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Straight gear interaction ?
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NachoCar
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PostPosted: Thu Mar 02, 2023 9:18 am    Post subject: Straight gear interaction ? Reply with quote

Long, long story but I was told by seller of project type 1 that the shortblock was assembled by seasoned VW tech. Knew it was a gamble but decided to finish and deal with engine once I got to that point. Eight or so years later, I put stock rebuilt carb, dist, etc. Engine ate a cam gear first time it got any load on it.

Been working on rebuild for bout 6 months, first build. Got case back from Nick couple weeks ago cut 2 over. Been thru a couple sets of main bearings learning how to get the crank located and set.

Aftermarket cam gear was too tight. Decide to go with straight cut gears as a way to avoid trying to spend time and money finding looser OEM cam gears, that may or may not be correct. Read no worries with gear lash.

Well....SOMETHING is killing me. During mock-ups with crank torqued, everything is fine.

Mock-up with cam did get tight so went with diff cam bearings. Still binding a bit when torqued. Bearing scraper on order but tried sanding cam bearing thrusts on paper (I know, a big no-no). But worked and got a nicely spinning cam even when in properly torqued case with all the nuts/bolts even peripheral 13 mm's.

But damn it to hell, when I put crank, cam, lifters, dist drive in together starts to bind when I torque the two 13 mm at what I call the nose. You know the ones on either side of the #4 bearing (unsure if that is correct number and too pissed to verify). I mean I tried every combination of sequence and torque in little baby steps of torque.

Knowing my main bearing experience, I thought for sure the last time (Prob 5/6th time) I KNEW everything was perfect so I could button her up. Nope....

This is after opening up the last time. Ya'll see anything incorrect? I didn't

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


I'm wondering if I missed info on the straight cam gears interacting once the case is torqued down?

I also read cam endplay is not AS important on straight cut cam gears!?!

There are quite a few possibilities/variables as far things like Main bearing ID's being off, but I did test that variable when I torqued crankshaft in case (with ALL hardware) by itself. Just like when I torqued down cam shaft by itself with all hardware (Nuts and bolts)

All I can think of is there must be gear lash, or something else to check.

I pulled crank out but main bearings looked fine and rotated alright?

Any next steps or missing adjustments????

A little knowledge is an expensive and time consuming thing...... Brick wall Brick wall Brick wall
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NachoCar
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PostPosted: Thu Mar 02, 2023 9:24 am    Post subject: Re: Straight gear interaction ? Reply with quote

I did wipe down edges with Acetone before the above pictures.

Noticed these a bit later:

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

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


Could be acetone washing down Permatex aviation I used to seal case half surfaces post case splitting last time or, I guess it could be from while I was trying different torque sequences.......but would maybe bind when torqued??

I'm really reaching here guys.....

Thanks for any help given.

I need it, obviously.
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chrisflstf
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PostPosted: Thu Mar 02, 2023 10:00 am    Post subject: Re: Straight gear interaction ? Reply with quote

That dowel pin looks bad. It may be sticking up too high, pinching the bearing and why is it distorted on one side?
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NachoCar
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PostPosted: Thu Mar 02, 2023 10:07 am    Post subject: Re: Straight gear interaction ? Reply with quote

Good Eye! or maybe you have 2.

Stock size dowel pin, 8mm was warned to me to be too short by aviation mechanic. I guess it had been pushed in too much in some previous life?!?

Ordered 10 mm pins and ground down. I did measure upon assembly by marking with sharpie then fitting into bearing hole.

The crank turned beautifully when test fit in case without cam shaft and all hardware....even 13 mm nuts torqued to spec.

Thanks!


Last edited by NachoCar on Thu Mar 02, 2023 10:16 am; edited 1 time in total
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txoval
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PostPosted: Thu Mar 02, 2023 10:16 am    Post subject: Re: Straight gear interaction ? Reply with quote

Way to much sealer, itís all over your bearingsÖ
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NachoCar
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PostPosted: Thu Mar 02, 2023 10:18 am    Post subject: Re: Straight gear interaction ? Reply with quote

agreed. I wondered if that happened after I spit the case and wiped some off or not.

either way it's too much.

Thanks
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NJ John
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PostPosted: Thu Mar 02, 2023 10:32 am    Post subject: Re: Straight gear interaction ? Reply with quote

Are the lifters binding when the cam is at full lift?
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PostPosted: Thu Mar 02, 2023 10:55 am    Post subject: Re: Straight gear interaction ? Reply with quote

Why do you have the distributer, distributer gear, oil cooler, etc. all installed already while you are trying to figure out and assembly problem? Get rid of the unnecessary items, including the oil pump, and especially the drive gear, put them on after you figure out the binding problem. Have you been turning engine over with dist. drive in place with no distributor? Stop shooting the cannon at this thing, be methodical, and listen to your advise. I am just trying to get you to step back and take a breath, one step at a time.
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NachoCar
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PostPosted: Thu Mar 02, 2023 12:08 pm    Post subject: Re: Straight gear interaction ? Reply with quote

Oil pump is out. Under the impression it wouldn't hurt to leave dist drive and dist in place once verified to mesh with crank.

I have read not to rotate the crank backwards with drive in place and dis bolted down as the gear would poss mess up brass gear on crank ?!? I'm not really rotating backwards now that I don't need to check the stock type cam gear is too tight by rotating crank backwards.

Rem I have made dang sure the crank does not bind in case when torqued fully all fasteners. Seemed smart to try it with dist drive in place.

That is true as well for cam, when not in case with crank.

I appreciate the help guys as I know there is a whole lifetime of experience some of you have. I also know I don't know shit. Guess I'll have to watch the lifters closer.
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NachoCar
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PostPosted: Thu Mar 02, 2023 1:20 pm    Post subject: Re: Straight gear interaction ? Reply with quote

so straight gears are pretty much set cam endplay and go?

as long as backlash does not occur?


Last edited by NachoCar on Thu Mar 02, 2023 1:42 pm; edited 1 time in total
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bsairhead
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PostPosted: Thu Mar 02, 2023 1:27 pm    Post subject: Re: Straight gear interaction ? Reply with quote

With the distributor in place it's fine to turn the crank backwards. That's how you check valves by the book. Without the distributor set the drive will walk out if the crank is turned CCW
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Pruneman99
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PostPosted: Thu Mar 02, 2023 4:01 pm    Post subject: Re: Straight gear interaction ? Reply with quote

You can leave the crank, cam and everything in the one case half. Grab the two rods sticking up and cycle the engine. If the cam gears are too tight, the cam will want to walk out of the bearings.
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PostPosted: Thu Mar 02, 2023 4:35 pm    Post subject: Re: Straight gear interaction ? Reply with quote

Is that a stock crank, 311b rods and straight gears.?
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PostPosted: Thu Mar 02, 2023 5:16 pm    Post subject: Re: Straight gear interaction ? Reply with quote

You need to get a tube of Prussian blue and paint the crank gear with it and see what contact pattern you get on the cam gear and maybe lay a couple of strips of plasti gage afterwards to see if there is any clearance. Was the case ever align bored the mains may be off a little.
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PostPosted: Fri Mar 03, 2023 7:31 am    Post subject: Re: Straight gear interaction ? Reply with quote

Pruneman99 wrote:
You can leave the crank, cam and everything in the one case half. Grab the two rods sticking up and cycle the engine. If the cam gears are too tight, the cam will want to walk out of the bearings.


Double checked this and cam did not lift out of bearings!

Checked for interference from new lifter on new cam and looked ok.

Removed main bearings 1 and 4 and cleaned the fire outta everything to make sure no aviation permatex was anyway. There was a crapload everywhere. I was certain that was the issue.

It is a freshly bored case (twice over) from Nick on here and crank was mic'ed and polished measured one ground and a hair loose but was told to run it. This sentence took about 5 months to accomplish cause machine services escapades cause machine shop prioritized other higher paying jobs for more than 2 months.

It IS a 69 mm oem crank, oem rods (unsure number). and went with straight gear as it seemed the least expensive and quickest way to eliminate finding OEM cam gear that played well with corresponding crank gear. Maybe stupid but I couldn't find why except maybe general straight cut gear knowledge I did find in my research.

WHat I did find is sealant everywhere was not THE biggest culprit. Bolted crank and cam in case and torqued. Spun well with just larger nuts fully torqued but then seized up when the front two 13 mm nuts torqued even halfway to find torque spec of 14 ftlbs.

Nick said, and I now agree the silverline main bearings must be off. Specifically the one in the front by pulley.

But should this be true even when All six 19 mm are fully torqued?

Thanks Guys.
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PostPosted: Fri Mar 03, 2023 8:30 am    Post subject: Re: Straight gear interaction ? Reply with quote

Unfortunately new bearings are pretty sloppy now. You'll need to torque the case without the bearing and measure the bore for #4.

Then measure the OD of the bearing to determine crush.

If that's OK, then put the bearing in the case, torque everything again, and measure the ID of the bearing.

Compare that to the crank journal.

From your description, I think you may find an issue with one or more of these measurements with your #4.
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PostPosted: Fri Mar 03, 2023 9:02 am    Post subject: Re: Straight gear interaction ? Reply with quote

And you know the deal with the front nearest the pulley. The one in your last pic. Amateurs have a hell of a time getting that one seat.
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NachoCar
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PostPosted: Fri Mar 03, 2023 9:14 am    Post subject: Re: Straight gear interaction ? Reply with quote

NJ John wrote:
And you know the deal with the front nearest the pulley. The one in your last pic. Amateurs have a hell of a time getting that one seat.


much harder than thrust and #3

are there 'tricks'?? I had to remove my dist drive gear, and turned crank and push front and rearward.

Thank you for your time and help!!!!!
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NachoCar
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PostPosted: Fri Mar 03, 2023 9:18 am    Post subject: Re: Straight gear interaction ? Reply with quote

Pruneman99 wrote:
Unfortunately new bearings are pretty sloppy now. You'll need to torque the case without the bearing and measure the bore for #4.

Then measure the OD of the bearing to determine crush.

If that's OK, then put the bearing in the case, torque everything again, and measure the ID of the bearing.

Compare that to the crank journal.

From your description, I think you may find an issue with one or more of these measurements with your #4.


YES! 1000% agree.

Have you ever heard of bearings getting 'Crushed" when torqued by bore?

I have plenty of experince with crushed by pin/dowel not in sync with bearing hole. But what if the bore was off enough to compress down the bearing and deform?

I think it's prob a misshapen bearing of varied thickness in my case as Nick pointed out there are several recent threads dealing with silverline slop
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PostPosted: Fri Mar 03, 2023 11:06 am    Post subject: Re: Straight gear interaction ? Reply with quote

I haven't had the problem with too much bore crush. That's not to say that's not what might be happening here though. If there is too much crush, that little bearing could be crushing on the ID, and grabbing the crank.
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