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Post-Mortem of a 1904: Need some input
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vwracerdave
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PostPosted: Sat Jan 09, 2021 9:49 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Your cheapest solution and what I would do is get 5.5" I-beam rods and use .080" cylinder shims (or you could use a .040" cylinder shim and a silly .040" copper head shim).
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PostPosted: Sun Jan 10, 2021 5:31 am    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

The problem w/ this thread is too many damn cooks and the OP is all confused.

The issue it trying to accommodate a lopsided deck height -seems to me the only issue is #3 @ 0.055" - swap the rods around to the #4 @ 0.058" and see if it improves. If not, then run it like that - the #1/2 side will be looser in deck = I will put the tighter CC head on this side and the looser CC head on the 3/4 side.

YOu are just splitting hairs here. And the lack of machining services into this build makes it moot point. And the case has been decked. YOu cannot even tell if the case was decked even to begin with...as someone already pointed out.

~ 0.066" decks are about what the factory did. It is not that big. If you are fine-tuning a purpose built motor and have all the machinetools nearby to correct whatever dimension you like, sure you can split hairs.

I have done many ASYMETRIC engines when the heads had different deck-to-rocker pads dimensions. If you try to even them exactly, you will end up w/ different lengths pushrods between left and right banks. So the best way i found is to machine the heads so the motor can use same length pushrods.

Another way when the head chambers are different volumes and you have tight and loose decks side to side. Just do a best-fit = loose decks get the tight heads...and tight decks get the loose heads.

YOu get differences in decks when the machine shop just slaps the case halves on the mill and cuts before they look which side is tight or not.

tHe case is usually the culprit when you have uneven decks.

Goodness.
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D/A/N
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PostPosted: Sun Jan 10, 2021 1:37 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Looks like Iíve got a lot to think about! While nsracing is correct that Iím definitely a bit confused, I do see an end in sight.

Also Iíve yet to cc the heads that were on this engine but will hopefully get to that later today.

Pruneman99 wrote:
Easiest way to fix excessive deck is to use a longer rod. Keep your "B" pistons.

What rod is in there now? Stock?


Yeah, stock rods for now. Which makes me wonder if another ďtestĒ might be useful. I still have the A pistons the builder didnít want to go with because they gave too much positive deck. Would it be useful to mock things back up using that A piston kit? Then, I could see what the positive deck is all around and order shims? Hell....maybe Iíll be lucky and find out that the deck is equally positive all around.....
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Pruneman99
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PostPosted: Sun Jan 10, 2021 1:59 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

If you want to use the A pistons, use a shorter 5.325 rod. Small shim, Bob's your uncle.
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PostPosted: Sun Jan 10, 2021 5:30 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Mock it up with the A's and then use a .010" thinner shim on the long side.

Done.

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PostPosted: Sun Jan 10, 2021 5:49 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

With A pisotns .110 wider than stock, which is fine IMO.

With mahle B pistons is .110 narrower than stock,

B pistons and 5.5 rod would be closest to stock width.
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PostPosted: Sun Jan 10, 2021 6:45 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Thanks, modok, Brian, and pruneman. More good stuff to think about.

Also this. When I was putting the cylinders for the B pistons in yesterday I thought I noticed something strange on the cylinder walls. When removing them today, I confirmed something is strange looking to say the least.

What the heck is this mark from? The hone is still there but the metal feels ever so slightly smoother than in the rest of the cylinder.

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


Rotating the cylinder shows that itís a little less dark on the other side, but still there.

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

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PostPosted: Sun Jan 10, 2021 6:57 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Light scoring from some dirt that became embedded in the piston skirt.
A little of that is to be expected with these soft pistons, not a big deal, it can be FAR worse.
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PostPosted: Sun Jan 10, 2021 6:59 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

modok wrote:
Light scoring from some dirt that became embedded in the piston skirt.
A little of that is to be expected with these soft pistons, not a big deal, it can be FAR worse.


Ok, good. Wasnít hoping for bad news. Also, what you said above about A pistons and being .110 wider than stock, what rod size is that with?
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PostPosted: Sun Jan 10, 2021 7:08 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

stock (137mm), 5mm more stroke puts the piston that much farther out, .098 now that I think about it.
Not sure why my brain said .110......but close enough
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PostPosted: Sun Jan 10, 2021 7:20 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

That looks like it had pin buttons in it. Which is strange, because buttons will fall out with most B pistons.

Did it have them? Or maybe when the A pistons were in there? Or Modok could be right, just from the piston skirt.
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PostPosted: Sun Jan 10, 2021 7:53 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Pruneman99 wrote:
That looks like it had pin buttons in it. Which is strange, because buttons will fall out with most B pistons.

Did it have them? Or maybe when the A pistons were in there? Or Modok could be right, just from the piston skirt.


Can you please explain why buttons would fall out with B pistons?

I can see how they are not compatible with slipper skirt pistons but fail to see how they would just fall out of a B piston but not an A.
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PostPosted: Sun Jan 10, 2021 7:56 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Pruneman99 wrote:
That looks like it had pin buttons in it. Which is strange, because buttons will fall out with most B pistons.

Did it have them? Or maybe when the A pistons were in there? Or Modok could be right, just from the piston skirt.

Good guess, but 74 stroke would not pull the piston pin all the way to the bottom of the cylinder, that takes 84 stroke at least.
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PostPosted: Sun Jan 10, 2021 8:04 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

modok wrote:
Pruneman99 wrote:
That looks like it had pin buttons in it. Which is strange, because buttons will fall out with most B pistons.

Did it have them? Or maybe when the A pistons were in there? Or Modok could be right, just from the piston skirt.

Good guess, but 74 stroke would not pull the piston pin all the way to the bottom of the cylinder, that takes 84 stroke at least.


That's a good point.
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PostPosted: Sun Jan 10, 2021 8:07 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Paul Jr wrote:
Pruneman99 wrote:
That looks like it had pin buttons in it. Which is strange, because buttons will fall out with most B pistons.

Did it have them? Or maybe when the A pistons were in there? Or Modok could be right, just from the piston skirt.


Can you please explain why buttons would fall out with B pistons?

I can see how they are not compatible with slipper skirt pistons but fail to see how they would just fall out of a B piston but not an A.


Most A pistons are full round and have long pins. The button gets trapped between the end of the pin, and the cylinder wall.

Most B pistons have short pins. The button doesn't get trapped, so it will fall out.
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PostPosted: Sun Jan 10, 2021 9:45 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

I've been running .062" deck for 8 years and 43,000 miles. It runs just fine.
Put a .010 shim on the one side and finish it.



D/A/N wrote:
modok wrote:
the simple thing to do is put .010 shims on one side, or just leave it alone. But I assume you are frustrated with halfassery at this point.


It's a shame to be be re-machining the case AND honing and replacing the rings just for the sake of .010" or .015" but by traditional wisdom that's what should be done.
If the rings are broken in, you should not make the piston run higher in the cylinder than it did before.
On the plus side done right, you will know the case is right, and have better ring seal than new cylinders.

Dial calipers are adequate to check the rod length and pin height, but checking the case is going to require at least some combination of things you probably don't have. I've tried all kinds of ways, does not seem to be an easy way.


Yeah, the rings are broken in. Mahle 1st and 3rd rings and Total Seal 2nd rings.

I could do a .010 ring on one side which would bring the deck height all around to about .065 and thatís big, no? Per the CB engine calculator, Iíd need combustion chambers of 53ccís.

Though according to that calculator, if I had .050 deck height, Iíd need 55cc chambers to get my desired compression ratio of 8.5 which begs the question (for me anyway) of does a larger deck matter all that much if desired CR can be achieved by taking 2 ccís out of the chamber?

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PostPosted: Mon Jan 11, 2021 5:36 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

I get it that Iím splitting hairs and that I could more or less run the engine as is but Iím actually interested in learning more about how all this shit goes together and how to solve the different problems that arise along the way. And Iím working from home right now and have more time and blah blah blah.

I also have a stock motor Iím going to build from the ground up but I started with this one because itís all together and I thought itíd be easier to solve the problems it presents. That hasnít quite been the case but Iím grateful for all the help so far. Sorry if it sounds like Iím beating a dead horse. But I never liked horses much anyway so.....

In other news, I slapped the A piston and cylinder on #1 and measured about .122Ē of positive deck. Iím still going to check the other 3 cylinders just for fun but If I was aiming for, say, a deck height of .045 Iím looking at a stack of about .167Ē in shims on #1 and isnít that on top of the .098 wider than stock modok pointed out yesterday? Iím understanding this correctly the total width would be just over 1/4Ē at .265.

So at what point would the engine be too wide to get all my tin and crap to fit correctly?
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PostPosted: Mon Jan 11, 2021 6:17 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

When you fitted the A pistons to your cylinders, aren't those cylinders the original ones that have been shortened at the bottom? If so, then you'll certainly have a large positive deck/exposed piston top with the A's. Do you have a single uncut 90.5 mm cylinder to test fit the A piston and determine the deck height? You could use a junked cylinder as long as the total length has not been cut, and still has a near-full perimeter along the case side. Maybe somebody could send you a junked one (e.g., rust pockmarks on inner surface) for the cost of shipping.

Remember too, as pointed out that if you space the cylinders outward using the 0.167" shims or the other suggestions, you are moving the head away from the case. You'll need longer pushrods so that your rockers still operate somewhat correctly. If you want to keep the A pistons and just get new cylinders, aircooled.net sells just the cylinders. Cylinder length is the same for 90.5 A or B sets.
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PostPosted: Mon Jan 11, 2021 7:03 pm    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Rome wrote:
When you fitted the A pistons to your cylinders, aren't those cylinders the original ones that have been shortened at the bottom? If so, then you'll certainly have a large positive deck/exposed piston top with the A's. Do you have a single uncut 90.5 mm cylinder to test fit the A piston and determine the deck height? You could use a junked cylinder as long as the total length has not been cut, and still has a near-full perimeter along the case side. Maybe somebody could send you a junked one (e.g., rust pockmarks on inner surface) for the cost of shipping.

Remember too, as pointed out that if you space the cylinders outward using the 0.167" shims or the other suggestions, you are moving the head away from the case. You'll need longer pushrods so that your rockers still operate somewhat correctly. If you want to keep the A pistons and just get new cylinders, aircooled.net sells just the cylinders. Cylinder length is the same for 90.5 A or B sets.


The A cylinders were honed but not otherwise machined. Itís the B pistons that were trimmed.

Iím now starting to see the wisdom of either the Aís with a shorter rod or the Bís with a longer one....

I figured Iíd need new pushrods and have to mess with rocker geometry and whatnot but I donít even have an order in for new heads yet.
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PostPosted: Tue Jan 12, 2021 5:43 am    Post subject: Re: Post-Mortem of a 1904: Need some input Reply with quote

Quote:
The A cylinders were honed but not otherwise machined. Itís the B pistons that were trimmed.

Your comment below is why I wrote that your cylinders have been shortened:
Quote:
I dug into the build notes and emails from the builder from back in 2013 and found that he had the cylinders trimmed at the end where they seal to the case in order to get rid of positive deck

If you want to test stock-length uncut cylinders with the intent of building the engine back up with them, then you will have to check the pushrod lengths, rocker geometry, carb linkage width, possibly the muffler/header width. The engine will be wider than when built. I think the easiest way to get the engine running slightly better, without a full disassembly, is to fit those 0.010" shims to the "low" cylinder pair as several others have recommended. But "cc" your heads so you can determine the engine's compression ratio. Then you have the additional option per nsracing, to swap the tighter head (smaller cc volume) to the engine side with the larger deck heights. I remember this scenario was mentioned by Gene Berg in one of his newsletters, or another publication that I read with great interest in my early engine-building days in the late '80's to early '90's.
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