I’m rebuilding a W123 turbo OM617 engine to be installed into an early W123 non-egr chassis.

I recently picked up a set of W116 non-egr manifolds and noticed the port diameter on the exhaust manifold to be a larger diameter than the later W123 manifold.

Question – I know this is going back a few years but does anyone remember if the exhaust ports in the W116 head where larger than the W123s? If so, I imagine the W116 head would flow a few more CFM over the W123 head… I checked EPC and both heads used the same head gasket and cam. A local mechanic says there were some difference in cooling passages but didn’t remember if port sizes were the same or not?

Thoughts?

Regards
Scotte
SoCal

An interesting discovery!

The 617.950 engines used in the W116s were actually rated at less power than the later 123 engines, so the 123 heads (.952) can't be worse for flow than the .950 ones if my logic is correct...

Something tells me the head castings themselves are near identical from when the 617 was first born right through to when they stopped making them in the 90s.

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

As far as i know all 617 turbo heads are the same, except for the SLS pump connection on the wagon heads.

__________________

76 240 D. Bought in 1998 for $25.
85 300D. Got it for free with a bad engine. ( Sold )
60 Unimog 404. What was left of it, was given to me. Now powerd by 617A.
88 560 SEL. Bought without engine and trans. Now powerd by 617A.
67 250 SE. Cuope. For resto or sale.
64 220SE. For resto.

Castings are the same, so the ports sizes are the same. The non-EGR exhaust manifolds on the other hand definitely had larger ports than the EGR counterpart. My theory on this they wanted less volume in the runners to promote more velocity of the exhaust gas to quickly spool the turbo at low RPMs.

__________________
1983 123.133 California
- GreaseCar Veg System

Thanks for everyone's response.

I also found some information suggesting that the larger exhaust manifold runners are used for reversion control and therefore should not be ported to be gasket matched...

The difference between my cylinder head port diameter and exhaust manifold port diameter is 3mm to 5mm.

I went back and remeasured the W116 and W123 manifold port sizes and while they appear to be the same, the overall W123 manifold volume is less and I have to agree with DeliveryValve's comment on increase velocity.