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  #1  
Old 08-14-2016, 09:17 PM
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M117 CAM SPECS, HEAD DIFFERENCES?

Does anyone have or know where to find the factory cam specs for different m117/m116 engines? 3.5,3.8,4.5,5.6? Im also trying to find out head differences between different engines including us vs euro of the same numbers. I have found some info on the 117.982 and 117.985 us and euro, strange thing is that the us and euro .985 and euro .982 share the same heads according to EPC, but us .982 has a different part number. i believe the .982 is d-jet and .985 is k-jet. I have seen pics of two different shaped combustion chambers and there are multiple piston top designs i know. i k now the 3.5 m116 heads will increase compression significantly. I'd love to have a set of them.
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  #2  
Old 08-14-2016, 10:42 PM
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I know I've seen somewhere the differences in the Pistons and combustion chambers, Apparently all the US Spec pistons are flat on top, and must not come up quite as high with a bigger "quench" area or something like that. I recall a discussion with terms like "quench" and some other terms. If you search those terms, you might be able to find the thread.

I believe that some of these piston differences might not matter whether d-jet or k-jet.

Remember that euro ~1974 450slc that is rotting away with a trunk full of NOS parts? Hmm...
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  #3  
Old 08-15-2016, 02:22 AM
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Yes I found the thread with that piston info. The pics of the different heads were confusing though. I did read up on quench and related things going on in the combustion chamber. I'm curious if a combo of the different heads/Pistons we have can be used to up the compression a bit. 73 d-jet 4.5 has different Pistons and heads than the 78 k-jet 4.5 in my slc. I've read the 5.6 heads will lower compression, but the cams may improve airflow. I've also considered retarding the cams a bit for higher rpm power. The manual trans and higher numerical gear will make this much better than in a stock Sl or slc. Is there any reason these motors can't rev to 7000rpm safely with everything tuned for it? Milling the heads for compression and doing some port work could be good for some power I'm sure too.
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Old 08-15-2016, 06:57 AM
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I think the rpm limitation is due to the maximum metal-on-metal movement speed. The 3.5 has a higher redline because the strike is shorter.

But it's just an iron block 4.5 that's common enough. So blowing one up isn't too big of a deal. Right?

On the other hand, I'd expect the redline to be beyond the "power band" anyway.
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  #5  
Old 08-15-2016, 01:36 PM
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rwd:

Have a look through the Vintage section for posts by Tony H, such as this one:

http://www.peachparts.com/shopforum/vintage-mercedes/321240-project-iron-block-5-6-a.html?highlight=Tony
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  #6  
Old 08-15-2016, 01:46 PM
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No piston speed shouldn't be an issue. The 4.5 is still a relatively short stroke engine so unless there is a bad ring design causing ring flutter that shouldn't be a problem. I was thinking about the oil pump chain, maybe the distributer bieng limited to a certain rpm, either internationally or mechanically unable to fire accurately after a certain point. Stock redline is 5800rpm on the 4.5 and 6500 on the 3.5. Then onto valve train issues. Will it float valves and bend stuff? Break timing chain guides? The engine stock falls off quickly after 5500 rpm I think I saw on a dyno graph somewhere, but changing valve timing moves the power and up. With the stick shift I'm not worried about low end power, it doesn't make much anyway.
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  #7  
Old 08-15-2016, 01:49 PM
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Quote:
Originally Posted by Frank Reiner View Post
rwd:

Have a look through the Vintage section for posts by Tony H, such as this one:

http://www.peachparts.com/shopforum/vintage-mercedes/321240-project-iron-block-5-6-a.html?highlight=Tony
Yes thanks frank. I have read that a while back but couldn't remember Tony's handle here. I definitely want to pick his brain a bit since I do have alloy 5.6 motors available for parts.
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Old 08-17-2016, 11:43 AM
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Hey guys. Does anyone have any good suggestions on the easiest or best ways to determine what heads are on this 4.5 with a manual trans attached to it?

The heads have "R116" numbers on them, but I see that many 4.5 heads are listed with this number on them.

Would a compression test to determine approximate compression ratio make sense? I've got a cheap harbor freight compression tester that's been used on a smoking w108 4.5 (avg maybe 150 psi with some 170 readings 8:1 compression?) and a 1981 (dual row TC) 380slc (avg 170 with some 160 and 180 readings, 8.3:1 compression?) . Assuming that the compression ratio is the biggest benefit of having 3.5 heads on a 4.5 engine, wouldn't a compression test be pretty valuable?

Are there any ways to tell from the top?

Might we look for anything like solid lifters or something else that would be out of place on a 1978 450slc?

The reason for asking these questions is the 116 marking on the heads along with the manual transmission that I would assume came from a 3.5.
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  #9  
Old 08-17-2016, 01:45 PM
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Cranking cylinder pressure is a function of three variables:
1) Swept volume
2) Combustion chamber volume
3) Inlet valve closing point

If Swept volume and Inlet closing point are kept constant, and the Chamber volume is decreased, cranking pressure will increase.
If the Swept volume and the Chamber volume are now held constant, and the Inlet closing point occurs later (a "bigger" cam or a retarded cam), cranking pressure will decrease.
Simply making value judgements on the basis of a change in one indicator (cranking pressure) can be a bit misleading.
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  #10  
Old 08-17-2016, 02:08 PM
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Quote:
Originally Posted by Frank Reiner View Post

Simply making value judgements on the basis of a change in one indicator (cranking pressure) can be a bit misleading.

Thanks. I was simply thinking that we might see higher numbers than the 380slc if it doesn't have stock heads, maybe numbers closer to my w108 4.5 if they are stock.

Do you know any other easy way to try and determine if the heads are stock?

Maybe look at the stampings on the backs of the camshafts to determine if they are a special grind or anything?

(I recall someone spotting one GTS camshaft on my 450slc 5.0, but finding that the camshafts were standard grinds with regular stamps in the backside, something like x01 and x02 where x was some other letter or number.)
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  #11  
Old 08-19-2016, 12:46 PM
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The 3.5 and 4.5 cams are spec'd the same, IIRC. The heads are nearly identical, with the 4.5 having more of the chamber ground out to lower compression (and I have personally seen two 4.5 head designs, which seem to correspond to differing 4.5 power numbers and compression ratios). Otherwise, the valve specs are the same, springs, etc... so valve float would not be why the 4.5 redline is lower. Couldn't be. The only difference in the engines is the 4.5 has a longer stroke, so it's GOT to be why the redline is lower. That being said, I'm fairly sure I went above 6k on my 4.5 after I put on 3.5 heads, maybe with stock compression the engine power drops so much it just tops out @ 5800 or whatever and has no guts to go higher in top gear?

Since a pic is worth a thousand words, here's a 3.5's combustion chamber. Yes, dirty in the pics, but you can see that the only portion that would extend above the deck/gasket is the wedge around the valves. On the 4.5, what is pictured on the bottom half is cut out - with more cut out for the 8.0 heads than the 8.8 heads. I measured volume with a syringe and although it isn't 100% accurate I was within about 90% accuracy... you would need to use the forum's search to find it, I did it years ago.
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  #12  
Old 08-19-2016, 03:35 PM
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Thanks Tomguy. I've found pictures of three different combustion chamber shapes. Two have the "wall" where the spark plug comes in cut back like you were saying and one that actually had the flat deck of the head cut
Back slightly. Maybe an aluminum block head. The thing I want to figure out is if I did get a set of 3.5 heads, is if my kjet Pistons displace the same amount with the valve cutouts and center dimple as the flattop djet Pistons down in the hole (3.4 mm lower compression height))I'm assuming you had. If so compression would be higher, maybe too high for pump gas. Did you figure out what you're CR was with you setup?I think I'll have less volume to the deck height which means I could buy some compression with djet heads on the kjet motor. I have a set of djet heads I have to look at at my shop.
I found a site called boodmo with piston specs for a bunch of Mercedes engine, usually have to look at the part number for the oversize Pistons.
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Old 08-21-2016, 12:47 AM
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I never measured the actual CR comparisons before and after. Martin calculated it here, and I think he did a good job and it is likely right:

http://www.peachparts.com/shopforum/vintage-mercedes/318200-300sel-3-5-anyone-installed-117-cylinder-heads-116-engine.html
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  #14  
Old 08-26-2016, 06:40 AM
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it appears that from what i read there that the k-jet heads are smaller chamber and the d-jet pistons even though in the hole, displace more than the dished US pistons. so i could gain compression with d_jet pistons in A K-jet engine. but ive read that not having the squish band(the raised area around the dish on the piston top) on the piston top that approaches the heads deck surface much more closely really affects detonation resistance because the piston coming within .040' ideally, to the head lets it transfer heat from the piston crown to the head which can release it to the cooling system. sound logical to me. I have also read d-jet engine a very susceptible to detonation. i guess i need to optimize cam and exhaust for more power and hope i stumble onto a good euro 4.5 or 3.5. i need to learn more about the volvos with turbo k-jet too. if i could make that work i think i could get away with a junkyard turbo setup for lemons racing. megasquirt wont be let in without serious penalty laps.
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  #15  
Old 08-26-2016, 07:52 AM
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Contact that car dealer with the euro 450slc in the industrial equipment yard. He wanted a ridiculous $1800 for the d-jet pile of rust, but hopefully he will come around. See if you can meet him in person.
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