and I've been so excited with the end result I just had to share it with fellow DDKer's.What started as an investigation into the poor running of my 2.2S turned into a full rebuild by Autofarm when investigation revealed a worn cam that had churned bits throughout the engine, a single tired piston and knackered throttle body shafts and bushes
. Somewhere during the rebuild it seemed like a good idea to build a period-correct twin plug, high compression 2.3 litre ST engine, since the next car to roll off the production line from mine (chassis 9110300948) was the shell liveried ST driven by Laurousse to 3rd place on the 1970 Tour de France (chassis 949).It all seemed so logical at the time
: if you’re going to have to replace cams, pistons and sort out the throttle bodies, why not put RSR cams, 10.5:1 high compression forged slipper skirt race pistons, and larger 906-spec butterflies into it, especially since racing bits paradoxically were cheaper than originals? For instance I couldn’t believe new 2.2S barrels and pistons were £2,700 from Mahle, whereas new J&E pistons with lightweight pins and indentations for valves were £560! Deal! What I didn’t anticipate were all the add-ons. For instance, did you know 2.2S rod bolts were slightly longer than the 2 litre ones even though they have the same stroke of 66mm, so none of the modern high rpm bolts fitted?
I didn’t want to risk polished standard rod bolts so the only alternative was to buy a set of Carillo’s (ouch) to reliably take 8,500rpm…. For those interested in some of the other technical details, the engine features:
· RSR sprint cams providing 318 and 300 degrees duration (inlet and exhaust) and 0.46 and 0.45 lift along with hydraulic pressure-fed chain tensioners
· 2.2S 46 inlet and 40mm exhaust valves (as per ST) with shotpeened, stress relieved and modified rocker assembly for higher revs
· 66mm forged steel Carillo rods
· Standard mechanical fuel injection rebuilt with 906-spec 40mm butterflies
· Factory competition R/ST/RSR 24 inch megaphones and SSI tuned headers, complete with heat exchangers
· Standard production cooling is used as per the ST but a later 930 turbo scavenge pump has been installed to improve oil circulation
· The original production 2.2S Biral barrels were used (cast iron w/ bonded aluminium fins), machined to accept the 1mm increase in bore
· The original crankcase was shuffle-pinned, boat-tailed and had over 40 hours of work done to it to ensure it survives at high rpm
· Twin plugs have been fitted to the heads, but a 12 point Marelli distributor is silly money and rarer than rocking horse shite so that’s on the xmas shopping list for now.
· Power output for the engine was quoted by the factory at 230bhp at 7,800rpm and 170 lb/ft torque at 6,200rpm
So what’s it like to drive? With the megaphones it’s on the limit of driveability for the street as it’s pretty cammy and noisy enough to wake the dead. There’s a stumble at exactly 3,000rpm while cams, air intake speed and fueling all crash together, but it clears it’s throat at 3,200 and then provides a mechanical symphony only the devil himself could produce. Small dogs cower and bark, mothers look on disapprovingly as we rumble by, but all the blokes smile. I’m sure I will end up prematurely deaf!
With the twin outlet silencer the exhaust is sufficiently muffled so the sash windows don’t rattle in their frames and the cams are less obvious: it will tootle along at 1,500rpm and then pull cleanly through to rev itself to bits if you keep your foot down. It’s also shockingly fast and a hoot to drive... just don’t ask me what it cost
I'll try and post a pic tonight but am technically illiterate so it might take me a while!
I have a similar recording of a Aston 6.3 conversion V8, different kettle of fish, but stirs the soul.
