Merak SS 'S' engine idea

I was speaking with a Merak guy the other day (George, great chatting with you) and the gears started grinding a bit......again. The C114 engine is really a perfect little race engine with its inboard timing chains, it's a remarkable robust idea of an engine, but it needs some internal work to make sense of performance.

I started doing some research with regards to the Merak crankshaft and innerds, both of which I am pretty familiar with but I needed some more finite information such as block width/depth and crank journal/rod sizes. The idea is to get more poke out of Merak SS without changing a stock look, which is precisely what I did with my 308 engine which now has a 79mm stroke Ferrari 360 crankshaft in place and makes around 330bhp with 265lbs torque. A Merak making close to the same would be brilliant.

The Merak engine requires a bit more thought to really optimize what it's capable of beginning with the size of the crankshaft journals with specifically the rods, which are entirely too large to spin the engine high.

Current rod journals are about 2.250, I would like to offset grind them to 2.000 and use a high performance small block 2.000" bearing and possibly custom rod if I cannot find something already on the market which fits my needs. This would provide a revised stroke of a bit over 87mm, up from 75mm. Ferrari rod journals are well under 2.000 and those engines spin to the moon, but an even 2.000 should be adequate for the rev range I'd like to operate in, which is somewhere around 7500rpm max.

Such a stroke will heavily change the shape of the piston, so I will most likely end up with a flat or dished top which I will poke out of the deck .010 to go for a .040 quench area. losing the piston dome altogether is the goal. 93mm bore should be adequate as well. Going for 10.5-11:1 static.

Valves, I've measured the SS intake throat area and there is room to open the valve seat ID a bit to place a slightly larger OD valve seat in place. What I would like to do is change the ID of the throat and bowl area to yield more high lift flow as flow with these heads IIRC really lays down to nothing at anything above .275 lift. 2mm larger intake valve with around 1mm larger ID at the seat with plenty of bowl work can probably yield another 12-15% flow on its best day. Merak engines and 308 engines have a very similar problem with their intake ports in that they are just a very poor design, but they didn't know any better in that day so I cannot blame them.

The SS cams are not terrible, but with flow potential from the ported heads I believe I could push lift to .400 with right around 245 duration @ .050 using a somewhat radical cam ramp profile. The stock SS cam timing employs a pretty tight lobe separation angle (102 degrees IIRC) which is common with all Italian engines of this era. I would not change the timing radically as I know a 90 degree V6 is going to vibrate with a terrible harmonic no matter how the combustion occurs. Peak power would probably be made right around 7200rpm which may even be too high as I haven't quite worked out if the main journals are also too big to rev anywhere near 7000rpm.

The 44dcnfs would need a larger main venturi, probably 38mm.

Total displacement would nearly 3.6L, and I believe I could see 320bhp with 275lbs torque.


My question is, can the Citroen gearbox handle such power? It's my understanding they aren't really strong units.


Anyway, I'm sort of in the market for the 'right' Merak to possibly get my hands into such a project. There's lots of potential with these little engines.

 

That's what I'm wondering. I think JS2 did in fact use that gearbox at Le Mans. not 100% sure though.

 

wonderful website. thank you. I am aware of what they did with the Esprits. The Renault 'box used in the Stevens cars wasn't much better IMO. Shifting-wise anyway.

 

JS2 did indeed run this 'box at Le Mans.

 

Before I would commit to that rod size I want to have the block and crank in there to really measure what can be done. Sounds like a good option though