Wednesday, March 26, 2014

"Scamp" Porter's Race winning R8 Gordini Modifications

"Scamp" Porter's Gordini Modifications carried out for South African Saloon Car Sprint Racing, 1966-69.


Body, Chassis
Renault  homologated fender spats (4" and 2") attached to front and rear wheel fenders
Use of widened 13" delta-mic composite wheels, approx  6" front, up to 8" in rear
Fitting of a front radiator in the spare wheel well, allowing air to exit through luggage boot.
Shaving Gordini front brake caliper where contacted by 13" wheels.
The brake booster was thrown out as reaction time was too delayed.
DS11 brake pads on Gordini rotors.
Bending front stub axles to give 1.5 degrees negative camber.(Later cars used bent Gordini stub axles, which proved superior under Rally conditions - thicker - though there were no failures of standard ones). This modification raised the upper ball joint about 20 mm and moved the front suspension role centre closer to the centre of gravity.  It also supposedly added a little negative camber on lean, though, with the strength of the sway bar, it is doubtful whether much suspension compression occurred.
Bending steering arms to remove all bounce steer.
Quick ratio 1.5 turns lock to lock (Pierre Ferry) steering pinion and offset bushings,
(re-centralising spring discarded)
1" steel anti roll bar fabricated to original shape and fit opened out mounts.
Front springs cut approx 1.25 coils (extended track of outward widened wheels automatically lowers car)
Discarding of rear brake pressure regulator for superior rear braking performance.
Use of lighter standard R8 rear crossmember with single shock absorbers
Rear R8 springs cut approx 1.5 coils, to allow for 4.5 degrees negative camber.
De Carbon gas shocks (perhaps from Dauphine).
Specially fabricated rear axle shafts with larger diameter wheel carrying spigots to accept larger wheel bearings.  (With all the extra grip and racing tyre technology, snapping axles at the bearing joint was the weakest link)
Plexiglass side and rear windows as allowed by regulations (Internal roll cages were either not thought up yet, or not allowed by FIA regulations)
Hanging the standard oil cooler in the air stream
Some lightening, as with removal of extra headlights ( R8s did not come so equipped) bumpers, spare wheel
Full seat belt harness and extra side bolstered driver's seat.

Cooling System
As much as the wide track, 13" wheels and large anti-roll bar contributed to the handling, modifying the cooling system  assisted and stabilized the engine performance.  Regulations allowed certain radiator alterations, to strict height limits. So the standard radiator was hung at an angle in the front spare-wheel well with ducting and routing along the heater hose hoses.

Engine compartment cooling and heat removal was a major area of attention, as it was discovered early in development that the vehicle was considerably quicker when, during practice, the engine bonnet was removed, especially so when the original rear radiator was required by the regulations.
Ducts and passages were cut behind rear inner fenders to allow cool air to the motor area. A large insulated longitudinal divider was fabricated to seal off hot air from exhaust side getting to intake side of the motor, and a sealed intake air duct routed to the carburetters  from the rear hood louvers (which received a moving stream of outside air). Under hood exhaust pipes were wrapped with asbestos tape to prevent heat radiating into engine compartment.  Original under-engine pressed steel air ducting out from engine retained where possible.


Gearbox and Drive
Gordini 5 speed with optional 7/32(4.57) ring gear and pinion ratio.
4 Pinion gears in differential rearranged so that two opposite ones intermeshed and prevented all rotation (locking up diff)
1st, 2nd, 3rd, 4th gears specially fabricated to allow closer ratios between 2nd to 5th to keep engine performance in a better part of the power curve.

Major Engine Alterations
Use of basic 1135 (1255cc) engine, components lightened and polished where possible
French Alpine Engineering Gordini 1297cc pistons (75.7mm)
Carefully lightened and polished and balanced internal components, after stress analysis.
Engine block height and sleeves lowered 1mm to cater for piston machining and allow higher compression.
Pistons valve cutouts machined and smoothly bevelled to cope with high lift cam, shortened block, larger valves and early intake cam timing.
Lifter bores' and block face angled pushrod scallops deepened for clearance with altered camshaft.
Large Gordini deep oil pan double baffled to prevent surge in corners
Smaller Alconi crank pulley,  removed engine fan
Lightened flywheel and fabricated scintered brass twin plate clutch
45mm Weber carburators with 36mm primary venturis
Fabricated 4 into 2 into 1 exhaust system of 1.5" by 16" primary, 1.625 by 24" secondary,
and 1.75 by 34" final length, underbody parts wrapped in asbestos! (later fiberglass) tape to endeavour to eliminate under-bonnet heat which tended to affect performance after a few laps.
(4 into 1 exhaust was tried but results were disappointing - perhaps gear ratios were not close enough)
Huge plastic separation plates to isolate exhaust/engine heat from intake side, and  carefully sealed ducts and covers to allow intake to obtain air from engine lid louvres
Isky/Alconi camshaft of 7.3mm lift (10.6mm valve lift), 285 degrees duration, intake 42 -63, exhaust 75 - 30 degrees.
Valve clearance 0.45mm.

Cylinder Head Upgrades
Fitting  of shortened 39.1mm AJS/Matchless motorcycle intake valves, intake guides reamed to 7.14mm (AJS/Matchless 9/32 valve stem diameter)
Use of Gordini 35mm intake valves as exhausts
Fiat 1500 heavy duty valve springs manufactures by British Terry Company.

The head was quite delicate and very expensive, and had to be treated especially carefully.
Fabricated and fitted large brass or iron valve inserts always looked good, but, due to the  Gordini designed cavity under the spark plug, the head in that area seemed to overheat, and was prone to small cracks and movement, so this was always a suspect condition requiring careful inspection,  because it could cause an expensive engine failure.  (Many standard Gordini heads also suffered from these cracks but we can't recall ever seeing a dropped valve insert)


Opening the under valve ports to blend to the large valves, and seating the valves low in their seats, one of the most important flow areas and secrets for obtaining the best engine horsepower. This shaping, even today, sorts the superior horsepower heads from the mediocre.
Valve guides had to be shortened under the spring area to allow for the high (about 10.5mm) valve lift.
Because of this, the high revs and quick lift, guide wear became unacceptable. Adding 2 extra lubrication holes at inner valve spring seat, through into the guide solved this wear problem.
Together, with all moving parts lightened and polished, the rpm limit was upped to about 8600-8800,
which was considered adequate at the time.  However, it must be stressed that just one over rev or missed gear change could destroy the engine.  There were no safeguards, so the drivers in general used only 8000-8200rpm through the gears, and allowed the engine to pull more in top gear only, if the straight was long enough!

Ignition  advance altered to give 10 degrees static advance, maximum of 26 degrees at 3000 rpm

One difficulty that was not solved, was the tendency of the timing chain tensioner to strip its ratcheting device every race. The camshaft design probably contributed to this peculiarity.  It never caused any other collateral damage, but was not overcome, although an experiment  using  Dauphine engine cam drive gears and idler in the system instead was under way.  The problem was blamed for a deterioration of about  3/10 seconds in lap times well into every race.
In this form the engine produced around 98KW (130bhp) at 7800-8000rpm at the Johannesburg altitude of 5800ft above sea level.