The Holden Grey motor is often referred to as the Holden side plate. The engine earned its name as they were painted grey from the factory. They came in 2 sizes, 138ci and 132ci. More engineering and after market modifications have gone into this engine than any other engine in Australian automotive history.

June 02, 2015

Waggot Twin Cam Head Holden

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THE evolution of the Holden as a racing sedan has been little short of dramatic.  Holden’s with twice the manufacturer's horse-power are now common. Enthusiasts like Lou Kingsley with bored-out,. Repco-headed Holden’s are talking of 140 b.h.p. But the latest competition Holden is likely to have something like three times the stock power — which, for the record. is 62 b.h.p. at 4,000 r.p.m. (nett) or 70 SAE horsepower at 4,000 r.p.m. (gross). 

Waggot Twincam Head


The most powerful Holden conversion to date has been carried out by Merv Waggott of Waggott Engineering, a very active firm of general engineers in Greenacre, a Sydney suburb.  
The sedan belongs to Bill Thompson and there is talk of Jack Myers piloting it in scratch races, with Bill at the wheel for handicap events. For a completely new engine the power unit gave a quietly impressive account of itself at the G.P. meeting at Bathurst.  With Jack Myers driving it gained third place in the scratch section of the second race.  

Merv Waggot
Merv Waggot, the man who designed most of the engine
 
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Earlier, in practice, clutch trouble was experienced.  During the race itself there was also carburettor manifold trouble, and as the race went on the motor began to sound less and less clean.  Jack Myers reports that on certain parts of the course on every lap, in exactly the same place, the engine was starving for fuel and he was forced to drive accordingly.  A fractured manifold was suspected and Jack could not reach maximum speed.  An engine speed of 6,000 r.p.m. in top gear gave him a road speed of 111 m.p.h.  However, maximum engine speed Is expected to be around 7,000 r.p.m. , although a limit of 6,500 will be imposed on the indirect gears.  After the fuel check at the end of the event the engine refused to start and Merv Waggott found that petrol was spraying out of the carburettor union and the rear carburettor, which was held on by the pipes and linkages alone.

A scorching hot thee liter ex-family car 
with double overhead camshafts, sever bearing
crankshaft and a power to weight ration that
betters the Three PointFor Jaguar - can the go further?

Only two Stromberg carburet-tors were fitted for the Bathurst event as the car was completed just in time for the meeting. For future events, however, six Amals will be used. Merv Waggott, who has been responsible for both the engine design and machining, is not a man given to guess work. For this reason, he declines to estimate the likely power or speed of the engine. But with the specifications before us our guess is that it will produce about 175 b.h.p. at 6,000 r.p.m.
Most believe that the evolution of bored-out special Holden engines has reached its zenith.  This viewpoint is strengthened by the decision of Merv Waggott to lengthen the stroke of the engine in his quest for more power.  By doing this he has raised the capacity to 2995 c.c.. or nearly three litres.
A special seven bearing crankshaft has been made to withstand the extra strain and the cylinder head is the well known Waggott "double knocker" with twin overhead camshafts.  The compression ratio is 9 to 1 and the induction system will include six Amal carburettors. 


The Waggott-Thompson Holden has a power to weight ratio of about 150 b.h.p. per laden ton. This compares favourably with stock 3.4-litre Jaguar, which has 145 b.h.p. per laden ton. But the engine is not the only major modification. The stock gearbox has been replaced by a four-speed unit from an XK 120; the clutch is a composite unit made up of two Holden clutch plates, a Holden pressure plate.
Jaguar centres and a fabricated steel centre plate fitted between the clutch plates. For the Bathurst meeting a standard pressure plate was used with this special clutch. It failed, however, during the last lap of practice. This was not apparent until Myers went to the line for the start of the first sedan race. Bad vibration occurred and he could not select low gear—a sign that the pressure plate springs had collapsed.

A new pressure plate was fitted for the second day's racing, but Waggot Engineering is at presently modifying the clutch to give positive driving location.  The suspension remains reason-ably standard, apart from stiffer coil springs at the front and more powerful shock absorbers all round. Repco-Holden brakes will be fitted at the front and possibly also at the rear. The three-litre engine capacity has been obtained by boring out the cylinder bores to 81 mm. (roughly 3/16" oversize) and lengthening the stroke to 96 mm., which is roughly x. longer than normal. The seven bearing crankshaft has been designed and machined by Merv Waggot himself. It was cut from solid 60 ton high tensile steel, It is fitted to the Holden block by the use of an Ingenious "cage" which is bolted to the lower half of the engine. 
 

7 Bearnign crank for grey motor

 As our photograph shows, the cast iron cage has been designed with seven bearing caps cast integrally. It is bolted to the block, using the holes normally filled by the four bearing cap studs. The three additional bearings are retained by caps which can be bolted to the cage itself.  This means that the crankshaft assembly is clamped to the cage before it is bolted to the engine block. Initially, standard connecting rods were used. Later special rods will be made in the light of any lessons learned from the early operation of the new power unit, the pistons have been specially cast and were machined by Waggott Engineering.


Waggot 7 bearking cranck for grey motor

The contours of the camshaft are half way between semi and full race and the engine will be reasonably flexible. The compression ratio is 9 to 1, so that pump fuel can be used to comply with sedan car regulations. A standard oil pump is used, as past experience has shown that the gears of the drive shaft are likely to shear if the oil pressure is raised. A full flow Volks oil filter will be used. The ignition will be normal, apart from a Delco twin breaker point distributor.
The cylinder head is similar to that used on Jack Myers' W.M Cooper. The camshafts were machined from the solid by Waggott Engineering, but the special valves were made by an outside firm. Maximum engine speed is expected to be around 7,000 r.p.m., but a limit of 6,500 or even 6.000 will be amposed for the indirect gears. Maximum speed will be governed by the choice of rear axle ratio, but is likely to be around 120 m.p.h. Extra engine cooling has been affected in two ways. First the radiator core has been thickened to help keep the operating temperatures of the engine down, and secondly an oll radiator has been added. So far this unusual Holden is still in the experimental stages. But few men have had more experience with modified Holden engines than Merv Waggott, Jack Myers and Bill Thompson are a formidable driving team. With this backing the new car should prove unusually fast.

Article by Pedr Davis

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