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  #1  
Old 07-10-2012, 01:43 PM
Tony
 
Join Date: Oct 2005
Location: Genoa, Nv
Posts: 882
Project: Iron block 5.6

I'm starting a new thread concerning my project to build an iron block 5.0 engine since it's progressed from concept to actual construction. I am removing about 28g of weigh from the pistons by machining the tops down to accommodate the longer stroke. This will require the engine to be rebalanced-no big deal-it's done all the time.
The connecting rods have large balancing pads on the big and small end-much larger than required to weight match the rods. Since I'm rebalancing anyway my thought is to lighten the connecting rods by removing the excess balance pad. Not sure why there is so much excess-is there some reason? It seems to just add unnecessary weight to the connecting rod. Reading other engine building forums it seems common practice.
Also check out these cool Megasquirt trigger wheels I found on Ebay:

36-1 Trigger Wheel Custom EFI VEMS Megasquirt Megajolt Mercedes M116 M117 95 mm | eBay

The seller also has the bracket to mount the VR sensor.
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1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #2  
Old 07-11-2012, 03:30 PM
Registered User
 
Join Date: Feb 2011
Location: Modesto CA
Posts: 2,180
Some specifics of your project would be of interest to many, I think.
Bore and stroke, source of crankshaft, rods, pistons.
Original compression height vs. new comp. hgt.
Photos of your reworked parts.
Etc., etc., etc.
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  #3  
Old 07-11-2012, 05:03 PM
Tomguy's Avatar
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Join Date: Aug 2002
Location: Not where I want to
Posts: 5,016
I don't think there's an issue in removing it. And IMO if you're trying to do a performance engine you may want to shave some weight off the flywheel and rebalance it to the new engine/crank assembly so it revs faster (shaving extra weight off the rods helps this too).

I would like to see the info on this too. I'm wondering why you chose a 4.5 block vs a 5.0 block since the iron is so much heavier. I personally would love a neat project like this, but I'd probably use a 4.2 block since it's the lightest and try to bore/stroke that
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  #4  
Old 07-14-2012, 02:50 AM
Tony
 
Join Date: Oct 2005
Location: Genoa, Nv
Posts: 882
Some of this is redundant and on another post so sorry if it’s long . My intention is not to build a “performance” engine but a larger, higher compression version of the stock engine. I want to go with the iron block for simplicity and to retain some form or originality. The extra weight is not that big of a deal. By using a 5.6 crankshaft and rods in a 4.5 engine one can increase the stroke from 85mm to 94.8mm bumping the displacement to 5041cc and also increase the compression ratio from 8.0 to about 9.5:1. The problem is there are no “stroker” pistons for this application. The piston tops need about 5mm taken off the top. Fortunately the K-jet engine has pistons with a 9mm dish so there is somewhere to take the material from.
Stock engine specs:
Bore=92mm
Stroke=85
Connecting rod bearing=52mm
Main bearing=64mm
Piston compression height=48.5mm
Block height=245mm
Rod length=154.55mm
Displacement=4520cc
K-jet combustion chamber=45cc
Piston dish about 30cc

Stroked engine specs:
Bore=92mm
Stroke=94.8mm
Connecting rod bearing=48mm
Main bearing=64mm
Compression height=43.55mm
Block height=245mm
Rod length=154.55mm
Displacement=5041cc
Piston dish cc TBD after the valve pockets are cut
CR about 9.5 to 9.75:1
rod ratio=1.63 which is ideal.
Should be a really strong bottom end.
The lighter pistons(compared to the 5.6 ones) will require the engine to be rebalanced so everything from flywheel to front pulley is going in for balancing. I have not decided what camshafts I am going with yet. I plan on using a 5.6 intake and port matching it to the heads. I’m using megasquirt and EDIS ignition. To go further gets expensive(head work and custom cams) and I’m not going for all out performance but a decent power increase for not much more $ than a stock rebuild.
This is a major distraction from my restoration but the idea intrigued me and I went with it.
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1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #5  
Old 07-14-2012, 05:39 AM
t walgamuth's Avatar
dieselarchitect
 
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 30,993
I'd be concerned about taking five mm off the tops of the pistons. Most pistons would not be thick enough there to do this without weakening them.

Cannot find shorter rods?
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  #6  
Old 07-14-2012, 10:39 AM
Tony
 
Join Date: Oct 2005
Location: Genoa, Nv
Posts: 882
Even after the material removal there is a remaining dish of about 4mm so I am well above the crown. If these were flat top pistons there is no way this would work. I posted a picture of my prototype piston on another thread and can't figure out how to reuse it on this thread but here's the link to the thread:
m117 4.5 block measurement
Quote:
Originally Posted by t walgamuth View Post
I'd be concerned about taking five mm off the tops of the pistons. Most pistons would not be thick enough there to do this without weakening them.

Cannot find shorter rods?
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Tony H
1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #7  
Old 07-14-2012, 02:28 PM
Registered User
 
Join Date: Feb 2011
Location: Modesto CA
Posts: 2,180
Re: The Deves ring question on your other thread, I used them for some years in a SCCA H Production Sprite (948cc) with very good results.
That said, consider sourcing rings from companies such as Sealed Power/Speed Pro, Hastings, TRW, etc. By entering their listings for bore dimension and ring width, you may be able to find appropriate part #s.
Rings can be purchased separately by type, i.e., compression in the correct bore and width as one part #, and oil as another part #. They do not have to be purchased as application specific sets.
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  #8  
Old 07-14-2012, 07:00 PM
Brian Ostosh
 
Join Date: Mar 2007
Location: San Diego
Posts: 504
I order Deves by dimension and block material.
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  #9  
Old 07-15-2012, 02:32 PM
Tony
 
Join Date: Oct 2005
Location: Genoa, Nv
Posts: 882
I did search for rings based on dimension and there are no others I can find. Deves, Goetze, and ITM (?) seem to be the only off the shelf rings available. I don't know why Deves is getting a bad rap. My machine shop told me not to use them (I didn't even ask)
Goetze is a Federal-Mogul brand but the only one of their ring brands that has listings for Mercedes.
I even toyed with the idea of having custom pistons manufactured. It's not as expensive as one might think.
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Tony H
1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #10  
Old 07-15-2012, 03:30 PM
Brian Ostosh
 
Join Date: Mar 2007
Location: San Diego
Posts: 504
Just call Deves and talk to them, they will do it dimensionally. Thickness and bore size, you may have to do the end gap.

I had a set of 6 M130 4-ring pistons with the top ring land just hammered and I had a machine shop re-cut the top groove to the next metric size. Make a part-off lathe tool the width and 4 jaw chuck- um, indicate true up and cut, this cost $120 to save 6 expensive pistons.
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  #11  
Old 07-15-2012, 05:17 PM
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Join Date: Dec 2007
Location: DFW, Texas
Posts: 279
very interesting...

this sounds pretty cool. I too am very interested in following this project and reading all about the particulars. Seems well thought out and being well executed. Keep us updated with all the details! Can't wait to hear how the finished product turns out!
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  #12  
Old 07-15-2012, 05:41 PM
Tony
 
Join Date: Oct 2005
Location: Genoa, Nv
Posts: 882
Might be awhile as the car it's going into is ALONG way from finished. It's looking more and more like a retirement project-especially if I keep getting distracted by projects like this!
Quote:
Originally Posted by gear-head View Post
this sounds pretty cool. I too am very interested in following this project and reading all about the particulars. Seems well thought out and being well executed. Keep us updated with all the details! Can't wait to hear how the finished product turns out!
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1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #13  
Old 07-15-2012, 07:50 PM
Registered User
 
Join Date: Jun 2004
Location: brisbane,Qld.Australia
Posts: 2,042
The pad on the end of the rod is to counter balance the gudgeon pins mass. Do not remove it. It is also used to balance the rod. Unless you have shaved the rods to polish them do not bother rebalancing as they are very close as it is.
I have had a look at a few old pistons here and yes it's OK to shave the crowns . They will be better anyway,with less moving mass at high feet per second rates. Imagine the piston coming up at several hundred feet per second,then being yanked or pushed back down again ,..the strain is enourmous .
I am building few engines here at moment and an old friend has a stack of rings made by Teves and thompson. The Quality is absolutely beautiful!. Some of his stiock is close to 50 years old so I doubt if Teves still make rings ( may have been bought out by TRW in the 70's I think) .
Do not remove metal from the flywheel etc. The old thinking of less mass equals more horsepower has been debunked now with many Drag racers etc fitting heavier mass flywheels to increase torque effect. on all out circuit race engines they run without flywheels ( sprint cars etc ) but that is at the outer ends of engine speeds.
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  #14  
Old 07-17-2012, 01:05 AM
Tony
 
Join Date: Oct 2005
Location: Genoa, Nv
Posts: 882
Thanks for the comments Ron-well taken. I have no plans to modify the flywheel. Rods will remain unmodified also-thanks for the input. I want to keep the engine as stock as possible and perform a high quality rebuild.
I have removed about 4mm from the piston which puts the top ring 6mm from the top. That's still twice as far as many engines today and I feel it should not be a problem.
I found a NOS set of made in Sweden Deves rings I bought years ago for my 3.5 but they fit the 4.5 also. Maybe I will use them.
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Tony H
1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #15  
Old 10-04-2012, 01:56 PM
Tony
 
Join Date: Oct 2005
Location: Genoa, Nv
Posts: 882
Time to make a decision about what bore to use

I am about to take my block in for preparation so I need to make a decision on whether to stay with the 92mm bore or bore the engine for the 560 96.5 pistons. The cost will be about the same-if I use the turned down 92.5 pistons I will need the engine rebalanced which will cost about the same as the extra machine work for boring to 96.5. If I use the 560 pistons I have the entire original 560 rotating assy so I should not need rebalancing. The flywheel is statically balanced and not balanced as an assembly like an externally balanced engine. My main concerns are the head gasket and piston rings if I go with the 96.5 bore. I found a company that will modify the 450 head gaskets with larger dia fire rings for the bigger bore so I feel comfortable with that.
I don’t feel there is an issue with the coating on the 560 pistons-it has very little ferrous content and a very strong magnet will barely stick to it. As long as it is not steel there should not be any compatibility issues with the iron cylinders. What I am struggling with is which piston rings to use with the 560 pistons. The original rings are steel or ductile iron which is incompatible with an iron cylinder. Deves has cast iron rings for this application but I keep hearing about rapid cylinder wear, etc. Is this just BS?
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1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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