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Sealing rings at top/bottom of cylinders
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RalphWiggam
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PostPosted: Sat Mar 24, 2018 4:42 am    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

Sombitch. I already red loctited the rods on the crank because all the measurements I took with plastigage, big end gap, etc were good. I guess I need to break out the torch.
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RalphWiggam
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PostPosted: Sat Mar 24, 2018 6:47 am    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

Ok. Took all of the rods back off the crank.

When I lay them flat on a piece of glass and push down on the small end to make that surface flush with the glass, the large end rises above the glass. When I flip them over there is no rocking at the small end, but there is a gap between the top large end bore and the glass.

This indicates that the outside surface of the small end of the rod is not perfectly parallel with the large end outside surface. I don't really have a way to tell if that translates to the bores themselves not being parallel.

Every single rod is the exact same way and I don't see how they could all be bent the same amount unless they were manufactured like that.


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


When I mapped the curve on the rod with a sharpie, I noticed that all the rods are curved in the same direction relative to one another based on the tang side of the big end.

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


If I layout all of the rods in their respective crank position with the tangs facing down (per tom Wilson book) number 1 and 2 cylinder would be curved towards the front of the van and 3 and 4 would be curved towards the back.

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


Are we 100% sure it wasn't manufactured this way? Seems oddly coincidental that everything would be uniform like this.
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PostPosted: Sat Mar 24, 2018 8:27 am    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

RalphWiggam wrote:
Ok. Took all of the rods back off the crank.

When I lay them flat on a piece of glass and push down on the small end to make that surface flush with the glass, the large end rises above the glass. When I flip them over there is no rocking at the small end, but there is a gap between the top large end bore and the glass.

This indicates that the outside surface of the small end of the rod is not perfectly parallel with the large end outside surface. I don't really have a way to tell if that translates to the bores themselves not being parallel.

Every single rod is the exact same way and I don't see how they could all be bent the same amount unless they were manufactured like that.


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


Any more ideas to check? Are we 100% sure they aren't manufactured like this (slight offset or something)?



My bad.....I forgot.....in general the small end width iw about 1.04"-ish....and the big end width ...which will vary a bit from rebuilding several times...is about 1.01"-ish.

So they will not lay flat without a shim on your plate..... Rolling Eyes ...sorry....I forgot.

But.....twist or bend....can be subtle. You may not see it on a plate of basic glass....as thin float glass is not actually that flat. Ground glass....yes.

So do not assume they are not bent. This is what a rod rebuilder checkw on a surface plate and on a precison jig.

Without being there to see this variance you are having....in person......let me reiterate/orient this so I can make sure ai am visualising it correctly.

So with crank and rods and pistons in the case.....case on an engine stand.....and say....cylinders 3 and 4 installed and standing vertical...so engine on its side......and you standing next to it with piston of #3 at TDC.....and you have your steel rule across the top of the cylinder....the ruler is running fore to aft at 3 and 9 o'clock on the cylinder....parallel to both crank and piston pin.....right so far?

And one side of piston like at 3:00 compared to 9:00.... is like .020" higher than the other?

That.....could...as all have noted......really be caused by a few things:
1. As noted....a bent rod
2. A pin bushing honed at an angle.....and there is enough meat in these bushings that the bore INSIDE the bushing can be perfectly round and smooth....but was bored at an angle because the rod was bent or cocked on the mill or rod machine.

3. There could be serious sag in the case between the cylinders.....so to check for that.....lay the ruler ...again running between 3:00 on #4 and 9:00 on #3.....across the tops of both cylinders....and look for a gap between ruler and cylinder at 3:00 on #3 and 9:00 on #4.

More than about .0015" can cause problems.

The other thing....which is vaguely possible if the case has ever been align bored.....and done poorly....is that the crank is way off on the centerline. This can be measured but ro not worry about this yet.

4. Its possible......that a piston may have its pin journals bored crooked. I highly doubt this but just had to mention the vague possibility. Ray
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PostPosted: Sat Mar 24, 2018 8:34 am    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

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

.

Stuff a wrist pin down through all the ends in a stack like that and see if the big ends are still all flat with each other, not super scientific, but it'll expose a grossly deformed one.
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PostPosted: Sat Mar 24, 2018 9:37 am    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

on a t1 engine it matters where the tangs face. One a T4 engine there is no difference.

The layman's way to tell is rods are straight is to lay them on each other. Bent rods are rather rare except in a hydro-locked engine or one with a severely dropped valve. If the rod has spun and seized then the rod is probably so noticeably bent it was tossed out.

In thousands rods I re-machined back in the 1970's - 1980's maybe we measured two or three that were bent enough to matter. Stock rods, especially VW are quite robust.

Wrist pin fit is by feel and not measurement. The pin should slide thru slowly under its own weight with a little 30 wt oil on it. If it sticks it is too tight and if it just falls thru instantly it is too tight. If it is used one must clean the varnish out first.

as BD said, measure the deck height at the wrist pins.

you should have zero run out in the cam lash or it will cause the crank and cam to walk forwards and backwards, opening up both crank and cam end play.

No Ray it was not you.
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PostPosted: Sat Mar 24, 2018 9:50 am    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

RalphWiggam wrote:


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


Are all the rods the same? This picture makes it look like the sides of the large and small ends are parallel but offset, kind of Type 1'ish.
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PostPosted: Sat Mar 24, 2018 10:21 am    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

Wildthings wrote:
RalphWiggam wrote:


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


Are all the rods the same? This picture makes it look like the sides of the large and small ends are parallel but offset, kind of Type 1'ish.


All the rods are the same. If you flip it over though, there is no gap when you press down on the small end like in the picture. They are all "curved" the exact same.

I checked the case decks again and everything is perfectly flat there.

I did some more cylinder deck measuring and this is what I find when all the rods are installed with the bearing tangs facing down (per book). The tops of all of the cylinders were also checked for flatness across the pairs (perfect).


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


Notice anything? All the decks vary from front to back on the piston. The weird thing is that the short deck sides are all towards the middle of the case. The only thing I can point my finger towards is maybe all of the rod small ends were machined at an angle?
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PostPosted: Sat Mar 24, 2018 10:31 am    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

Ah.....from your records.....has this case been align bored before?.....

That....looks like what I speculated in my last post.

If the case was align bored....and not mounted straight to the mandrel......the crank could be sitting diagonal in the case.

You get a little of this from the factory from case to case.....a little. Usually the crabk is slightly closer to one side or the other. Occasionally you find one that is off in the vertical axis...closer to top or bottom.

Two quick ways to check this on the case:

1. Use a dial depth gauge on the main bearing bores on each case half....I will post a picture shortly of that tool, or......

2. With crank in the case......rotate it to TDC on each bore ....with cylinders removed.....and. heck with a depth mic or dial depth gauge....to the highest point on each crank throw.

And......its also possible.....the crank....of its been deground.....that it is ground offset. I cannot imagine the machine shop crank grinder error that produced that.... unless.....the crank is bent.
Ray
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PostPosted: Sat Mar 24, 2018 1:30 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

Got some more measurements and findings. I think I've taken this thing apart and back together 14 times today. I noticed when measuring the wrist pin angle that the angle slightly changed if I moved the crank front to back axially.

When I saw this I decided to put the flywheel shims on and install the flywheel so the crank would be in its operating position. After that I measured the piston to cylinder deck heights again. It looks much better to me now. There is a max variance per piston of .2mm. That is .007". Seems more normal to me. Here is the new chart.

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


Is .007" deck height variance front/back OK? I don't have the rings installed so that could change things slightly as well...A .1mm vertical change at 45mm out from center would be a nearly undetectable angle change if the wrist pin bore was mismachined.
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PostPosted: Sat Mar 24, 2018 2:40 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

You don't want the rods bound up by being forced to run at an angle. What I would say to do is assemble the crank and bolt the case halves together and the with the crank at bottom dead center for each cylinder in turn see how close the rods are to being centered in the bore for cylinders. They should be very well centered, don't know what the acceptable variant is. Get back to us with your results.
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PostPosted: Sat Mar 24, 2018 2:54 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

RalphWiggam wrote:
Got some more measurements and findings. I think I've taken this thing apart and back together 14 times today. I noticed when measuring the wrist pin angle that the angle slightly changed if I moved the crank front to back axially.

When I saw this I decided to put the flywheel shims on and install the flywheel so the crank would be in its operating position. After that I measured the piston to cylinder deck heights again. It looks much better to me now. There is a max variance per piston of .2mm. That is .007". Seems more normal to me. Here is the new chart.

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


Is .007" deck height variance front/back OK? I don't have the rings installed so that could change things slightly as well...A .1mm vertical change at 45mm out from center would be a nearly undetectable angle change if the wrist pin bore was mismachined.


That looks a lot better. You are obviously getting some piston cock or rock.

And....actually.....if the wrist pin bushings were bored/honed on a good machine in good condition.....enough angle change to make .1mm....which is .0039" at the piston edge.....should have been seen easily.

Its alwo good to keep in mind that the pistons are used. There will be some variation with heat cycling.....but it would be good to find out exactly where these variances are and what is causing them....

What exactly did you have done to the rods besides having new bushings installed?
Ray
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PostPosted: Sat Mar 24, 2018 2:58 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

I hope the rod caps are numbered together, and that the arrows on the pistons are aligned correctly. Was the crankshaft Vee blocked? A deviance would account for some piston deviation and cam run out.
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PostPosted: Sat Mar 24, 2018 3:31 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

SGKent wrote:
I hope the rod caps are numbered together, and that the arrows on the pistons are aligned correctly. Was the crankshaft Vee blocked? A deviance would account for some piston deviation and cam run out.



Yep....I am thinking that may be where some of this variance is.

Also....as noted....I want to hear about what was done to the rods. If they were not checked for straightness, corrected if need be and resized.....there can be errors if just doing bushings. Ray
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PostPosted: Sat Mar 24, 2018 4:48 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

Here's an idea to try, maybe?

When the old SPG roller cranks were shipped,
they had a rod that went through all of the small end bushings,
Presumably partly to show how straight they all were..?

Maybe mock up something like this?

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


Always had the idea to just whttle up something like this on the lathe with some leftovers..
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PostPosted: Sat Mar 24, 2018 5:08 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

SGKent wrote:
I hope the rod caps are numbered together, and that the arrows on the pistons are aligned correctly. Was the crankshaft Vee blocked? A deviance would account for some piston deviation and cam run out.


The rod caps are numbered together and the pistons all aligned correctly. I don't know what vee blocked means. The crank was fully balanced and micro polished. Then the whole assembly was balanced together.

The rods we all balanced and the big end resized. The wrist pin bores all have new bushings.

From what I measured a .1mm drop over a radius of 45mm = a possible .127° wrist pin bore angle. Maybe that is a lot to a machinist. I doubt I could see .127°.

Can someone just say with 100% certainty that I should see NO variance in deck height when measured at different point's on the piston? If so, I guess I will have to take all my parts back to a different machinist and have them check everything. I'm out of ideas.


Last edited by RalphWiggam on Sat Mar 24, 2018 5:49 pm; edited 1 time in total
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PostPosted: Sat Mar 24, 2018 5:47 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

RalphWiggam wrote:
SGKent wrote:
I hope the rod caps are numbered together, and that the arrows on the pistons are aligned correctly. Was the crankshaft Vee blocked? A deviance would account for some piston deviation and cam run out.


The rod caps are numbered together and the pistons all aligned correctly. I don't know what vee blocked means. The crank was fully balanced and micro polished. Then the whole assembly was balanced together.

The rods we all balanced and the big end resized. The wrist pin bores all have new bushings.


A vee block places the ends of the crankshaft into a vee at each end and when it is turned it is measured for run out. One can use a notched set of 2x4's as a quick test if a professional one is not owned. However you said the crank was polished and balanced so it is unlikely it has run out. For the rods you can also put two rods together using one wrist pin and see how parallel the rods are to one another. Type 4 motors don't care which way the rods go onto the crank - type one engines are offset and the rods have to go one way only. It is possible for wrist pins bore to be bored off center on a piston but uncommon. Normally the deck height is taken with no rings to make it easier to work with but rings break easy so practice spreading rings using some old rings first - wear gloves because they are like a razor sometimes on the edges or if they break.

What are you using to bolt the cylinders down? It takes something heavy duty. I had these aluminum blocks made. I think Randy bought a custom rig that Phil made. There are torque plates made for type one engines but I have not seen a retail one for a type 4 engine.

Also - if you have access to a lathe you can use Clatter's suggestion to have a bar made to run between the rods to see if the rods are parallel. Otherwise put two together with a wrist pin and it will be obvious if one is bent or twisted. Use a dial indicator to find TDC like the photo when you measure the deck.

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

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PostPosted: Sat Mar 24, 2018 7:01 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

RalphWiggam wrote:
SGKent wrote:
I hope the rod caps are numbered together, and that the arrows on the pistons are aligned correctly. Was the crankshaft Vee blocked? A deviance would account for some piston deviation and cam run out.


The rod caps are numbered together and the pistons all aligned correctly. I don't know what vee blocked means. The crank was fully balanced and micro polished. Then the whole assembly was balanced together.

The rods we all balanced and the big end resized. The wrist pin bores all have new bushings.

From what I measured a .1mm drop over a radius of 45mm = a possible .127° wrist pin bore angle. Maybe that is a lot to a machinist. I doubt I could see .127°.

Can someone just say with 100% certainty that I should see NO variance in deck height when measured at different point's on the piston? If so, I guess I will have to take all my parts back to a different machinist and have them check everything. I'm out of ideas.


Ok....all of this is good.

Truthfully.....if all you were out is .007"....its not uncommon on 40 year old engine parts with several rebuilds on them.

But....look closely at your map of measurements. Do you see the diagonal oddity/similarity?.....3 and 2 and 1 and 4?

Seeing .003" to .005" variance from side to side on the pistons....is not uncommon. Your average of .007"-.008" is pushing it.

It will make a little difference in compression but certainly no worse than what most peoppe have just from normal ring wad valve seating variance. But....you will have some of that too....so no since in making it excessive.

Buy... its not the compression we are worried about. We are worried about the pistons traveling straight in the bore.

Normally.....the variances you are measuring ....we see as piston rock betwen 6 and 12 oclock when looking at the piston from the side of the engine.....NOT at 3 and 9 oclock.

The piston rotates about the wrist pin between 6 and 12....but must be as straight as possible between 3 and 9 oclock.

So.....everything looks good with what you had done to the rods....except....did they check them for straightness....AND correct any that were bent?

Also.....lets say for a minute that for some reason the crank was slightly bent. If so....it will have a wobble when mounted in the main bearing journals. Wiyh me so far?

If they slapped that into the crank grinder without checking for that in the V-blocks... ...the rod journals would now be ground offset about the axis of the wobble of the crank......and that right there will put both an angle on the rod journals and give each rod diagonal to the bend...and offset TDC.

So....question: by going through the records your dad kept....did the engine ever seize up, lockup or drop a valve or anythiny like that to be the cause of one of the previous rebuilds?

If so....that can cause slightly bent rods and crank.

So....if these turn out to be just variations in the casting and machine work of the pistons.....and nothing to do with crank, case or rods.....the amounts your piston TDCs are off will not be a problem. You can run them just fine.

What I want to know is were the rods checked for straightness and corrected. And....if not....have them checked. If any are bent....and I mean more than .001"....they need to be corrected or replaced and then the bushing must be replaced and rehoned.

Typically a maximum of .001" per 1" or rod length is allowed for staright bend in either axis before this will cause the pin hushing to squeeze oil out. Some state up to .004" measured in twist.

These need to be checked with a wrist pin on a rod checking jig.
Ray

And....put the crank in V-blocks and check the TDC on each throw. That takes minutes at the machine shop.
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PostPosted: Sat Mar 24, 2018 7:53 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

Ralph - yes thank you for ignoring whatever pissed Clatter off at me and my responses to him. Sorry you are in the middle. I do understand - "Hey guys I just want to build my engine..."

there are so many places and ways that the deck height can vary. Only you can answer them but here are a few and I am sure others can add to this.

* are the cylinder landing areas parallel? Often overtime they collapse a little - that is normal. When it is really bad they can be milled parallel to the case center line. A new case would not have this but the cylinders sink into the heads and case a little to correct minor imperfections. A drag racer wouldn't want it but a street bus isn't going to have a problem with it.

* How well are you bolting the cylinders down before measuring? I tried using really snug tight on a good strap of steel the first T4 I built and found that the variance in cylinder height was significant. That is why I had flat thick aluminum bars and blocks milled so I could torque the cylinders down evenly to measure deck height. That is the only way I found that my measurements were consistent.

* You should have ZERO run out on the cam gear. You'll not only hear any run out when the cam goes back and forth, but it will cause excessive cam bearing and thrust bearing wear. That may be an issue you need to investigate.

* When you take your deck measurements you should be at TDC on the wrist pin line using a dial indicator. Mine has a magnetic base because it makes it easy to move around. It is really easy to have some drop and not know it unless you have a dial indicator on the piston.

* How are you taking your depth measurements? Feeler gauges? That alone can account for variances. Below are some photos of tools other folks built to take really precise measurements. Feeler gauges are fine but do it ten times and each one will be slightly different.

* On the rod issue. If you have a professional square, you can put the wrist pin in and then the square on it. See how it looks then flip the square over to the other side of the rod. See how it looks there. The rod is going to self center in the piston. What is important is that the rod isn't bent. These are stock rods and there will be some variance in slight offset but because the rod will slide on the pin that shouldn't matter. Did you confirm that the arrows were all to the flywheel?

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

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PostPosted: Sat Mar 24, 2018 8:15 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

I went back out and did a bunch of swapping rods around and moving p/c sets to different locations. This is the best combination I came up with....

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


Maximum variance on the deck is observed on #3 with .11mm variance. That is .004". Does this look better? The other cylinders are about .001 variance now.

The cylinders were lightly torqued down with spacers. I don't have a block.

My dad did have the case lined bored back in 92 or something I think. I don't know what the cause of needing to have that done was.

The case decks on each side are perfectly flat. I don't know how to check if they are parallel through the case. The tops of the cylinders all also perfectly flat with no gaps or rock when I lay a straightedge across them.

I don't know what I can do to achieve zero lash on the cam gear. I agree that .004 is too much but who sells degreed cam gears that fit on my T4S cam?

I'll be honest I'm eyeballing tdc for measuring the deck on each piston. I am using the depth probe on my caliper gauge.
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PostPosted: Sat Mar 24, 2018 8:24 pm    Post subject: Re: Sealing rings at top/bottom of cylinders Reply with quote

Ralph, you don't need big fat blocks of aluminum bar stock to clamp your cylinders against the case. It's not like the goal is to crush them down against the deck...and besides, as you can see from the pictures above, they really hamper your ability to measure the deck height in multiple locations across the piston crown.

Get some 1/2" copper tubing, or even some pre-cut galvanized tubes at the hardware store, just the right length to take up the shank lengths and simulate a cylinder head, and GENTLY snug them down (only need two, diagonally positioned). The idea is to just snug them and hold the cylinders snugly against the case while you take deck measurements. Just don't overtighten them and bend/snap a fin off a cylinder.

The hyperbolic drama queens will have you think this will destroy your cylinders and not provide enough clamping force, but they'll be full of shit. Trust me, I've done it this way for hundreds of years, and I've built hundreds of thousands of multi-million dollar race motors for the biggest names in the business, and it works.
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