to hold the cam shaft down in the
case, and it would appear the camshaft is not actually seated in the
case.
_________________
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'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities

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[SGKent]

[kkirwin]

Well, I wrote this right before I left for lunch. I went back out to the garage when I got back and looks like the mechanic sold us the wrong cam which is actually a -1 and not a +1 and the part number on the original is 113.109.111A and the new one is 113.109.019D, damn.

As far as checking backlash the Wilson book says, Quote "This is a difficult measurement to take, requiring a dial indicator, and most mechanics don't actually measure this clearance. Instead, they use two tests that experience has shown to be accurate (ie. rotating the crank backward to see if the cam walks out of the bearings and checking for clunking by rocking the cam and crank gear against each other)". Hmmm, I thought this was the best manual out there but now you are saying it is inaccurate makes me think I should trash it. Damn it again.
_________________
1978 Riviera FI Auto Trans
1973 Super Beetle
2003 Dodge Ram 1500 4X4 5.7 HEMI
2012 Suzuki VStrom DL1000
2006 Yamaha WR450

[kreemoweet]

The "best manual out there" is the Bentley service manual. I can see nothing difficult about the measurement in question,
it all looks perfectly straightforward to me.
Measuring gear backlash (and numerous other things) with a dial indicator and other precision measurement tools is
SOP for any kind of engine rebuild. When you're dealing with specs like .000-.002 inches (as in the present case),
any talk of a "clunk test" is ridiculous. It's true that VW engines are assembled by the thousands without benefit
of appropriate measuring tools, but those efforts can not really be termed "rebuilds", at least not with a straight face.
_________________
'67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities

Stop dead photo links! Post your photos to The Samba Gallery!

[hill]

[Desertbusman]

Wilson's book is great and the best one you can get. Also be refering to Bentley. If you are on your toes you will find a different error in both books. But not relating to the cam and gear mesh.

Well if the cam doesn't even sit down in the bearings why would you even expect the gears to match up? Either pull the gear off the cam or lift out the crank and get it out of the way. Try the bare cam in it's bearings and make sure it is seating properly. Don't even be concerned with the gear mesh until you get the cam and bearing issue straightened out.

There is nothing at all wrong with the Wilson method. If it walks out the engagement is too tight. If it is too loose precision fingers and feel can determine that. If what you said about what your mechanic said it's time to not listen to him.

Now evidently you are using an aftermarket performance cam with an aluminum bolt on gear since you had been talking about a different sized gear. Stock cams are rivited on and you're really not going to swap them.
_________________
71 Superbug
71 Westy

[kkirwin]

[SGKent]

teeth angle -1 is looser than +1. If the old cam is a +1 and the new one -1 then that isn't right. If +1 was perfect then -1 should have lots of play. Read them again.
_________________
Canned Water - the new California approved parts cleaner (except in a drought in which case rub it with sand).

George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."

Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"

[kkirwin]

[Desertbusman]

First you need to get the crank out of the way and see if the cam rides in the bearings. The bearings fitting on the cam tell you very little.
_________________
71 Superbug
71 Westy

[SGKent]

on the back of the camgear there will be a small number stamped. That is what the gear is. If the gear has no stamp it is meaningless and whatever someone wished it to be to make the sale = Hey Joe - what number do I put on this box?
_________________
Canned Water - the new California approved parts cleaner (except in a drought in which case rub it with sand).

George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."

Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"

[kreemoweet]

My guess is that "standard " size cam gears did not have any size marking (i.e. no "0" )? Also, did not the different size cam gears have
different VW part No.'s on them?

Here's a quote from the 66-69 Beetle Bentley service manual:

"Check camshaft timing gear for backlash. If the camshaft and
crankshaft gears are to run quietly, play between them must be kept at the minimum. To check, rock the gears back and forth while
gradually turning the camshaft timing gear through a complete
revolution. If excessive play does exist, this check will reveal it."

Also:

"Camshafts with gears of various sizes are available as replacement parts to reduce backlash. The marking on a replacement gear (-1, +1, +2, etc.) tells in hundredths of a millimeter how much the pitch radius differs from the design size."
_________________
'67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities

Stop dead photo links! Post your photos to The Samba Gallery!

[Tcash]

Here is a good Tech article. Thank's gowesty.com
Cam Backlash: The Whole Story

[SGKent]

Your old cam has a marking you just haven't found it. Look harder. It is probably a -3 or -4.
_________________
Canned Water - the new California approved parts cleaner (except in a drought in which case rub it with sand).

George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."

Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"

[Desertbusman]

What P/No and identification do you have on the backside of the gear?
Part numbers are cast and size identification is stamped since it is determined by the machining of the gear blank.

Of some I have laying around I believe one came out of a VW factory built replacement engine of '73 or later vintage. It's a VW 113.109.111A 18H casting identification. It has a -2 stamped into the inner side outer machined ring right under the teeth.
Same location of the small size stamping on a real old Brazilian gear.
_________________
71 Superbug
71 Westy

[kkirwin]

[busdaddy]

[SGKent]

-1 tp -2 isn't much of a change. Get the dial indicator out on the -2 and see what the lash is in 3 or 4 spots. The walk backwards test isn't the best. you need a little lash so oil can get between the cam bearing and cam journal. The green book of an unspeakable name gives the lash specs.
_________________
Canned Water - the new California approved parts cleaner (except in a drought in which case rub it with sand).

George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."

Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"