Post-Mortem of a 1904: Need some input

[vwracerdave]

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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1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
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[nsracing]

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.

[D/A/N]

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

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

[Pruneman99]

If you want to use the A pistons, use a shorter 5.325 rod. Small shim, Bob's your uncle.

[Brian_e]

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

Done.

Brian
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[modok]

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.

[D/A/N]

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.

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

_________________
'69 Fuel Injected Squareback. "B" D-jet. 1600 with balanced rotating assembly and lightened flywheel. Full flow and external filter.

'70 Riviera. 1904cc w/ 40mm Dellortos, 019 distributor, Steve Tims “super stock” 37x32 heads, Web Cam 218, Vintage Speed SS143 Super Speed exhaust, 1 1/2” heater boxes

[modok]

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.

[D/A/N]

[modok]

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

[Pruneman99]

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.

[Paul Jr]

[modok]

[Pruneman99]

[Pruneman99]

[clonebug]

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]

I get it that I’m splitting hairs and that I could more or less run the engine as is but I’m 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 I’m working from home right now and have more time and blah blah blah.

I also have a stock motor I’m going to build from the ground up but I started with this one because it’s all together and I thought it’d be easier to solve the problems it presents. That hasn’t quite been the case but I’m grateful for all the help so far. Sorry if it sounds like I’m 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 .122” of positive deck. I’m still going to check the other 3 cylinders just for fun but If I was aiming for, say, a deck height of .045 I’m looking at a stack of about .167” in shims on #1 and isn’t that on top of the .098 wider than stock modok pointed out yesterday? I’m understanding this correctly the total width would be just over 1/4” at .265.

So at what point would the engine be too wide to get all my tin and crap to fit correctly?
_________________
'69 Fuel Injected Squareback. "B" D-jet. 1600 with balanced rotating assembly and lightened flywheel. Full flow and external filter.

'70 Riviera. 1904cc w/ 40mm Dellortos, 019 distributor, Steve Tims “super stock” 37x32 heads, Web Cam 218, Vintage Speed SS143 Super Speed exhaust, 1 1/2” heater boxes

[Rome]

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.

[D/A/N]

[Rome]