Project: Iron block 5.6 - Page 6 - PeachParts Mercedes-Benz Forum

Tony H · #1 05-24-2017, 11:30 PM

It's been a while since I have done anything with my project other than packing it up and putting it in storage since we are moving but I'm doing some armchair engineering. I'm trying to keep my project as straightforward as possible and I started thinking about my cylinder head choice(again). I had previously decided to use the 5.6 heads with their larger valves/ports and they will fit with some machine work but the downside is the large combustion chambers, the cooling/oil passages need to be matched, the long cam bolts don't line up and the accessories don't fit like the 4.5. I have some K-jet 4.5 heads and took a fresh look at what it would take to turn them into 5.6 heads. The valve guide basic bores are the same so no problem there. New valve seats are no problem and I have 5.6 heads to copy the port design. My concern is breaking through during porting. I'm thinking about experimenting with some junk heads before I go to the expense of new valves.

Frank Reiner · #2 05-25-2017, 03:49 PM

Quote:

Originally Posted by Tony H

I have some K-jet 4.5 heads and took a fresh look at what it would take to turn them into 5.6 heads. The valve guide basic bores are the same so no problem there. New valve seats are no problem and I have 5.6 heads to copy the port design. My concern is breaking through during porting. I'm thinking about experimenting with some junk heads before I go to the expense of new valves.

Tony, it seems fair to note that the valve sizes and port area of the 4.5 heads will provide sufficient air flow for over 300HP, particularly with the cams that you have chosen (56/57). I may be mistaken, however, information at hand says inlet valve diam. > 44.2mm(1.74"), exhaust > 39mm(1.54"), inlet port @ manifold > 41mm, exh. port > 34mm.
Why did the 5.6 engine receive larger valves, most notably the inlet? As you have pointed out, the valve timing has been retarded (and shortened), again most notably on the inlet, which results in rather fewer degrees of valve open time while the piston is descending on the inlet stroke. To compensate, an increase of flow area has been provided.
The 56/57 cams open the inlet sooner, are longer, and quite importantly, have lobe centers that are 16 degrees closer than the 18/19 cams of the 5.6 (104 vs. 120). The close lobe centers provide a big overlap flow increase, along with higher velocity, without requiring a larger valve.
A bit of careful cleanup work on a flow bench is likely to yield good results.

Tomguy · #3 05-25-2017, 01:04 PM

I wouldn't be surprised if the heads actually had the room inside without worrying about breaking through. The only way to know for sure would probably be to have them sonically examined which would likely cost more than a trip to a U-Pull-It to grab a head to experiment on.

Tony H · #4 05-26-2017, 07:00 PM

Thanks for your comments Frank. I will be using the 02/03 cams. They are similar to the 56/57 cams but hydraulic, have the higher lift of the 560 cams and a 106 deg LSA. I agree the larger valves would probably not provide any benefit. I already have new valves/guides/springs I was going to use on my 3.5.

rwd4evr · #5 12-16-2017, 02:48 PM

My understanding is that the squish band is there to get as close as possible to the flat "deck" areas of the combustion chamber to allow heat transfer from the piston to help battle detonation. The kjet heads are missing that flat area compared to the djet 3.5 heads if I remember correctly? The djet US motors had the piston down in the bore to lower compression that leads to detonation I think.

I have picked up a set of 3.8 euro cams, I believe they say k70 and 71 on them. Have you ever looked at these? I'm looking for high end power and the 92mm bore 3.8 redlines at 6700rpm so I figure the cam timing has to be different than all the others. My 4.5 really falls on it's face after 6000. Not sure if it's Valve float starting or just the cams being setup for low end power with the terrible auto. I'm not even 100% sure its got stock us kjet cams actually. But it just stops revving. Drifting it in third is tough so I really was giving it to it in second.

Frank Reiner · #6 12-16-2017, 05:14 PM

Quote:

Originally Posted by rwd4evr

My understanding is that the squish band is there to get as close as possible to the flat "deck" areas of the combustion chamber to allow heat transfer from the piston to help battle detonation. The kjet heads are missing that flat area compared to the djet 3.5 heads if I remember correctly? The djet US motors had the piston down in the bore to lower compression that leads to detonation I think.

The quench (aka, squish) is not to transfer heat from piston to the head, but rather to 1) concentrate as much mixture as possible in the combustion chamber, and 2) to keep the mixture remaining in the quench area at a temperature that is below ignition temperature, hence the term "quench", i.e., to lower the temperature, to cool.

See post #37 of this thread: the total quench area of the 3.5 head is greater than that of the 5.6 head, however, the upper (away from the spark plug) portion of the 5.6 head is greater than the corresponding area of the 3.5 head by virtue of a greater bore diameter.
The downsides of the 3.5 head are smaller ports, smaller valves, and greatly shrouded valves.

Quote:

I have picked up a set of 3.8 euro cams, I believe they say k70 and 71 on them. Have you ever looked at these? I'm looking for high end power and the 92mm bore 3.8 redlines at 6700rpm so I figure the cam timing has to be different than all the others. My 4.5 really falls on it's face after 6000. Not sure if it's Valve float starting or just the cams being setup for low end power with the terrible auto. I'm not even 100% sure its got stock us kjet cams actually. But it just stops revving. Drifting it in third is tough so I really was giving it to it in second.

The 70/71 profile is decidedly mild (179 degrees); 60/61 (190 deg) would be preferred. However, cams intended for use in M116s have less lift than those for M117s. 00/01 and 02/03 profiles would be better yet.

rwd4evr · #7 12-16-2017, 05:46 PM

what do you mean 179 vs 190 degree? they aren't 179/190 degree duration of crank rotation are they? duration at 0.050"?

Frank Reiner · #8 12-16-2017, 07:10 PM

Quote:

Originally Posted by rwd4evr

what do you mean 179 vs 190 degree? they aren't 179/190 degree duration of crank rotation are they? duration at 0.050"?

Sit down - pour yourself a stiff drink!!

Mother Benz's duration specs are given at a valve lift of 2mm. That lift at the valve corresponds to approximately .050" at the lobe.
And no, Virginia, there is no camshaft Santa Claus such as many folks imagine as being the chief engineer of CompCams, Isky, Howard, etc.
Published duration numbers from The Mother are decidedly short by comparison with familiar US data; the longest street use, production profile is on the order of 204 deg @ 2mm lift.

Tony H · #9 12-20-2017, 02:26 PM

Quote:

Originally Posted by rwd4evr

My 4.5 really falls on it's face after 6000. Not sure if it's Valve float starting or just the cams being setup for low end power with the terrible auto. I'm not even 100% sure its got stock us kjet cams actually. But it just stops revving. Drifting it in third is tough so I really was giving it to it in second.

Worn valve guides will cost power-especially at high RPM. These heads are notorious for worn valve guides. The heads I just got have wobbly valves as every used Mercedes head I have ever disassembled does. Carbon'ed up intake valves/ports will hurt flow. As you mentioned weak valve springs will prevent the valves from properly sealing along with the worn valve guides. This all hurts high RPM performance.
I did some research and these valve sizes will support 330HP in theory.

rwd4evr · #10 01-13-2018, 02:49 AM

I've decided to go for a turbo setup on the 4.5. i may steal tony idea and bore it to 5.0 though. i have a 5.0 liter aluminum block that i sold the cams out of for more than i could turn down but its got a ton of miles on it. if they arent too bad im sure i can have the machinist get the bores set to the pistons and hand file the rings. that has to be done anyway for turbo. I'm usuing the WUR from a Porsche 930 turbo for controlling the fuel curve. One thing i found out was that my 4.5 wasnt running out of breath at 6000 like i thought. I cant really see the tach with the tiny wheel in my car so i took a video to see when it hitts its limit and where it drops to in third gear. HOly Moley!! my tach is a little high about 2-300 last i checked but damn! it hits 7100 rpm on the tach. and its still pulling hard when it falls on its face. not sure if its valve float or what really.

https://www.youtube.com/watch?v=FVohN3a1Epk

Now im super curious what cams are in it or why its redlined at 5800 if its stock. its gonna rock with a turbo on it. not getting too crazy but 8-10 psi will be in the 400 hp range according to calculators. would the us 5.6 cams be a good choice with a turbo?

rwd4evr · #11 12-17-2017, 03:07 AM

Not sure really. The car had been modified before I got it with parts from a manual SL or slc so it stands to reason it could have euro parts or even the whole engine. It had euro lights. Assuming not modified it's a 78 450slc with a 180hp 8.0-1 compression. It's definitely not a 3.5 so I don't think the trans donor could have been a 4.5 correct? No euro 4.5 manuals exist right? I don't think it's 4.5 euro 225hp fast. But maybe it's got the better euro cams. I have to say I'm liking the idea of just boring a 4.5 kjet motor and dropping in a 5.6 bottom end. I've got it all laying there...

Tony H · #12 12-16-2017, 07:14 AM

So I bought a decent pair of 4.5 K-jet heads from a car that had never had the heads off and no coolant in the oil and the head gaskets were not blown. It's always a crap shoot buying used parts from a car that ceased to function for some reason. The donor car looked like it spend decades in someone's backyard. anyway I decided to use 4.5 heads vs 5.6 heads on my project-a lot less issues to overcome. The 5.6 heads could be modified to fit but it adds a lot of unknowns. My calculated CR is just shy of 10:1 but my research has shown a open, small combustion chamber used with a dished piston that has squish bands is a very efficient and pre-ignition resistant combination that should not require a lot of ignition advance to produce max power. In case someone did not read through the entire post the reason I am using K-jet heads is they have a better combustion chamber that allows actual squish.

Tony H · #13 12-16-2017, 06:48 PM

The 4.5 K-jet heads do have squish bands-they correspond to the bands on the 5.6 pistons. Here is a picture of a 3.5 and 4.5 K-jet combustion chamber-very similar except a little less area around the exhaust valve. You can see the valve shrouding Frank mentioned.
Don't know about the cams

rwd4evr · #14 01-13-2018, 12:58 PM

I'm also curious on your opinion of the bottom end structure of the iron block vs aluminum block engines. I know they aren't six bolt side bolted like the aluminum. It's been quite awhile since I looked at one opened up out of a car and I wasn't thinking about building it for power when I did. It's 4 bolt mains correct? I'd love to save weight with aluminum but the hassle of swapping my manual trans and boring or even having custom Pistons made for the aluminum block "outweighs"�� the savings.

Tony H · #15 01-14-2018, 06:12 PM

The iron block is 4 bolt. I think the iron block is strong enough for any power one would be likely to obtain. My first idea was to stroke the engine only and not bore it. I even machined one 4.5 piston for the longer stroke to test my theory. I had to take about 5mm off the top and some off the skirt but there was still a small dish left and the rings were still about 5mm down. That would have resulted in a 5L engine with about 10:1 CR if your cylinders and pistons were good enough to be honed for new rings. If you need new pistons you might as well bore it.