300SEL 3.5: Anyone installed 117 cylinder heads on a 116 engine?

[Tony H]

Martin,
I personally cc'ed the heads from a K-jet 4.5 engine I bought for my 5.6 project and they are 45cc. I don't have a d-jet 4.5 head but from looking at pictures I found on Ebay auctions the area around the edge of the combustion chamber looks recessed instead of flat like the K-jet heads. I'm thinking of pulling one of the heads on my 3.5 just to see for myself what the cc is.

Originally Posted by werminghausen

Tony, you are correct.
Assuming the 117 K-jet has a 45cc head and compression is 8:1
resulting in VR 117 = 565.046ccm/ 8.0 -1 = 80.72ccm (this is the volume of the final burning chamber)

The recessed pistons plus gasket must make a volume of 80.72cc - 45cc = 35.72cc
3.14 (9.2cm) (9.2cm) /4 * x cm = 35.72cc.... x= 0.53cm = 5.3mm
This means: 35.72cc are the part volume (of the 80.72cc total burning chamber) with the piston ending about 5.3mm below the head surface. This includes head gasket and dished surfaces on the piston.
Do you agree?

For any further speculations I need more precise and confirmed data: like the compression rate of the 450 engine this head came from. Is it very likely that the compression rate was 8:1?
Is it very likely that the compression rate for my 3.5 is 9.5:1?
Martin

[werminghausen]

here are a few pictures of the 2 heads 116 and 117 I have on my bench.
You'll see the bigger combustion chamber in the 'clean' 117 head (first 2 pics) and the smaller chamber on the 116 head (last 3 pics). The 116 head has an oval edge while the 117 head has a circular edge with a one side cut off.

I hope this helps.
Martin

[Tomguy]

Martin,

You have a set of what appears to be 8.0:1 m117 heads, and a set of 9.5:1 3.5 heads. The set that came off my 4.5 were 8.0:1 m117 heads. Tony says the 8.8:1 m117 heads don't have that little cutout that the sets like yours & mine do. I didn't clean the m116 heads in my pics below but I did clean the 4.5 ones. You can see aside from old used valves & more worn seats that they're pretty much the same as your set, and still workable. My 4.5 has 3.5 heads and TBH I'm going to be getting rid of the car soon most likely, but probably not soon enough for your needs for its heads (and shipping to Oman is probably insane). These heads have the CC volumes you found on one of my earlier posts.

[Tomguy]

Using Paint.NET I estimated the two different head volume types (8.8:1 m117 and 9.5:1 m116) based off the 8.0:1 m117 head.

[Tony H]

Here is what the K-jet head looks like. I cc'ed it again and came up with 44cc. The combustion chamber is obviously larger than the 3.5 but smaller than the D-jet 4.5. It is actually a 8.0:1 CR engine even with the smaller combustion chamber because the pistons have a 9mm dish.

[Tomguy]

It makes sense that they would, later on, use the pistons to change the ratio as opposed to heads. It's much easier to machine the same piece from aluminum castings (heads) and use different pistons than the other way around. It also means all you need is earlier version 4.5 pistons to get 8.8:1 comp ratio which is a great way to boost power with easier to find and cheaper parts.

[werminghausen]

Originally Posted by Tony H

Here is what the K-jet head looks like. I cc'ed it again and came up with 44cc. The combustion chamber is obviously larger than the 3.5 but smaller than the D-jet 4.5. It is actually a 8.0:1 CR engine even with the smaller combustion chamber because the pistons have a 9mm dish.

Hi Tony,
so you are saying both K-jet and D-jet 4.5 engine have a CR of 8:1...correct?
I'll cc both my heads of the D-jet 3.5 and 4.5. With what medium did you cc? ATF?
Best, Martin

[Tomguy]

I used ATF in one of those printer refill syringes. Just be aware that the syringe won't be any good after because the oil will eat the rubber on the plunger and it won't fit right anymore.

[werminghausen]

Here we go.

I cc'd both heads
116 head was around 40cc
117 head was around 46cc
Difference is 6cc

VR116 = 437.41ccm/ 9.5 -1 = 51.46ccm
compression 116 engine with 117 head: VR 117 head = VR116 + 6cc= 57.46cc
CPnew = (VP +VR117head)/ VRhead117
= (437.412cc+ 57.46cc)/ 57.46cc = 8.61:1

Martin

[Tony H]

I guess loosing a few hp is worth it if the d-jet heads enable you to drive your car and the 3.5 heads will not work for what ever reason. You could always get some 3.5 heads at a later time.
Thanks for the cc information. I thought the 3.5 heads were smaller but things like seat wear and valve recession can increase the cc.

[werminghausen]

The question now is how much do you guess is the loss on hp going with CR from 9.5 to 8.6?

9.5 is 200 hp....and 8.6 is.....

[mercmad6.3]

ha ha that is almost one whole point of compression, which in Engine terms is a LOT. Like ,as has been suggested already, the thing is to get the car mobile and fix the high compression heads later.
i have done a ton of work on engines to get compression up i to 2 points and the difference it made was very noticeable.

[werminghausen]

Originally Posted by mercmad6.3

ha ha that is almost one whole point of compression, which in Engine terms is a LOT. Like ,as has been suggested already, the thing is to get the car mobile and fix the high compression heads later.
i have done a ton of work on engines to get compression up i to 2 points and the difference it made was very noticeable.

Very interesting:
1) Can you put numbers to the points. What means noticeable
I mean if you have a stock engine (let's say a 3.5 with 200hp) with CR 9.5:1
and add a point (CR 10.5:1) ...or lose a point (CR 8.5:1)...
What is the gain/loss of hp roughly?
2) Is there an easy way to increase CR for the low compression head in front of me?
I know the head gasket can't be reduced ( I think reducing by 0.7 mm would compensate the loss in my case) Planing the head by another 1mm would make it...but I'd need to compensate the chain 'stretch'.
Can 'material' be added to the chamber? Welding...ah....bolting...ah. I know it sounds crazy.
Martin

[Tomguy]

The gains and losses are different. An increase of 10% may increase power 5%, but a decrease 10% may decrease power 20%. There are way too many variables to guess what the power differences are. If you keep the 3.5 cams, designed for higher compression, on an engine with 4.5 heads, you may have even more power loss. You will lose at least 20HP but likely more. Also, your gas mileage will go down. As said, the engine will run, and if it's your only option because the 3.5 heads are toast, do it. But if the 3.5 heads can go another 10k or until you make it back to the US (if you come back), keep them on.

Edit:
One other thing to point out is that the 4.5 heads you have were milled - a LOT. Compare the depth of the ridge (to lower compression) on your heads to my original 4.5 ones. Aluminum heads don't usually require too much milling, and the manual even specs a certain tolerable amount because torquing down the heads helps flatten them. The valve to piston clearance in a 3.5 is already tight, with cutouts in the pistons for the valves. The milling combined with the high seats in your 4.5 heads may cause clearance issues. Also, compare your CC volume for the 4.5 heads you have with the value I found for mine. I'd say they were probably milled 0.030" or so.

[werminghausen]

Thanks Tomguy

You measured 52.6cc for the the same type 117 head?
I had 46cc...
So you are saying that the difference will be the milling? Quite a bit to reduce 6.6cc hey!


In order to gain 6cc you'd need to mill the head at least 1mm if my math is correct.
So you fear that this milling might be over the top?
Does anyone know the limits these heads can be milled?

Martin