Cam Replacement T4

[SGKent]

This question has come up many times during rebuilds.

To clear the oil pump on a T4 engine the cam gear must be milled so the bolts that replace the rivets sit deeper. Then the bolts must have a special thin head to clear the pump. The first photo is of the two different kinds of bolts commonly available - I find the flat ones clear better. Red Loctite on clean non-oiled threads is used to make sure the bolts hold. The other photos show the cam milling.

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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Amskeptic]

[SGKent]

After a long hard think thru and knowledge that star and split washers bring the cam bolts closer to the oil pump, and that some have a tendency to break after time, the decision was made to go without washers, and to be sure the red Loctite was in there good. I just didn't trust the star washers. I might have found circular high grade internal star washers or spring washers to go under it, but I do remember that I chose not to use the external stars. As you may know rods don't take washers, nor do main caps on many engines. I did make sure that the bolts were torqued to what the engineering handbooks specify to get the correct stretch with some allowance for Loctite. I understood why VW chose rivets for that spot.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[airschooled]

The new Web Cam kit for bolting gears to their stock and performance camshafts included the thin profile hex bolts, and the 20-point star washers Colin speaks of.

For the record, many modern tools are sent with a deep "chamfer" around the inside of the socket walls to facilitate getting the socket on bolt heads. This chamfer is sometimes so pronounced, that the tool can not effectively grab the walls of the thin profile hex nuts for final torquing. (The same goes for the 14mm valve adjusting lock nuts on later Type 4 engines.)

For these applications, I have had to grind down the socket about 3mm with a bench or angle grinder. (vvolfbus, do you have a picture of our handy creation?) Doing this makes it a fraction of a percent harder to get the socket on the fastener, but precision work doesn't allow for wrench slippage.

Robbie
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[SGKent]

I have seen the star washers. Don't trust them. I have both 6 and 12 point socket sets, and thin wall sets. Usually one of them will fit. Rimco did the milling on my cam gears when Ed owned them. The bolts were torqued. I let them set a week then applied a force to see how well they held. They were near impossible to loosen. Then I removed them, cleaned everything up and did it again. I might have even peened the back side with a stake when I was finally done, that would be my style.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Hoody]

Have the cam gear properly milled, low profile hex bolts, no washers, red loctite, clearance the protruding bolt threads on the back side of the cam gear, center punch the back side of cam gear bolts. Done. This allows for the needed clearance for a type 1 pump in a type 4 case. So if you had a properly modified type one pump with the correct gears you could go from the type 4 pump to a type 1 pump if you had to and vice versa if type 1 pump is causing issues.

[tommu]

I'm hoping this picture might help someone visualize how to remove a cam gear without damaging it. Grind the rivets off from the back and do not drill them out. With the head of the rivet ground off they just punch out.

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[CrRusty]

I might have even peened the back side with a stake when I was finally done, that would be my style.[/quote]

I will strongly agree. Peening is possibly the next best thing to rivets. Too important to ignore. Lots of insurance here.

[gerald79westy]

Currently about to get Cam gear milled. How much does everyone take off ? Without star washers I could get away with grinding a small amount off the studs on oil pump and should clear but would rather have gear milled .

[SGKent]

The old Rimco did all of mine. Can't say how much.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[orwell84]

I hope this question adds to the discussion. I think it comes up a lot. I used a webcam kit with their gear, thread locker, bolts and star washers. I don't remember anything special about the bolts but could probably scrounge a photo.

I am currently running a CB performance maxi pump and plan to change it for a stock pump. The pump to cam bolt clearance is something I was unaware of when assembling my engine.

Obviously the bolts aren't hitting the oil pump boss at this point , though I am aware of the issues when the cam thrust bearing surface starts to wear and end play increases.

I will be installing a rebuilt stock pump and was wondering if there was a quick and dirty way to measure the boss to bolt clearance before installing the pump. (To at least ballpark it) before installing the pump and checking it more closely with putty. I'm also not sure how to check it with putty as I have never done this. I have learned to ask questions about obvious things because I no longer underestimate my ability to fuck it up completely.

The other question is about removing material from the idler shaft boss. I have heard that it can make it more likely for the shaft to move out of the pump body. That makes sense as there is less material holding the shaft in place. But what about those pumps where the shafts are deep in the pump body and its obvious they were made that way. I would assume that you could take a lot of material off the boss because it's not exerting any force on the idler shaft. But you know what they say about assuming...

Thank you.

[SGKent]

you can see it when assembling. Just lay the cam and the pump in and spin it. If it is already assembled and you are swapping the pump, align a bolt head with where the pump's highest spot is relative to the cam bolt heads and use a piece of modeling clay to get the depth. Spinning it will knock the clay off so do it statically.

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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[orwell84]

Thank you. Yes it is assembled. It’s pretty much what I thought it was

[Amskeptic]

[orwell84]

[SGKent]

I think mine was somewhere arpund.125". I went with the flat bolts, red Loctite and no star washer.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Clatter]

[raygreenwood]

About .080" with machined hex cap screws on aftermarket new cam gears is as little as you want to have for cam gear to pump boss clearance.

This is actually pretty easy to get with a stock pump. As SGKent notes......125"with buttonheads should not be hard to get either.

Although .045" to .050" is plenty even if the cam thrust fails and you get real slop.....its nice to have as much as you can easily get.
I say this because....make damn sure the stock pump nuts and your cam bolts are vwry secufely locktighted and held in. If one ever backs out.....the extra clearance may save your engine.
Ray

[Wasted youth]

[airschooled]