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Cam end play after assembly
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mcjweller
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PostPosted: Thu Jul 03, 2025 4:48 pm    Post subject: Cam end play after assembly Reply with quote

So, I finally have my case halves assembled, glued and torqued. I think I must have done 3 pre assemblies in total, checking a million things to get to this point.

before assembly, using my Bently, I checked axial play on the cam as they prescribe, in the case half with a dial gauge. I measured it on both case halves, because I have double thrust bearings and of course each case half ay have its own machining tolerances, etc. I lightly dressed the thrust ends of the bearings until I had .003" axial play (within spec).

I later decided to use a different camshaft. So I did the same thing, noted that the axial play was now .004"...getting a bit sloppy but still within spec.

Assembled the case.

Today, just for interest sake, I decided to measure axial end play wondering how a torqued case would change it, and if there would be any deflection at the thrust surfaces on the bearings. Using a long screwdriver through the side of the block pushing from behind the thrust boss on the cam itself (not prying on it or anywhere), I felt no movement. Going from the top looking down the breather hole, I tried to push the cam gear back toward the flywheel, nothing. So I pulled the oil pump drive gear checking to see if it interferes, it doesn't. Gear removed, still no play. Got the bore scope to see if the end of the pump body itself was contacting, no, about 1/8 to 3/16" clearance. Finally, I lightly tapped a drift on the end of the cam to knock it back toward the flywheel, put a dial on the end of the cam though the pump drive gear bore, and used the screwdriver to push it back in the opposite direction once again through the side of the block. Nothing.

Now I should note, the whole thing turns over like butter. No noise, no vibration or friction to be felt, its perfect.

So how does one go from .004" axial play on each case half, to zero when assembled? Is that by design, from bearing crush? Should I be concerned?
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PostPosted: Thu Jul 03, 2025 5:58 pm    Post subject: Re: Cam end play after assembly Reply with quote

End play for the cam and the crank always need to be checked with the case assembled like it will be running. Most likely the two halves of your cam bearings aren’t perfectly aligned.

If you pulled it back apart, you would probably see shiny spots on one half shell, and another shiny spot opposite on the other half.

You can try knocking the cam forward and back with a drift. This usually squares up the thrust shoulders on the cam, and it will usually get you .001-.002” clearance.

This is yet another example of why you should never use any sealer until the engine has been mocked up all the way out to the valve covers.

Brian
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mcjweller
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PostPosted: Fri Jul 04, 2025 4:25 am    Post subject: Re: Cam end play after assembly Reply with quote

Hi Brian,

there is absolutely nothing in the Bently that calls for that, everything was checked (like 3 times over) according to all the references and materials available. So this time, not a case of assembling too soon. In other words, it got assembled fully to the valve covers (and all the prescribed checks) 3 times.

If it has to come apart again, I think I will just sell the project lock stock and barrel. It's getting a little ridiculous for all the "oh by the ways..." that aren't referenced anywhere, that keep coming along...
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PostPosted: Fri Jul 04, 2025 5:22 am    Post subject: Re: Cam end play after assembly Reply with quote

mcjweller wrote:
Hi Brian,

there is absolutely nothing in the Bently that calls for that, everything was checked (like 3 times over) according to all the references and materials available. So this time, not a case of assembling too soon. In other words, it got assembled fully to the valve covers (and all the prescribed checks) 3 times.

If it has to come apart again, I think I will just sell the project lock stock and barrel. It's getting a little ridiculous for all the "oh by the ways..." that aren't referenced anywhere, that keep coming along...


Don’t get discouraged! The Bentley manual assumes a stock build with all factory quality parts. We know that is just not possible, as the quality of many of the aftermarket parts is all over the place. Keep at it. I built a 2287 last winter, using a TF-1 case and I had the engine apart many times. Hang in there, you will get it done!
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mcjweller
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PostPosted: Fri Jul 04, 2025 5:43 am    Post subject: Re: Cam end play after assembly Reply with quote

I hear you Rick, but at this point I think the odds of ending up with a running, reliable motor are diminishing quickly. For reference this was a car that "needed nothing" and it turned out to need absolutely everything. I bought it for my wife, I already have a classic car hobby, and it has ended up eating my spare time and cash for the past 3 years and we haven't even been able to drive it once in that time. Sometimes it pays to know when to stop. I'm not keen to have to tell her sorry, we won't be running it this year (again) despite the time and $$$ dumped into it.
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PostPosted: Fri Jul 04, 2025 6:24 am    Post subject: Re: Cam end play after assembly Reply with quote

Its possible the 2 thrust bearings have different flange thickness's and/or the backside of flange does not fit the other case saddle as well, you may have to relieve the saddle edge a bit with a file, that saddle wasn't meant to have a flange bearing on it so could be the issue, or sand down the flange on bearing that is proud to the other one, measure 10 times assemble 2 or 3 times Surprised not uncommon.
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mcjweller
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PostPosted: Fri Jul 04, 2025 7:05 am    Post subject: Re: Cam end play after assembly Reply with quote

Ok so, I have to ask this. And no sarcasm implied, because everyone on here really has been helpful and I mean no anger to anyone on here. My frustration is with the build, and the endless stream of little but consequential tidbits that to be honest, after 35 years building American cars, are not conventional logic, or listed in the "bible" manuals everyone swears by.

So - I will ask the hail Mary question:

What else needs to be checked before final assembly, besides what I have already done which includes:

Crank end play
cam end play (in the case halves, separately)
lifter to cam clearance
Lifter to lifter bore clearance
oil pump body to cam clearance
oil pump drive to cam clearance
distributor drive play/clearance
main bearing clearance
rod journal clearance
rod to case clearance
rod to pin clearance
pin to piston clearance
piston to cylinder clearance
ring gaps
ring to ring land clearance
valve geometry
Degreeing the camshaft
Cam to cam bearing clearance
Oil gallery to bearing alignment
oil pump gear to cover clearance
oil pump gear to gear tolerance
oil pump body to case clearance/fit
cylinder to case clearance
Cylinder to head clearance
deck height
compression ratio
case surface parallel to crank - cylinder mounting surfaces
Cam parallel to crank
bearing web contact/crush (new case, its ok but still checked)
bearing alignment

Please, if there is anything else missing from this list, please tell me now. I will have either forgotten to write it down here (but did do it already) or possibly it may be something new...
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PostPosted: Fri Jul 04, 2025 8:24 am    Post subject: Re: Cam end play after assembly Reply with quote

Cam end play is not checked in the case halves separately. That was bad advice.

You install the cam/bearings and torque the case together. Hit the cam end with a brass drift 3-4 times to set the thrust bearing and check end play. If not achieved, then you clearance as needed…and check again.
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PostPosted: Fri Jul 04, 2025 8:32 am    Post subject: Re: Cam end play after assembly Reply with quote

2 I can think of -

Rod to cam clearance (case needs to be bolted together for this one, rods suspended between the cylinder studs using the rubber band trick)

Cam lobe to crank counterweight clearance

Sorry if you already got those..
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mcjweller
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PostPosted: Fri Jul 04, 2025 8:39 am    Post subject: Re: Cam end play after assembly Reply with quote

I did, but I appreciate it!

Looking for Brian to chime in...who twice now has told me I've glued it together too soon but has been quiet about when to know its ready...Smile
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PostPosted: Fri Jul 04, 2025 8:52 am    Post subject: Re: Cam end play after assembly Reply with quote

mcjweller wrote:
Hi Brian,

there is absolutely nothing in the Bently that calls for that, everything was checked (like 3 times over) according to all the references and materials available. So this time, not a case of assembling too soon. In other words, it got assembled fully to the valve covers (and all the prescribed checks) 3 times.

If it has to come apart again, I think I will just sell the project lock stock and barrel. It's getting a little ridiculous for all the "oh by the ways..." that aren't referenced anywhere, that keep coming along...



The double thrust cam bearings mod is an excellent one. However, there were never any from the factory so it's not in the Bentley. As others have mentioned, the Bentley while it's excellent, is nowhere near 100% complete even for bone stock engines.

Why? How can I say that?.....because the most of the current parts that are available and the modifications required to make them fit even for a stock build.....are very different from what the factory put in on the assembly line.

As for the "rap on the cam" to de-stress and orient the cam bearings shells....I would wager that this was also done on the assembly line by workers....when necessary. Meaning, if you just torqued a case and the properly fitting camshaft now is stiff to turn, a quick rap fixes that. And, the Bentley was not written from the assembly line point of view.

All of that said, there are several dimensions that the rap fore and aft of the cam sets correct. There are at least two dimensions in the actual flange of the cam thrust bearing....but there are also the orientation of the other non-thrust bearings.

This is because they are all "crush" oriented bearings. And, once you push them into their case halves with your fingers, if you observe very closely, there are differences in depth and angle on each bearing half in each side of the case and how much under lap and overlap with the case edge there is. So, when you bolt it together, it pushes the bearing shell halves around and loads stress onto them.

Even if you do not "rap" the cam, these stresses will work out quickly after start up....so it's not an issue....BUT....not orienting them during assembly will also not allow you to accurately know if your axial and radial play/backlash are correct.

I found all of that out by installing camshaft during mockup with the thrust bearing just to see what I had....and they were tight as hell. A quick fore and aft rap....fixed that! So the light bulb in my head goes on and I realize that it's not JUST the thrust bearing that needs this "rap" orientation.

Further, I also found that once I verified that I have correct axial and backlash play in my cam bearing set.....anytime that I disassembled the case again and then reassembled it....even though I KNOW the bearings ard correct....they will bind up again with stress and need a quick rap to turn freely again. Same bearings cam and case.

This is because of the crush/spring of the bearing shells. Each time you load them into the case....each side of the bearing shell pushes each other around....building of twisting forces.

Here is a link to a thread I made just about double thrust cam bearing installation and modifications. It's fairly complete.

https://www.thesamba.com/vw/forum/viewtopic.php?t=694420&highlight=double+thrust

Ray
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PostPosted: Fri Jul 04, 2025 9:07 am    Post subject: Re: Cam end play after assembly Reply with quote

Your initial problem was due to lack of experience. But the end result is , no problem. The endplay is correct. So you should be happy, rather than trying to complain someone pointing out your error

Next time, you will be ahead based on some experience you have now. I dont see that as a problem. Read Rays thread for a lot of good info
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mcjweller
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PostPosted: Fri Jul 04, 2025 9:09 am    Post subject: Re: Cam end play after assembly Reply with quote

Thank you!

I did give it a smack backward (and because the cam button was installed, I had to use a long bar to try to "push" the cam forward again - not on the lobes but pushing against the thrust boss on the cam itself - and got no movement.

Only thing I can think of is this...when I dressed the thrust bearing surfaces on the bearings themselves, I used a set of calipers to keep track of their thickness. Wanting to avoid having two halves that dimensionally fit but are different to each other in each thrust thickness (therefore making an interference). Dressing the thrust surfaces (required, would not even insert into the cam otherwise) essentially made them directional, with the possibility of the left side shell getting turned around (no tang or tang relief in the case on the left case half). Sadly, the only way I will know will be to take it apart.
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PostPosted: Fri Jul 04, 2025 11:00 am    Post subject: Re: Cam end play after assembly Reply with quote

Update

So, it had to come apart. BTW, I used loctite 518 on the case halves, as recommended by so many people, and black RTV under the main case bolt washers. First of all, I was a little shocked how RTV has ZERO bond to magnesium. Despite the surface being cleaned thoroughly. Secondly, the 518 was not much better. 80% of it peeled off, the remaining bits were easily handled with a rag and acetone. Brand new case, and thoroughly cleaned...perhaps the machined surfaces are too machined? Do you guys scotch brite these things first? I was told to never do that. But...

Anyway, what I suspected above is exactly what happened. I removed the cam, took out the left side thrust bearing shell, rotated it 180 degrees, put it back in, torqued the case closed. With the dial gauge on it, I have exactly .003" end play using my fingers (one at the pump end, one at the flywheel end, no "thumping" with a hammer required.

Everything was measured, everything was checked. in the end, it came down to a very easy error...dressing the bearing halves makes them directional, in an assembly that does not prevent incorrect orientation. I'll assume this is why VW didn't do double thrust bearings in the first place, because it can be a nightmare to match clearnace where two totally separate assemblies meet. Not very practical in mass production.

So...I'm not gluing this together again until all the little hidden secrets are flushed out. I'd be happy to hear from anyone else who wants to add to my list of checks....even though this issue would not have been caught by any of them...even if I did check end play installed, nothing would have prevented me from reinstalling the shell 180 degrees out after final cleaning and sealing prep. But I'd like to be sure there are no other checklist items that could save some more haslte.

I wonder how many non-VW guys have gone mad working on these things?
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PostPosted: Fri Jul 04, 2025 12:55 pm    Post subject: Re: Cam end play after assembly Reply with quote

I’ll also say you probably could have ran it and never had a problem with your cam end play…but good that you checked it. With dual thrust you have to mark them specifically to each case half.

Did you use the 518 primer before applying? It comes in a spray can…

I built my first VW engine at 14 and didn’t do half of these checks and it ran fine and was abused by a 16 year old Very Happy

Don’t beat yourself up.
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PostPosted: Fri Jul 04, 2025 1:00 pm    Post subject: Re: Cam end play after assembly Reply with quote

I recommend mocking up the engine all the way to the valve covers and cooling tins. Make sure to measure everything and make adjustments as needed.
Get your valve geometry sorted, so it doesn't become an issue once you get there on final assembly.

Then, tear it down and clean all the goodies.

Once everything is clean, lube the bearings and camshaft lobes and seal the case.

This is just part of good engine building practices.

Sure mistakes are/can be made and can be corrected ahead firing off the engine.

Before buttoning up a case, I'll send a pic of the internals to knowledgeable friends for a sanity check before sealing a case.
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PostPosted: Fri Jul 04, 2025 1:34 pm    Post subject: Re: Cam end play after assembly Reply with quote

Your list looks pretty good and complete.

Did you get the rocker geometry sorted out during your mockups? There isn’t anything in the Bentley about it because they were dealing with OE parts on 100% stock engines. Any new parts you buy today are not OE quality.

Is this engine you are building stock? Can you tell us about it? You are using a new case as mentioned. If you are using new heads, or a different cam, or different rockers, you will need to address the rocker geometry, and most likely cut pushrods.

The main reason I always subject a 100% mock up is first timers will usually have to turn the engine over 100 times while figuring the rocker geometry. All your special cam lube will be wiped off by the time you get it figured out. It also helps to get the head studs figured out and make sure they don’t need to be cut down. Noting worse than having to cut head studs that are installed on a fresh assembled and sealed engine.

I have heard countless V8 guys talk about how finicky and annoying VW engines are. My local V8 machine guy can build some amazing huge power race v8’s, but he won’t even touch an aircooled vw engine. He respects them because he got his ass kicked by one back in the early 90’s while driving his big block Chevy street racer, but he won’t touch them.

Brian
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PostPosted: Fri Jul 04, 2025 2:40 pm    Post subject: Re: Cam end play after assembly Reply with quote

This is all good stuff!

On the 518 - no I didn't use the primer. I have it (for other things), but I had actually called loctite ahead of time and they insisted it was not necessary and "a waste of product and time" to use primer with 518 on the magnesium...that it was actually designed for it and aluminum unlike other sealers they carry. But the primer is 90% acetone, and that's what I used to prep the surface before application anyway.

Yes - I have built this motor out to the valve covers, and tins (3 times), the tins only once though...I have to mod the front piece slightly to accommodate the full flow oiling and wanted to get that done and painted ahead of time.

Valve geometry - yes check that (twice, because it was perfect with no shimming, and I didn't believe it).

The motor is a 1776:

New AS41 Autolinea case
AA 90.5 cylinders and pistons
Autolinea stock dual port heads with an "EMPI valve job", seems to be stock springs, valves, steel (not stainless) valves. I lapped the valves (because EMPI didn't) and vacuum tested them to 35hg. 51cc chambers
69mm stock crank
Engel W100 cam and lifters
Dual Solex 34 carbs
8.1:1 compression

So, intended to be a mild motor with a bit more torque than a stock 1600, and with those carbs I'm not super concerned about big valves or exhaust. Still running the stock 1964 trans, stock brakes and stock everything else so this isn't going to be a screamer...just a fun little ride.

When I checked rocker geometry, I ended up with the rocker tip exactly flat on the top of the valve at half lift. Thought it was a fluke, checked several valves and it was consistent. The cylinders have 0.030" spacers under them and given all the new parts I expected to have to either shim the rocker shaft mounts or get new pushrods (or both) which is why I was so surprised that everything lined up. Also, used die to mark the contact path across the face of the vavlve stem tip...it is perfect through the entire travel of the rocker.

Ass kicked? Yeah I think so. I have a buddy who builds and races professionally and has for over 30 years...He built 5 Porsche motors when he was running a Porsche and said it like this...to build a race-prepped Ford or Chevy race motor "his way", is 3-4 days, 8 hours a day. The Porsche? 2 weeks full time...if everything goes well. While he enjoyed it, he doesn't really want to build any more air cooled motors. Just so much complication packed into them
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PostPosted: Fri Jul 04, 2025 3:24 pm    Post subject: Re: Cam end play after assembly Reply with quote

I’d argue with whoever said you don’t need the primer.

Steel case…not needed. Aluminum or mag absolutely.

I used 518 on one engine with primer…SOB was glued together.

Loctite SF 7649 Primer
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PostPosted: Fri Jul 04, 2025 4:12 pm    Post subject: Re: Cam end play after assembly Reply with quote

Acetone is a good cleaner for gasket surfaces
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