m117 4.5 block measurement - Page 2 - PeachParts Mercedes-Benz Forum

1960mog · #16 08-31-2011, 10:35 PM

Don't tell me you actually go and try that conversion.
Remember, what I wrote in my previous posts is only theoretical.
I never did that type of conversion.

Use 450 heads for the larger combustion chamber.
Make sure the dish in the 450s pistons is about 9mm deep.
Yes, the way the 450 cylinders look is normal, if there are no up and down scratches in them.
Keep us posted with pictures.
Good luck.

Tony H · #17 08-31-2011, 11:51 PM

The engine is very inexpensive Even after I get the 560 crank and rods I won't have much in it. The alum block heads don't fit a iron block engine-the head bolts are in a different pattern. I do not plan on using 3.5 heads-I want the early Djet 4.5 heads. I realize this is just a experiment. If it does not work out I will at least have a good 4.5 bottom end to put my 3.5 heads and cams on. If it will work I will put the $ into getting it done right. I'm not going to spend a fortune on head work to get a few extra hp-just whatever it takes to get the correct cc for the CR I want.
Speaking of cams-I did a rough measurement of lift with a caliper on a 5.6 there and the 5.6 cam has about .5mm more lift at the cam than my 3.5 cams. I'm sure i could have some cams reground if my project gets that far. There are many cam grinding companys that have 1000's of profiles on file.
I am going to get the engine this weekend. It might be a long time until I have time to work on it. i will keep updating my progress. The engine is just one small piece of a very large project. My coupe is totally dissasembled on a rolling stand that I built. It holds the body several feet off the floor giving good access all around.

GGR · #18 09-01-2011, 07:54 AM

Tony,

I second what 1960mog says. Unless you're doing it for fun and for the sake of doing something unique, it would be much more cost effective with better end results to make an adaptor plate to fit your trans onto a 5.6. You most seemingly will need to get a 5.6 engine to get the crankshaft and rods anyway. The 5.6 is lighter, has a bigger displacement than a stroked 4.5, has bigger valves, bigger inlet and outlet head ports, bigger intake runners and throttle body and bigger diameter exhaust manifolds (you will need to use some 560SL manifolds to clear your W111 Chassis). In short, it is more powerul and has even a greater potential than your end result with a stroked 4.5, for a total cost you will have reached anyway before even starting modifying the 4.5.

Keep us posted.

Tony H · #19 09-01-2011, 11:54 AM

I agree with everything said regarding the 5.6 engine. If max HP and torque were my only objective the 5.6 would be the idea solution. At first it seemed like a good idea but keeping with the iron 4.5 is plug and play. The stroking idea was something I was tossing around. I can get a 5.6 crank and rods for almost nothing at the pick n pull but to buy a known good, running 5.6 that has not been overheated or abused would require buying a doner car-not going to happen.
In the end I will probably just put my 3.5 heads on it.

GGR · #20 09-02-2011, 03:20 PM

the 3.5 pistons are the same diameter as the 4.5 and they have different p/n than the 4.5 pistons, including for euro engines with similar CR. With a bit of luck the pin is a bit higher and they may fit your application without shaving. Worth comparing the pin height when you have both pistons side by side.

1960mog · #21 09-03-2011, 12:23 PM

The 71 euro 3.5 pistons have a compression hight of 45.9 mm and a small cavity that is 3.8 mm deep.
The 78 450 pistons have a compression hight of 48.5 mm but there cavity is 8.8 mm deep and I think larger in diameter.
You have to cut at minimum of 2.4 mm of the 350 pistons and a minimum of
5 mm of the 450 pistons.
But the 450 pistons will have the larger cavity in the end.
You will need that cavity to lower your compression.

Tony H · #22 03-13-2012, 11:46 PM

Got the 5.6 crank, rods and pistons. Crank fits in the 4.5 block fine, crankcase will require some minor clearancing. Flywheel fits fine. Found a place that will remove the iron coating on the pistons or I might try walnut shells. Need to do some research on piston rings and head gaskets. Pistons have a 30cc dish and with the 45cc K-jet heads it works out to about 9.25 CR which is about right. Still have a very small investment but it gets more expensive from here if I proceed.
I'll post some pics tomorrow.

Tony H · #23 03-14-2012, 01:19 PM

It's laying on my garage floor because I could not fit the flywheel with it in the engine stand. this weekend I will fit one of the 4.5 pistons to a 5.6 rod and check clearance with the rods to the crankcase.

GGR · #24 03-14-2012, 02:17 PM

This is a very interesting project !

Tony H · #25 03-14-2012, 04:30 PM

After giving it considerable thought-If I actually proceed-I don't think I will bore the engine-only stroke it. Since the engine has dished pistons I can machine down the ridge to the proper deck height and achive increased displacement and CR with a minimal effort. I will need to have the engine rebalanced since the piston weight will be different than the 5.6 pistons.
Over the weekend I will mock it up with a 4.5 piston to see how the rod clearance is.

GGR · #26 03-14-2012, 04:42 PM

Pistons wear cylinders in an oval manner that is related to the stroke. Changing the stroke would in theory require reboring to eliminate the oval pattern as it wouldn't match the stroke anymore. You should at leat measure ovalization and talk to your machine shop guy to see what he thinks.

Tony H · #27 03-14-2012, 07:14 PM

Thanks. Before I put any real money or effort into this I am going to check everything out very carefully.

Tony H · #28 03-18-2012, 12:56 AM

Latest update for anyone following this crazy idea. 10 minutes with the grinder knocking off a few nubs in the crankcase and the 5.6 crank is spinning freely. Put one of the 4.5 pistons on a 5.6 rod and as expected it pokes 5mm out the top. Rods clear crankcase just fine but a small inference between the bottom of the piston and the crankshaft at BDC-a little machine work on the pistons will clean it up. So now I need to mic everything to see if my parts are worth working with, check crank and block for straightness, etc.

GGR · #29 03-18-2012, 07:50 AM

You may end up having to bore the block to eliminate any hedges on the top of the cylinders (remember, you rings will travel higher so you don't want the top ones to bump on any hedge created by the older stroke)and to eliminate any ovalization pattern. In that case your 4.5 pistons may not be usable anymore.

It would be worth considering what it would cost to put the 5.6 pistons on a lathe and remove that iron coating (4.5 pistons would also need machining to shave them anyway) and see if you can find rings that would fit the 5.6 pistons for iron cylinders.

It may not be all that much more expensive, and you would gain more than 10% displacement in the process.

I guess what your machinist will tell you about the current condition of your cylinders will determine your options. Also, see if the 5.6 head gasket would work on a 4.5 block/heads before boring it.

Tony H · #30 03-18-2012, 06:34 PM

I have given much thought to the head gasket if I go the boring route. I could have the 4.5 gaskets modified for the larger bore with new fire rings. I don't know if the 5.6 gasket will work and I don't want to buy one at this point just to find out.
I found out that a purple Scotch Brite pad removes the iron coating from the5.6 pistons with very little effort and no damage. So if my block/pistons are out of spec I might revisit the boring idea. I'm trying to find some old 5.6 head gaskets I can use to see how close they are or if they can be modified to work on the 4.5 block.
One plus with boring the engine is that I won't have to rebalance since I will use the entire 5.6 rotating assembly.