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Type 4 double thrust cam bearing installation
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lil-jinx
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PostPosted: Sat Feb 17, 2018 7:33 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

Well i have to poke in here just to see if I can pee as far as you two.
I don't think that it is a must to use double thrust bearings,and I don't think it's a bad idea.My take on it is it may improve the life of the engine and reduce wear.I say this because we know that material gets imbedded into the bearing,the bearing is made to accept this,I would not think that the material would be thicker then the oil layer between the two surfaces.
Has the cam moves against the bearing the oil lubes and cushions the impact,so if you double the area of the cushion then you would half the impact,which should reduce the amount of oil being forced out from between the two surfaces,leaving a thicker film of oil reducing contact and wear.
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PostPosted: Sun Feb 18, 2018 2:20 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

the question is whether the oil splash cools the single thrust or oil pressure. When the double thrust is put in the splash goes away. I have a suspicion that when two engines are compared after 100,000 miles the cam thrust area will be more worn and the bearings less.

That said last night I could see Ray's engine failure. I suspect what happened was that there was no lash when the engine was built. The pressure from the crank gear broke the base of the teeth, and there was still enough pressure on the cam gear to turn it. See the stripped area in the center - that was the crank gear trying to turn the cam gear until it all stripped away. If there has been lash that could not have happened.

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PostPosted: Sun Feb 18, 2018 2:23 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

SGKent wrote:
the question is whether the oil splash cools the single thrust or oil pressure. When the double thrust is put in the splash goes away. I have a suspicion that when two engines are compared after 100,000 miles the cam thrust area will be more worn and the bearings less on the double thrust - being about the same as the single thrust.

That said last night I could see Ray's engine failure happening in my mind right before falling asleep. I suspect what happened was that there was no lash when the engine was built, even preload regardless what the builder will say because of the evidence. The pressure from the crank gear broke the base of the teeth and cut into the area between the teeth. There was still enough pressure on the cam gear to turn it until the center completely stripped out. See the stripped area in the center - that was the crank gear trying to turn the cam gear until it all stripped away. If there had been lash that could not have happened.

Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Sun Feb 18, 2018 4:22 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

Steve...no need to invest a bunch of thought time in it...though I do appreciate those that do. I do that all the time....spend a ton of thought time diagnosing other peoples problems I see here.

However......the failure of that engine...the one that gear came from....had absolutely nothing to do with cam or timing gear lash.

I built that engine...and it was nowhere near my first one....probably somewhere around my 50th type 4 engine build....and that was 23 years ago.

BUT...I will say I learned some important lessons on that engine. It was essentially my fault. Even though the START OF FAILURE WAS caused by the thrust flange cracking off....the utter engine destruction was caused by not enough clearance between the highest point of the cam and the back of the oil pump

I already KNOW what killed it. It was NOT a mystery. I found both parts of the thrust flanges in the case when I tore it down.

As I carefully noted....in my last post....The thrust bearing failed. Whether
it was the inner or outer one first...or both at one time...I have no idea.


That extra slack in the cam thrust....allowed one of the bolt heads of the cam...to ding on one of the studs of the oil pump. The studs in the pump were lock-tighted in as well as the bolts on the cam (web #73).

I know it was the cam bolt that made first contact (meaning I also know for a fact that the oil pump studs were still seated)...because the lock washers Web STILL sells...had some thickness variance due to their fit...and this was back in the day before Web started selling the cam kits with clearanced bolt heads like they do no. I had to clearance them myself. They had some variance.

In 360* rotation checking...the closest point of contact measured between any of the bolts of the cam and the boss of the oil pump....was .060"....and that "MAY" sound like plenty....but its NOT!

If you lose the inner thrust flange....that right there is 0.047" to 0.049" right there when brand new. Add in a few thousandths of wear (it was at about 90K miles)...and you are easily at .052"-ish. Then....you add in metal expansion.

Slightly after start up one morning on a freeway ramp at 3500 rpm....


....The cam bolt literally sheared one stud off of oil pump....which had no place to go inside of the cam gear well....except into the gear mesh...which is what sheared every tooth off of that gear in seconds and destroyed the whole engine.

Image may have been reduced in size. Click image to view fullscreen.

You can see where a cam gear bolt was grinding on the boss (red arrow). And...you can see where it got enough purchase on the oil pump nut that it sheared off the stud and mangled it (yellow arrow)

Image may have been reduced in size. Click image to view fullscreen.

And....you can see the mangled bolt hole of the one stud (red circle). That bolt was still in the cam and smashed over.

At 3000-3500 rpm....of course half that at cam speed...no telling how many revs that nut and stud made around the inside of the gear...doing the damage to the gear face you see here....before it jammed at the edge of the gear...hopped out of the face recess...and landed in the gear mesh...stripping all of the teeth off the gear.

the big black mark at 2:00 on the gear is most probably where it jammed and popped out. Yes....it did some case damage inside the gear well also...but that is no big deal.

For reference...the cam gear lash was actually SET perfect even though the gear is slightly undersized by about .002"from what came in that engine originally.

The original factory cam has a +2 gear in it. This cam gear was a "0"...all thats available. I got it to middle of EXACT factory specs....because I have a whole stack of type 4 steel crank gears.

Thats another thing alot of people do not know. There is just enough variation in the steel crank gears...less in diameter than there is in gear "chord" across the teeth...that if you are willing to do the extra work of pulling gears off an on...and you only need .001"-.002" gear lash correction...you can do it with the steel gear.

In this case...I used a brand new NOS German made gear in the box from a dealer close out. Sadly....the nut that thrashed that aluminum cam gear also thrashed the steel crank gear.

AND....and this is amazing....it also thrashed the crank. It locked up so hard it actually "wrung" the crank gear. The gear space on the crank is damaged, the key way is damaged...and the gear is permanently oversized by about .002" on the inside

And for reference...the installed clearance at the thrust bearing on the cam....was .0025".

The takeaway's...lessons learned from that debacle are:

1. Use no less than .080" (if I can get it...if not I MAKE it) for cam gear bolts to oil pump boss clearance. There is no spec for clearance between cam gear rivets or bolts in any of the books. They assume you will be using a stock cam and that there will NEVER be an issue even if you lose the thrust flanges.

2. Use a second thrust bearing shell. Its just damn cheap insurance.

It is a fact...that the thrust bearing flange cracking off is what started this chain of events.

3. A few years after this build and before this happened....I sold off a bunch of parts I had laying around. I sold about 10 crank gears...and kept 2 as nice spares. That was stupid. I have a few now an I will be collecting a few more.

Buy a gear here and there when you can. No on is making type 4 crank timing gears new...except for straight cut gears..."noisemakers".

This is yet another stock type part that is no longer made and few people bother to take in a spare...because they generally do not get worn enough to worry...but they do wear a little...and they CAN get damaged. Damn fine reason to do the little things to help conserve these parts.

The fact that the crank timing gear in this engine was damaged and "new" are rarely available...is just another GOOD reason to spend $40 and do the small insurance of adding double thrust...in my opinion.

Its the only one of my engines that has ever done this....but its not the only one I have ever seen this happen to.

Ray
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PostPosted: Mon Feb 26, 2018 3:29 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

raygreenwood wrote:
So…if you have to lap your bearings……use the finest grit paper you can…wash them with a soap and very hot water. Then rinse them in a dilute acid wash for just a minute or two….then rinse again with very hot water. Blow dry with compressed air….and oil them. No grit of a micron size worth worrying about survives this.


What acid would you use for the wash Ray?
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PostPosted: Mon Feb 26, 2018 4:05 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

tommu wrote:
raygreenwood wrote:
So…if you have to lap your bearings……use the finest grit paper you can…wash them with a soap and very hot water. Then rinse them in a dilute acid wash for just a minute or two….then rinse again with very hot water. Blow dry with compressed air….and oil them. No grit of a micron size worth worrying about survives this.


What acid would you use for the wash Ray?


The easiest one to use....and I give that with a warning...is muriactic acid. But you have to dilute it. YOU MUST DILUTE IT.

I say easiest because its the most common to get in small quantities for cheap. You can buy it in 4, 8, and 16 oz bottles at many pools supply houses and home stores.
But you need safety glasses, gloves and either be upwind or have a respirator with yellow and magenta acid/VOC cartridges.

You can also use glacial acetic acid. this is the same acid that vinegar is made of. The problem with vinegar is that at 5% for store vinegar...its too weak....it soaks too long and is not as effective.

Many lab shops and canning supplies sell acetic acid in pints. It cheap. Still a strong acid but nothing like muriatic or hydrochloric acid to handle.

You can buy it on ebay in 99% form or many bee keepers use it for something in the 80% form. If you use acetic acid....add 20%water to it and use that. wear gloves.

Let me give you the complete...best cleaning practice:

When you are doing the hot soapy water wash...stop at the hardware store and buy a 1lb box of Trisodium phosphate in the paint department...about $2. Get the one with phosphate in it.

You can do this....or use something liquid The purple stuff with sodium hydroxide or sodium silicate in it. Read the labels. I think castrol super clean no longer has this.

Clean well with purple stuff...or

Mix about 1/3 cup per gallon of hot water and store until dissolved. Then add your soap. dishwashing liquid is fine.

Scrub/rub the bearings all over well with a gloved hand.

Then into the acid wash.

With muriatic acid...you can use a dilution of about 7 to 3 water to acid...about 30%. Add the acid into water...never water into acid. Get a soft swab like a sponge paint brush and brush them over completely. Just brush them long enough to get them completely covered and worked over....or use teh acetic acid wash in the same way.

Then dip them in a bowl filled with water and about 2 tablespoons of baking soda stirred in. they may fizz a little as the acid is neutralized.

Rinse well and then dip in a bowl of distilled water....then blow dry with compressed air and oil.

Dispose of the acid by pouring it into a tub of water about 5 times teh volume you have. The bath tub works fine or a laundry sink. Then pour ink baking soda slowly and stir until is completely stops fizzing. It may change color to a tan or light orange. No issue.

Then run it down the drain. The by products are mainly chlorine and salt water. Ray
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PostPosted: Wed Mar 14, 2018 6:54 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

So I just installed my double thrust cam bearings that I made from 2 new sets of Brazilian Kolbenschmidts. I ground the corner of each thrust flang, just as Ray described, then bolted everything together in the case and the cam locked tight. The problem was not the Thrust bearings, but instead it was the plain bearing shells at the flywheel end. I went through 6 of these that were all too tight until I just reused the old Metal Leve bearings, and that solved the problem. So now I have brand new KolbenSchmidt double thrust and middle bearings but used flywheel end bearings. does anybody think that will cause an issue? Axial play is .002” after doing the hammer tap each way..
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PostPosted: Wed Mar 14, 2018 7:26 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

69BahamaYellow wrote:
So I just installed my double thrust cam bearings that I made from 2 new sets of Brazilian Kolbenschmidts. I ground the corner of each thrust flang, just as Ray described, then bolted everything together in the case and the cam locked tight. The problem was not the Thrust bearings, but instead it was the plain bearing shells at the flywheel end. I went through 6 of these that were all too tight until I just reused the old Metal Leve bearings, and that solved the problem. So now I have brand new KolbenSchmidt double thrust and middle bearings but used flywheel end bearings. does anybody think that will cause an issue? Axial play is .002” after doing the hammer tap each way..


Slow down.

How did you ascertain that it was not at least partially the thrust bearings (not that I am saying you are wrong).

Did you install a single thrust and then "set"/adjust the bearing position with a mallet?

Bear in mind.....as I noted.....ALL of the three bearing sets take on a slight twist wgen the bearing crush comes into play.

Whacking the camshaft back and forth....IS NOT....just for the thrust bearing. Its for the other two bearing sets as well.

Put the new bearings back in with a single thrust shell and whack the cam back and forth lightly.

If it changes only partially.....but changes some....that tells you something.

Remove all the thrust bearing shells and just insert the cam with the two plain bearings in it. Torque the case....whack the cam back and forth. If it improves but is still too tight.....inspect the amount of bearing sticking up for the crush area. You may need to take. 001" ofc of each side on a file. Ray
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PostPosted: Thu Mar 15, 2018 5:01 am    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

raygreenwood wrote:
How did you ascertain that it was not at least partially the thrust bearings


Well it took assembling, torqueing, did-assembling the case about 10 times to determine it was actually the wide plain bearing shells that were causing the problem.

After my first assembly, I noticed all the bearings had a few shiny spots, but the thrust bearings had virtually none, so the second attempt was with a single thrust and plain shell at the gear end. That made no difference. In fact, rotating the cam while the case bolts were only slightly tight made a noticeable grinding sound. I then just removed the new KS thrust bearings and re-assembled with the old Metal Leve Thrust. Still no luck. After that, I removed the thin middle bearing shells and replaced with the old Metal Leve shells; again, cam still binding.

At this point, I knew the large plain shell bearings at the flywheel end were the culprit, so I put the new double thrust and middle KolbenSchmidt bearings back in and put the old Metal Leve shells in the flywheel end. After doing this, the cam spun freely, and I confirmed axial play was .002" with this setup after full torque of the case bolts.

I should also add that I was assembling the case with the timing gear off the crankshaft, so I could check rotation of cam and crank independently.

Since 2 sets of new cam bearings will have 6 plain shell bearings that fit the flywheel end of the cam shaft, I tried various combinations of those remaining 6 shells to see if that would make a working set, but it did not. All 6 were duds....

So at this point, I'm very satisfied with the fit of the double thrust bearings, I dressed the corners of the thrust flanges with a diamond Dremel tool to prevent distortion during crush, so I feel like they are perfect.

It's kind of odd that all those new bearing shells would be too tight, so I'm going to spend some time measuring my cam next, just to make sure there's not an out of round journal, or bend, or something that works with an old bearing shell, but not a new one.....
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PostPosted: Thu Mar 15, 2018 8:33 am    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

69BahamaYellow wrote:
raygreenwood wrote:
How did you ascertain that it was not at least partially the thrust bearings


Well it took assembling, torqueing, did-assembling the case about 10 times to determine it was actually the wide plain bearing shells that were causing the problem.

After my first assembly, I noticed all the bearings had a few shiny spots, but the thrust bearings had virtually none, so the second attempt was with a single thrust and plain shell at the gear end. That made no difference. In fact, rotating the cam while the case bolts were only slightly tight made a noticeable grinding sound. I then just removed the new KS thrust bearings and re-assembled with the old Metal Leve Thrust. Still no luck. After that, I removed the thin middle bearing shells and replaced with the old Metal Leve shells; again, cam still binding.

At this point, I knew the large plain shell bearings at the flywheel end were the culprit, so I put the new double thrust and middle KolbenSchmidt bearings back in and put the old Metal Leve shells in the flywheel end. After doing this, the cam spun freely, and I confirmed axial play was .002" with this setup after full torque of the case bolts.

I should also add that I was assembling the case with the timing gear off the crankshaft, so I could check rotation of cam and crank independently.

Since 2 sets of new cam bearings will have 6 plain shell bearings that fit the flywheel end of the cam shaft, I tried various combinations of those remaining 6 shells to see if that would make a working set, but it did not. All 6 were duds....

So at this point, I'm very satisfied with the fit of the double thrust bearings, I dressed the corners of the thrust flanges with a diamond Dremel tool to prevent distortion during crush, so I feel like they are perfect.

It's kind of odd that all those new bearing shells would be too tight, so I'm going to spend some time measuring my cam next, just to make sure there's not an out of round journal, or bend, or something that works with an old bearing shell, but not a new one.....


Excellent answers and method!

You did the right range of checks.....and found what I thought you would find.

Its easy to say what you "think" it is.....and though you "may" be correct.....the best way to "know" is to assemble, disassemble and re-measure until you are sure what it is.

Yes.....it's odd. Have seen more than a few bearing sets where the crush area "legs" are too long.

The way to fix them is flat out tedious. I mark both edges with blue or red sharpy marker.....mask the bearing area with tape.....and then stand them up vertically on a sheet of glass or granite block so the crush edges are at 6:00 and 12:00....and give each crush edge about 5-7 clean strokes with a flat diamond needle file to remove the marker.
Measure from the back of the arch. Looking to take off about .002" inches at a time.

Then reassemble.....repeat.....tedious. Ray
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PostPosted: Sun Apr 01, 2018 8:33 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

Thanks for this thread Ray. I have one set of these bearings I got, along with the 9550 kit, from Jake 8 years ago. You inspired me to break the crust on this rebuild project. I've punched the tang, and tapped the cam back and forth.and it rolls like glass in the right half, with a touch of endplay (no dial yet).
Image may have been reduced in size. Click image to view fullscreen.

The cam just came out of the wrapper for the first time and no burrs that I can feel. This is my first new cam build after a lifetime of throwing used stuff together. And my first T4 bottom end. I may do a thread on this one shortly.
Image may have been reduced in size. Click image to view fullscreen.


I did the double thrust mod on my T1 case back when I got it align-bored, ~15 yrs. ago. It's next. Very Happy
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PostPosted: Sun Apr 01, 2018 10:09 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

Nice! Glad it was useful!

Ray
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PostPosted: Mon Jun 04, 2018 9:39 am    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

The question whether a single or double thrust bearing works better can only be measured over the life of an average engine. The extra thrust area increases friction between the cam thrust area and the thrust bearing. Whether that extra friction will cause additional wear requires testing of multiple engines at mileage intervals to see which engines are wearing less. If all that a double thrust does is move wear to the cam side then the net gain is -0-. If an engine has too much cam gear runout and the gear hammers a single thrust until failure then the primary cause was a gear with too much run out. A mis-cut cam with side thrust could cause this too. It is like someone has a failure where a load bearing 2x4 breaks because someone keeps hitting it with a sledge hammer - so their fix is to double up the 2x4. The correct fix is to take the hammer away from the source of the hammering. On the other hand if the 2x4 is failing because the load was under-estimated then doubling up is needed. Considering that in general VW single thrust engines last a very long time - 60,000 - 80,000 on T1 BUSES and 100,000 - 150,000 on T4 BUSES, it is unlikely the failure from a thrust bearing is an engineering failure. More likely it is quality control of either the bearing, or some other factor like cam gear run out. Personally, and it is just my opinion. I don't see double thrust cam bearings extending the life of the engines. It might offset hammering from gear run out or excessive end play, but the sledge hammer in my example is still in there hammering. It might be harder for it to damage the load bearing 2x4 but none-the-less over time it will.

On the other hand, adding a double thrust likely won't cause reliability issues but I have no way of measuring that until engines with higher miles are looked at. That is why I refuse to endorse the "double thrust" bearings at this time. Come back with a dozen engines of each at 120,000 miles and we can compare the wear. If double thrust engine thrust areas are more worn then double thrust can be said to cause additional wear. If double thrust are worn less then we can say they save wear. And if the wear is the same then what?
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PostPosted: Mon Jun 04, 2018 10:32 am    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

You just STILL are not getting it.

The extra "friction" to the cam thrust face is irrelevent. Its NOT just about friction....and in fact its not about friction at all.

If its about anything its about "load".

All bearings...whether plain oil bearings, ball bearings or roller bearings.....have both load control and friction coefficents. Crudely put.....a bearing of twice the surface area....while it will it "may"...and probably will..... have twice the friction....it also has twice the side load and shock load carrying capacity......which is a great function to have.
The cam thrust bearing is so little of a friction worry ...with either single or double thrust.....that worrying about friction is kind of meaningless.....unless you have a rough thrust face on the cam.

As everyone notes.....and it getting hung up on.....the cam works with either single or double.
The double thrust cam bearing has only one function.....insurance. and its cheap insurance unless you are paying someone to do this.

With double the load capacity and the insurance factor.....I still cannot figure out why you are working so hard to dissuade anyone from using it.

It has not one single negative factor. Its never going to destroy your engine....but may well slow the destruction in the event of a thrust flange loss....long enough for you to repair it.

Ray
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PostPosted: Mon Jun 04, 2018 10:43 am    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

raygreenwood wrote:
You just STILL are not getting it.

The extra "friction" to the cam thrust face is irrelevent. Its NOT just about friction....and in fact its not about friction at all.

If its about anything its about "load".

All bearings...whether plain oil bearings, ball bearings or roller bearings.....have both load control and friction coefficents. Crudely put.....a bearing of twice the surface area....while it will it "may"...and probably will..... have twice the friction....it also has twice the side load and shock load carrying capacity......which is a great function to have.
The cam thrust bearing is so little of a friction worry ...with either single or double thrust.....that worrying about friction is kind of meaningless.....unless you have a rough thrust face on the cam.

As everyone notes.....and it getting hung up on.....the cam works with either single or double.
The double thrust cam bearing has only one function.....insurance. and its cheap insurance unless you are paying someone to do this.

With double the load capacity and the insurance factor.....I still cannot figure out why you are working so hard to dissuade anyone from using it.

It has not one single negative factor. Its never going to destroy your engine....but may well slow the destruction in the event of a thrust flange loss....long enough for you to repair it.

Ray


I get it completely Ray but I don't agree with you. Not dissuading people who have their minds made up to use double thrust. Just stating that it will cause additional wear to the cam thrust area and I honestly can't say how much. If we saw many T4 factory built engines sitting by the side of the road due to thrust failures I might be concerned. I can only say that of the worn single thrust cams I have had lying around for their gears, most had opened up to the wear limit. I am not sure that double thrust bearings won't make that worse. I am not saying don't do it - I AM saying there may be consequences that may be other than expected.


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PostPosted: Sat Mar 14, 2020 2:22 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

great write up ray. helped me a lot when doing my new cam (type 1).

one issue - endplay 0.07 mm (in each half) reduces to 0.04 mm when torqued. which is the minimum end of bentley's recommended tolerance. cam still rotates very smooth and easy. but i'm probably going to take a little more off the bearing thrust faces just to be sure.

and what about citric acid for washing bearings?
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PostPosted: Sat Mar 14, 2020 10:53 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

I think using new rivets to hold gear on would be a good idea, all the work done to other things that are less critical, one could easily hammer or press (vice) new rivets in, they stop all movement of the cam gear to cam, alternately, if using bolts use flat/spring washers and BHCS for more clearance, then I peen/center punch the end of the bolt on the other side of the cam gear, rather then locktite, IMHO ext. toothed lock washers don't belong inside an engine especially against aluminum, they tend to shred and tear the alum. then shed bits of alum. or break a tooth, use int. toothed one's if you must.
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raygreenwood
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Location: Oklahoma City
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PostPosted: Sat Mar 14, 2020 11:39 pm    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

daos wrote:
great write up ray. helped me a lot when doing my new cam (type 1).

one issue - endplay 0.07 mm (in each half) reduces to 0.04 mm when torqued. which is the minimum end of bentley's recommended tolerance. cam still rotates very smooth and easy. but i'm probably going to take a little more off the bearing thrust faces just to be sure.

and what about citric acid for washing bearings?


Until this year I would probably think it was fine to use a product like citric acid. Do you mean "actual" citric acid....or some kind of citrus terpene "citrus-sol" cleaner?

If its actual citric acid...I would say no. Vinegar no as well. Acids in general....no.

The problem is getting them all off. Really a good rule of thumb I am finding that you should neutralize about 2X the amount of time they spend in an acid.

I'm working on plating this week so its all relevant at the moment.

Any good solvent. Very light, thin solvent. Not acetone...not alcohol. They do not dissolve oils well. Methanol or white gas....is a decent exception to no alcohols.

Wash very well with degreaser and hot water when done. Dry quickly. Ray

EDIT:

The reason I question about using acids.....is not because I dont use acids for cleaniing.....I use them ALOT. But I only use them when absolutely necessary because they have a couple of specific issues.

1. On high tensile steel parts...even a very mild acid causes some level of hydrogen embrittlement. That is not a worry with these bearings. I'm just stating that its one of the reasons acids should be used with careful thought and with exact knowledge of solution strength, polarity, mixability etc.

2. I say its hard to get off/ neutralize......true....but its not really that hard. But I also feel that there is to much scare mongering with the use of acids in some situations.....or none at all....instead of using accurate information ...like.....use the correct acid in the correct strength and neutralize it when done and tell how to neutralize it.

I am wary after this year of suggesting that someone use an acid with a metal.....without knowing exactly HOW they are going to use that metal part.

Meaning.....are you going to store it as a spare? If you install it will it be 100% fully engulfed with oil flow (which will readily neutralize anything you miss)? And very importantly.....will water/moisture EVER be present? Will there be contact with the acid washed part....with dissimilar metals? Will it be subjected to heat?

Who cares?

I spent half of this last year....tracking an acidic breakdown of a product that was being used ...with metals.....with moisture and heat present.....that was damaging circuits for one of tje largest computer manufacturers in the world. The type of damage it caused and the eventual twisted path that were the root cause of it.....were nothing short of diabolical.

So.....don't use acid unless its really whats required. Ray
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jpaull
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PostPosted: Thu Nov 17, 2022 8:41 am    Post subject: Re: Type 4 double thrust cam bearing installation Reply with quote

Great post on double thrust cam bearings Ray. This is VERY helpful for both type 1 and type 4 builds.
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