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> Bought a 2+L Mystery Engine, what's would you do next .
Literati914
post Apr 3 2018, 09:00 PM
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95.9mm bore

(IMG:http://www.914world.com/bbs2/uploads_offsite/i65.tinypic.com-7222-1522810827.1.jpg)
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Literati914
post Apr 3 2018, 09:03 PM
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71.28mm stroke

(IMG:http://www.914world.com/bbs2/uploads_offsite/i65.tinypic.com-7222-1522811005.1.jpg)
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Literati914
post Apr 3 2018, 09:05 PM
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Chunky Push Rods, looks like aluminum ?

(IMG:http://www.914world.com/bbs2/uploads_offsite/i68.tinypic.com-7222-1522811138.1.jpg)
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Literati914
post Apr 3 2018, 09:12 PM
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valves = 35.42mm & 41.86
Plugs = Bosch Platinum 'WR7CP'
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r_towle
post Apr 3 2018, 09:14 PM
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Looks like a 2.0 liter
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Dave_Darling
post Apr 3 2018, 09:26 PM
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You mean 2056, right? 96mm bore by 71mm stroke...

--DD
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Literati914
post Apr 3 2018, 09:32 PM
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QUOTE(r_towle @ Apr 3 2018, 10:14 PM) *

Looks like a 2.0 liter


96mm bores x 71mm stroke, does that equal a 2056 displacement? all be it the bores are technically 95.9 so ever so smaller...
BTW, the piston tops are dished. Do they come that way stock? and, those are not stock push rods are they?
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Boomingbeetle
post Apr 3 2018, 11:06 PM
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[/quote]

96mm bores x 71mm stroke, does that equal a 2056 displacement? all be it the bores are technically 95.9 so ever so smaller...
BTW, the piston tops are dished. Do they come that way stock? and, those are not stock push rods are they?
[/quote]

That is 2056cc if you calc it. The dished pistons may or may not be stock depending on year and CR of the motor. You can calculate that too, an Internet search will tell you how. Those are indeed stock aluminum pushrods for the type 4. Big difference from type 1 bug motors.
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falcor75
post Apr 4 2018, 02:34 AM
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[quote name='Boomingbeetle' date='Apr 4 2018, 07:06 AM' post='2595900']
[/quote]

96mm bores x 71mm stroke, does that equal a 2056 displacement? all be it the bores are technically 95.9 so ever so smaller...
BTW, the piston tops are dished. Do they come that way stock? and, those are not stock push rods are they?
[/quote]

That is 2056cc if you calc it. The dished pistons may or may not be stock depending on year and CR of the motor. You can calculate that too, an Internet search will tell you how. Those are indeed stock aluminum pushrods for the type 4. Big difference from type 1 bug motors.
[/quote]

Ummm, how can the pistons possibly be stock if the cylinders have been upgraded to 96's? The pistons are most likely aftermarket aswell is my guess.
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Boomingbeetle
post Apr 4 2018, 10:57 AM
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QUOTE(falcor75 @ Apr 4 2018, 01:34 AM) *


Ummm, how can the pistons possibly be stock if the cylinders have been upgraded to 96's? The pistons are most likely aftermarket aswell is my guess.


Doh! That’s what happens when you post to the forum way past bedtime! My guess is that they used a big-bore bus engine kit for the lower compression dished pistons. They look pretty clean, so the motor is likely rebuilt as OP says. Can you still see cross-hatch in the bore?
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Dave_Darling
post Apr 4 2018, 04:51 PM
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You'd have to measure the piston dish and the combustion chamber volume, plus the deck height, in order to calculate the compression ratio. I don't know that there were any "Bus kits" specifically with low compression, but it is possible.

The pushrod in your photo above is aluminum and is stock. The steel pushrod tube retaining wire will rub a notch in the softer aluminum pushrod if you don't seat it against the "lip" on the end of the tube...

--DD
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Literati914
post Apr 4 2018, 09:07 PM
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It didn't dawn on me, but you could have a low compression and a hi-compression 2056... Lot's of people do 2056 when rebuilding a 2.0, is it usually with dished pistons or flat tops? Why would you want low compression - besides turboing? Is there a problem with valves hitting piston tops or something? Is it that some people want to use low octane fuel? Is there an advantage to it? ... also would the extra volume that the dish creates increase the displacement, technically?
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jcd914
post Apr 4 2018, 09:49 PM
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I have never seen dished 96mm pistons until these pictures but obviously someone made them.
All that I have seen were flatop including the set in my shed.

The OE 2.0L pistons were dished. Bus pistons had the biggest dish, US 914 2.0 pistons a smaller dish than bus and Euro 914 2.0 pistons had smaller yet.

Valves hitting the pistons is a possibility depending on the valve lift, valve diameter and cam profile.
Usually valve pockets are cut into the pistons to prevent contact rather than dishing the piston tops.

Jim
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Literati914
post Apr 5 2018, 08:08 PM
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Do these valve diameters look stock = 35.42mm & 41.86 ?

Been looking, I can not find any dished 96mm pistons..maybe these are old and no longer in production?

Questions: All other things being equal, what will dished pistons in a 2056 do for performance vs flat tops? I mean low compression is going to produce a weak low end torque, right? But overall HP should be the same as w/ flat tops? Will it rev as well as a higher comp engine?

What kind of HP/torque can usually be expected from a 2056 anyway
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Literati914
post Apr 7 2018, 06:27 PM
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OK well, stock 2.0L pistons are 94mm, right? and I know the US versions were dished...so, wouldn't the stock bores measure something like 95.9mm (my quick and dirty measurement), to account for rings ? I'm feeling like these dished pistons are stock and if that's the case, then this engine is stock and not overbored. Is this plausable ?
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jcd914
post Apr 8 2018, 12:59 AM
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No stock 94mm 2.0L cylinders measure right about 94 mm, pistons are slightly smaller.
I don't know the specific sizes but I can look them up.
The rings are recessed into the ring grooves in the pistons.

Jim
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Literati914
post Apr 14 2018, 12:31 PM
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IF you guys bought a 2056 and discovered it had dished pistons (low compression), would you want to replace them with flat top pistons, for a spiritedly driven street car that may participate in autocross from time to time ?

There's a local guy who's got a set of 2.0L 96mm pistons and cylinders for $75, that I could pick up. I've got a message out to him inquiring of the condition.
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Boomingbeetle
post Apr 14 2018, 12:59 PM
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I think you will need to measure head cc and deck to find your compression ratio before you decide. Maybe they dished the pistons because the heads or cylinders were milled down in a rebuild and CR was too high. Also those flat pistons might not have the same wrist pin size or location to line up with your rods. You’d have to take one off the motor to compare. $75 is a good price though depending on make.
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Spoke
post Apr 15 2018, 09:10 AM
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I bought a 2L "mystery" engine with dual Weber carbs as well. My goal was to build it into a 2056 engine with 96mm pistons.

When I took it apart, I found out the pistons were already 96mm and have the dished pistons like the OP.

Instead of taking it completely apart and rebuilding with new 96mm pistons, I tried putting it all back together and trying it out. Cleaned up the case, bolted it back together, reinstalled the carbs without rebuilding, and it ran like a champ. The engine is in the car and runs real good.


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porschetub
post Apr 15 2018, 04:28 PM
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QUOTE(Dougster @ Apr 15 2018, 06:31 AM) *

IF you guys bought a 2056 and discovered it had dished pistons (low compression), would you want to replace them with flat top pistons, for a spiritedly driven street car that may participate in autocross from time to time ?

There's a local guy who's got a set of 2.0L 96mm pistons and cylinders for $75, that I could pick up. I've got a message out to him inquiring of the condition.


Don't place too much importance on the dished pistons ,the difference in power won't be that much unless you have a highly modified engine,go with what you have as spoke pointed out,for a street motor you have the benefit of the lower compression helping it to run a bit cooler,IMO fuel quality isn't what it used to be.
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